A&P Lecture, exam 3

Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell.

95%

motor unit function

A Motor Neuron branches to form axon, axon goes to the muscle fibers and attaches with the axon terminal.

motor unit

A motor neuron and all of the muscle fibers it innervates

Define motor unit.

A motor unit is a motor neuron and all the muscle fibers that it controls

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?

A myosin head bound to actin

Define the term synergist as it relates to muscle action.

A synergist is a muscle that helps the agonist perform its actions more efficiently.

After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?

ATP binds to the myosin head

Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?

Acetylcholine is degraded by acetylcholinesterase.

The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?

Acetylcholine is released by axon terminals of the motor neuron.

Alfredo believes he is only exercising one muscle (the biceps brachii) when he performs the elbow flexion exercises Jessica told him about. What other muscle is a synergist that also participates in these exercises?

Brachialis

Think about the insertions of the muscles involved in elbow flexion and the positioning of the bones in the exercises described. Which of the elbow flexors does doing the "hammer curl" exercise probably emphasize?

Brachioradialis

How do calcium ions (Ca2+) in the sarcomere affect the contraction cycle?

By binding to troponin, Ca2+ causes it to shift position and move tropomyosin, exposing the binding sites on actin.

Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?

Calcium ions are stored in the sarcoplasmic reticulum.

What event initiates the contraction cycle?

Calcium ions arrive within the zone of overlap.

What specific event triggers the uncovering of the myosin binding site on actin?

Calcium ions bind to troponin and change its shape.

When does cross bridge cycling end?

Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.

What structure is the functional unit of contraction in a skeletal muscle fiber?

The sarcomere

Muscle A abducts the humerus and muscle B adducts the humerus. What is the relationship between the two muscles.

The two muscles are antagonists to each other.

Tetanus is most likely to result from which condition?

a deep puncture wound, such as that from a nail

creatine phosphate

a high energy compound that can be broken down for energy and used to regenerate ATP

Polio

a viral disease that attacks motor neurons in the spinal cord and brain

The tensor fascia latae is involved in hip __________.

abduction

Excitability

ability to receive and respond to stimuli

elasticity of muscle tissue

ability to return to original shape after being stretched

Myosin molecules form cross-bridges when they attach to __________.

actin

Which of the following proteins contains the active site involved in cross-bridge formation?

actin

Which phase of the contraction cycle directly requires that calcium ions bind to troponin?

active-site exposure

Damage to the pectoralis major would interfere with a person's ability to

adduct the humerus.

Which process can, by itself, power the greatest number of twitches, based on the energy sources available in a typical muscle fiber?

aerobic metabolism of glycogen

The smallest of the posterior extensors of the elbow joint is the __________.

anconeus

Motor units are activated on a rotating basis to reduce fatigue. What is this mechanism called?

asynchronous motor unit summation

The muscle that generates the most power during elbow flexion is the __________.

brachialis

If you were contracting and relaxing your masseter, what would you probably be doing?

chewing or eating

The pectoralis major muscle can be divided into groups of fibers superior, or __________, and inferior, or __________.

clavicular; sternocostal

The names of the muscles can indicate all of the following except

collagen content of the muscle.

troponin

consists of 3 globular subunits; one binds to tropomyosin, one binds to the G-actin and a third subunit has a receptor that binds two calcium ions

Calcium ions are bound to troponin during which of the following steps.

contraction phase

The brachialis muscle is located __________ to the biceps brachii muscle.

deep

What is the type of chemical reaction used to rebuild ADP into ATP?

dehydration synthesis

Name the muscle that abducts the arm.

deltoid

ATP binding leads to which of the following actions?

detaching and resetting cross-bridges

Muscles of the shoulder can be divided into groups based on __________.

distribution and functional relationships

Individual muscle cells are surrounded by what connective tissue?

endomysium

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.

extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

The extensor muscle that branches to form four tendons on the back of the hand is the __________.

extensor digitorum

Superficial muscles that position or stabilize an organ are called

extrinsic.

The brachioradialis is a strong forearm __________.

flexor

Which superficial flexor muscle of the forearm is the most lateral?

flexor carpi radialis

Which muscle is a superficial anterior flexor muscle?

flexor digitorum superficialis

Which muscle of the wrist and fingers is a deep anterior flexor?

flexor pollicis longus

The prime mover of hip extension is the __________.

gluteus maximus

Which muscle of the gluteal group acts in extension and lateral rotation at the hip?

gluteus maximus muscle

Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products?

glycolysis

Mature skeletal muscle fibers:

individually contain hundreds of nuclei just internal to the plasma membrane.

The origin of the long head of the triceps brachii is on the __________.

infraglenoid tubercle of the scapula

The tensor fasciae latae stabilizes the hip joint and the __________ joint.

knee

Which of these would NOT lead to increased oxygen consumption?

lactic acidosis

Myofibrils are __________.

made of a series of sarcomeres

The Na+/K+ ion pump is responsible for

maintaining the sodium/potassium concentration gradients constant.

