Chapter 9: Muscular System

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

a. masseter b. orbicularis oculi c. orbicularis oris d. platysma e. sternocleidomastoid

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

a. subscapularis b. coracobrachiallis c. biceps brachii d. deltiod

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

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

action potentials

A muscle that functions to cause 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

Contraction of muscles of the ______ group of the thigh is primarily responsible for flexion of the thigh at the hip.

anterior

Muscles that move the thigh at the hip joint are classified into three groups based on their location. The psoas major and the iliacus are members of the (blank) group.

anterior

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

anterior

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

axon

flexion

biceps brachii brachioradialis

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

hamstrings; quadriceps femoris

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

heat

What type of contraction is observed when a muscle shortens?

isotonic

The muscles of mastication include the medial and lateral pterygoid,(blank) and (blank) .

masseter;temporalis

The masseter, the temporalis, and the two pterygoid muscles are the four muscles responsible for ______.

mastication

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

pelvic girdle femur

Muscles that move the thigh are attached to the (blank) girdle and the (blank)

pelvic; femur

Muscles that move the thigh are attached to the (blank) girdle and the (blank) .

pelvic;femur

Contraction of muscles of the ______ group of the thigh can result in extension, abduction, or rotation of the thigh.

posterior

Where are the extensors of the hand located?

posterior side of forearm

A single muscle acts to extend the elbow joint. This muscle is located on the ______.

posterior surface of the humerus

The gluteus maximus and piriformis are part of the ______ group of muscles that move the thigh. The pectineus and gracilis are part of the ______ group.

posterior; medial

on this diagram of the shoulder and arm, the arrow indicates the (blank) muscle

subscapularis

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

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

summation

rotation

supinator pronator quadratus

What four pairs of muscles are considered muscles of mastication?

temporalis masseter lateral pterygoid medial pterygoid

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

Categorize the muscles that move the thigh, indicating whether each is found on the anterior, posterior, or medial group of the muscles.

Medial group: - adductor longus, adductor magnus, gracilis Posterior Group: - gluteus maximus, gluteus medius, tensor fasciae latae Anterior Group: - psoas major, iliacus

To move the foot upwards towards the shin is known as (blank) . To turn the sole of the foot medially is known as (blank)

dorsiflexion; inversion

When is lactic acid produced?

during anaerobic metabolism

How many myofibrils and sarcomeres are found in a muscle fiber?

each muscle fiber contains many myofibrils, each made of many sarcomeres joined end to end

What type of muscle cells lack striations?

smooth muscle

Which type of muscle can change length without changing tautness?

smooth muscle

List the four components of a lever.

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

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.

Indicate three characteristics of cardiac muscle.

-cells have large transverse tubules -single nucleus -cells have abundant mitochondria

Place the following steps of excitation-contraction coupling in order.

1. calcium is released from the sarcoplasmic reticulum 2. calcium binds to troponin 3. troponin changes shape and alters the position of tropomyosin 4. binding sites on actin filaments are exposed 5. myosin heads bind to actin

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

1. nerve impulse arrives at a distal end of the axon 2. acetylcholine is released. 3. acetylcholine diffuses across the 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 the muscle.

1. the nerve signal ceases 2. acetylcholine released into the synaptic cleft stops ACh already in the synaptic cleft is broken down 3. calcium is actively transported into the sarcoplasmic reticulum and Ca+2 diffuses away from troponin 4. troponin returns to its relaxed configuration, causing tropomyosin to cover the myosin binding sites on actin

Match the three groups of muscles that move the thigh to the type of movement produced at the hip joint.

Anterior group: - primarily flexes the hip Posterior group: - primarily extends the hip and abducts or rotates the thigh Medial Group: - primarily adducts the thigh

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

True or false: Myofilaments shorten during contraction.

False

Choose all characteristics of smooth muscle cells.

They are not striated. They have a single nucleus. Their sarcoplasmic reticula are not well developed.

True or false: Muscles tend to atrophy with age.

True

A sarcomere extends from one ______ to the next.

