Unit 3 Test Human anatomy

The basic function of skeletal muscles is to contract in order to generate a force called muscle tension. The ability to generate muscle tension allows skeletal muscles to produce body movements, or actions, as they are called in muscle physiology. Tension production also enables muscles to perform another task—generate heat.

Summarize the major functions of skeletal muscles.

A spiral muscle may wrap around a bone or have the twisted appearance of a towel wrung out to dry (e.g., the supinator muscle in the forearm).

What is a Spiral muscle

Synergists (SIN-er-jists) are muscles that work together with the agonist. But synergists are more than just "secondary movers"—they help guide the movement and ensure it is smooth.

What is a Synergist muscle?

Line bisecting the I band. Both the thin and elastic filaments anchor to the Z-discs, which also attach myofibrils to one another

What is a Z-disc

a circular muscle encircles a structure, such as the opening of the eye, to close or constrict it when it contracts ex. the orbicularis oculi muscle. Circular muscles are often referred to ​as sphincters

What is a circular Muscle

A convergent muscle is broad at one end and uniformly tapers to a single tendon (see Figure. Triangular muscles, such as the pectoralis major muscle in the chest, usually have a convergent fascicle arrangement.

What is a convergent muscle

A first class lever is a lever system in which the fulcrum is located between the applied force and the load to be moved. In a First-class lever, the load to be moved is on one side of the lever, the fulcrum is in the middle, and the force is applied to the other side of the lever. An example of a first-class lever, is a simple seesaw. In the body we can compare this to the atlanto-occipital joint.

What is a first class lever

A fusiform muscle is thicker in its belly, or middle region, and tapered at its ends (e.g., the biceps brachii muscle.

What is a fusiform muscle

The specialized region of the skeletal muscle fiber plasma membrane that contains receptors for acetylcholine

What is a motor end plate

A neuron that transmits motor impulses from the central nervous system to a muscle or gland cell

What is a motor neuron

The location where a neuron communicates with a muscle fiber

What is a neuromuscular junction?

A pennate muscle has fibers and fascicles that attach to the tendon at an angle in such a way that the muscle resembles a feather. The pennate pattern has three basic variations.

What is a pennate muscle

A second class lever in which the fulcrum is located farther from the applied force, with the load moved in between. the load to be moved is in the middle, and the force to move the load is applied on the other end of the lever. An example of a simple second-class lever is a dolly. Second-class lever systems are uncommon in the body, but one example is the motion of rising up on your toes. In this example, the metatarsophalangeal joints are the fulcrums and the weight of the body in the middle is the load. The force is provided by contraction of the posterior leg muscles—as they contract, they lift the body's weight up onto the toes.

What is a second class lever

The location where presynaptic neuron communicates with its target cell

What is a synapse

a membrane-enclosed structure in an axon terminal that contains neurotransmitters

What is a synaptic vesicles?

The Endomysium blends with surrounding connective tissue and so is often referred to as connective tissue. The endomysium holds the muscle cells together within muscle tissue and transmits tension generated by muscle cells to neighboring cells.

what is the endomysium?

Elastic filaments serve several purposes in addition to holding the thick filaments in place. Some of these functions include resisting excessive stretching and providing elasticity to the muscle fiber—that is, helping it to "spring" back to its original length after it is stretched.

what is the purpose of elastic filaments

myogram

An instrument records the twitch and generates a recording known as a

Skeletal: Long, cylindrical striated muscle fibers; cells are multinucleated function: produces movement of the body; Cardiac: Short, wide, branching striated cardiac muscle cells with intercalated discs; cells have a single nucleus or two nuclei. Its an involuntary muscle and the function is to produce a beating heart. Smooth: Thin, smooth muscle cells, generally joined by gap junctions; cells have a single nucleus they are involuntary and their function is to change the diameter of hollow organs causes hair to stand up and adjusts the shape of the lens and pupil of the eye

Compare and contrast skeletal, cardiac, and smooth muscle

Muscle names based on size use words such as major, minor, longus, brevis (brief or short), or vastus (vast or broad). Those based on location use directional terms like superior, inferior, medial, and lateral, often slightly modified based on their Greek or Latin roots. For example, the vastus lateralis muscle of the thigh is a broad muscle on the lateral side of the femur. Some muscles have names that reveal the structures to which they attach. For instance, let's look at the sternocleidomastoid muscle. The name of this neck muscle sounds complex, but within its name you can learn that it is attached to the sternum (sterno-), clavicle (cleido-), and mastoid process of the temporal bone.

