Week 6 Quiz

glycolysis

anaerobic breakdown of glucose to ATP-- (non-oxygen-dependent) process that breaks down glucose (sugar) to produce ATP; however, glycolysis cannot generate ATP as quickly as creatine phosphate. Thus, the switch to glycolysis results in a slower rate of ATP availability to the muscle. The sugar used in glycolysis can be provided by blood glucose or by metabolizing glycogen that is stored in the muscle.

A sprinter would experience muscle fatigue sooner than a marathon runner due to ________.

anaerobic metabolism in the muscles of the sprinter

infrahyoid muscles

anterior neck muscles that are attached to, and inferior to the hyoid bone

urogenital triangle

anterior triangle of the perineum that includes the external genitals

oblique

at an angle

Which of the following properties is not common to all three muscle tissues?

at rest, uses shielding proteins to cover actin-binding sites

Which muscles stabilize the pectoral girdle?

axial and scapular

How are cardiac muscle cells similar to and different from skeletal muscle cells?

Cardiac and skeletal muscle cells both contain ordered myofibrils and are striated. Cardiac muscle cells are branched and contain intercalated discs, which skeletal muscles do not have.

Another feature of cardiac muscle is its relatively long action potentials in its fibers, having a sustained depolarization "plateau." The plateau is produced by Ca++ entry though voltage-gated calcium channels in the sarcolemma of cardiac muscle fibers. This sustained depolarization (and Ca++ entry) provides for a longer contraction than is produced by an action potential in skeletal muscle. Unlike skeletal muscle, a large percentage of the Ca++ that initiates contraction in cardiac muscles comes from outside the cell rather than from the SR.

Cardiac muscle is striated muscle that is present only in the heart. Cardiac muscle fibers have a single nucleus, are branched, and joined to one another by intercalated discs that contain gap junctions for depolarization between cells and desmosomes to hold the fibers together when the heart contracts. Contraction in each cardiac muscle fiber is triggered by Ca++ ions in a similar manner as skeletal muscle, but here the Ca++ ions come from SR and through voltage-gated calcium channels in the sarcolemma. Pacemaker cells stimulate the spontaneous contraction of cardiac muscle as a functional unit, called a syncytium.

Physical training alters the appearance of skeletal muscles and can produce changes in muscle performance.

Conversely, a lack of use can result in decreased performance and muscle appearance. Although muscle cells can change in size, new cells are not formed when muscles grow.

What causes the striated appearance of skeletal muscle tissue?

Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell cause the entire cell to appear striated.

extensor retinaculum

band of connective tissue that extends over the dorsal surface of the hand

flexor retinaculum

band of connective tissue that extends over the palmar surface of the hand

sartorius

band-like muscle that flexes, abducts, and laterally rotates the leg at the hip

somites

blocks of paraxial mesoderm cells - adjacent to neural tube form blocks of cells. . Skeletal muscles, excluding those of the head and limbs, develop from mesodermal somites, whereas skeletal muscle in the head and limbs develop from general mesoderm. Somites give rise to myoblasts

Which muscle type(s) (skeletal, smooth, or cardiac) can regenerate new muscle cells/fibers? Explain your answer.

Smooth muscle tissue can regenerate from stem cells called pericytes, cells found in some small blood vessels. These allow smooth muscle cells to regenerate and repair much more readily than skeletal and cardiac muscle tissue.

Why can smooth muscles contract over a wider range of resting lengths than skeletal and cardiac muscle?

Smooth muscles can contract over a wider range of resting lengths because the actin and myosin filaments in smooth muscle are not as rigidly organized as those in skeletal and cardiac muscle.

latissimus dorsi

broad, triangular axial muscle located on the inferior part of the back

belly

bulky central body of a muscle- muscles that seem to be plump have a large mass of tissue located in the middle of the muscle, between the insertion and the origin, which is known as the central body. - when a muscle contracts the contractile fibers shortern it to an even larger bulge. For example, extend and then flex your biceps

superficial anterior compartment of the forearm

flexor carpi radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum superficialis, and their associated blood vessels and nerves

deep anterior compartment

flexor pollicis longus, flexor digitorum profundus, and their associated blood vessels and nerves

muscle tension

force generated by the contraction of the muscle; tension generated during isotonic contractions and isometric contractions - or shorterning of the sarcomeres- tension also is generated when the muscle is contracting against a load that does not move, resulting in two main types of skeetal muscle contractions: isotonic contractions and isometric contractions

angiogenesis

formation of blood capillary networks--- The training can trigger the formation of more extensive capillary networks around the fiber, - supply oxygen and remove metabolic waste The training can trigger the formation of more extensive capillary networks around the fiber,

quadriceps femoris group

four muscles, that extend and stabilize the knee

plantar group

four-layered group of intrinsic foot muscles

frontalis

front part of the occipitofrontalis muscle --- forehead

myotube

fusion of many myoblast cells--then fuse(s) to form a syncytium,As a myotube is formed from many different myoblast cells, it contains many nuclei, but has a continuous cytoplasm. This is why skeletal muscle cells are multinucleate, as the nucleus of each contributing myoblast remains intact in the mature skeletal muscle cell. However, cardiac and smooth muscle cells are not multinucleate because the myoblasts that form their cells do not fuse.

antagonist

muscle that opposes the action of an agonist-- Antagonists play two important roles in muscle function: (1) they maintain body or limb position, such as holding the arm out or standing erect; and (2) they control rapid movement, as in shadow boxing without landing a punch or the ability to check the motion of a limb.For example, to extend the knee, a group of four muscles called the quadriceps femoris in the anterior compartment of the thigh are activated (and would be called the agonists of knee extension). However, to flex the knee joint, an opposite or antagonistic set of muscles called the hamstrings is activated.

subscapularis

muscle that originates on the anterior scapula and medially rotates the arm

hyoglossus

muscle that originates on the hyoid bone to move the tongue downward and flatten it--

genioglossus

muscle that originates on the mandible and allows the tongue to move downward and forward- glossus- tongue - genio- chin allows moving downward and forward

palatoglossus

muscle that originates on the soft palate to elevate the back of the tongue

styloglossus

muscle that originates on the styloid bone, and allows upward and backward motion of the tongue

tibialis posterior

muscle that plantar flexes and inverts the foot

palmaris longus

muscle that provides weak flexion of the hand at the wrist

temporalis

muscle that retracts the mandible

plantaris

muscle that runs obliquely between the gastrocnemius and the soleus

subclavius

muscle that stabilizes the clavicle during movement

trapezius

muscle that stabilizes the upper part of the back

plantar aponeurosis

muscle that supports the longitudinal arch of the foot

psoas major

muscle that, along with the iliacus, makes up the iliopsoas

iliacus

muscle that, along with the psoas major, makes up the iliopsoa

synergist

muscle whose contraction helps a prime mover in an action---To lift a cup, a muscle called the biceps brachii is actually the prime mover; however, because it can be assisted by the brachialis, the brachialis is called a

adductor magnus

muscle with an anterior fascicle that adducts, medially rotates and flexes the thigh, and a posterior fascicle that assists in thigh extension

myoblast

muscle-forming stem cell Somites give rise to myoblasts

palmar interossei

muscles that abduct and flex each finger at the metacarpophalangeal joints and extend each finger at the interphalangeal joints

dorsal interossei

muscles that abduct and flex the three middle fingers at the metacarpophalangeal joints and extend them at the interphalangeal joints

intrinsic muscles of the hand

muscles that move the wrists, hands, and fingers and originate in the palm-- allows us to type and write

extrinsic muscles of the hand

muscles that move the wrists, hands, and fingers and originate on the arm

transversospinales

muscles that originate at the transverse processes and insert at the spinous processes of the vertebrae

intercostal muscles

muscles that span the spaces between the ribs--The principal role of the intercostal muscles is to assist in breathing by changing the dimensions of the rib cage (Figure).

internal intercostal

muscles the intermediate intercostal muscles that draw the ribs together-- 11 pairs of internal intercostal muscles, just under the externals, used for expiration because they draw the ribs togeher to constrict the rib cage

masseter

main muscle for chewing that elevates the mandible to close the mouth

sternocleidomastoid

major muscle that laterally flexes and rotates the head

obturator externus

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

obturator internus

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

piriformis

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

quadratus femoris

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

superior gemellus

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

gluteus medius

muscle deep to the gluteus maximus that abducts the femur at the hip

pelvic diaphragm

muscular sheet that comprises the levator ani and the ischiococcygeus-- spanning anteriorly to posteriorly from the pubis to the coccyx, comprises the levator ani and the ishiococcygeus. its openings include the anal canal and urethra, and the vagina in the women. ---- It resists the pressure produced by contraction of the abdominal muscles so that the pressure is applied to the colon to aid in defecation and to the uterus to aid in childbirth

tensor fascia lata

muscle that flexes and abducts the thigh---is a thick, squarish muscle in the superior aspect of the lateral thigh. It acts as a synergist of the gluteus medius and iliopsoas in flexing and abducting the thigh

coracobrachialis

muscle that flexes and adducts the arm

flexor carpi ulnaris

muscle that flexes and adducts the hand at the wrist

lumbrical

muscle that flexes each finger at the metacarpophalangeal joints and extend each finger at the interphalangeal joints

flexor hallucis longus

muscle that flexes the big toe

flexor pollicis longus

muscle that flexes the distal phalanx of the thumb

flexor digitorum longus

muscle that flexes the four small toes

flexor digitorum superficialis

muscle that flexes the hand and the digits

popliteus

muscle that flexes the leg at the knee and creates the floor of the popliteal foss

flexor digiti minimi brevis

muscle that flexes the little finger

flexor digitorum profundus

muscle that flexes the phalanges of the fingers and the hand at the wrist

flexor pollicis brevis

muscle that flexes the thumb

diagastric

muscle that has anterior and posterior bellies and elevates the hyoid bone and larynx when one swallows; it also depresses the mandible

fusiform

muscle that has fascicles that are spindle-shaped to create large bellies- meaning it tapers as it extends to its origin and insertion

omohyoid

muscle that has superior and inferior bellies and depresses the hyoid bone

extensor

muscle that incrase the angle at the joint

abductor pollicis longus

muscle that inserts into the first metacarpal

extensor pollicis longus

muscle that inserts onto the base of the distal phalanx of the thumb

extensor pollicis brevis

muscle that inserts onto the base of the proximal phalanx of the thumb

From which embryonic cell type does muscle tissue develop?

myoblast cells

skeletal muscle fiber contracts

myosin heads attach to actin to form cross-bridges followed by the thing filaments sliding over the thick filaments as the heads pull the actin, results in sarcomere shorterning, creating tension of muscle contraction The cross-bridges can only form where thin and thick filaments already overlap, so that the length of the sarcomere has a direct influence on the force generated when the sarcomere shortens. This is called the length-tension relationship.

extensor indicis

muscle that inserts onto the tendon of the extensor digitorum of the index finger

iliotibial tract

muscle that inserts onto the tibia; made up of the gluteus maximus and connective tissues of the tensor fasciae latae

extensor digitorum longus

muscle that is lateral to the tibialis anterior

extensor hallucis longus

muscle that is partly deep to the tibialis anterior and extensor digitorum longus

teres minor

muscle that laterally rotates and extends the arm

infraspinatus

muscle that laterally rotates the arm- inferior to the spine of the scapula - abduct the arm, laterally rotate the arm

mylohyoid

muscle that lifts the hyoid bone and helps press the tongue to the top of the mouth

pubococcygeus

muscle that makes up the levator ani along with the iliococcygeus

iliococcygeus

muscle that makes up the levator ani along with the pubococcygeus

occipitofrontalis

muscle that makes up the scalp with a frontal belly and an occipital belly -- muscle that moves up the scalp and eyebrows

medial pterygoid

muscle that moves the mandible from side to side

lateral pterygoid

muscle that moves the mandible from side to side- helps with chewing and moving food within the mouth

supinator

muscle that moves the palm and forearm anteriorly

pectoralis minor

muscle that moves the scapula and assists in inhalation

opponens pollicis

muscle that moves the thumb across the palm to meet another finger

aponeurosis

mysia- fuses with this and broad, tendon-like sheet of connective tissue that attaches a skeletal muscle to another skeletal muscle or to a bone or to fascia, the connective tissue between skin and bones. The broad sheet of connective tissue in the lower back that the latissimus dorsi muscles (the "lats") fuse into is an example of an aponeurosis.

splenius cervicis

neck muscle that inserts into the cervical region

splenius capitis

neck muscle that inserts into the head region

suprahyoid muscles

neck muscles that are superior to the hyoid bone

corrugator supercilii

prime mover of the eyebrows

hyperplasia

process in which one cell splits to produce new cells-- Similar to skeletal and cardiac muscle cells, smooth muscle can undergo hypertrophy to increase in size. Unlike other muscle, smooth muscle can also divide to produce more cells, a process --This can most evidently be observed in the uterus at puberty, which responds to increased estrogen levels by producing more uterine smooth muscle fibers, and greatly increases the size of the myometrium.

