Microscopic Anatomy and Organization of Skeletal Muscle Chapter 14

perimysium

connective tissue ensheathing a bundle of muscle cells

fascicle

Bundle of muscle cells.

sarcomere

contractile unit of muscle

fiber

a muscle cell

endomysium

thin reticular connective tissue surrounding each muscle cell

sarcolemma

plasma membrane of the muscle fiber

myofibril

a long filamentous organelle with a banded appearance found within muscle cells

myofilament

actin or myosin containing structure

tendon

cord of collagen fibers that attaches a muscle to a bone

List 3 reasons why the connective tissue wrappings of skeletal muscle are important.

1). Bundle the muscle fibers together, increasing coordination of there activity. 2). Add strength to the muscle. 3). Provide a route for entry and exit of blood vessels and nerves to the muscle fibers.

Why are there more indirect - that is, tendinous - muscle attachments to bone than there are direct attachments?

They conserve space (less bulky than fleshy muscle attachments) and are more durable than muscle.

How does an aponeurosis differ from a tendon structurally?

An aponeurosis is a sheet of white fibrous connective tissue, a tendon is a band of cord of the same tissue

How is an aponeurosis functionally similar to a tendon?

Both serve to attach muscles to bones or to other muscles.

The junction between a motor neuron's axon and the muscle cell membrane is

neuromuscular or myoneural

A motor neuron and all of the skeleton muscle cells it stimulates is called a ?

Motor Unit

The actual gap between the axon terminal and the muscle cell is called a ?

synaptic cleft

Within the axon terminal are many small vesicles containing a neurotransmitter substance called ?

Acetylcholine

When the _______ reaches the ends of the axon, the neurotransmitter is released and diffuse to the muscle cell membrane to combine with receptors there. The combining of the neurotransmitter with the muscle membrane receptors causes the membrane to become permeable to both sodium and potassium.

Action potential

The greater influx of sodium ions results in ______ of the membrane. Then contraction of the muscle cell occurs.

Depolarization

What is not true of skeletal Muscles?

1) It enables you to manipulate your environment. 2). It influences the body's contours and shape. 3). It is one of the major components of hollow organs. 4). It provides a means of locomotion.

It is one of the major components of hollow organs.

Because the cells of skeletal muscle are relatively large and cylindrical in shape, they are known as ?

Fibers

True or False? Skeletal muscle cells have more than one nucleus?

True

The two contractile proteins that make up the myofilaments of skeletal muscles are?

Actin and Myosin

Each muscle cell is surrounded by thin connective tissue called the?

Endomysium

A strong cordlike structure that connects a muscle to another muscle or bone is?

A tendon

The junction between a nerve fiber and a muscle cell is called a ?

neuromuscular or myoneural junction.

True or False - The neuron and muscle fiber membranes do not actually touch but are separated by a fluid - filled gap.

True

The bulk of the body's muscle is called?

skeletal muscle

LABEL - TENDON

LABEL (A)

LABEL - EPIMYSIUM

LABEL (B)

LABEL - ENDOMYSIUM

LABEL (C)

LABEL - FASCICLE

LABEL (D)

LABEL - PERIMYSIUM

LABEL (E)

LABEL - BONE

LABEL (F)

LABEL - EPIMYSIUM

LABEL (G)

LABEL - MUSCLE FIBER

LABEL (H)

LABEL - ENDOMYSIUM

LABEL (I)

LABEL - PERIMYSIUM

LABEL (J)

All of the following are functions of muscle EXCEPT -

body support.

production of body heat.

movement.

protection.

posture maintenance.

protection.

An entire skeletal muscle is surrounded by

epimysium

As an axon enters a muscle, it branches into a number of axonal terminals, each of which forms a neuromuscular junction with a single muscle fiber. A motor neuron and all the muscle fibers it supplies is called a

motor unit

During muscle contraction, all of the following occur EXCEPT -

hemoglobin concentration in muscle fibers increases.

myosin heads bind to actin.

calcium concentration in the sarcomere increase.

the I bands shorten and H zones disappear.