Explain how the name of a muscle can help to identify its action, appearance, &/or location.

anaerobic catabolism

Glycolysis requires no oxygen directly, which is why it is sometimes called_____However, the fate of the product of glycolysis depends on the availability of oxygen to the muscle fiber.

First the I bands and H zone narrow. This happens because the myosin heads of the thick filaments "grab" the thin filaments and pull them toward the M line. This pulling action brings the Z-discs closer together and causes the sarcomere as a whole to shorten. Remember, though, that none of the filaments themselves actually shorten—the thin filaments simply move toward the M line.

How do sarcomere change during contraction?

True

In contractions the filaments do not shorten. T or F

excitation-contraction coupling

Once a muscle fiber is excited by such stimulation, a process called______?

ACh release stops, the remaining ACh in the synaptic cleft is broken down, and the calcium ion concentration in the cytosol returns to its resting level.

What are the three components to muscle relaxation?

muscle twitch

The smallest muscle contraction, known as a _______, is the response of a muscle fiber to a single action potential in a motor neuron.

a myofilament that consists of the structural protein titin

What are elastic filaments

Myofibrils are long cylindrical organelles composed of muscle proteins in a muscle fiber

What are myofibrils?

A large muscle of the facial expression is the epicranius muscle, which is composed of two distinct muscle bellies: the frontalis and occipitalis muscles. The greater portion of the epicranius muscle is not actually muscle tissue, but a sheet of connective tissue called the epicranial aponeurosis that connects the two muscle bellies. The most important actions of this muscle are to elevate the eyebrows and skin of the forehead into horizontal wrinkles, as we do when looking surprised.

What are some muscles of the facial expressions

Enlarged regions of the sarcoplasmic reticulum where it contacts t-tubules

What are terminal cisternae

The ​masseter muscle​ is a thick, bandlike muscle that originates from the zygomatic arch and inserts into the lateral surface of the mandible. The ​temporalis muscle​ is a fan-shaped, convergent muscle that originates from the flat portion of the temporal bone and inserts into the coronoid process of the mandible. Together, these two muscles provide much of the force needed for elevating the mandible to masticate.

What are the muscles of mastication?

Just before we begin to swallow, muscles of mastication elevate the mandible. At the same time, muscles originating from the temporal bone and mandible and inserting into the hyoid bone contract, an action that elevates the hyoid bone. When this bone is elevated, the tongue and floor of the mouth rise in preparation for swallowing, and food is pushed posteriorly toward the pharynx. Muscles involved in these movements include the ​digastric​, ​stylohyoid​, ​mylohyoid​, and ​geniohyoid​ muscles.

What are the muscles that help push food posteriorly toward the pharynx?

contractility, excitability, conductivity, distensibility, elasticity

What are the properties of muscle cells

Three important muscles move the skin around the eyes: the orbicularis oculi, levator palpebrae superioris, and corrugator supercilii muscles. As we mentioned previously, the orbicularis oculi muscle is a circular muscle surrounding the orbit and within the eyelids of each eye. One action of this muscle is to pull the eyelid closed, as in blinking or winking. Its antagonist, the levator palpebrae superioris muscle, is located posterior to the orbit. It inserts into the connective tissue and skin of the upper eyelid and pulls it open. Both the orbicularis oculi muscle and the corrugator supercilii muscle produce squinting: The orbicularis oculi muscle draws the skin around the eye like a purse string, and the corrugator supercilii muscle pulls the eyebrows inferiorly and medially to produce vertical wrinkles, as in frowning.

What are the three muscles that move the skin around the eyes?

thick filaments, thin filaments. and elastic filaments

What are the three types of myofilaments?

The medial pterygoid muscle originates from the posterior mouth and pharynx (throat) mostly by attachment to the pterygoid process of the sphenoid bone. It then inserts along the inner surface of the inferior mandible, which allows it to elevate the mandible as a synergist to the masseter and temporalis muscles. Notice in the figure that the lateral pterygoid muscles attach at a different angle than the other muscles of mastication, originating from the sphenoid bone and inserting into the mandibular condyle near the temporomandibular joint. This allows them to depress (lower) the mandible rather than elevate it. The lateral pterygoid muscles also work together with the medial pterygoid muscles to produce two additional actions: They pull the mandible forward, an action known as protraction, and they produce the side-to-side movements necessary for grinding food during mastication.