SO fibers possess large number of mitochondria and cap[able for contracting for longer periods because of large amount of ATP they can produce

relatively small diameter and dont produce large amount of tension

dense body

sarcoplasmic structure that attaches to the sarcolemma and shortens the muscle as thin filaments slide past thick filaments- analogous to the Z-discs of skeletal and cardiac muscle fibers and is fastened to the sarcolemma. Calcium ions are supplied by the SR in the fibers and by sequestration from the extracellular fluid through membrane indentations called calveoli.

Which cell type helps to repair injured muscle fibers?

satellite cells

enlargement of neurons that release neurotransmitters into synaptic clefts

smooth muscle found in the walls of visceral organs

synaptic cleft

space between a nerve (axon) terminal and a motor end-plate -- ACh nolecules diffuse across a minute space and bind to ACH receptors

sarcoplasmic reticulum (SR)

specialized smooth endoplasmic reticulum, which stores, releases, and retrieves Ca++

innermost intercostal

the deepest intercostal muscles that draw the ribs together-- act as synergists for the action of the internal intercostals

triad

the grouping of one T-tubule and two terminal cisternae-- membranes of SR on either side

Depolarization of the sarcolemma means ________.

the inside of the membrane has become less negative as sodium ions accumulate

What is the origin of the wrist flexors?

the medial epicondyle of the humerus

Which is moved the least during muscle contraction?

the origin

Which muscle extends the forearm?

triceps brachii

In relaxed muscle, the myosin-binding site on actin is blocked by ________.

tropomyosin

linea alba

white, fibrous band that runs along the midline of the trunk

soleus

wide, flat muscle deep to the gastrocnemius

thyrohyoid

muscle that depresses the hyoid bone and elevates the larynx's thyroid cartilage

sternothyroid

muscle that depresses the larynx's thyroid cartilage

Every skeletal muscle fiber is supplied by a motor neuron at the NMJ. Watch this video to learn more about what happens at the neuromuscular junction. (a) What is the definition of a motor unit? (b) What is the structural and functional difference between a large motor unit and a small motor unit? Can you give an example of each? (c) Why is the neurotransmitter acetylcholine degraded after binding to its receptor?

(a) It is the number of skeletal muscle fibers supplied by a single motor neuron. (b) A large motor unit has one neuron supplying many skeletal muscle fibers for gross movements, like the Temporalis muscle, where 1000 fibers are supplied by one neuron. A small motor has one neuron supplying few skeletal muscle fibers for very fine movements, like the extraocular eye muscles, where six fibers are supplied by one neuron. (c) To avoid prolongation of muscle contraction.

The release of calcium ions initiates muscle contractions. Watch this video to learn more about the role of calcium. (a) What are "T-tubules" and what is their role? (b) Please also describe how actin-binding sites are made available for cross-bridging with myosin heads during contraction.

(a) The T-tubules are inward extensions of the sarcolemma that trigger the release of Ca++ from SR during an Action Potential. (b) Ca++ binds to tropomyosin, and this slides the tropomyosin rods away from the binding sites.

Watch this video to learn more about macro- and microstructures of skeletal muscles. (a) What are the names of the "junction points" between sarcomeres? (b) What are the names of the "subunits" within the myofibrils that run the length of skeletal muscle fibers? (c) What is the "double strand of pearls" described in the video? (d) What gives a skeletal muscle fiber its striated appearance?

(a) Z-lines. (b) Sarcomeres. (c) This is the arrangement of the actin and myosin filaments in a sarcomere. (d) The alternating strands of actin and myosin filaments.

calcaneal tendon

(also, Achilles tendon) strong tendon that inserts into the calcaneal bone of the ankle

prime mover

(also, agonist) principle muscle involved in an action

epicranial aponeurosis

(also, galea aponeurosis) flat broad tendon that connects the frontalis and occipitalis- skull looks like an apple

rotator cuff

(also, musculotendinous cuff) the circle of tendons around the shoulder joint--- When baseball pitchers undergo shoulder surgery it is usually on the rotator cuff, which becomes pinched and inflamed, and may tear away from the bone due to the repetitive motion of bring the arm overhead to throw a fast pitch.

quadriceps tendon

(also, patellar tendon) tendon common to all four quadriceps muscles, inserts into the patella

fibularis brevis

(also, peroneus brevis) muscle that plantar flexes the foot at the ankle and everts it at the intertarsal joints

fibularis longus

(also, peroneus longus) muscle that plantar flexes the foot at the ankle and everts it at the intertarsal joints

agonist

(also, prime mover) muscle whose contraction is responsible for producing a particular motion

circular

(also, sphincter) fascicles that are concentrically arranged around an opening - when they relex, the sphincters concentrically aragned bundles of muscle fibers increase the size of the opening when they contract, the size of the opening shrinks to the point of closure. The orbicularies oris muscle is a circular muscle that goes around the mouth. When it contracts, the oral opening becomes smaller, as when puckering the lips for whistling. Another example is the orbicularis oculi, one of which surrounds each eye. Consider, for example, the names of the two orbicularis muscles (orbicularis oris and oribicularis oculi), where part of the first name of both muscles is the same. The first part of orbicularis, orb (orb = "circular"), is a reference to a round or circular structure; it may also make one think of orbit, such as the moon's path around the earth. The word oris (oris = "oral") refers to the oral cavity, or the mouth. The word oculi (ocular = "eye") refers to the eye.

anterior compartment of the arm

(anterior flexor compartment of the arm) the biceps brachii, brachialis, brachioradialis, and their associated blood vessels and nerves

anterior compartment of the forearm

(anterior flexor compartment of the forearm) deep and superficial muscles that originate on the humerus and insert into the hand

deep posterior compartment of the forearm

(deep posterior extensor compartment of the forearm) the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, extensor indicis, and their associated blood vessels and nerves

The names of the extrinsic tongue muscles commonly end in ________.

-glossus

The muscles of a professional marathon runner are most likely to have ________.

20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers

The muscles of a professional sprinter are most likely to have ________.

80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers

geniohyoid

muscle that depresses the mandible, and raises and pulls the hyoid bone anteriorly

stylohyoid

muscle that elevates the hyoid bone posteriorly

extensor carpi radialis brevis

muscle that extends and abducts the hand at the wrist

extensor radialis longus

muscle that extends and abducts the hand at the wrist

Smooth muscle fibers are spindle-shaped (wide in the middle and tapered at both ends, somewhat like a football) and have a single nucleus; they range from about 30 to 200 μm (thousands of times shorter than skeletal muscle fibers), and they produce their own connective tissue, endomysium.

Although they do not have striations and sarcomeres, smooth muscle fibers do have actin and myosin contractile proteins, and thick and thin filaments.

What would be the drawback of cardiac contractions being the same duration as skeletal muscle contractions?

An action potential could reach a cardiac muscle cell before it has entered the relaxation phase, resulting in the sustained contractions of tetanus. If this happened, the heart would not beat regularly.

extensor carpi ulnaris

muscle that extends and adducts the hand

Hypertrophy is an increase in muscle mass due to the addition of structural proteins. The opposite of hypertrophy is atrophy, the loss of muscle mass due to the breakdown of structural proteins. Endurance exercise causes an increase in cellular mitochondria, myoglobin, and capillary networks in SO fibers. Endurance athletes have a high level of SO fibers relative to the other fiber types. Resistance exercise causes hypertrophy. Power-producing muscles have a higher number of FG fibers than of slow fibers. Strenuous exercise causes muscle cell damage that requires time to heal. Some athletes use performance-enhancing substances to enhance muscle performance. Muscle atrophy due to age is called sarcopenia and occurs as muscle fibers die and are replaced by connective and adipose tissue.

ATP provides the energy for muscle contraction. The three mechanisms for ATP regeneration are creatine phosphate, anaerobic glycolysis, and aerobic metabolism. Creatine phosphate provides about the first 15 seconds of ATP at the beginning of muscle contraction. Anaerobic glycolysis produces small amounts of ATP in the absence of oxygen for a short period. Aerobic metabolism utilizes oxygen to produce much more ATP, allowing a muscle to work for longer periods. Muscle fatigue, which has many contributing factors, occurs when muscle can no longer contract. An oxygen debt is created as a result of muscle use. The three types of muscle fiber are slow oxidative (SO), fast oxidative (FO) and fast glycolytic (FG). SO fibers use aerobic metabolism to produce low power contractions over long periods and are slow to fatigue. FO fibers use aerobic metabolism to produce ATP but produce higher tension contractions than SO fibers. FG fibers use anaerobic metabolism to produce powerful, high-tension contractions but fatigue quickly. `

Is aerobic respiration more or less efficient than glycolysis? Explain your answer.

Aerobic respiration is much more efficient than anaerobic glycolysis, yielding 36 ATP per molecule of glucose, as opposed to two ATP produced by glycolysis.

teres major

muscle that extends the arm and assists in adduction and medial rotation of it

Explain how a synergist assists an agonist by being a fixator.

Agonists are the prime movers while antagonists oppose or resist the movements of the agonists. Synergists assist the agonists, and fixators stabilize a muscle's origin.

Aging and Muscle Tissue

Although atrophy due to disuse can often be reversed with exercise, muscle atrophy with age, referred to as sarcopenia, is irreversible. This is a primary reason why even highly trained athletes succumb to declining performance with age. This decline is noticeable in athletes whose sports require strength and powerful movements, such as sprinting, whereas the effects of age are less noticeable in endurance athletes such as marathon runners or long-distance cyclists. As muscles age, muscle fibers die, and they are replaced by connective tissue and adipose tissue (Figure). Because those tissues cannot contract and generate force as muscle can, muscles lose the ability to produce powerful contractions. The decline in muscle mass causes a loss of strength, including the strength required for posture and mobility. This may be caused by a reduction in FG fibers that hydrolyze ATP quickly to produce short, powerful contractions. Muscles in older people sometimes possess greater numbers of SO fibers, which are responsible for longer contractions and do not produce powerful movements. There may also be a reduction in the size of motor units, resulting in fewer fibers being stimulated and less muscle tension being produced.

Agonist- Biceps brachii: in the anterior compartment of the arm

Antagonist Triceps brachii: in the posterior compartment of the arm

Describe the fascicle arrangement in the muscles of the abdominal wall. How do they relate to each other?

Arranged into layers, the muscles of the abdominal wall are the internal and external obliques, which run on diagonals, the rectus abdominis, which runs straight down the midline of the body, and the transversus abdominis, which wraps across the trunk of the body.

Physical Therapist

As muscle cells die, they are not regenerated but instead are replaced by connective tissue and adipose tissue, which do not possess the contractile abilities of muscle tissue. Muscles atrophy when they are not used, and over time if atrophy is prolonged, muscle cells die. It is therefore important that those who are susceptible to muscle atrophy exercise to maintain muscle function and prevent the complete loss of muscle tissue. In extreme cases, when movement is not possible, electrical stimulation can be introduced to a muscle from an external source. This acts as a substitute for endogenous neural stimulation, stimulating the muscle to contract and preventing the loss of proteins that occurs with a lack of use. Physiotherapists work with patients to maintain muscles. They are trained to target muscles susceptible to atrophy, and to prescribe and monitor exercises designed to stimulate those muscles. There are various causes of atrophy, including mechanical injury, disease, and age. After breaking a limb or undergoing surgery, muscle use is impaired and can lead to disuse atrophy. If the muscles are not exercised, this atrophy can lead to long-term muscle weakness. A stroke can also cause muscle impairment by interrupting neural stimulation to certain muscles. Without neural inputs, these muscles do not contract and thus begin to lose structural proteins. Exercising these muscles can help to restore muscle function and minimize functional impairments. Age-related muscle loss is also a target of physical therapy, as exercise can reduce the effects of age-related atrophy and improve muscle function. The goal of a physiotherapist is to improve physical functioning and reduce functional impairments; this is achieved by understanding the cause of muscle impairment and assessing the capabilities of a patient, after which a program to enhance these capabilities is designed. Some factors that are assessed include strength, balance, and endurance, which are continually monitored as exercises are introduced to track improvements in muscle function. Physiotherapists can also instruct patients on the proper use of equipment, such as crutches, and assess whether someone has sufficient strength to use the equipment and when they can function without it.

Explain the difference between axial and appendicular muscles.

Axial muscles originate on the axial skeleton (the bones in the head, neck, and core of the body), whereas appendicular muscles originate on the bones that make up the body's limbs.

