Chapter 9: Muscular System

List in order the events leading to excitation of a muscle fiber.

1. Nerve impulse arrives at distal end of axon. 2. Acetylcholine is released. 3. Acetylcholine diffuses across synaptic cleft. 4. Acetylcholine binds to its receptors on the muscle fiber sarcolemma. 5. The permeability of sarcolemma to sodium ions increases.

Place in order the steps leading to the relaxation of muscle.

1. Nerve signal ceases. 2. Acetylcholine release into the synaptic cleft stops and ACh already in synaptic cleft is broken down. 3. Calcium is actively transported into the sarcoplasmic reticulum and Ca2+ diffuses away from troponin. 4. Troponin returns to its relaxed configuration, causing tropomyosin to cover the myosin binding sites on actin.`

The process of a neuron, its axon, conducts electrical impulses called ______ ______ towards the end of the axon that innervates a target cell.

action; potential/potentials

A muscle that functions to cause an action is referred to as the ______.

agonist

The process of glycolysis is ______.

anaerobic

Glycolysis is used to produce ATP for muscle contraction and is best described as ______.

anaerobic breakdown of glucose to produce ATP

Muscles found on the ______ surface of the humerus cause flexion of the forearm at the elbow.

anterior

The flexors of the hand are located on the _____ side of the forearm.

anterior

Muscles of the _________ muscle group flex the knee and those of the ______ muscle group extend the knee.

hamstrings; quadriceps muscles

Muscle contractions generate _____, which is important for the overall functioning of the body.

heat

During a(n) ______ muscle contraction, the muscle either lengthens or shortens, while the tension stays constant.

isotonic

The muscles of mastication include the medial and lateral pterygoid, ______ and ______.

masseter/masseter muscle; temporalis/temporalis muscle

Muscles that move the thigh are attached to the ______ girdle and the ______.

pelvic; femur

On this diagram of the shoulder and arm, the arrow indicates the ______ muscle.

subscapularis

When the frequency of stimulation of a muscle fiber increases, eventually the individual twitches combine by the process of ______ which results in a sustained contraction.

summation

Muscle fatigue is a condition described by _____, and is usually caused by prolonged use of a muscle.

the loss of a muscle's ability to contract

What generates the force that shortens the sarcomeres to bring about muscle contraction?

Myosin cross-bridges pulling on the actin filaments

Which of the following muscles is a flexor of the hand?

Palmaris longus

Which of the following is a characteristic of slow-twitch (type I) fibers?

Red in color

Which type of motor unit is more easily stimulated and, thus, is recruited first?

Small motor units (fewer muscle fibers)

What type of muscle cells lack striations?

Smooth muscle

Which type of muscle can change length without changing tautness?

Smooth muscle

When a muscle fiber is stimulated at a high enough frequency that it doesn't have time to relax, the forces of the individual twitches combine. What is this process called?

Summation

To move the foot upward towards the shin is known as ______. To turn the sole of the foot medially is known as ______.

dorsiflexion/dorsiflex; inversion/invert

The ______ diaphragm is the deep layer of muscle at the pelvic outlet, serving to support the pelvic viscera.

pelvic

What four pairs of muscles are considered muscles of mastication?

- Masseter - Temporalis - Medial pterygoid - Lateral pterygoid

List the four components of a lever.

- Object to move - Force - Rigid bar or rod - Pivot point

In order for muscles to move the thigh, they need to have attachments (origins and insertions) at what two areas?

- Pelvic girdle - Femur

What is a motor unit composed of?

- Several muscle fibers - A single motor neuron

What are the three types of muscles found in the human body?

- Smooth - Cardiac - Skeletal

Choose all characteristics of slow-twitch fibers.

- They are also called red fibers. - They contain large amounts of myoglobin. - They are well supplied with capillaries and mitochondria.

Which of the following are muscles that move the pectoral girdle?

- Trapezius - Levator scapula - Rhomboid major - Serratus anterior

Which three characteristics are signs of aging in the muscular system?

- Weak contractions - Slow reflexes - Atrophy

On this diagram depicting muscles in the back, match each letter with the name of the muscle.

A : Deltiod B : Trapezius C : Latissimus dorsi D : Rhomboid major

Match each facial muscle with the arrow that points to it.

A : Masseter B : Orbicularis oculi C : Orbicularis oris D : Platysma E : Sternocleidomastoid

Use this diagram of the anterior shoulder and arm to match the letters to the muscles they indicate.

A : Subscapularis B : Coracobrachialis C : Deltoid E : Biceps brachii

What is a muscle fascicle?

A bundle of skeletal muscle fibers

What is a muscle fiber?

A muscle cell

What is an isotonic contraction?

A muscle changes in length, but its tension stays constant.

During excitation of a muscle fiber, which one of the following events comes immediately after the release of acetylcholine from the motor neuron?

Acetylcholine diffuses across the synaptic cleft

What is the name of the process on a neuron that carries electrical impulses toward the cell to be stimulated?

Axon

The latissimus dorsi muscle is indicated by letter ______.

C

Muscle tissue that has a well-developed sarcoplasmic reticulum, many mitochondria, and branching cells with one nucleus is classified as ______ muscle.