What are the two additional muscles for mastication?

(1) reactions in the cytosol that immediately add a phosphate group to ADP, (2) glycolytic catabolism in the cytosol, and (3) oxidative catabolism in the mitochondria.

What are three ways that Atp regeneration can occur

Hallow inward extensions of the muscle fiber sarcolemma that surround myofibrils; filled with extracellular fluid

What are transverse tubules

The pivot or hinge point around which movement is produced when a muscle or group of muscles contracts.

What does fulcrum mean? What is the degree of movement?

myosin looks somewhat like two golf clubs twisted together, with two globular "heads" and two intertwining polypeptide chains making up a "tail." The heads protrude from the myosin tail on a "neck." The neck of each myosin protein is flexible where it meets the tail at a point called the hinge. Each myosin head includes a site that binds to a thin filament, among other functional components

What does myosin look like

transmission of a signal from the motor neuron to the sarcolemma of a muscle fiber. This phase, which occurs at the neuromuscular junction

What does the excitation phase involve?

A parallel muscle has evenly spaced fascicles attaching to a tendon that is about the same width as the muscle. This orientation often produces a straplike muscle, an example of which is the sartorius muscle in the thigh.

What does the fascicle pattern and muscle shape when its parallel

the ability of cells to contract. You might think that "contracting" means "shortening," but the term contraction actually refers to the ability of proteins within muscle cells to draw together, a muscle cell does not necessarily shorten when it contracts.

What is Contractility?

Muscle cells can also return to their original shape after being stretched, a property called elasticity. Often, elasticity is mistaken for stretch, but distensibility, not elasticity, refers to stretch.

What is Elasticity?

Muscle cells are excitable or responsive, in the presence of various stimuli; these might include chemical signals from the nervous or endocrine systems, mechanical stretch signals, or local electrical signals. Such stimuli generate electrical changes across the plasma membrane of the muscle cell.

What is Excitability

Between 10 and 100 muscle fibers are bundled together into a group known as a fascicle, which is surrounded by a connective tissue sheath called the perimysium.

What is Perimysium

It is the plasma membrane of a muscle fiber

What is Sarcolemma?

The A band is the dark region of a striation, which contains thick filaments. Thick filaments block more light than thin filaments, making the A band appear darker in micrographs.

What is a "A band"

The I band is the light region of a striation. It appears lighter because it contains only thin filaments, which allow more light to pass through them.

What is a "I band"

A fascicle which is surrounded by a connective tissue sheath called the perimysium. All the fascicles in a muscle are surrounded by another layer of connective tissue, the epimysium. The epimysium is continuous with the most superficial connective tissue sheath, known as the fascia, which separates individual muscles from one another. These interconnected connective tissues merge and taper down to become tendons or other structures that attach the muscle to the bone or other part that the muscle moves.

What is a Fascicle

Fixators are muscles that hold a bone in place, an anchoring function that makes movement more efficient and reduces the risk of injury. You can easily visualize the role of a fixator if you imagine trying to push open a door while wearing roller blades. If you're not careful, you are just as likely to push yourself backward as you push the door forward. But if you lock the wheels of the roller blades in place, all of your force goes forward into opening the door. In our example of lifting the glass of water, several scapular muscles, such as the supraspinatus muscle, act as fixators of the shoulder joint. Without the actions of these fixators, the movement wouldn't be smooth and water would splash out of the glass.

What is a Fixator muscle

A third class lever in which the applied force is closer to the fulcrum, which the load is moved farther away from the fulcrum. In a Third-class lever system, the load to be moved is on one end of the lever, the force moving the load is applied in the middle, and the fulcrum is at the other end of the lever. An everyday example of a third-class lever is a pair of tongs. Third-class lever systems are very common in the body, as illustrated with a muscle to which you've already been introduced—the biceps brachii muscle. In the figure, note that the fulcrum is at the elbow joint and the load is the weight of the forearm and hand. The force that moves the forearm and hand is the contraction of the biceps brachii muscle. As you can see, this muscle inserts between the elbow (the fulcrum) and the forearm and hand (the load).