Anesthesia and the tongue muscles

Before surgery, a patient must be made ready for general anesthesia. The normal homeostatic controls of the body are put "on hold" so that the patient can be prepped for surgery. Control of respiration must be switched from the patient's homeostatic control to the control of the anesthesiologist. The drugs used for anesthesia relax a majority of the body's muscles. Among the muscles affected during general anesthesia are those that are necessary for breathing and moving the tongue. Under anesthesia, the tongue can relax and partially or fully block the airway, and the muscles of respiration may not move the diaphragm or chest wall. To avoid possible complications, the safest procedure to use on a patient is called endotracheal intubation. Placing a tube into the trachea allows the doctors to maintain a patient's (open) airway to the lungs and seal the airway off from the oropharynx. Post-surgery, the anesthesiologist gradually changes the mixture of the gases that keep the patient unconscious, and when the muscles of respiration begin to function, the tube is removed. It still takes about 30 minutes for a patient to wake up, and for breathing muscles to regain control of respiration. After surgery, most people have a sore or scratchy throat for a few days.

What are some similarities and differences between the diaphragm and the pelvic diaphragm?

Both diaphragms are thin sheets of skeletal muscle that horizontally span areas of the trunk. The diaphragm separating the thoracic and abdominal cavities is the primary muscle of breathing. The pelvic diaphragm, consisting of two paired muscles, the coccygeus and the levator ani, forms the pelvic floor at the inferior end of the trunk.

Why do muscle cells use creatine phosphate instead of glycolysis to supply ATP for the first few seconds of muscle contraction?

Creatine phosphate is used because creatine phosphate and ADP are converted very quickly into ATP by creatine kinase. Glycolysis cannot generate ATP as quickly as creatine phosphate.

extensor digitorum

muscle that extends the hand at the wrist and the phalanges

There are also skeletal muscles that do not pull against the skeleton for movements. For example, there are the muscles that produce facial expressions. The insertions and origins of facial muscles are in the skin, so that certain individual muscles contract to form a smile or frown, form sounds or words, and raise the eyebrows. There also are skeletal muscles in the tongue, and the external urinary and anal sphincters that allow for voluntary regulation of urination and defecation, respectively. In addition, the diaphragm contracts and relaxes to change the volume of the pleural cavities but it does not move the skeleton to do this.

Defecating, urination, and even childbirth involve cooperation between the diaphragm and abdominal muscles (this cooperation is referred to as the "Valsalva maneuver"). You hold your breath by a steady contraction of the diaphragm; this stabilizes the volume and pressure of the peritoneal cavity. When the abdominal muscles contract, the pressure cannot push the diaphragm up, so it increases pressure on the intestinal tract (defecation), urinary tract (urination), or reproductive tract (childbirth).

The sarcomere is the functional unit of the muscle fiber. The sarcomere itself is bundled within the myofibril that runs the entire length of the muscle fiber and attaches to the sarcolemma at its end. As myofibrils contract, the entire muscle cell contracts. Because myofibrils are only approximately 1.2 μm in diameter, hundreds to thousands (each with thousands of sarcomeres) can be found inside one muscle fiber.

Each sarcomere is approximately 2 μm in length with a three-dimensional cylinder-like arrangement and is bordered by structures called Z-discs (also called Z-lines, because pictures are two-dimensional), to which the actin myofilaments are anchored (Figure).

FG fibers primarily use anaerobic glycolysis as their ATP source. They have a large diameter and possess high amounts of glycogen, which is used in glycolysis to generate ATP quickly to produce high levels of tension. Because they do not primarily use aerobic metabolism, they do not possess substantial numbers of mitochondria or significant amounts of myoglobin and therefore have a white color.

FG fibers are used to produce rapid, forceful contractions to make quick, powerful movements. These fibers fatigue quickly, permitting them to only be used for short periods. Most muscles possess a mixture of each fiber type. The predominant fiber type in a muscle is determined by the primary function of the muscle.

The proportion of SO muscle fibers in muscle determines the suitability of that muscle for endurance, and may benefit those participating in endurance activities. Postural muscles have a large number of SO fibers and relatively few FO and FG fibers, to keep the back straight (Figure).

Endurance athletes, like marathon-runners also would benefit from a larger proportion of SO fibers, but it is unclear if the most-successful marathoners are those with naturally high numbers of SO fibers, or whether the most successful marathon runners develop high numbers of SO fibers with repetitive training. Endurance training can result in overuse injuries such as stress fractures and joint and tendon inflammation.

What changes occur at the cellular level in response to endurance training?

Endurance training modifies slow fibers to make them more efficient by producing more mitochondria to enable more aerobic metabolism and more ATP production. Endurance exercise can also increase the amount of myoglobin in a cell and formation of more extensive capillary networks around the fiber.

extensor digiti minimi

muscle that extends the little finger

The ideal length of a sarcomere to produce maximal tension occurs at 80 percent to 120 percent of its resting length, with 100 percent being the state where the medial edges of the thin filaments are just at the most-medial myosin heads of the thick filaments (Figure). This length maximizes the overlap of actin-binding sites and myosin heads. If a sarcomere is stretched past this ideal length (beyond 120 percent), thick and thin filaments do not overlap sufficiently, which results in less tension produced. If a sarcomere is shortened beyond 80 percent, the zone of overlap is reduced with the thin filaments jutting beyond the last of the myosin heads and shrinks the H zone, which is normally composed of myosin tails.

Eventually, there is nowhere else for the thin filaments to go and the amount of tension is diminished. If the muscle is stretched to the point where thick and thin filaments do not overlap at all, no cross-bridges can be formed, and no tension is produced in that sarcomere. This amount of stretching does not usually occur, as accessory proteins and connective tissue oppose extreme stretching.

Antagonist

Extensor digitorum: in the posterior compartment of the forearm

Why does a motor unit of the eye have few muscle fibers compared to a motor unit of the leg?

Eyes require fine movements and a high degree of control, which is permitted by having fewer muscle fibers associated with a neuron.

FO fibers are sometimes called intermediate fibers because they possess characteristics that are intermediate between fast fibers and slow fibers. They produce ATP relatively quickly, more quickly than SO fibers, and thus can produce relatively high amounts of tension. They are oxidative because they produce ATP aerobically, possess high amounts of mitochondria, and do not fatigue quickly. However, FO fibers do not possess significant myoglobin, giving them a lighter color than the red SO fibers.

FO fibers are used primarily for movements, such as walking, that require more energy than postural control but less energy than an explosive movement, such as sprinting. FO fibers are useful for this type of movement because they produce more tension than SO fibers but they are more fatigue-resistant than FG fibers.

What effect does fascicle arrangement have on a muscle's action?

Fascicle arrangements determine what type of movement a muscle can make. For instance, circular muscles act as sphincters, closing orifices.

Which of the following statements is true?

Fast fibers have large glycogen reserves.

Agonist

Flexor digitorum superficialis and flexor digitorum profundus: in the anterior compartment of the forearm

extensor digitorum brevis

muscle that extends the toes

Agonist

Hamstrings: group of three muscles in the posterior compartment of the thigh

Cardiac muscle tissue is only found in the heart. Highly coordinated contractions of cardiac muscle pump blood into the vessels of the circulatory system. Similar to skeletal muscle, cardiac muscle is striated and organized into sarcomeres, possessing the same banding organization as skeletal muscle (Figure).

However, cardiac muscle fibers are shorter than skeletal muscle fibers and usually contain only one nucleus, which is located in the central region of the cell. Cardiac muscle fibers also possess many mitochondria and myoglobin, as ATP is produced primarily through aerobic metabolism. Cardiac muscle fibers cells also are extensively branched and are connected to one another at their ends by intercalated discs

Except for the hypertrophy that follows an increase in the number of sarcomeres and myofibrils in a skeletal muscle, the cellular changes observed during endurance training do not usually occur with resistance training. There is usually no significant increase in mitochondria or capillary density.

However, resistance training does increase the development of connective tissue, which adds to the overall mass of the muscle and helps to contain muscles as they produce increasingly powerful contractions. Tendons also become stronger to prevent tendon damage, as the force produced by muscles is transferred to tendons that attach the muscle to bone.

For effective strength training, the intensity of the exercise must continually be increased. For instance, continued weight lifting without increasing the weight of the load does not increase muscle size. To produce ever-greater results, the weights lifted must become increasingly heavier, making it more difficult for muscles to move the load. The muscle then adapts to this heavier load, and an even heavier load must be used if even greater muscle mass is desired.

If done improperly, resistance training can lead to overuse injuries of the muscle, tendon, or bone. These injuries can occur if the load is too heavy or if the muscles are not given sufficient time between workouts to recover or if joints are not aligned properly during the exercises. Cellular damage to muscle fibers that occurs after intense exercise includes damage to the sarcolemma and myofibrils. This muscle damage contributes to the feeling of soreness after strenuous exercise, but muscles gain mass as this damage is repaired, and additional structural proteins are added to replace the damaged ones. Overworking skeletal muscles can also lead to tendon damage and even skeletal damage if the load is too great for the muscles to bear.

Why is muscle that has sustained significant damage unable to produce the same amount of power as it could before being damaged?

If the damage exceeds what can be repaired by satellite cells, the damaged tissue is replaced by scar tissue, which cannot contract.

Skeletal muscles are even used during sleep. The diaphragm is a sheet of skeletal muscle that has to contract and relax for you to breathe day and night. If you recall from your study of the skeletal system and joints, body movement occurs around the joints in the body. The focus of this chapter is on skeletal muscle organization. The system to name skeletal muscles will be explained; in some cases, the muscle is named by its shape, and in other cases it is named by its location or attachments to the skeleton.

If you understand the meaning of the name of the muscle, often it will help you remember its location and/or what it does. This chapter also will describe how skeletal muscles are arranged to accomplish movement, and how other muscles may assist, or be arranged on the skeleton to resist or carry out the opposite movement. The actions of the skeletal muscles will be covered in a regional manner, working from the head down to the toes.

Describe the different criteria that contribute to how skeletal muscles are named.

In anatomy and physiology, many word roots are Latin or Greek. Portions, or roots, of the word give us clues about the function, shape, action, or location of a muscle.

Why is elasticity an important quality of muscle tissue?

It allows muscle to return to its original length during relaxation after contraction.

flexor carpi radialis

muscle that flexes and abducts the hand at the wrist

Why are the muscles of the face different from typical skeletal muscle?

Most skeletal muscles create movement by actions on the skeleton. Facial muscles are different in that they create facial movements and expressions by pulling on the skin—no bone movements are involved.

A sarcomere is the smallest contractile portion of a muscle. Myofibrils are composed of thick and thin filaments. Thick filaments are composed of the protein myosin; thin filaments are composed of the protein actin. Troponin and tropomyosin are regulatory proteins. .

Muscle contraction is described by the sliding filament model of contraction. ACh is the neurotransmitter that binds at the neuromuscular junction (NMJ) to trigger depolarization, and an action potential travels along the sarcolemma to trigger calcium release from SR. The actin sites are exposed after Ca++ enters the sarcoplasm from its SR storage to activate the troponin-tropomyosin complex so that the tropomyosin shifts away from the sites. The cross-bridging of myposin heads docking into actin-binding sites is followed by the "power stroke"—the sliding of the thin filaments by thick filaments. The power strokes are powered by ATP. Ultimately, the sarcomeres, myofibrils, and muscle fibers shorten to produce movement

When most people think of muscles, they think of the muscles that are visible just under the skin, particularly of the limbs. These are skeletal muscles, so-named because most of them move the skeleton. But there are two other types of muscle in the body, with distinctly different jobs. Cardiac muscle, found in the heart, is concerned with pumping blood through the circulatory system. Smooth muscle is concerned with various involuntary movements, such as having one's hair stand on end when cold or frightened, or moving food through the digestive system. This chapter will examine the structure and function of these three types of muscles.

Muscle is one of the four primary tissue types of the body, and the body contains three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle

Movements of the body occur at joints. Describe how muscles are arranged around the joints of the body.

Muscles work in pairs to facilitate movement of the bones around the joints. Agonists are the prime movers while antagonists oppose or resist the movements of the agonists. Synergists assist the agonists, and fixators stabilize a muscle's origin.

What would happen to skeletal muscle if the epimysium were destroyed?

Muscles would lose their integrity during powerful movements, resulting in muscle damage.

A muscle that has a pattern of fascicles running along the long axis of the muscle has which of the following fascicle arrangements?

PARALLEL

What are the five primary functions of skeletal muscle?

Produce movement of the skeleton, maintain posture and body position, support soft tissues, encircle openings of the digestive, urinary, and other tracts, and maintain body temperature.

visceral muscle.

Smooth muscle is organized in two ways: as single-unit smooth muscle, which is much more common; and as multiunit smooth muscle. The two types have different locations in the body and have different characteristics. Single-unit muscle has its muscle fibers joined by gap junctions so that the muscle contracts as a single unit. This type of smooth muscle is found in the walls of all visceral organs except the heart (which has cardiac muscle in its walls), and so it is commonly called

Antagonist

Quadriceps femoris: group of four muscles in the anterior compartment of the thigh

Relaxation of a Skeletal Muscle

Relaxing skeletal muscle fibers, and ultimately, the skeletal muscle, begins with the motor neuron, which stops releasing its chemical signal, ACh, into the synapse at the NMJ. The muscle fiber will repolarize, which closes the gates in the SR where Ca++ was being released. ATP-driven pumps will move Ca++ out of the sarcoplasm back into the SR. This results in the "reshielding" of the actin-binding sites on the thin filaments. Without the ability to form cross-bridges between the thin and thick filaments, the muscle fiber loses its tension and relaxes.

