Anatomy & Physiology Exam 3

Muscle Physiology and The Muscular System

Which of the following is correct with respect to the structure and activity of the three types of muscle tissue?

1 nucleus per cell, unbranched, involuntary activity: Smooth

How is the sarcoplasm of muscle cells unique compared to other cells?

Many mitochondria, many nuclei

A single skeletal muscle fiber contraction is known as ______

a twitch

Which type of muscle fiber has a low amount of myoglobin?

Fast glycolytic fiber

During the cross bridge cycle, what causes the myosin head to become energized and oriented at a 90° angle?

Hydrolysis of ATP

What is the role of tropomyosin in regulating muscle contraction?

Blocks the myosin-binding sites on actin

T or F: Within a sarcomere the “I band” has only thin filaments and the “A band” has only thick filaments.

False

T or F: When voltage-gated sodium channels via action potential, a small part of the membrane is depolarized, which causes more voltage-gated sodium channels to open.

True

Which of the following are made of dense irregular connective tissue?

Epimysium, Perimysium

The strength of a muscle contraction increases with…

More motor units, multiple motor units responding, high frequency of stimulation

T or F: Both fast and slow oxidative fibers aerobically synthesize ATP in the mitochondria via oxidative phosphorylation.

True

Why do males generally have stronger muscle contractions than females?

Males have more muscle mass

During the cross bridge cycle, what causes the myosin head to detach from actin?

Binding to ATP

Which of the following best defines a motor unit?

A motor neuron and all the muscle fibers it innervates.

How does the size of a motor unit affect the strength of muscle contraction?

Larger motor units allow stronger, less precise contractions.

List the following structures of skeletal muscle from most to least inclusive (which surrounds the most other structures and which surrounds the fewest).

Epimysium, perimysium, fascicle, endomysium

Skeletal muscle fibers contain contractile protein fibers. Select the appropriate name match.

Myosin - thick filaments; Actin - thin filaments

Put the following steps of muscle contraction in the correct order:

I) sodium-channels open

II) calcium-channels open

III) acetylcholine is released

IV) depolarization of the sarcolemma

III, I, IV, II

Which of the following best describes the sliding filament mechanism during muscle contraction?

Actin filaments are pulled toward the M line, shortening the sarcomere.

All the following are characteristics of a single skeletal muscle fiber, except they are not __________.

singularly nucleated.

What is the function of the sarcoplasmic reticulum?

Calcium storage, release, and uptake

What is the functional significance of a motor unit in muscle contraction?

It allows fine control or powerful contractions depending on the number of fibers it controls.

Which of the following types of muscle tissue is correctly matched with its function?

Smooth: Move food, regulate blood pressure

The name “flexor carpi radialis” tells you the muscle _________.

flexes the wrist and is located near the radius.

A muscle with fascicles located on both sides of a central tendon is described as __________.

bipennate

During a biceps curl (flexion), the brachialis is acting as a ________.

synergist

The rectus abdominis is named according to its ________.

direction of fibers

Intercostal muscles are named based on their __________.

location

Orbicularis oris is an example of which fascicle arrangement?

Circular

When a muscle contracts, which part moves toward which?

insertion moves toward the origin.

Which of the following is named based on location?

Gluteus maximus

The orbicularis oculi is named for which combination?

Shape and location

Which term describes a muscle that assists the prime mover by adding extra force or reducing unnecessary movements?

Synergist

Muscles that are arranged with fascicles on one side of the tendon are called ______ muscles.

unipennate

Muscles with a fascicle arrangement that runs the length of the long axis of the muscle are described as:

Parallel

What are all the ways skeletal muscles can be named:

Size, Shape, Direction of fibers, Location, and Type of movement (action)

The adductor longus muscle is named for both its:

Size and Action

The immovable attachment site of a muscle is called its _________ and the movable attachment site of a muscle is called its _______.

origin, insertion

Which type and attachment involves the epimysium forming a tendon that attaches to bone?

Indirect attachment

The deltoid muscle displays which type of fascicle arrangement?

Multipennate

In elbow flexion, the triceps brachii acts as the:

Antagonist

The biceps brachii is named for which characterstics?

Number of origins

The term “minimus” in a muscle name tells you the muscle is:

Small

T or F: In direct attachments of skeletal muscles, the perimysium attaches to the bone.

False

Which fascicle arrangement has a broad origin and converges toward a single tendon insertion?

Convergent

The primary muscle responsible for producing a specific movement is called the:

Agonist

The term “oblique” in “external oblique” refers to:

The direction of muscle fibers

The sternocleidomastoid is named for:

Location of origins and insertion

If a muscle is named “triceps,” how many points of origin does it have?

Three

The Stages of the Cross Bridge Cycle:

1. Cross-Bridge Formation (myosin attaches to actin)

2. The Power Stroke (actin is pulled toward the M line)

3. Cross-Bridge Detachment (myosin lets go of actin)

4. Cocking the Myosin Head (myosin stands back up)

Steps in Muscle Contraction

1. A neuron releases acetylcholine (ACh)

2. Chemically-gated sodium (Na⁺) channels open

3. The membrane of a muscle fiber depolarizes

4. The calcium (Ca²⁺) channels are pushed open

5. Calcium binds to troponin

6. Tropomyosin unblocks the myosin-binding sites on actin

7. Myosin attaches to (and slides past) actin

Skeletal Muscle

Location: Attached to bones

Function: Move skeleton

Characteristics: Multinucleated, Unbranched

Movement: Activity is voluntary.

Cardiac Muscle

Location: Heart

Function: Pump blood

Characteristics: 1 or 2 nuclei, branched

Movement: Activity is involuntary.

Smooth Muscle

Location: Hollow organs, blood vessels, intestines, etc.

Function: Move food, help regulate blood pressure, etc.

Characteristics: Single nucleus, Unbranched

Movement: Activity is involuntary.