What is a third class lever

a t-tubule and two adjacent terminal cisternae in a muscle fiber

What is a triad

A neurotransmitter involved in a wide variety of processes, including those of the autonomic nervous system and muscle contraction

What is acetylcholine?

is a bead shaped contractile proteins found in muscle fibers and motile cells

What is actin?

an agonist muscle provides most of the force required for a given movement also known as a prime mover. An agonist is typically easy to identify as one of the larger muscles spanning the joint to be moved.

What is an agonist muscle

The antagonist usually lies on the opposite side of a joint from its agonist partner, and tends to oppose and slow the action. Many of our slower, more graceful movements result from highly controlled action by antagonists. Gymnastics, ballet, and yoga all involve carefully balancing the force of agonists and antagonists. Even lifting a glass of water requires an antagonist: the triceps brachii muscle.

What is an antagonist muscle

a knoblike structure at the end of an axon that contains synaptic vesicles with neurotransmitters

What is an axon terminal

When a muscle cell is excited, the electrical changes across the plasma membrane do not stay in one place. Instead, they are rapidly conducted along the entire length of the plasma membrane, similar to how an electrical impulse is conducted through a copper wire.

What is conductivity?

Most cells will rupture when stretched, but muscle cells are distensible—they can be stretched up to three times their resting length without damage. Distensible is a property of a cell by which it can be stretched without damage

What is distensibility

This potential is simply a local depolarization in the area of the motor end plate.

What is end-plate potential?

A series of ATP-producing reactions that occur in the cytosol of cells in which glucose is broken down into two molecules of pyruvate; these reactions do not require oxygen to proceed

What is glycolytic or anaerobic catabolism?

A club-shaped contractile protein found in muscle fibers and cells that are motile.

What is myosin?

The middle line of the A band; contains structural proteins that hold the thick filaments in place

What is the "M" line

The middle portion of the A band in which only thick filaments are found

What is the H zone

Deep to the fascia is another layer of connective tissue, the epimysium, which surrounds the whole muscle. The epimysium blends with a deeper layer of connective tissue, the perimysium, to form tendons, which bind the muscle to its attaching structure.

What is the epimysium

Latent period. The latent period is the 1- to 2-ms (millisecond) time that it takes for the action potential to spread through the sarcolemma. It begins with the start of the action potential, and by the end, the action potential has spread past the T-tubules and triggered the release of calcium ions from the terminal cisternae of the SR. These ions then bind to troponin, and tropomyosin moves away from the active sites of actin. The myofibril is now ready to enter a crossbridge cycle. Note that

What is the first stage of a muscle twitch

1. Acetylcholinesterase degrades the remaining ACh, and the final repolarization occurs.

What is the first step to muscle relaxation

1. An action potential arrives at the axon terminal and triggers Ca2+ channels in the axon terminal to open. An action potential from the brain or spinal cord reaches the axon terminal of the motor neuron.

What is the first step to the excitation phase?

4. Acetylcholine binds to ligand-gated ion channels in the motor end plate. ACh diffuses across the cleft until it reaches and binds to ACh receptors on the motor end plate. These receptors are ligand-gated ion channels in the sarcolemma.

What is the fourth step of the excitation phase?

Troponin shifts and pulls tropomyosin back into position to block the active sites of actin, and the muscle relaxes

What is the fourth step to muscle relaxation

A lever system has four components: (1) the lever itself; (2) the load, or object, you are trying to move; (3) the force applied to the lever to move the load; and (4) the fulcrum, or hinge point, around which the lever moves. In moving the body, the bones are the levers, the load is the weight of the body part being moved, the force is the tension generated by muscle contractions, and the fulcrum is the joint at which the movement occurs.

What is the lever system

The sarcoplasmic reticulum is the specialized smooth endoplasmic reticulum of a muscle fiber that stores calcium ions

What is the sarcoplasmic reticulum

2. Calcium ion entry triggers exocytosis of synaptic vesicles. The action potential causes voltage-gated calcium ion channels in the membrane of the axon terminal to open, and calcium ions follow their electrochemical gradient and enter the cytosol of the axon terminal. This entry of calcium ions triggers exocytosis of the synaptic vesicles.

What is the second step of the excitation phase?

The sarcolemma returns to its resting membrane potential, and calcium ion channels in the SR close.

What is the second step to muscle relaxation

6. Entry of sodium ions depolarizes the sarcolemma locally, producing an end-plate potential. As sodium ions enter the fiber, a small area of the sarcolemma depolarizes, producing an effect called an End-plate potential. This potential is simply a local depolarization in the area of the motor end plate.