What changes occur at the cellular level in response to resistance training?

Resistance exercises affect muscles by causing the formation of more actin and myosin, increasing the structure of muscle fibers.

Describe the differences between single-unit smooth muscle and multiunit smooth muscle.

Single-unit smooth muscle is found in the walls of hollow organs; multiunit smooth muscle is found in airways to the lungs and large arteries. Single-unit smooth muscle cells contract synchronously, they are coupled by gap junctions, and they exhibit spontaneous action potential. Multiunit smooth cells lack gap junctions, and their contractions are not synchronous.

Skeletal muscles contain connective tissue, blood vessels, and nerves. There are three layers of connective tissue: epimysium, perimysium, and endomysium. Skeletal muscle fibers are organized into groups called fascicles. Blood vessels and nerves enter the connective tissue and branch in the cell. Muscles attach to bones directly or through tendons or aponeuroses. Skeletal muscles maintain posture, stabilize bones and joints, control internal movement, and generate heat.

Skeletal muscle fibers are long, multinucleated cells. The membrane of the cell is the sarcolemma; the cytoplasm of the cell is the sarcoplasm. The sarcoplasmic reticulum (SR) is a form of endoplasmic reticulum. Muscle fibers are composed of myofibrils. The striations are created by the organization of actin and myosin resulting in the banding pattern of myofibrils.

lever system of muscle and bone interactions

Skeletal muscles do not work by themselves. Muscles are arranged in pairs based on their functions. For muscles attached to the bones of the skeleton, the connection determines the force, speed, and range of movement. These characteristics depend on each other and can explain the general organization of the muscular and skeletal systems. The skeleton and muscles act together to move the body. Have you ever used the back of a hammer to remove a nail from wood? The handle acts as a lever and the head of the hammer acts as a fulcrum, the fixed point that the force is applied to when you pull back or push down on the handle. The effort applied to this system is the pulling or pushing on the handle to remove the nail, which is the load, or "resistance" to the movement of the handle in the system. Our musculoskeletal system works in a similar manner, with bones being stiff levers and the articular endings of the bones—encased in synovial joints—acting as fulcrums. The load would be an object being lifted or any resistance to a movement (your head is a load when you are lifting it), and the effort, or applied force, comes from contracting skeletal muscle.

endurance exercise

Slow fibers are predominantly used in endurance exercises that require little force but involve numerous repetitions. The aerobic metabolism used by slow-twitch fibers allows them to maintain contractions over long periods. Endurance training modifies these slow fibers to make them even more efficient by producing more mitochondria to enable more aerobic metabolism and more ATP production. Endurance exercise can also increase the amount of myoglobin in a cell, as increased aerobic respiration increases the need for oxygen. Myoglobin is found in the sarcoplasm and acts as an oxygen storage supply for the mitochondria.

Which of the following statements is false?

Slow fibers have a small network of capillaries.

Muscle is the tissue in animals that allows for active movement of the body or materials within the body. There are three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. Most of the body's skeletal muscle produces movement by acting on the skeleton. Cardiac muscle is found in the wall of the heart and pumps blood through the circulatory system.

Smooth muscle is found in the skin, where it is associated with hair follicles; it also is found in the walls of internal organs, blood vessels, and internal passageways, where it assists in moving materials.

Performance-Enhancing Substances

Some athletes attempt to boost their performance by using various agents that may enhance muscle performance. Anabolic steroids are one of the more widely known agents used to boost muscle mass and increase power output. Anabolic steroids are a form of testosterone, a male sex hormone that stimulates muscle formation, leading to increased muscle mass. Endurance athletes may also try to boost the availability of oxygen to muscles to increase aerobic respiration by using substances such as erythropoietin (EPO), a hormone normally produced in the kidneys, which triggers the production of red blood cells. The extra oxygen carried by these blood cells can then be used by muscles for aerobic respiration. Human growth hormone (hGH) is another supplement, and although it can facilitate building muscle mass, its main role is to promote the healing of muscle and other tissues after strenuous exercise. Increased hGH may allow for faster recovery after muscle damage, reducing the rest required after exercise, and allowing for more sustained high-level performance. Although performance-enhancing substances often do improve performance, most are banned by governing bodies in sports and are illegal for nonmedical purposes. Their use to enhance performance raises ethical issues of cheating because they give users an unfair advantage over nonusers. A greater concern, however, is that their use carries serious health risks. The side effects of these substances are often significant, nonreversible, and in some cases fatal. The physiological strain caused by these substances is often greater than what the body can handle, leading to effects that are unpredictable and dangerous. Anabolic steroid use has been linked to infertility, aggressive behavior, cardiovascular disease, and brain cancer. Similarly, some athletes have used creatine to increase power output. Creatine phosphate provides quick bursts of ATP to muscles in the initial stages of contraction. Increasing the amount of creatine available to cells is thought to produce more ATP and therefore increase explosive power output, although its effectiveness as a supplement has been questioned.

elasticity

ability to stretch and rebound- muscle can return to its original length when relaxed due to quality of muscle tissue - can recoil back to its original length due to elastic fibers

projection of the sarcolemma into the interior of the cell--- For the action potential to reach the membrane of the SR, there are periodic invaginations in the sarcolemma, You will recall that the diameter of a muscle fiber can be up to 100 μm, so these T-tubules ensure that the membrane can get close to the SR in the sarcoplasm.

T-tubule (T is transverse

Which muscles form the quadriceps? How do they function together?

The rectus femoris, vastus medialis, vastus lateralis, and vastus intermedius form the quadriceps. The quadriceps muscles extend the leg at the knee joint.

excitability

ability to undergo neural stimulation

hypotonia

abnormally low muscle tone caused by the absence of low-level contractions to muslce tone-- can result from damage - can result from damage to parts of the central nervous system, such as the cerebellum, or from loss of innervations to a skeletal muscle as in poliomyelitis

The tendons of which muscles form the rotator cuff? Why is the rotator cuff important?

Tendons of the infraspinatus, supraspinatus, teres minor, and the subscapularis form the rotator cuff, which forms a foundation on which the arms and shoulders can be stabilized and move.

Skeletal muscles each have an origin and an insertion. The end of the muscle that attaches to the bone being pulled is called the muscle's insertion and the end of the muscle attached to a fixed, or stabilized, bone is called the origin. The muscle primarily responsible for a movement is called the prime mover, and muscles that assist in this action are called synergists. A synergist that makes the insertion site more stable is called a fixator. Meanwhile, a muscle with the opposite action of the prime mover is called an antagonist. Several factors contribute to the force generated by a skeletal muscle. One is the arrangement of the fascicles in the skeletal muscle. Fascicles can be parallel, circular, convergent, pennate, fusiform, or triangular. Each arrangement has its own range of motion and ability to do work.

The Greeks and Romans conducted the first studies done on the human body in Western culture. The educated class of subsequent societies studied Latin and Greek, and therefore the early pioneers of anatomy continued to apply Latin and Greek terminology or roots when they named the skeletal muscles. The large number of muscles in the body and unfamiliar words can make learning the names of the muscles in the body seem daunting, but understanding the etymology can help. Etymology is the study of how the root of a particular word entered a language and how the use of the word evolved over time. Taking the time to learn the root of the words is crucial to understanding the vocabulary of anatomy and physiology. When you understand the names of muscles it will help you remember where the muscles are located and what they do (Figure, Figure, and Table). Pronunciation of words and terms will take a bit of time to master, but after you have some basic information; the correct names and pronunciations will become easier.

Which of the following statements is correct about what happens during flexion?

The angle between bones is decreased.

Movement

The biceps brachii flexes the forearm, whereas the triceps brachii extends it.

Which muscles form the hamstrings? How do they function together?

The biceps femoris, semimembranosus, and semitendinosus form the hamstrings. The hamstrings flex the leg at the knee joint.

hypertonia

abnormally high muscle tone-- excessive muslce tone-- accompanied by hyperreflexia (excessive reflex responses), often the result of damage to upper motor neurons in the CNS. Hypertonia can present with muscle rigidity (as seen in Parkinson's disease) or spasticity, a phasic change in muscle tone, where a limb will "snap" back from passive stretching (as seen in some strokes).

Smooth muscle is found throughout the body around various organs and tracts. Smooth muscle cells have a single nucleus, and are spindle-shaped. Smooth muscle cells can undergo hyperplasia, mitotically dividing to produce new cells. The smooth cells are nonstriated, but their sarcoplasm is filled with actin and myosin, along with dense bodies in the sarcolemma to anchor the thin filaments and a network of intermediate filaments involved in pulling the sarcolemma toward the fiber's middle, shortening it in the process. Ca++ ions trigger contraction when they are released from SR and enter through opened voltage-gated calcium channels. Smooth muscle contraction is initiated when the Ca++ binds to intracellular calmodulin, which then activates an enzyme called myosin kinase that phosphorylates myosin heads so they can form the cross-bridges with actin and then pull on the thin filaments. Smooth muscle can be stimulated by pacesetter cells, by the autonomic nervous system, by hormones, spontaneously, or by stretching.

The fibers in some smooth muscle have latch-bridges, cross-bridges that cycle slowly without the need for ATP; these muscles can maintain low-level contractions for long periods. Single-unit smooth muscle tissue contains gap junctions to synchronize membrane depolarization and contractions so that the muscle contracts as a single unit. Single-unit smooth muscle in the walls of the viscera, called visceral muscle, has a stress-relaxation response that permits muscle to stretch, contract, and relax as the organ expands. Multiunit smooth muscle cells do not possess gap junctions, and contraction does not spread from one cell to the next.

Movement

The flexor digitorum superficialis and flexor digitorum profundus flex the fingers and the hand at the wrist, whereas the extensor digitorum extends the fingers and the hand at the wrist.

Movement

The hamstrings flex the leg, whereas the quadriceps femoris extend it.

What factors contribute to the amount of tension produced in an individual muscle fiber?

The length, size and types of muscle fiber and the frequency of neural stimulation contribute to the amount of tension produced in an individual muscle fiber.

Some muscle names indicate the number of muscles in a group. One example of this is the quadriceps, a group of four muscles located on the anterior (front) thigh. Other muscle names can provide information as to how many origins a particular muscle has, such as the biceps brachii. The prefix bi indicates that the muscle has two origins and tri indicates three origins.

The location of a muscle's attachment can also appear in its name. When the name of a muscle is based on the attachments, the origin is always named first. For instance, the sternocleidomastoid muscle of the neck has a dual origin on the sternum (sterno) and clavicle (cleido), and it inserts on the mastoid process of the temporal bone. The last feature by which to name a muscle is its action. When muscles are named for the movement they produce, one can find action words in their name. Some examples are flexor (decreases the angle at the joint), extensor (increases the angle at the joint), abductor (moves the bone away from the midline), or adductor (moves the bone toward the midline).

which arrangement best describes a bipennate muscle

The muscle fibers feed in on an angle to a long tendon from both sides.

Describe the muscles of the anterior neck.

The muscles of the anterior neck are arranged to facilitate swallowing and speech. They work on the hyoid bone, with the suprahyoid muscles pulling up and the infrahyoid muscles pulling down.

List the general muscle groups of the shoulders and upper limbs as well as their subgroups.

The muscles that make up the shoulders and upper limbs include the muscles that position the pelvic girdle, the muscles that move the humerus, the muscles that move the forearm, and the muscles that move the wrists, hands, and fingers.

SO fibers are extensively supplied with blood capillarires to supply oxygen from red blood cells in the bloodstream

The myoglobin stores some of the needed O2 within the fibers themselves (and gives SO fibers their red color). All of these features allow SO fibers to produce large quantities of ATP, which can sustain muscle activity without fatiguing for long periods of time.

What are the opposite roles of voltage-gated sodium channels and voltage-gated potassium channels?

The opening of voltage-gated sodium channels, followed by the influx of Na+, transmits an Action Potential after the membrane has sufficiently depolarized. The delayed opening of potassium channels allows K+ to exit the cell, to repolarize the membrane.

The head, attached to the top of the vertebral column, is balanced, moved, and rotated by the neck muscles (Table). When these muscles act unilaterally, the head rotates. When they contract bilaterally, the head flexes or extends. The major muscle that laterally flexes and rotates the head is the sternocleidomastoid. In addition, both muscles working together are the flexors of the head. Place your fingers on both sides of the neck and turn your head to the left and to the right. You will feel the movement originate there. This muscle divides the neck into anterior and posterior triangles when viewed from the side (Figure).

The posterior muscles of the neck are primarily concerned with head movements, like extension. The back muscles stabilize and move the vertebral column, and are grouped according to the lengths and direction of the fascicles. The splenius muscles originate at the midline and run laterally and superiorly to their insertions. From the sides and the back of the neck, the splenius capitis inserts onto the head region, and the splenius cervicis extends onto the cervical region. These muscles can extend the head, laterally flex it, and rotate it (Figure).