Cardiac

Which of the following are types of muscles and are involuntary?

Cardiac

Which type of muscle has striated cells that form interconnected, branching, three-dimensional networks?

Cardiac muscle

What is the first source of energy that is used to convert ADP to ATP after a contraction in a skeletal muscle cell begins?

Creatine phosphate

By definition, what is muscle fatigue?

Decreased ability of a muscle to contract

Match the action of the foot with the description.

Dorsiflexion : Move the foot upwards Plantar flexion : Move the foot downward Inversion : Turn the sole of the foot medially Eversion : turn the sole of the foot laterally

When is lactic acid produced?

During anaerobic metabolism

True or false: Myofilaments shorten during contraction.

False

Place the muscles into the appropriate category based on the action on the knee.

Flex the knee : Biceps femoris; Semitendinosus; Semimembranosus Extend the knee : Vastus lateralis; Vastus medialis; Rectus femoris

Match muscles responsible for forearm movements (at the elbow joint) to their actions. Instructions

Flexion : Biceps brachii; Brachioradialis Extension : Triceps brachii Rotation : Supinator; Pronator quadratus

Which facial muscle is indicated by the arrow?

Frontalis

Why does summation result in an increased force of contraction?

Individual twitches combine due to high frequency of stimulation.

What is the role of creatine phosphate during skeletal muscle contraction?

It is used to quickly regenerate ATP from ADP.

Consider the naming of the temporalis muscle. What does the name tell you about the muscle?

It provides information about the locations of the origins and/or insertions for the muscle

Consider the naming of the triceps brachii muscle. What does the name tell you about the muscle?

It provides information about the number of heads (origins)

Which type of motor unit produces more force when recruited?

Large motor unites (more muscle fibers)

Which end of a skeletal muscle is called its origin?

The end that is attached to a relatively unmovable or fixed part of a joint

What is the meaning of the term threshold stimulus?

The minimum strength of an electrical impulse that can stimulate contraction in an isolated muscle fiber

When describing the roles of muscles in an action, what is the role of the agonist?

To cause an action

What is the function of the linea alba?

To provide attachment for abdominal muscles

Of the following muscles, which one moves the pectoral girdle?

Trapezius

True or false: Muscles generate heat when they contract.

True

True or false: Muscles tend to atrophy with age.

True

A skeletal muscle fiber is ______.

a single muscle cell

During muscle relaxation, calcium levels in the sarcoplasm fall because _____.

calcium is actively transported into the sarcoplasmic reticulum

On this diagram showing muscles in the back, arrow A is pointing to the ______ muscle and arrow B is pointing to the ______ muscle.

deltoid; trapezius

A bundle of skeletal muscle fibers enclosed by a perimysium forms a(n) ______ within a muscle.

fascicle, muscle fascicle, or fasciculus

During high-intensity exercise, anaerobic metabolism results in the production of pyruvic acid, which is then converted to ______ acid.

lactic

When a part of the body moves, the muscles and bones responsible for the movement act as a mechanical device known as a(n) ______

lever or levers

Some abdominal muscles are attached to a band of connective tissue that extends from the xiphoid process of the sternum to the pubic symphysis called the ______ ______.

linea; alba

The point of attachment for a muscle that remains relatively stationary is its ______.

origin or muscle origin

The trapezius, the rhomboid major and minor, and the levator scapulae are all muscles that move the ______ girdle.

pectoral

The knee is flexed by the action of the three muscles in the hamstring group, and the ______ muscle.

sartorius

Compared to skeletal muscle, smooth muscle is ___ to contract and ___ to relax.

slower; slower

The cells of ______ muscle are tapered, lack striations, and have a sarcoplasmic reticulum that is not very extensive.

smooth

During muscle contraction, the sarcomeres shorten because ______.

thick and thin filament slide past one another, increasing their overlap

In a muscle contraction, the force that shortens the sarcomeres comes from the myosin cross-bridges pulling on the ______ filaments.

thin/actin

If a muscle fiber is subjected to stronger and stronger electrical impulses, it will initially be unresponsive until a strong enough impulse is applied which causes it to contract. The level of electrical stimulation needed to stimulate contraction is called the _______.

threshold stimulus

The muscles that move the foot attach the femur, ______, , and fibula to bones in the foot, generating four types of movement: dorsiflexion, plantar ______, inversion and eversion.

tibia; flexion

In excitation-contraction coupling, the protein called ______ moves to expose binding sites on the actin filaments that can form cross-bridges.

tropomyosin

During excitation-contraction coupling, calcium binds to ______.

troponin

When a single muscle fiber contracts when stimulated by a single impulse, the contractile response is called a(n) ______.

twitch

A muscle response called a(n) ______ consists of a period of contraction during which the fiber pulls at its attachment, followed by a period of ______ during which the pulling force decreases.

twitch; relaxation

Muscle fibers with abundant mitochondria and myoglobin that are typically red in color are called ______ fibers.

type I

A motor neuron and the muscle fibers that it controls constitute a motor ______.

unit

The ______ is part of the perineum, and is located within the pubic arch.

urogenital diaphragm