Z line

What is an isotonic contraction?

a muscle changes in length, but its tension stays constant

A skeletal muscle fiber is ______.

a single muscle cell

Match each letter with the correct facial muscle.

a. epicranial aponeurosis b. frontalis c. occipitalis d. temporalis

Match the labels to the correct muscles in the anterior thigh

a. iliacus b. tensor fasciae latae c. pectineus d. vastus medialis

What are myofibrils?

bundles of proteins in a muscle cell

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

cardiac muscle

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

cardiac, smooth,skeletal

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 muscle to contract

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

fascicle

Muscle cells are also known as muscle fibers. In a skeletal muscle, muscle fibers are found as bundles called (blank) , each enclosed in a connective tissue sheath, called the (blank) .

fascicle; perimysium

Prolonged or intense exercise can lead to a condition called muscle (blank) , defined as the loss of a muscle's ability to contract.

fatigue

Due to their shape, muscle cells are also called muscle (blank)

fibers

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

it is used to quickly regenerate ATP and 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 muscles

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)

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

lactic

Which type of motor unit produces more force when recruited?

large motor unites (more muscles fibers)

A fulcrum, a force, and an object moved against resistance make up a ______.

lever

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

lever

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 (blank) (blank)

linea alba

Muscles with attachment points at the (1) pelvic girdle and (2) the femur will cause what type of movement?

movement of the thigh

Which statements correctly describe changes in a skeletal muscle cell during muscle contraction?

muscles shorten during contraction sarcomeres shorten during contraction myofilaments overlap during contraction

The sarcoplasm of a muscle fiber contains many parallel structures made of proteins. These structures are called ______.

myofibrils

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

myosin cross-bridges pulling on the actin filaments

What are the two major protein types found in myofibrils?

myosin; actin

Within myofibrils, thick filaments are composed of the protein (blank) , while thin filaments primarily contain (blank) .

myosin; actin

What is a motor unit composed of?

one motor neuron and all the muscle fibers it innervates

The end of a muscle that is fixed (relatively immovable) is called its ______.

origin

The point of attachment for a muscle that remains relatively stationary is its (blank)

origin

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

pectoral

The thigh muscle labeled as A is the ______ muscle. The muscle labeled as B is the ______ muscle.

psoas major; iliacus

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

red in color

During which phase are calcium ions actively transported into the sarcoplasmic reticulum?

relaxation

Within myofibrils, the area between two successive Z lines is called a(n) ______.

sarcomere

Myofibrils are formed by many ______ positioned end-to-end.

sarcomeres

The (blank) are repeating units within muscle fibers that act as the functional units of muscle contraction.

sarcomeres

The membranous organelle within muscle fibers, called the (blank) reticulum, corresponds to the smooth endoplasmic reticulum of other cells.

sarcoplasmic

What is the name of the network of membranous channels that surrounds each myofibril within a muscle fiber?

sarcoplasmic reticulum

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

sartorius

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

slower;slower

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

small motor units (fewer muscle fibers)

During muscle contraction, the sarcomeres shorten because ______.

thick and thin filaments 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 (blank) filaments.

thin

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

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

trapezius rhomboid major serratus anterior levator scapula

extension

triceps brachii

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

tropomyosin

During excitation-contraction coupling, calcium binds to ______.

troponin

True or false: Muscles generate heat when they contract.

true

True or false: Smooth muscle can maintain a forceful contraction longer than skeletal muscle.

true

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

twitch

A muscle response called a(n) (blank) consists of a period of contraction during which the fiber pulls at its attachment, followed by a period of (blank) 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 1

For a typical muscle fiber in its optimal state, how many action potentials generated by a motor neuron must arrive at the neuromuscular junction to reach the threshold stimulus?

typically, a single action potential is enough to bring the muscle fiber to the threshold

A motor neuron and the muscle fibers that it controls constitute a motor (blank)

unit

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

urogenital

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

urogenital diaphragm

On this diagram of the muscles in the thigh, the letter D indicates

vastus lateralis

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

weak contractions slow reflexes atrophy