Mnemonic Device for Latin Roots Example Latin or Greek Translation Mnemonic Device ad to; toward ADvance toward your goal ab away from n/a sub under SUBmarines move under water. ductor something that moves A conDUCTOR makes a train move. anti against If you are antisocial, you are against engaging in social activities. epi on top of n/a apo to the side of n/a longissimus longest "Longissimus" is longer than the word "long." longus long long brevis short brief maximus large max medius medium "Medius" and "medium" both begin with "med." minimus tiny; little mini rectus straight To RECTify a situation is to straighten it out. multi many If something is MULTIcolored, it has many colors. uni one A UNIcorn has one horn. bi/di two If a ring is DIcast, it is made of two metals. tri three TRIple the amount of money is three times as much. quad four QUADruplets are four children born at one birth. externus outside EXternal internus inside INternal

The skeletal muscle's anatomical location or its relationship to a particular bone often determines its name. For example, the frontalis muscle is located on top of the frontal bone of the skull. Similarly, the shapes of some muscles are very distinctive and the names, such as orbicularis, reflect the shape. For the buttocks, the size of the muscles influences the names: gluteus maximus (largest), gluteus medius (medium), and the gluteus minimus (smallest). Names were given to indicate length—brevis (short), longus (long)—and to identify position relative to the midline: lateralis (to the outside away from the midline), and medialis (toward the midline). The direction of the muscle fibers and fascicles are used to describe muscles relative to the midline, such as the rectus (straight) abdominis, or the oblique (at an angle) muscles of the abdomen.

The suprahyoid muscles raise the hyoid bone, the floor of the mouth, and the larynx during deglutition. These include the digastric muscle, which has anterior and posterior bellies that work to elevate the hyoid bone and larynx when one swallows; it also depresses the mandible. The stylohyoid muscle moves the hyoid bone posteriorly, elevating the larynx, and the mylohyoid muscle lifts it and helps press the tongue to the top of the mouth. The geniohyoid depresses the mandible in addition to raising and pulling the hyoid bone anteriorly.

The strap-like infrahyoid muscles generally depress the hyoid bone and control the position of the larynx. The omohyoid muscle, which has superior and inferior bellies, depresses the hyoid bone in conjunction with the sternohyoid and thyrohyoid muscles. The thyrohyoid muscle also elevates the larynx's thyroid cartilage, whereas the sternothyroid depresses it to create different tones of voice.

Contractions of the heart (heartbeats) are controlled by specialized cardiac muscle cells called pacemaker cells that directly control heart rate. Although cardiac muscle cannot be consciously controlled, the pacemaker cells respond to signals from the autonomic nervous system (ANS) to speed up or slow down the heart rate. The pacemaker cells can also respond to various hormones that modulate heart rate to control blood pressure.

The wave of contraction that allows the heart to work as a unit, called a functional syncytium, begins with the pacemaker cells. This group of cells is self-excitable and able to depolarize to threshold and fire action potentials on their own, a feature called autorhythmicity; they do this at set intervals which determine heart rate. Because they are connected with gap junctions to surrounding muscle fibers and the specialized fibers of the heart's conduction system, the pacemaker cells are able to transfer the depolarization to the other cardiac muscle fibers in a manner that allows the heart to contract in a coordinated manner.

Which of the following statements describes smooth muscle cells?

They are resistant to fatigue.

Which of the following is unique to the muscles of facial expression?

They insert into the skin.

The number of cross-bridges formed between actin and myosin determines the amount of tension produced by a muscle. The length of a sarcomere is optimal when the zone of overlap between thin and thick filaments is greatest. Muscles that are stretched or compressed too greatly do not produce maximal amounts of power. A motor unit is formed by a motor neuron and all of the muscle fibers that are innervated by that same motor neuron. A single contraction is called a twitch. A muscle twitch has a latent period, a contraction phase, and a relaxation phase. A graded muscle response allows variation in muscle tension. Summation occurs as successive stimuli are added together to produce a stronger muscle contraction. Tetanus is the fusion of contractions to produce a continuous contraction. Increasing the number of motor neurons involved increases the amount of motor units activated in a muscle, which is called recruitment. Muscle tone is the constant low-level contractions that allow for posture and stability.

Think about the things that you do each day—talking, walking, sitting, standing, and running—all of these activities require movement of particular skeletal muscles. Skeletal muscles are even used during sleep. The diaphragm is a sheet of skeletal muscle that has to contract and relax for you to breathe day and night. If you recall from your study of the skeletal system and joints, body movement occurs around the joints in the body. The focus of this chapter is on skeletal muscle organization. The system to name skeletal muscles will be explained; in some cases, the muscle is named by its shape, and in other cases it is named by its location or attachments to the skeleton. If you understand the meaning of the name of the muscle, often it will help you remember its location and/or what it does. This chapter also will describe how skeletal muscles are arranged to accomplish movement, and how other muscles may assist, or be arranged on the skeleton to resist or carry out the opposite movement. The actions of the skeletal muscles will be covered in a regional manner, working from the head down to the toes.

physical therapists

Those who have a muscle or joint injury will most likely be sent to a physical therapist (PT) after seeing their regular doctor. PTs have a master's degree or doctorate, and are highly trained experts in the mechanics of body movements. Many PTs also specialize in sports injuries. If you injured your shoulder while you were kayaking, the first thing a physical therapist would do during your first visit is to assess the functionality of the joint. The range of motion of a particular joint refers to the normal movements the joint performs. The PT will ask you to abduct and adduct, circumduct, and flex and extend the arm. The PT will note the shoulder's degree of function, and based on the assessment of the injury, will create an appropriate physical therapy plan. The first step in physical therapy will probably be applying a heat pack to the injured site, which acts much like a warm-up to draw blood to the area, to enhance healing. You will be instructed to do a series of exercises to continue the therapy at home, followed by icing, to decrease inflammation and swelling, which will continue for several weeks. When physical therapy is complete, the PT will do an exit exam and send a detailed report on the improved range of motion and return of normal limb function to your doctor. Gradually, as the injury heals, the shoulder will begin to function correctly. A PT works closely with patients to help them get back to their normal level of physical activity.

Describe how tendons facilitate body movement.

When a muscle contracts, the force of movement is transmitted through the tendon, which pulls on the bone to produce skeletal movement.

Exercise and Stretching

When exercising, it is important to first warm up the muscles. Stretching pulls on the muscle fibers and it also results in an increased blood flow to the muscles being worked. Without a proper warm-up, it is possible that you may either damage some of the muscle fibers or pull a tendon. A pulled tendon, regardless of location, results in pain, swelling, and diminished function; if it is moderate to severe, the injury could immobilize you for an extended period. Recall the discussion about muscles crossing joints to create movement. Most of the joints you use during exercise are synovial joints, which have synovial fluid in the joint space between two bones. Exercise and stretching may also have a beneficial effect on synovial joints. Synovial fluid is a thin, but viscous film with the consistency of egg whites. When you first get up and start moving, your joints feel stiff for a number of reasons. After proper stretching and warm-up, the synovial fluid may become less viscous, allowing for better joint function.

How would muscle contractions be affected if ATP was completely depleted in a muscle fiber?

Without ATP, the myosin heads cannot detach from the actin-binding sites. All of the "stuck" cross-bridges result in muscle stiffness. In a live person, this can cause a condition like "writer's cramps." In a recently dead person, it results in rigor mortis.

How would muscle contractions be affected if skeletal muscle fibers did not have T-tubules?

Without T-tubules, action potential conduction into the interior of the cell would happen much more slowly, causing delays between neural stimulation and muscle contraction, resulting in slower, weaker contractions.

Which of the following terms would be used in the name of a muscle that moves the leg away from the body?

abductor

skeletal muscle

ability to contract and cause movement. Produce movement but also stop movment, resisting gravity to maintain posture.

extensibility

ability to lengthen (extend) muscle tissue has quality- stretches as well

Which element is important in directly triggering contraction?

`calcium (Ca++)

tetanus

a continuous fused contraction

What is the linea alba?

a long tendon that runs down the middle of the rectus abdominis

anterior scalene

a muscle anterior to the middle scalene

medial compartment of the thigh

a region that includes the adductor longus, adductor brevis, adductor magnus, pectineus, gracilis, and their associated blood vessels and nerves

Which of the following helps an agonist work?

a synergist

contractility

ability to shorten (contract) forcibly

The location of a muscle's insertion and origin can determine ________.

action

power stroke

action of myosin pulling actin inward (toward the M line) -As actin is pulled, the filaments move approximately 10 nm toward the M-line.- as movement of the thin filament occurs at this step (Figurec). In the absence of ATP, the myosin head will not detach from actin.

change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal; unique to neurons and muscle fibers--- travels along the axon of a motor neuron then along individual branches to termiante at the NMJ.

action potential

hypertrophy

addition of structural proteins to muscle fibers- process - so cell diamter increases

wave summation

addition of successive neural stimuli to produce greater contraction

oxidative fibers contain more mitochondria than glycolytic fibers

aerobic metabolic - uses oxygen in the metabolic pathway, occurs in mitochondria

sarcopenia

age-related muscle atrophy- cellular components of muscles undergo changes in response to changes in muscle use

The muscles

all begin the actual process of contracting (shortening) when a protein called actin is pulled by a protein called myosin. This occurs in striated muscle (skeletal and cardiac) after specific binding sites on the actin have been exposed in response to the interaction between calcium ions (Ca++) and proteins (troponin and tropomyosin) that "shield" the actin-binding sites. Ca++ also is required for the contraction of smooth muscle, although its role is different: here Ca++ activates enzymes, which in turn activate myosin heads. All muscles require adenosine triphosphate (ATP) to continue the process of contracting, and they all relax when the Ca++ is removed and the actin-binding sites are re-shielded.

contractility

allows muscle tissue to pull on its attachment points and shorten with force.

According to the sliding filament model, binding sites on actin open when ________.

calcium ion levels rise

Muscle relaxation occurs when ________.

calcium ions are actively transported into the sarcoplasmic reticulum

During muscle contraction, the cross-bridge detaches when ________.

calcium ions bind to troponin

Sarcopenia

can be delayed to some extent by exercise, as training adds structural proteins and causes cellular changes that can offset the effects of atrophy. Increased exercise can produce greater numbers of cellular mitochondria, increase capillary density, and increase the mass and strength of connective tissue. The effects of age-related atrophy are especially pronounced in people who are sedentary, as the loss of muscle cells is displayed as functional impairments such as trouble with locomotion, balance, and posture. This can lead to a decrease in quality of life and medical problems, such as joint problems because the muscles that stabilize bones and joints are weakened. Problems with locomotion and balance can also cause various injuries due to falls.

T-Tubules

carry the action potential into the interior of the cell, which triggers the opening of calcium channels in the membrane of the adjacent SR, causing Ca++ to diffuse out of the SR and into the sarcoplasm. It is the arrival of Ca++ in the sarcoplasm that initiates contraction of the muscle fiber by its contractile units, or sarcomeres.

desmosome

cell structure that anchors the ends of cardiac muscle fibers to allow contraction to occur-- is a cell structure that anchors the ends of cardiac muscle fibers together so the cells do not pull apart during the stress of individual fibers contracting

pacesetter cell

cell that triggers action potentials in smooth muscle- spontaneously trigger action potentials and contractions in the muscle

What is the action of the masseter?

chewing

mastication

chewing

orbicularis oculi

circular muscle that closes the eye

orbicularis oris

circular muscle that moves the lips

perimysium

connective tissue that bundles skeletal muscle fibers into fascicles within a skeletal muscle- MIDDLE Layer of connective TISSUE

Cardiac muscles differ from skeletal muscles in that they ________.

contain intercalated discs

During which phase of a twitch in a muscle fiber is tension the greatest?

contraction phase

skeletal muscles

contribute to maintain homeostasis in the body by generating heat

glycolytic fibers

create APP through anaerobic glycolysis producing less ATP per cycle - glycolytic fibers fatigue at a quicker rate

There are three mechanisms by which ATP can be regenerated:

creatine phosphate metabolism, anaerobic glycolysis, and fermentation and aerobic respiration.

inferior extensor retinaculum

cruciate ligament of the ankle

sarcoplasm

cytoplasm of a muscle cell

transversus abdominis

deep layer of the abdomen that has fascicles arranged transversely around the abdomen--- similar to the front of a belt on a pair of pants. arrangement of three bands of muscles in different orientations allows various movements and rotations of the trunk.

deep transverse perineal

deep perineal muscle in men--- role in ejaculation

compressor urethrae

deep perineal muscle in women

sphincter urethrovaginalis

deep perineal muscle in women

speed of contraction

depends on myosin's ATPase hydrolyzses ATP to produce cross-bridge action

popliteal fossa

diamond-shaped space at the back of the knee

perineum

diamond-shaped space between the pubic symphysis (anteriorly), the coccyx (posteriorly), and the ischial tuberosities (laterally), lying just inferior to the pelvic diaphragm (levator ani and coccygeus).

