Chapter 9 Quiz - Muscles

The following layers are associated with skeletal muscles. Place them in order from superficial to deep.

(Superficial).....Fascia, Epimysium, Perimysium, Endomysium, Sarcolemma....(deepest).

Consider the elbow joint. Muscles such as the biceps brachii have their origin and insertion on the anterior of the arm. Thus, contraction of this muscle causes flexion of the elbow joint.

Biceps brachii; flexion

In order for muscle contraction to occur, cross-bridges form between __________.

Myosin and actin Cross-bridge formation allows the thick filaments to pull on the thin filaments in order to shorten the sarcomeres.

Name the type of synapse that occurs between a motor neuron and a muscle fiber.

Neuromuscular junction *Synapses between motor neurons and muscle fibers are the site of neurotransmitter release and stimulation of the muscle.

One end of a skeletal muscle attaches to a relatively immovable point called its origin and the other end attaches to a more movable point, called the insertion.

Origin; insertion

Within a skeletal muscle, fascicles are separated from each other by connective tissue called the __________ , and muscle fibers are separated from each other by connective tissue called the __________ .

Perimysium; endomysium Connective tissue within a skeletal muscle isolates the muscle components, allows the parts to move somewhat independently, and provides pathways for nerves and blood vessels.

Place in chronological order the events that occur at a neuromuscular junction.

1. Nerve impulse arrives at distal end of motor neuron axon. 2. Some vesicles release acetylcholine. 3. Acetylcholine diffuses across synaptic cleft. 4. Acetylcholine binds to receptors on motor end plate. 5. Membrane permeability to sodium is increased (opening of sodium channels). 6. Sodium enters muscle cell. 7. Triggers an electrical impulse along sarcolemma.

Complete the sentences describing the connective tissue associated with skeletal muscles. Then put the sentences in the correct order to list the connective tissue layers from superficial to deep.

1. The layer of connective tissue that closely surrounds a skeletal muscle is called the epimysium. 2. Another layer of connective tissue, called the perimysium, extends inward from the epimysium and separates the muscle tissue into groups of muscle fibers. These groups are called fascicles. 3. Each muscle fiber within a fascicle is surrounded by a thin covering called a(n) endomysium. 4. Therefore, as described, layers of connective tissue enclose and separate the various parts of a skeletal muscle. *The structure of a skeletal muscle is compartmentalized by a series of connective tissue layers.

Muscles that flex the wrist are found on the __________ side of the forearm while those that extend the wrist are found on the __________ side of the forearm.

Anterior; posterior *Flexion involves decreasing the angle of a joint. Therefore, muscles that act as flexors would be positioned so that their contraction decreases the joint angle. The opposite applies to extensors.

Label the connective tissue structures associated with skeletal muscle.

Aponeurosis and tendons

How does an electrical impulse travel into the interior of a muscle fiber?

By way of the transverse tubules The electrical impulse needs to get down into the muscle cell in order to stimulate the release of calcium from the sarcoplasmic reticulum.

Muscles that move the thigh have their insertions on the __________.

Femur; Recall that the insertion point for the muscle is the part that moves upon contraction.

A runner collapses during a race and is examined by a doctor. They have lost the ability to plantar flex at the ankle. Which of the following is probably the injured muscle?

Gastrocnemius

By dragging and dropping each muscle name, indicate whether it flexes or extends the leg at the knee.

Leg extensors and flexors

A __________ includes a motor neuron and all of the muscle fibers that it controls.

Motor unit *An impulse from one motor neuron stimulates contraction of all of the muscle fibers that it controls. If a stronger contraction is needed, more motor neurons can fire, stimulating more muscle fibers to contract.

Classify the muscles that move the thigh as being in the anterior, posterior, or medial group.

Muscle positions that move the thigh.

Each label lists a muscle that belongs to one of three groups of muscles. Drag and drop each label into the appropriate group.

Muscles of the hamstring, quadriceps and shoulder.

Identify the muscles that move the scapula and arm, as seen in this anterior view.

Muscles that move the arm and scapula

Classify the myograms based on frequency of stimulation.

See image

Match the action with the muscles of the anterior shoulder and arm.

See image

Label the myofibril and its components.

See image. *Muscle fibers are highly organized cells designed to contract and generate tension.

Determine whether each label describes skeletal or cardiac muscle.

Skeletal and cardiac muscle functions

Compare skeletal muscle to smooth muscle.

Smooth muscle takes longer to contract and can stay contracted longer than skeletal muscle. *While skeletal muscle and smooth muscle share some of the same characteristics, their development of contraction differs.

Transverse (T) tubules are invaginations of the sarcolemma of a muscle cell.

TRUE Transverse tubules allow electrical impulses to travel deep into a muscle cell.

Muscle fatigue is due in part to decreased ATP levels in muscle cells.

TRUE; Muscle fatigue occurs when the muscle loses its ability to contract. There are many potential causes of muscle fatigue.

Name the cordlike structures that connect muscles to bone.

Tendons *When muscles contract, the force that is generated is transferred to the bone through a series of connective tissue structures.

Certain natural plant poisons and animal venoms contain substances that inhibit the function of acetylcholinesterase. If a person is poisoned by one of these substances, which of the following will be the cause of their symptoms?

Their muscles will be in a constant state of contraction because acetylcholine won't be broken down and cleared from the neuromuscular junction.

The smallest stimulus strength that triggers a contraction in a muscle fiber is called a __________ stimulus.

Threshold; Generating a muscle twitch requires that the muscle fiber be stimulated at or above some minimal stimulus strength.

The neurotransmitter that is released at neuromuscular junctions and that stimulates skeletal muscle to contract is __________ .

acetylcholine *The neurotransmitter release at synapses with skeletal muscle results in stimulation of the skeletal muscle. If enough neurotransmitter is released into the synaptic cleft, contraction will result.

An electrical impulse traveling along the sarcolemma and into transverse tubules causes calcium ions to diffuse from the __________ into the __________ .

sarcoplasmic reticulum; sarcoplasm Calcium released into the sarcoplasm is necessary to cause a muscle contraction.

Which of the following best describes the role of calcium in muscle contraction?

It binds to troponin, moving tropomyosin, so that myosin heads can bind to actin. The binding of calcium to a component of the thin filament allows for the formation of myosin cross-bridges.

Of the energy released during cellular respiration, less than half is used to produce ATP. What is the fate of the rest of the released energy?

It is released as heat. The conversion of energy from one form to another is never 100%. There is always some energy lost.

Describe the role of acetylcholinesterase in stimulation of a muscle fiber.

It is the enzyme that breaks down acetylcholine in the synaptic cleft, ending stimulation of the muscle fiber. The activity of acetylcholinesterase leads to the relaxation of a muscle fiber.

The location of these attachment points determine the type of movement that occurs at a joint.

Joint

In contrast, contraction of the triceps brachii, located on the posterior aspect of the arm, will cause extension of the elbow joint.

Triceps brachii; extension

Calcium ions bind to __________ in order to initiate a muscle contraction.

Troponin The binding of calcium to a component of the thin filament allows for the formation of myosin cross-bridges.

What is the term for the contractile response of a single muscle fiber to a single muscle impulse?

Twitch; A twitch consists of a latent period, a period of contraction, and a period of relaxation.

Rigor mortis affects skeletal muscles a few hours after death, due to

a decrease in ATP and increased permeability to calcium.