The key actions of the pectoralis major muscle are __________.

medial rotation and adduction

When acetylcholine binds to receptors at the motor end plate, the end plate membrane becomes

more permeable to sodium ions.

Neurons and ________ have electrically excitable membranes that propagate action potentials.

muscle cells

Interactions between actin and myosin filaments of the sarcomere are responsible for

muscle contraction

Contractibility

muscle fibers that are stimulated by nerves contract, or become short and thick, which causes movement

Synergist

muscle that helps larger agonist work efficiently -May provide additional pull or stabilize origin

Antagonist

muscle whose action opposes a particular agonist

Agonist or prime mover

muscle whose contraction is mostly responsible for producing the movement

Determine the correct structural hierarchy of skeletal muscles from microscopic to gross levels.

myofibril - fiber - fascicle - muscle

Which of the following is involved in the power stroke?

myosin

Name the proteins that make up a thick filament.

myosin and titin

Communication between axons and muscle fibers occurs at specialized synapses called

neuromuscular junctions.

People who are engaged in repetitive hand movements such as typing or playing the piano may suffer wrist pain, especially during palmar flexion. All of the following are true concerning this condition except that it

never causes muscle weakness.

Rigor mortis

occurs as the sarcoplasmic reticulum deteriorates, releasing calcium ions

The end of a muscle that remains stationary when the muscle contracts is called the

origin

inferior oblique

origin: maxillary bone at anterior portion of orbit insertion: inferior, lateral surface of eyeball action: eye rolls, looks superiorly and laterally

Occipitofrontalis (occipital belly)

origin: occipital and temporal bone insertion: epicranial aponeurosis action: tenses and retracts scalp

medial rectus

origin: sphenoid around optic canal insertion: medial surface of eyeball action: eye looks medially

Sternocleidomastoid

origin: sternum and clavicle insertion: mastoid process action: flexes neck

The palmaris longus inserts on the __________.

palmar aponeurosis

Sarcolemma

plasma membrane of a muscle cell

neuromuscular junction

point of contact between a motor neuron and a skeletal muscle cell

The muscles that extend the forearm are located __________.

posteriorly

Which of the following describes the action of the serratus anterior?

protracts the shoulder, abducts and medially rotates the scapula

All fibers of the triceps brachii are innervated by the __________.

radial nerve

The two heads of the biceps brachii combine to insert on the __________.

radial tuberosity

The interosseous membrane is located between the __________.

radius and ulna

The smooth but steady increase in muscular tension that is produced by increasing the number of active motor units is called __________.

recruitment

All of the following provides flexion of the knee except

rectus femoris.

The muscle that adducts and rotates the scapula downward is the

rhomboid

Muscles of the rotator cuff include all of the following except the

rhomboid.

The plasma membrane of skeletal muscle is called the

sarcolemma.

The repeating contractile unit of a skeletal muscle fiber is the

sarcomere.

Z lines define the edges of which of the following?

sarcomeres

The anterior muscles of the thigh that originate on the os coxae are __________.

sartorius; rectus femoris

Which of the following muscles are found in the cervical region and act in elevating the ribs?

scalenes

excitation-contraction coupling

sequence of events from motor neuron signaling to a skeletal muscle fiber to contraction of the fiber's sarcomeres

Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber

shortens

Which muscle types are voluntary, and which are involuntary?

skeletal muscle is voluntary, and cardiac and smooth muscles are involuntary

Tropomyosin

strands of tropomyosin cover the sites of G-actin and prevent actin-myosin interaction

The endomysium __________.

surrounds the individual muscle fiber

A muscle that assists the muscle that is primarily responsible for a given action is a(n)

synergist

Fixators

synergists that assist by preventing movement at another joint

Muscles that laterally rotate the thigh include all of the following except the

tensor fasciae latae.

Within a resting skeletal muscle fiber, where is the greatest concentration of Ca2+?

terminal cisternae of the sarcoplasmic reticulum

oxygen debt

the amount of oxygen required after physical exercise to convert accumulated lactic acid to glucose

Which of the following groups of muscles are not muscles of the shoulder?

the anterior flexor muscles

What has the greatest concentration of calcium?

the concentration of calcium ion in the sarcoplasmic reticulum of a resting muscle

In a first-class lever __________.

the fulcrum lies between the applied force and the load

Acetylcholine binds to its receptor in the sarcolemma and triggers __________.

the opening of ligand-gated cation channels

Which joint is considered the most flexible joint in the body?

the shoulder joint

Explain the function of sodium-potassium ion pumps.

the sodium-potassium ion pump maintains the resting membrane potential of a cell by exporting three sodium ions out in exchange for two potassium ions entering the cell

muscle fibers

they are sheathed in a delicate endomysium

Myosin molecules form what part of the sarcomere?

thick filament

actin

thin filaments

A muscle that dorsiflexes the foot is the

tibialis anterior

The prime mover of elbow extension is the __________.

triceps brachii

The muscle that extends the arm while doing push-ups is the

triceps brachii.