What is the sixth stage in the excitation phase?

The mechanism of contraction of a muscle cell in which the thin and thick filaments slide past one another while creating tension

What is the sliding-filament mechanism?

the small space between the axon terminal of a presynaptic neuron and its target

What is the synaptic cleft

Calcium ions are pumped back into the SR, returning the calcium ion concentration in the cytosol to its resting level. Active transport pumps in the SR membrane consume ATP to pump calcium ions from the cytosol back into the SR. This activity decreases the calcium ion concentration of the cytosol, returning it to its resting level.

What is the third step to muscle relaxation

titin is shaped like a spring that can uncoil when stretched and recoil to its original shape when the stretching force is removed. Titin runs through the core of the thick filament, which helps to stabilize the myofibril structurally (you can't see titin through the thick filaments in the figures because it is inside them)

What is titin?

tropomyosin a filamentous regulatory proteins that covers the active sites of actin subunits in a thin filament

What is tropomyosin

a regulatory proteins with three subunits that binds tropomyosin and calcium ions in a thin filament

What is troponin?

The platysma muscle is a broad, flat, sheetlike muscle found in the superficial neck. It helps produce that open-mouthed, "jaw-dropping" look of horror, and also tightens the skin of the neck.

What muscle aids with the jaw dropped look?

The orbicularis oris muscle Although this muscle is involved in facial expressions, it also controls the fine movements of the lips that are critical for eating, drinking, whistling, and proper speech. This muscle is now understood to have four curved quadrants (two per lip), which gives the muscle finer control over the lips.

What muscle controls fine movement of the mouth?

The buccinator muscle is the main muscle of the cheek (remember that the buccal region is the region over the cheek). This muscle pulls the cheeks inward, as we do when sucking, chewing food, or whistling.

What muscle has more subtle effects on facial expression?

The zygomaticus major and zygomaticus minor muscles insert into the skin and connective tissue around the corners of the mouth and so assist with smiling. Also attaching to the corners of the mouth are the ​risorius muscles​. This causes them to pull the corners of the mouth laterally to produce a closed-mouth smile or smirk.

What muscles assist with smiling/ smirking?

The depressor anguli oris, depressor labii inferioris, and mentalis muscles. The latter two muscles also protract (protrude) the lower lip, contributing to looks that might be described as pouting or doubting.

What muscles contribute to frowning?

The levator labii superioris muscle , which inserts into the skin of the upper lip, pulls the lip superiorly in folds, to produce a grimace or sneer.

What muscles make the grimace or sneer?

the two regulatory proteins tropomyosin and troponin help switch on and off the process of muscle contraction

What two regulatory proteins aid with muscle contraction?

contractile proteins, which produce tension; regulatory proteins, which control when the muscle fiber can contract; and structural proteins, which hold the myofilaments in their proper places and ensure the structural stability of the myofibril and the muscle fibe

What type of proteins are in myofilaments?

a single cycle of contraction and relaxation of a muscle fiber generated by a single action pontential

Whats a muscle twitch

Muscle proteins that make up a myofibril in a muscle fiber

Whats a myofilament?

5. Ion channels open and sodium ions enter the muscle fiber. When ACh binds, the ligand-gated ion channels of the ACh receptors open and allow sodium ions to follow their electrochemical gradient and enter the muscle fiber.

Whats the fifth step in the excitation phase?

3. Synaptic vesicles release acetylcholine into the synaptic cleft. These vesicles release the neurotransmitter ACh into the synaptic cleft between the axon terminal and the motor end plate of the muscle fiber.

Whats the third step of the excitation phase

Stored ATP

When contraction begins the main energy source of muscle fiber is ____.

Glycolytic or anaerobic catabolism

When immediate energy sources are depleted, muscle fibers turn to glycolysis, also known as______ to make ATP

They originate from connective tissue anterior to the ear and so course almost directly across the face.

Where does the muscles that make you smile originate

The muscles of facial expression differs from other muscles because they dont cause movement at a joint instead most of them insert into skin or connective tissue rather than bone, and so their actions produce shape changes to the skin and structures of the face.

Why are the facial muscles different from other muscles

Creatine phosphate

______ found in muscle fibers is about 5-6 times more abundant than ATP in the Cytosol