Which muscle pair plays a role in respiration?

diaphragm, scalene

Heat is noticeable

during exercise, sustain muscle movement causes body temperature to rise, in case of extreme cold when shivering produces random skeletal muscles contractions to generate heat

origin

end of a skeletal muscle that is attached to another structure (usually a bone) in a fixed position

insertion

end of a skeletal muscle that is attached to the structure (usually a bone) that is moved when the muscle contracts-- movable end of the muscle that attaches to the bone being pulled --

muscles contractions requires

energy, ATP is broken down, heat is produced.

varicosity

enlargement of neurons that release neurotransmitters into synaptic clefts-- also, visceral muscle in the walls of the hollow organs (except the heart) contains pacesette cells.

ATPase

enzyme that hydrolyzes ATP to ADP-- One part of the myosin head attaches to the binding site on the actin, but the head has another binding site for ATP. ATP binding causes the myosin head to detach from the actin (Figured). After this occurs, ATP is converted to ADP and Pi by the intrinsic ATPase activity of myosin. The energy released during ATP hydrolysis changes the angle of the myosin head into a cocked position (Figuree). The myosin head is now in position for further movement.

outer layer of connective tissue around a skeletal muscle- each muscle is wrapped in a sheath of dense, irregular connective tissue which allows muscle to contract and move powerfully while maintain its structural integrity.The epimysium also separates muscle from other tissues and organs in the area, allowing the muscle to move independently.

epimysium

There are three layers of connective tissue

epimysium, perimysium, and endomysium.

Muscle fatigue is caused by ________.

exhaustion of energy reserves and buildup of lactic acid levels

patellar ligament

extension of the quadriceps tendon below the patella

Which muscle name does not make sense?

extensor minimus longus

superficial posterior compartment of the forearm

extensor radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and their associated blood vessels and nerves

bundle of muscle fibers within a skeletal muscle - inside each skeeltal muscle, muscle fibers organzed into individualized bundles*---Skeletal muscle is enclosed in connective tissue scaffolding at three levels. Each muscle fiber (cell) is covered by endomysium and the entire muscle is covered by epimysium. When a group of muscle fibers is "bundled" as a unit within the whole muscle by an additional covering of a connective tissue called perimysium, that bundled group of muscle fibers is----Fascicle arrangement by perimysia is correlated to the force generated by a muscle; it also affects the range of motion of the muscle. Based on the patterns of fascicle arrangement, skeletal muscles can be classified in several ways. What follows are the most common fascicle arrangements.

fascicle

pennate

fascicles that are arranged differently based on their angles to the tendon-- muscles (penna = "feathers") blend into a tendon that runs through the central region of the muscle for its whole length, somewhat like the quill of a feather with the muscle arranged similar to the feathers. Due to this design, the muscle fibers in a pennate muscle can only pull at an angle, and as a result, contracting pennate muscles do not move their tendons very far. However, because a pennate muscle generally can hold more muscle fibers within it, it can produce relatively more tension for its size. There are three subtypes of pennate muscles.

parallel

fascicles that extend in the same direction as the long axis of the muscle- The majority of skeletal muscles in the body have this type of organization. Some parallel muscles are flat sheets that expand at the ends to make broad attachemtns. Other parallel muscles are rotund with tendons at one or both ends.

convergent

fascicles that extend over a broad area and converge on a common attachment site= when a muscle has a widespread expansion over a sizable area, but then the fascicles come to a single, common attachment point, the attachment point for a convergent muscle could be a tendon, an aponeurosis (flat, broad tendon) or a raphe (very slender tendon) . the large muscle on the chest, the pectoralis major is an example of a convergent muscle because it converges on the greater tubercle of the humerus via a tendon.

retinacula

fibrous bands that sheath the tendons at the wrist

The correct order for the smallest to the largest unit of organization in muscle tissue is ________.

filament, myofibril, muscle fiber, fascicle

internal oblique

flat, intermediate abdominal muscle with fascicles that run perpendicular to those of the external oblique

Sarco means

flesh

scalene muscles

flex, laterally flex, and rotate the head; contribute to deep inhalation

What is the largest muscle in the lower leg?

gastrocnemius

The large muscle group that attaches the leg to the pelvic girdle and produces extension of the hip joint is the ________ group.

gluteal

intermediate

group of midpalmar muscles

thenar

group of muscles on the lateral aspect of the palm

hypothenar

group of muscles on the medial aspect of the palm

biceps femoris

hamstring muscle

semimembranosus/ semitendinosus

hamstring muscle

autorhythmicity

heart's ability to control its own contractions

The fact that SO fibers can function for long periods without fatiguing makes them useful in maintaining posture, producing isometric contractions, stabilizing bones and joints, and making small movements that happen often but do not require large amounts of energy.

hey do not produce high tension, and thus they are not used for powerful, fast movements that require high amounts of energy and rapid cross-bridge cycling.

The region where

hick and thin filaments overlap has a dense appearance, as there is little space between the filaments. This zone where thin and thick filaments overlap is very important to muscle contraction, as it is the site where filament movement starts. Thin filaments, anchored at their ends by the Z-discs, do not extend completely into the central region that only contains thick filaments, anchored at their bases at a spot called the M-line. A myofibril is composed of many sarcomeres running along its length; thus, myofibrils and muscle cells contract as the sarcomeres contract.

pelvic girdle

hips, a foundation for the lower limb--

Intercalated discs are part of the sarcolemma and contain two structures important in cardiac muscle contraction: gap junctions and desmosomes. A gap junction forms channels between adjacent cardiac muscle fibers that allow the depolarizing current produced by cations to flow from one cardiac muscle cell to the next.

his joining is called electric coupling, and in cardiac muscle it allows the quick transmission of action potentials and the coordinated contraction of the entire heart. This network of electrically connected cardiac muscle cells creates a functional unit of contraction called a syncytium. The remainder of the intercalated disc is composed of desmosomes.

primary metabolic pathway used by a muscle fiber determines whether the fiber is classified as oxidative or glycolytic

if a fiber primarly produces ATP through aerobic pathways it is oxidative

Gap junctions develop

in the cardiac and single-unit smooth muscle in the early stages of development. In skeletal muscles, ACh receptors are initially present along most of the surface of the myoblasts, but spinal nerve innervation causes the release of growth factors that stimulate the formation of motor end-plates and NMJs. As neurons become active, electrical signals that are sent through the muscle influence the distribution of slow and fast fibers in the muscle.

Where is the inferior oblique muscle located?

in the eye socket

recruitment

increase in the number of motor units involved in contraction--As more strength is needed, larger motor units, with bigger, higher-threshold motor neurons are enlisted to activate larger muscle fibers.-- As more motor units are recruited, the muscle contraction grows progressively stronger. In some muscles, the largest motor units may generate a contractile force of 50 times more than the smallest motor units in the muscle. This allows a feather to be picked up using the biceps brachii arm muscle with minimal force, and a heavy weight to be lifted by the same muscle by recruiting the largest motor units.

myogram

instrument used to measure twitch tension

fast oxidative (FO)

intermediate muscle fiber that is between slow oxidative and fast glycolytic fibers--fibers have fast contractions and primarily use aerobic respiration, but because they may switch to anaerobic respiration (glycolysis), can fatigue more quickly than SO fibers

longissimus group

intermediately placed muscles of the erector spinae

segmental muscle group

interspinales and intertransversarii muscles that bring together the spinous and transverse processes of each consecutive vertebra

Tropomyosin

is a protein that winds around the chains of the actin filament and covers the myosin-binding sites to prevent actin from binding to myosin. Tropomyosin binds to troponin to form a troponin-tropomyosin complex. The troponin-tropomyosin complex prevents the myosin "heads" from binding to the active sites on the actin microfilaments. Troponin also has a binding site for Ca++ ions.

large motor unit

is an arrangement where a single motor neuron supplies a large number of muscle fibers in a muscle. Large motor units are concerned with simple, or "gross," movements, such as powerfully extending the knee joint. The best example is the large motor units of the thigh muscles or back muscles, where a single motor neuron will supply thousands of muscle fibers in a muscle, as its axon splits into thousands of branches.

small motorunit

is an arrangement where a single motor neuron supplies a small number of muscle fibers in a muscle. Small motor units permit very fine motor control of the muscle. The best example in humans is the small motor units of the extraocular eye muscles that move the eyeballs. There are thousands of muscle fibers in each muscle, but every six or so fibers are supplied by a single motor neuron, as the axons branch to form synaptic connections at their individual NMJs. This allows for exquisite control of eye movements so that both eyes can quickly focus on the same object. Small motor units are also involved in the many fine movements of the fingers and thumb of the hand for grasping, texting, etc.

fascicular organization

is common in muscles of the limbs; it allows the nervous system to trigger a specific movement of a muscle by activating a subset of muscle fibers within a bundle, or fascicle of the muscle.

Aerobic respiration

is the breakdown of glucose or other nutrients in the presence of oxygen (O2) to produce carbon dioxide, water, and ATP. Approximately 95 percent of the ATP required for resting or moderately active muscles is provided by aerobic respiration, which takes place in mitochondria. The inputs for aerobic respiration include glucose circulating in the bloodstream, pyruvic acid, and fatty acids. Aerobic respiration is much more efficient than anaerobic glycolysis, producing approximately 36 ATPs per molecule of glucose versus four from glycolysis. However, aerobic respiration cannot be sustained without a steady supply of O2 to the skeletal muscle and is much slower (Figurec). To compensate, muscles store small amount of excess oxygen in proteins call myoglobin, allowing for more efficient muscle contractions and less fatigue. Aerobic training also increases the efficiency of the circulatory system so that O2 can be supplied to the muscles for longer periods of time.

inferior gemellus

muscle deep to the gluteus maximus on the lateral surface of the thigh that laterally rotates the femur at the hip

Smooth muscles differ from skeletal and cardiac muscles in that they ________.

lack myofibrils

serratus anterior

large and flat muscle that originates on the ribs and inserts onto the scapula

erector spinae group

large muscle mass of the back; primary extensor of the vertebral column- controls the flexion, lateral flexion, and rotation of the vertebral column, maintains the lumbar curve. The erector spinae comprises the iliocostatlis (laterally placed) group, the longissiumus group and the spinalis medially placed group

maximus

largest

gluteus maximus

largest of the gluteus muscles that extends the femur

iliocostalis group

laterally placed muscles of the erector spinae

skeletal muscles

located throughout the body at the openings of internal tracts to control movement of various substances.

longus

long

myofibril

long, cylindrical organelle that runs parallel within the muscle fiber and contains the sarcomeres

rectus abdominis

long, linear muscle that extends along the middle of the trunk--- a pair of long linear muscles, situ up muscles- at the pubic crest and symphysis, extend the length of the body's trunk.

middle scalene

longest scalene muscle, located between the anterior and posterior scalenes

sarcomere

longitudinally, repeating functional unit of skeletal muscle, with all of the contractile and associated proteins involved in contraction. striated appearance of skeletal muscles is due to the arrangement of the myofilaments of actin and myosin in sequential order from one end of the muscle fiber to the other.

endomysium

loose, and well-hydrated connective tissue covering each muscle fiber in a skeletal muscle-- The endomysium contains the extracellular fluid and nutrients to support the muscle fiber. These nutrients are supplied via blood to the muscle tissue.

atrophy

loss of structural proteins from muscle fibers - lost and muscle mass decreases

muscle tone

low levels of muscle contraction that occur when a muscle is not producing movement-- Skeletal muscles are rarely completely relaxed, or flaccid. Even if a muscle is not producing movement, it is contracted a small amount to maintain its contractile proteins and produce muscle tone. The tension produced by muscle tone allows muscles to continually stabilize joints and maintain posture. Muscle tone is accomplished by a complex interaction between the nervous system and skeletal muscles that results in the activation of a few motor units at a time, most likely in a cyclical manner. In this manner, muscles never fatigue completely, as some motor units can recover while others are active.