When the sarcomere is at rest, what is covering the active sites on actin?

tropomyosin

At rest, active sites on the actin are blocked by

tropomyosin molecules

When calcium is released inside a muscle cell, what does it bind to?

troponin

Which thin filament-associated protein binds two calcium ions?

troponin

Which of the following muscles of the thigh is located most anteriorly?

vastus medialis muscle

muscle metabolism

when muscle are in use, lots of ATP is needed. This ATP comes from three sources: Creatine phosophate, Anaerobic cellular respiration, and Aerobic cellular resperation.

When does a muscle contraction begin?

when stored calcium ions are released into the sarcoplasm through gated calcium channels

Origin

where fixed end of a skeletal muscle attaches -Most are bones -Some are connective tissue sheaths or bands -Typically proximal to insertion in anatomical position

Insertion

where the movable end of a skeletal muscle attaches

Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP?

white fast twitch fibers

Which exercise below would be best at exercising the palmaris longus?

Holding a dumbbell in a supinated grip with arm horizontal and flexing the wrist

How would a torn calcaneal tendon affect movement at the ankle?

It would make extension difficult.

Occipitofrontalis (frontal belly)

Origin: Epicranial aponeurosis Insertion: Skin of eyebrow and bridge of nose Action: Raises eyebrows, wrinkles forehead

Orbicularis oris

Origin: Maxilla and mandible Insertion: Lips Action: Compresses, purses lips

Orbicularis oculi

Origin: Medial margin of orbit Insertion: Skin around eyelids Action: Closes eye

Inferior rectus

Origin: Sphenoid around optic canal Insertion: Inferior, medial surface of eyeball Action: Eye looks inferiorly

Buccinator

Origin: aveolar processes of the maxillae and mandible Insertion: corner of the mouth Action: compress cheeks

Platysma

Origin: fascia of chest Insertion: lower mandible Action: draws mouth downward

Lateral rectus

Origin: sphenoid around optic canal Insertion: lateral surface of eyeball Action: eye looks laterally

Superior rectus

Origin: sphenoid around optic canal Insertion: superior surface of eyeball Action: eye looks superiorly

superior oblique

Origin: sphenoid around optic canal Insertion: superior, lateral surface of eyeball Action: eye rolls, looks inferiorly and laterally

temporalis

Origin: temporal bone Insertion: mandible Action: closes jaw

Masseter

Origin: zygomatic arch Insertion: mandible Action: elevates mandible

Zygomaticus major

Origin: zygomatic bone Insertion: angle of mouth Action: retracts and elevates corner of mouth

The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________.

Pyruvic acid is converted back to lactic acid.

Calcium entry into the axon terminal triggers which of the following events?

Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.

myosin

The contractile protein that makes up the thick filaments of muscle fibers

How does the myosin head obtain the energy required for activation?

The energy comes from the hydrolysis of ATP.

Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?

The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.

Which of the following is correct regarding muscle fatigue and recovery?

During the recovery period, lactate can be recycled back to pyruvate.

Which of the following processes produces 36 ATP?

Krebs cycle and oxidative phosphorylation

Myofibrils

Microscopic protein filaments that make up muscle cells.

What happens to the lactate produced by skeletal muscle during peak activity?

Most of the lactate diffuses into the bloodstream and enters the liver where it is converted to pyruvate.

Which of the following statements is true concerning motor units?

Movement of the eyeball requires fewer muscle fibers with less tension being produced.

Define muscle hypertrophy and muscle atrophy

Muscle hypertrophy is an increase in the size of the muscle cells and muscle atrophy is a decrease in the size of the muscle cells.

Name the three types of muscle tissue, identify where they are found, and list their functions.

Skeletal muscle is directly or indirectly attached to bones and enables movement of the body. Cardiac muscle forms the heart and propels blood. Smooth muscle is found throughout the body and moves substances through hollow tubes, such as in the digestive tract and regulates the diameter of blood vessels.

Which of the following events must happen for the movement of the thin filament toward the M line (the center of the sarcomere)?

The myosin head binds to the active site on actin and pivots toward the M line.

What happens immediately after the myosin head binds to the active site on actin?

The myosin head pivots, moving the actin strand.

The interaction between the contractile proteins repeats over and over during a single contraction of a muscle cell. Which of the following choices allows the repeated separation and reactivation of the myosin head?

The presence of ATP

Explain why the propagation of action potentials along electrically excitable membranes occurs in only one direction

The refractory period prevents it from propagating back in the direction from which it began.