ATP is hydrolyzed

hemoglobin concentration in muscle fibers increases

What is the ion released from the terminal cisternae that combines with troponin and removes the blocking action of tropomyosin, resulting in formation of cross bridges?

Ca2+

Each skeletal muscle fiber is controlled by a neuron at a single

neuromuscular junction

In a skeletal muscle fiber, which of the following best describes the composition of the structure known as a triad?

Terminal cisterna, transverse tubule, and terminal cisterna

In the sliding filament model of muscle contraction, the myofilaments slide over each other, resulting in an overlapping of actin and _________.

myosin

Interactions between actin and myosin filaments of the sarcomere are responsible for

muscle contraction

The all-or-none response of a muscle fiber means that

a muscle fiber responds maximally to threshold stimulation or NOT at all.

The dense layer of collagen fibers that surround an entire skeletal muscle is the

epimysium

The functional unit of a skeletal muscle fiber is the

sarcomere

Which statement below does NOT represent a role of ionic calcium in muscle contraction?

Triggers sliding of myofilaments and ATPase activity

The action potential triggers Ca2+ release from the sarcoplasmic reticulum

Promotes glycogen breakdown and ATP synthesis

Promotes neurotransmitter release

Triggers diffusion of Na+ out of the cells

Triggers diffusion of Na+ out of the cells

The space between the neuron and the muscle is the

synaptic cleft

The term that means a continued mild or partial contraction of an entire muscle is muscle

tone

The type of muscle contraction in which the muscle fibers produce increased tension but the muscle neither shortens nor lengthens is called

isometric

What is the role of calcium ions in the contraction of skeletal muscle?

Calcium ions bind to the troponin-tropomyosin complex and remove their inhibitory action on actin/myosin interaction.

Which of the following statements about smooth muscle is true?

Fibers are small and spindle-shaped.

Which of the following statements is INCORRECT?

Skeletal muscle contractions help maintain body temperature.

Skeletal muscles are responsible for the pumping action of the heart.

Skeletal muscles support the weight of some internal organs.

Skeletal muscles are responsible for guarding the openings of the digestive and urinary tracts.

The contractions of skeletal muscles pull on tendons and move elements of the skeleton.

Skeletal muscles are responsible for the pumping action of the heart.

Which of the following types of muscle is found in the eye and are used to regulate the size of the pupil?

Multiunit smooth muscle

Which of the following substances increases in quantity during repetitive muscle contraction?

Lactic acid

The sequence of electrical changes that occurs along the sarcolemma when a muscle fiber is stimulated is known as the

action potential

In the early stage of repolarization, the sarcolemma is restored to its initial polarized state initially by

K+ diffusing rapidly out of the muscle fiber.

During repolarization, the initial events restore only the electrical conditions while the Na+/K+ pump restores the

ionic conditions.

Which of the following moves Ca2+ back into the tubules of the SR after a contraction?

The ATP-dependent calcium pump

Which of the following allows recoil of the muscle fiber when contraction ends?

Elastic filaments

Which one of the following binds calcium ions in a smooth muscle causing contraction?

Calmodulin

Which of the following events is something a smooth muscle can do but cardiac and skeletal muscle can not do?

Grow by hyperplasia or an increase in the number of cells.

What is the protein found on thick filament

Myosin

What is the protein found on thin filament

Actin

What are the features of skeletal muscle

Voluntary, striated

What is the contractile unit of muscle?

Sarcomere

Light bands have

Only Thin filament

A motor unit consists of

Muscle fibers and motor neuron

A bundle of muscle fibers is called

Fascicle

The areolar connective tissue that enclose each muscle fiber is called?

Endomysium

ACh is a(an) ______ released by the axon terminals

Neurotransmitter

Are skeletal muscle cells multinucleate?

yes