ATP produces during each metabolic cycle

makes fiber more resistant to fatigue

spinalis group

medially placed muscles of the erector spinae

medius

medium

voltage-gated sodium channels

membrane proteins that open sodium channels in response to a sufficient voltage change, and initiate and transmit the action potential as Na+ enters through the channel --- membrane depolarizes another set of ion channels- sodium ions enter muscle fiber, and an action potential rapidly spreads or fires alone the entire membrane to initiate excitation-contraction coupling .,. excitable membranes when you snap your fingers. immediately following depolarization of the membrane

joints

misaligned or dislocated entrirely by pulling on associated bones, muscles work to keep joints stable

graded muscle response

modification of contraction strength

gastrocnemius

most superficial muscle of the calf

motor unit

motor neuron and the group of muscle fibers it innervates-- actual group of muscle fibers in a muscle innervated by a single motor neuron- the size of a motor unit is variable depending on the nature of the muscle

abduct

move away from midline in the sagittal plane

flexion

movement that decreases the angle of a joint. bending the elbow—the brachioradialis assists the brachialis.

abductor

moves the bone away from the midline

adductor

moves the bone toward the midline

isotonic contraction

muscle contraction that involves changes in muscle length it also stays constant, a load is moved as the length of the muscle changes (shortens) There are two types of isotonic contractions: concentric and eccentric.

eccentric contraction

muscle contraction that lengthens the muscle as the tension is diminished and the muscle lengthens- in this case, the hand weight is lowered in a slow and controlled manner as the amount of cross-bridges being activated by nervous system stimulation decreases. In this case, as tension is released from the biceps brachii, the angle of the elbow joint increases. Eccentric contractions are also used for movement and balance of the body.

isometric contraction

muscle contraction that occurs with no change in muscle length-- occurs as the muscle produces tension without changing the angle of a skeletal joint. Isometric contractions involve sarcomere shortening and increasing muscle tension, but do not move a load, as the force produced cannot overcome the resistance provided by the load. For example, if one attempts to lift a hand weight that is too heavy, there will be sarcomere activation and shortening to a point, and ever-increasing muscle tension, but no change in the angle of the elbow joint. In everyday living, isometric contractions are active in maintaining posture and maintaining bone and joint stability. However, holding your head in an upright position occurs not because the muscles cannot move the head, but because the goal is to remain stationary and not produce movement. Most actions of the body are the result of a combination of isotonic and isometric contractions working together to produce a wide range of outcomes

concentric contraction

muscle contraction that shortens the muscle to move a load--An example of this is the biceps brachii muscle contracting when a hand weight is brought upward with increasing muscle tension. As the biceps brachii contract, the angle of the elbow joint decreases as the forearm is brought toward the body. Here, the biceps brachii contracts as sarcomeres in its muscle fibers are shortening and cross-bridges form; the myosin heads pull the actin

brachialis

muscle deep to the biceps brachii that provides power in flexing the forearm.

slow oxidative (SO)

muscle fiber that primarily uses aerobic respiration- fibers contract relatively slowly and use aerobic respiration (oxygen and glucose) to produce ATP

fast glycolytic (FG)

muscle fiber that primarily uses anaerobic glycolysis-- fibers have fast contractions and primarily use anaerobic glycolysis. The FG fibers fatigue more quickly than the others. Most skeletal muscles in a human contain(s) all three types, although in varying proportions.

fascicle

muscle fibers bundled by perimysium into a unit

iliopsoas group

muscle group consisting of iliacus and psoas major muscles, that flexes the thigh at the hip, rotates it laterally, and flexes the trunk of the body onto the hip

gluteal group

muscle group that extends, flexes, rotates, adducts, and abducts the femur

tibialis anterior

muscle located on the lateral surface of the tibia

iliocostalis cervicis

muscle of the iliocostalis group associated with the cervical region

iliocostalis lumborum

muscle of the iliocostalis group associated with the lumbar region

iliocostalis thoracis

muscle of the iliocostalis group associated with the thoracic region

longissimus cervicis

muscle of the longissimus group associated with the cervical region

longissimus capitis

muscle of the longissimus group associated with the head region

longissimus thoracis

muscle of the longissimus group associated with the thoracic region

multifidus

muscle of the lumbar region that helps extend and laterally flex the vertebral column

spinalis cervicis

muscle of the spinalis group associated with the cervical region

spinalis capitis

muscle of the spinalis group associated with the head region

spinalis thoracis

muscle of the spinalis group associated with the thoracic region

pectineus

muscle that abducts and flexes the femur at the hip

supraspinatus

muscle that abducts the arm-- superior to the spine of the scapula

abductor digiti minimi

muscle that abducts the little finger

abductor pollicis brevis

muscle that abducts the thumb

adductor brevis

muscle that adducts and medially rotates the thigh

gracilis

muscle that adducts the thigh and flexes the leg at the knee

adductor pollicis

muscle that adducts the thumb

adductor longus

muscle that adducts, medially rotates, and flexes the thigh

ischiococcygeus

muscle that assists the levator ani and pulls the coccyx anteriorly

rhomboid major

muscle that attaches the vertebral border of the scapula to the spinous process of the thoracic vertebrae

rhomboid minor

muscle that attaches the vertebral border of the scapula to the spinous process of the thoracic vertebrae

opponens digiti minimi

muscle that brings the little finger across the palm to meet the thumb

brachioradialis

muscle that can flex the forearm quickly or help lift a load slowly

buccinator

muscle that compresses the check- this muscle allows you to whistle blow suck and actions of chewing as well

sternohyoid

muscle that depresses the hyoid bone

acetylcholine (ACh)

neurotransmitter that binds at a motor end-plate to trigger depolarization

Drug X blocks ATP regeneration from ADP and phosphate. How will muscle cells respond to this drug?

none of the above

The fibularis bervis is BLANK to the popliteus.

none of the above: proximal, positioned, reduced

smooth muscle

nonstriated, mononucleated muscle in the skin that is associated with hair follicles; assists in moving materials in the walls of internal organs, blood vessels, and internal passageways-- Because the actin and myosin are not arranged in such regular fashion in-- he cytoplasm of a smooth muscle fiber (which has only a single nucleus) has a uniform, nonstriated appearance (resulting in the name smooth muscle). However, the less organized appearance of smooth muscle should not be interpreted as less efficient. Smooth muscle in the walls of arteries is a critical component that regulates blood pressure necessary to push blood through the circulatory system; and smooth muscle in the skin, visceral organs, and internal passageways is essential for moving all materials through the body.

For thin filaments t

o continue to slide past thick filaments during muscle contraction, myosin heads must pull the actin at the binding sites, detach, re-cock, attach to more binding sites, pull, detach, re-cock, etc.

cross-bridge formation

occurs when the myosin head attaches to the actin while adenosine diphosphate (ADP) and inorganic phosphate (Pi) are still bound to myosin (Figurea,b). Pi is then released, causing myosin to form a stronger attachment to the actin, after which the myosin head moves toward the M-line, pulling the actin along with it.

appendicular

of the arms and legs muscle

axial

of the trunk and head

Where is the temporalis muscle located?

on the side of the head

caval opening

opening in the diaphragm that allows the inferior vena cava to pass through; foramen for the vena cava-- the esophagus and attached nervs passes through esophageal hiatus --

extrinsic eye muscles

originate outside the eye and insert onto the outer surface of the white of the eye, and create eyeball movement--These muscles are located inside the eye socket and cannot be seen on any part of the visible eyeball (Figure and Table). If you have ever been to a doctor who held up a finger and asked you to follow it up, down, and to both sides, he or she is checking to make sure your eye muscles are acting in a coordinated pattern.

amount of oxygen needed to compensate for ATP produced without oxygen during muscle contraction--- which is the amount of oxygen needed to compensate for ATP produced without oxygen during muscle contraction. Oxygen is required to restore ATP and creatine phosphate levels, convert lactic acid to pyruvic acid, and, in the liver, to convert lactic acid into glucose or glycogen. Other systems used during exercise also require oxygen, and all of these combined processes result in the increased breathing rate that occurs after exercise. Until the oxygen debt has been met, oxygen intake is elevated, even after exercise has stopped.

oxygen debt

intercalated disc

part of the sarcolemma that connects cardiac tissue, and contains gap junctions and desmosomes- cardiac muscle cells to contract in a wave like pattern so that the heart can work as a pump

Which muscle has a convergent pattern of fascicles?

pectoralis major

levator ani

pelvic muscle that resists intra-abdominal pressure and supports the pelvic viscera-- two skeletal muscles of pubococcygeus and ilioccygeus

multipennate

pennate muscle that has a tendon branching within it--In some pennate muscles, the muscle fibers wrap around the tendon, sometimes forming individual fascicles in the process. . common example is a deltoid muslce of the shoulder, which covers the shoulder but has a single tendont ath insets on the deltoid tuberosity of the humerus. beacuse of fasicles, a portion of a multipennate muscle like the deltoid can be stimulated by the nervous system to change the direction of the pull. for example, when the deltoid muscle contracts, the arm abducts but when the only atnterior fascicle is stimulated, the arm will abduct and flex

unipennate

pennate muscle that has fascicles located on one side of the tendon--The extensor digitorum of the forearm is an example of a unipennate muscle

bipennate

pennate muscle that has fascicles that are located on both sides of the tendon-

relaxation phase

period after twitch contraction when tension decreases

creatine phosphate

phosphagen used to store energy from ATP and transfer it to muscle--- is a molecule that can store energy in its phosphate bonds. In a resting muscle, excess ATP transfers its energy to creatine, producing ADP and creatine phosphate. This acts as an energy reserve that can be used to quickly create more ATP. When the muscle starts to contract and needs energy, creatine phosphate transfers its phosphate back to ADP to form ATP and creatine. This reaction is catalyzed by the enzyme creatine kinase and occurs very quickly; thus, creatine phosphate-derived ATP powers the first few seconds of muscle contraction. However, creatine phosphate can only provide approximately 15 seconds worth of energy, at which point another energy source has to be used (Figure).

What aspect of creatine phosphate allows it to supply energy to muscles?

phosphate bonds

sarcolemma

plasma membrane of a skeletal muscle fiber

splenius

posterior neck muscles; includes the splenius capitis and splenius cervicis

quadratus lumborum

posterior part of the abdominal wall that helps with posture and stabilization of the body

occipitalis

posterior part of the occipitofrontalis muscle-- there is no muscle across the top of the head

anal triangle

posterior triangle of the perineum that includes the anus

What is the function of the erector spinae?

postural support

lactic acid

product of anaerobic glycolysis-- However, if oxygen is not available, pyruvic acid is converted to lactic acid, which may contribute to muscle fatigue. This conversion allows the recycling of the enzyme NAD+ from NADH, which is needed for glycolysis to continue. This occurs during strenuous exercise when high amounts of energy are needed but oxygen cannot be sufficiently delivered to muscle. Glycolysis itself cannot be sustained for very long (approximately 1 minute of muscle activity), but it is useful in facilitating short bursts of high-intensity output. This is because glycolysis does not utilize glucose very efficiently, producing a net gain of two ATPs per molecule of glucose, and the end product of lactic acid, which may contribute to muscle fatigue as it accumulates.

pyruvic acid

product of glycolysis that can be used in aerobic respiration or converted to lactic acid-- which can be used in aerobic respiration or when oxygen levels are low, converted to lactic acid (Figureb). If oxygen is available, pyruvic acid is used in aerobic respiration

aerobic respiration

production of ATP in the presence of oxygen

pronator teres

pronator that originates on the humerus and inserts on the radius

pronator quadratus

pronator that originates on the ulna and inserts on the radius

skeletal muscles

protect internal organs (abdominal and pelvic organs) by acting as an external barrier or shield to external trauama and support weight of organs

myosin

protein that makes up most of the thick cylindrical myofilament within a sarcomere muscle fiber (thick filament) with other support proteins

actin

protein that makes up most of the thin myofilaments in a sarcomere muscle fiber -- functional unit of a skeletal muscle fiber is the sarcomere, highly organized arrangement of contractile myofilaments (thin filament)

Which of the following abdominal muscles is not a part of the anterior abdominal wall?

quadratus lumborum

rectus femoris

quadricep muscle on the anterior aspect of the thigh

vastus lateralis

quadricep muscle on the lateral aspect of the thigh

vastus medialis

quadricep muscle on the medial aspect of the thigh

vastus intermedius

quadricep muscle that is between the vastus lateralis and vastus medialis and is deep to the rectus femoris

How would you get to the maximum contractile strength of a skeletal muscle?

recruit all motor units

The vastus intermedius muscle is deep to which of the following muscles?

rectus femoris

femoral triangle

region formed at the junction between the hip and the leg and includes the pectineus, femoral nerve, femoral artery, femoral vein, and deep inguinal lymph nodes

anterior compartment of the leg\

region that includes muscles that dorsiflex the foot

posterior compartment of the thigh

region that includes muscles that flex the leg and extend the thigh

anterior compartment of the thigh

region that includes muscles that flex the thigh and extend the leg

dorsal group

region that includes the extensor digitorum brevis

lateral compartment of the leg

region that includes the fibularis (peroneus) longus and the fibularis (peroneus) brevis and their associated blood vessels and nerves

posterior compartment of the leg

region that includes the superficial gastrocnemius, soleus, and plantaris, and the deep popliteus, flexor digitorum longus, flexor hallucis longus, and tibialis posterior

troponin

regulatory protein that binds to actin, tropomyosin, and calcium0000 each packet of these microfilaments and their regulatary proteins

tropomyosin

regulatory protein that covers myosin-binding sites to prevent actin from binding to myosin

calmodulin

regulatory protein that facilitates contraction in smooth muscles- Because smooth muscle cells do not contain troponin, cross-bridge formation is not regulated by the troponin-tropomyosin complex but instead by the regulatory protein--- ex:In a smooth muscle fiber, external Ca++ ions passing through opened calcium channels in the sarcolemma, and additional Ca++ released from SR, bind to calmodulin. The Ca++-calmodulin complex then activates an enzyme called myosin (light chain) kinase, which, in turn, activates the myosin heads by phosphorylating them (converting ATP to ADP and Pi, with the Pi attaching to the head). The heads can then attach to actin-binding sites and pull on the thin filaments. The thin filaments also are anchored to the dense bodies; the structures invested in the inner membrane of the sarcolemma (at adherens junctions) that also have cord-like intermediate filaments attached to them. When the thin filaments slide past the thick filaments, they pull on the dense bodies, structures tethered to the sarcolemma, which then pull on the intermediate filaments networks throughout the sarcoplasm. This arrangement causes the entire muscle fiber to contract in a manner whereby the ends are pulled toward the center, causing the midsection to bulge in a corkscrew motion

stress-relaxation response

relaxation of smooth muscle tissue after being stretched-- muscle fibers are not constrained by organization and stetchability limits of sarcomeres, This means that as the muscle of a hollow organ is stretched when it fills, the mechanical stress of the stretching will trigger contraction, but this is immediately followed by relaxation so that the organ does not empty its contents prematurely. This is important for hollow organs, such as the stomach or urinary bladder, which continuously expand as they fill. The smooth muscle around these organs also can maintain a muscle tone when the organ empties and shrinks, a feature that prevents "flabbiness" in the empty organ. In general, visceral smooth muscle produces slow, steady contractions that allow substances, such as food in the digestive tract, to move through the body.

fibrosis

replacement of muscle fibers by scar tissue-- If a cell is damaged to a greater extent than can be repaired by satellite cells, the muscle fibers are replaced by scar tissue in a process--Because scar tissue cannot contract, muscle that has sustained significant damage loses strength and cannot produce the same amount of power or endurance as it could before being damaged.

hypothenar eminence

rounded contour of muscle at the base of the little finger

thenar eminence

rounded contour of muscle at the base of the thumb

Duchenne muscular dystrophy (DMD)

s a progressive weakening of the skeletal muscles. It is one of several diseases collectively referred to as "muscular dystrophy." DMD is caused by a lack of the protein dystrophin, which helps the thin filaments of myofibrils bind to the sarcolemma. Without sufficient dystrophin, muscle contractions cause the sarcolemma to tear, causing an influx of Ca++, leading to cellular damage and muscle fiber degradation. Over time, as muscle damage accumulates, muscle mass is lost, and greater functional impairments develop. DMD is an inherited disorder caused by an abnormal X chromosome. It primarily affects males, and it is usually diagnosed in early childhood. DMD usually first appears as difficulty with balance and motion, and then progresses to an inability to walk. It continues progressing upward in the body from the lower extremities to the upper body, where it affects the muscles responsible for breathing and circulation. It ultimately causes death due to respiratory failure, and those afflicted do not usually live past their 20s. Because DMD is caused by a mutation in the gene that codes for dystrophin, it was thought that introducing healthy myoblasts into patients might be an effective treatment. Myoblasts are the embryonic cells responsible for muscle development, and ideally, they would carry healthy genes that could produce the dystrophin needed for normal muscle contraction. This approach has been largely unsuccessful in humans. A recent approach has involved attempting to boost the muscle's production of utrophin, a protein similar to dystrophin that may be able to assume the role of dystrophin and prevent cellular damage from occurring.

The cell membrane of a muscle fiber is called ________.

sarcolemma

motor end-plate

sarcolemma of muscle fiber at the neuromuscular junction, with receptors for the neurotransmitter acetylcholine - side of the synpace

Thin and thick filaments are organized into functional units called ________.

sarcomeres

excitation-contraction coupling

sequence of events from motor neuron signaling to a skeletal muscle fiber to contraction of the fiber's sarcomeres --- confuses or scares; for skeeltal muscle fiber to contract, membrane must be excist in other words- stimulated to fire an action potential. The muscle fiber action potential, which sweeps along the sarcolemma as a wave, is "coupled" to the actual contraction through the release of calcium ions (Ca++) from the SR. Once released, the Ca++ interacts with the shielding proteins, forcing them to move aside so that the actin-binding sites are available for attachment by myosin heads. The myosin then pulls the actin filaments toward the center, shortening the muscle fiber. -- all living cells have membrane potential or electrical gradients across their membranes. -60 to -90 mV cells membrane potential. Neurons and muscle cells use their membrane potentials to generate electrical signals. Both neurons and skeletal muscle cells are electircally excitable meaning generate action potentials.

brevis

short

pectoral girdle

shoulder girdle, made up of the clavicle and scapula, along with the proximal end of the humerus, and the muscles covering these three bones to stabilize the shoulder joint. The girdle creates a base from which the head of the humerus, in its ball-and-socket joint with the glenoid fossa of the scapula, can move the arm in multiple directions.

deltoid

shoulder muscle that abducts the arm as well as flexes and medially rotates it, and extends and laterally rotates it-----, the thick muscle that creates the rounded lines of the shoulder is the major abductor of the arm, but it also facilitates flexing and medial rotation, as well as extension and lateral rotation.

neurotransmitter

signaling chemical released by nerve terminals that bind to and activate receptors on target cells -- can also be called acetylcholine (ACH)

sequence of events in contraction of an individuals muscle fiber beings with

signal—the neurotransmitter, ACh—from the motor neuron innervating that fiber. The local membrane of the fiber will depolarize as positively charged sodium ions (Na+) enter, triggering an action potential that spreads to the rest of the membrane will depolarize, including the T-tubules. This triggers the release of calcium ions (Ca++) from storage in the sarcoplasmic reticulum (SR). The Ca++ then initiates contraction, which is sustained by ATP (Figure). As long as Ca++ ions remain in the sarcoplasm to bind to troponin, which keeps the actin-binding sites "unshielded," and as long as ATP is available to drive the cross-bridge cycling and the pulling of actin strands by myosin, the muscle fiber will continue to shorten to an anatomical limit.

twitch

single contraction produced by one action potential

diaphragm

skeletal muscle that separates the thoracic and abdominal cavities and is dome-shaped at rest---The change in volume of the thoracic cavity during breathing is due to the alternate contraction and relaxatio---t separates the thoracic and abdominal cavities, and is dome-shaped at rest. The superior surface of the diaphragm is convex, creating the elevated floor of the thoracic cavity. The inferior surface is concave, creating the curved roof of the abdominal cavity.

anconeus

small muscle on the lateral posterior elbow that extends the forearm

fibularis tertius

small muscle that is associated with the extensor digitorum longus

minimus

smallest

gluteus minimus

smallest of the gluteal muscles and deep to the gluteus medius

posterior scalene

smallest scalene muscle, located posterior to the middle scalene

myofibril

triad surrounds the cylindrical structure, which contains actin and myosin

satellite cell

stem cell that helps to repair muscle cells---is similar to a myoblast because it is a type of stem cell; however, satellite cells are incorporated into muscle cells and facilitate the protein synthesis required for repair and growth. These cells are located outside the sarcolemma and are stimulated to grow and fuse with muscle cells by growth factors that are released by muscle fibers under certain forms of stress. Satellite cells can regenerate muscle fibers to a very limited extent, but they primarily help to repair damage in living cells.

pericyte

stem cell that regenerates smooth muscle cells, which is found in some small blood vessels. Pericytes allow smooth muscle cells to regenerate and repair much more readily than skeletal and cardiac muscle tissue. Similar to skeletal muscle tissue, cardiac muscle does not regenerate to a great extent. Dead cardiac muscle tissue is replaced by scar tissue, which cannot contract. As scar tissue accumulates, the heart loses its ability to pump because of the loss of contractile power. However, some minor regeneration may occur due to stem cells found in the blood that occasionally enter cardiac tissue.

treppe

stepwise increase in contraction tension

Which of the following is a prime mover in head flexion?

sternocleidomastoid

If cardiac muscle cells were prevented from undergoing aerobic metabolism, they ultimately would ________.

stop contracting

Muscle contraction

stops when signaling from the motor neuron ends, which repolarizes the sarcolemma and T-tubules, and closes the voltage-gated calcium channels in the SR. Ca++ ions are then pumped back into the SR, which causes the tropomyosin to reshield (or re-cover) the binding sites on the actin strands. A muscle also can stop contracting when it runs out of ATP and becomes fatigued (Figure).

rectus

straight

Muscle that has a striped appearance is described as being ________.

striated

cardiac muscle

striated muscle found in the heart; joined to one another at intercalated discs and under the regulation of pacemaker cells, which contract as one unit to pump blood through the circulatory system. Cardiac muscle is under involuntary control. -- fibers each have one to two nuclei and are physically and electrically connected to each other so that the entire heart contracts as one unit (called a syncytium).

skeletal muscle

striated, multinucleated muscle that requires signaling from the nervous system to trigger contraction; most skeletal muscles are referred to as voluntary muscles that move bones and produce movement --fibers are multinucleated structures that compose the skeletal muscle.

latch-bridges

subset of a cross-bridge in which actin and myosin remain locked together- , keep the thick and thin filaments linked together for a prolonged period, and without the need for ATP. This allows for the maintaining of muscle "tone" in smooth muscle that lines arterioles and other visceral organs with very little energy expenditure.

external oblique

superficial abdominal muscle with fascicles that extend inferiorly and medially- closest to the surface- sliding one's four fingers into pants pockets

external intercostal

superficial intercostal muscles that raise the rib cage-- muscles aid in inspirtation of air during breathing because when they contract, they raise the rib cage, which expands it

The orbicularis oris is BLANK buccinator.

superior

muscles allow us to

swallow, urinate, and defecate - under voluntary control

deglutition

swallowing and speech

neuromuscular junction (NMJ)

synapse between the axon terminal of a motor neuron and the section of the membrane of a muscle fiber with receptors for the acetylcholine released by the terminal---- muscle fiber first responds to signaling by motor nueron

fixator

synergist that assists an agonist by preventing or reducing movement at another joint, thereby stabilizing the origin of the agonist--that stabilizes the bone that is the attachment for the prime mover's origin.

semispinalis thoracis

transversospinales muscle associated with the thoracic region

Which muscles rotate, abduct and also adduct the thigh?

tensor fasciae latae

The rhomboid major and minor muscles are deep to the ________.

trapezius

Which muscle produces movement that allows you to cross your legs

the sartorius

thick filament

the thick myosin strands and their multiple heads projecting from the center of the sarcomere toward, but not all to way to, the Z-discs

latent period

the time when a twitch does not produce contraction

excitability

their plasma membranes can change their electrical states (from polarized to depolarized) and send an electrical wave called an action potential along the entire length of the membrane. While the nervous system can influence the excitability of cardiac and smooth muscle to some degree, skeletal muscle completely depends on signaling from the nervous system to work properly. On the other hand, both cardiac muscle and smooth muscle can respond to other stimuli, such as hormones and local stimuli.

pectoralis major

thick, fan-shaped axial muscle that covers much of the superior thorax

thin filament

thin strands of actin and its troponin-tropomyosin complex projecting from the Z-discs toward the center of the sarcomere --- form strands that are thinner than the myosin

tri

three

hamstring group

three long muscles on the back of the leg

tendinous intersections

three transverse bands of collagen fibers that divide the rectus abdominis into segments-- six pack abs

triceps brachii

three-headed muscle that extends the forearm

rectus sheaths

tissue that makes up the linea alba- anterior midline of the body

depolarize

to reduce the voltage difference between the inside and outside of a cell's plasma membrane (the sarcolemma for a muscle fiber), making the inside less negative than at rest --- ACh receptor opens and positively charged ions can pass through into the nsucle fiber, causing it to depolarize, meaning that the membrane potential of the muscle fiber becomes less negative (closer to zero)

medialis

to the inside

lateralis

to the outside

superior extensor retinaculum

transverse ligament of the ankle

semispinalis cervicis

transversospinales muscle associated with the cervical region

semispinalis capitis

transversospinales muscle associated with the head region

To initiate muscle contraction

tropomyosin has to expose the myosin-binding site on an actin filament to allow cross-bridge formation between the actin and myosin microfilaments. The first step in the process of contraction is for Ca++ to bind to troponin so that tropomyosin can slide away from the binding sites on the actin strands. This allows the myosin heads to bind to these exposed binding sites and form cross-bridges. The thin filaments are then pulled by the myosin heads to slide past the thick filaments toward the center of the sarcomere. But each head can only pull a very short distance before it has reached its limit and must be "re-cocked" before it can pull again, a step that requires ATP.

fast fibers hydrolyze ATP

twice as quickly as slow fibers, resulting in much quicker cross-bridge cycling

contraction phase

twitch contraction phase when tension increases

bi

two

biceps brachii

two-headed muscle that crosses the shoulder and elbow joints to flex the forearm while assisting in supinating it and flexing the arm at the shoulder--