A&P Chp.9 Smartbook Assignment

Which of the following accurately describes the structure of a muscle?

-A skeletal muscle fiber is a single, long, cylindrical cell containing several peripherally located nuclei -A single skeletal muscle fiber can extend from one end of a muscle to the other

Identify characteristics of hypertrophy.

-Can occur in response to exercise -Is an increase in the size of a muscle fiber

True or false: During contraction, actin and myosin myofilaments change length causing the sarcomeres to shorten.

False

The myosin myofilament is indicated by which color?

Green

Each _____ includes a Z disk and extends from each side of the Z disk to the ends of the myosin myofilaments.

I band

Where do you find acetycholine?

In synaptic vesicles

What is the neuromuscular junction?

It is the site where the nerve fiber innervates the muscle fiber.

The middle of the H zone is the _____.

M line

_______________neurons have axons that extend to skeletal muscle fibers through nerves.

Motor

Name the green structure in the figure.

Myosin myofilament

Sodium is more abundant in which fluid compartment?

Outside the plasma membrane

With which phase are the following associated: myosin releases thin filaments, muscle tension declines, and cytoplasmic calcium levels fall?

Relaxation

What structure in a muscle fiber acts as a calcium reservoir or storage site?

Sarcoplasmic reticulum

What type of muscle cell is responsible for voluntary contraction or movement?

Skeletal muscle cells

What is the synaptic cleft?

Space between the presynaptic terminal and myofiber

What is the space between the presynaptic terminal and myofiber called?

Synaptic cleft

What are the transverse (T) tubules?

They are tube-like invaginations of the sarcolemma that extend inward throughout the muscle cell.

Which of the following molecules covers the active sites on the G-Actin molecule when the muscle fiber is relaxed?

Tropomyosin

True or false: A whole muscle is usually innervated by more than one neuron.

True

True or false: One motor neuron can innervate more than one muscle fiber.

True

The boundaries of the sarcomere are defined by the _____.

Z disks

A sarcolemma is ______.

a cell membrane

The perimysium is ______.

a thick connective tissue layer around each fasciculus

The neurotransmitter released by the synaptic vesicles at the neuromuscular junction is called ______.

acetylcholine

During contraction, the sarcomeres shorten because ______.

actin is pulled past myosin towards the M line of the sarcomere

G actin is part of a(n) _____.

actin myofilament

A sarcomere is formed from the arrangement of______________ and myosin myofilaments.

actin or thin

A skeletal muscle myofilament ______.

contains either actin or myosin proteins

The sarcomere is called the basic functional unit of a muscle fiber because it is the smallest part of the fiber that is capable of _____.

contracting

During a single contraction, each myosin molecule undergoes the cycle of cross-bridge formation, movement, release, and return to its original position many times. This process is called _______.

cross-bridge cycling

The sarcoplasm of a muscle fiber is its ______.

cytoplasm

The concentration of sodium ions is ______________in the cytosol of the cell at rest than it is in the surrounding extracellular fluid.

lower, smaller, less, lesser, or low

The concentration of sodium ions is_________________ in the cytosol of the cell at rest than it is in the surrounding extracellular fluid.

lower, smaller, less, lesser, or low

Typically, each motor neuron innervates _____.

more than one muscle fiber

A whole muscle is typically innervated by ______.

more than one neuron

A neuron that innervates skeletal muscle fibers is called a(n)_____________ neuron.

motor

Specialized nerve cells that stimulate muscles to contract are called ______.

motor neurons

The plasma membrane of a muscle fiber is called the .

sarcolemma

The _____ is the basic structural and functional unit of skeletal muscle.

sarcomere

The structure within a muscle fiber that extends from one Z disk to another Z disk is a(n) ______.

sarcomere

The basic structural and functional unit of a skeletal muscle fiber is called the_____________ ; it is the smallest unit of skeletal muscle that is capable of contracting.

sarcomere or sarcomeres

The sliding filament theory states that during contraction ______.

sarcomeres shorten because actin myofilaments slide past the myosin myofilaments

The actin and myosin myofilaments form highly ordered units called ______, which are joined end to end to form the ______.

sarcomeres, myofibrils

The cytoplasm of a muscle cell is called the .

sarcoplasm

________________reticulum in a muscle fiber stores calcium in between contractions.

sarcoplasmic

_____________reticulum is a modified form of smooth endoplasmic reticulum located in muscle cells.

sarcoplasmic

____________reticulum is a modified form of smooth endoplasmic reticulum located in muscle cells.

sarcoplasmic

In a muscle cell, the highly specialized, smooth endoplasmic reticulum is called the _________.

sarcoplasmic reticulum

Voluntary movements such as raising your hand are produced by the contraction of _________________muscle cells.

skeletal

List the types of muscle tissue.

skeletal, cardiac, smooth

When examined in a longitudinal section, skeletal muscle has alternating light and dark bands producing a(n) ______ appearance.

striated

At the neuromuscular junction, each presynaptic terminal contains numerous small, spherical sacs called _____, which contain acetylcholine.

synaptic vesicles

Muscles are connected to bones or the skin by

tendons

The cell bodies of motor neurons are located in ______ and the axons of the motor neurons extend to ______.

the brain and spinal cord, skeletal muscle fibers

What does the sliding filament theory of muscle contraction predict about myofilaments and sarcomere length?

-During contraction, the thin myofilaments slide past the thick myofilaments. -During contraction, the total length of the sarcomere decreases.

Describe troponin. (Select all that apply)

-It has a binding site for calcium ions. -It is bound to both actin and tropomyosin. -It is a globular protein composed of three subunits.

Which of the following are characteristics of a skeletal muscle fiber?

-Multinucleate -Cylindrical

List the actions that occur during the process known as cross-bridge cycling.

-Power stroke -Recovery stroke -Cross-bridge formation -Cross-bridge release

Myofibrils ______.

-are bundles of protein filaments -extend from one end of the muscle fiber to the other

The function of a tendon is to ______.

-connect muscles to bone -connect muscles to the skin

The synaptic vesicles of the presynaptic neuron of the neuromuscular junction ______.

-contain acetylcholine -contain ACh -contain neurotransmitters

The A band of the sarcomere ______.

-contains the H zone and M line -extends the length of the myosin myofilaments -contains both actin and myosin proteins

Describe the I band of the sarcomere. The I band ______.

-extends from each side of the Z disk to the ends of the myosin myofilaments -consists of actin myofilaments on each side of the Z disk

The cell bodies of motor neurons are located _______.

-in the brain -in the spinal cord

Acetylcholine ______.

-is stored in the synaptic vesicles of the presynaptic cell at the neuromuscular junction -acts as a neurotransmitter

The muscle plasma membrane in the area of the neuromuscular junction is the ______. Select all that apply.

-motor end plate -postsynaptic membrane

The epimysium of muscle ______.

-surrounds an entire muscle -is composed of dense collagenous connective tissue -lies under the muscular fascia

The properties of myosin heads that allow for sarcomere contraction include ______.

-the heads are ATPase enzymes -the heads have active sites for the binding of actin -the heads are attached to the rod portion by a hinge region that can bend and straighten during contraction

In the sliding filament theory, ATP is involved in ______.

-the uptake of calcium into the sarcoplasmic reticulum at the end of contraction -breaking the bond between actin and myosin -cocking or energizing the myosin heads

The area of the sarcomere where the actin and myosin myofilaments overlap is called the ______.

A band

The figure represents a cross section through the sarcomere. This cross section was most likely taken from which of the following areas?

A band

Which color structure represents the Z disks?

Blue

Describe the epimysium.

The epimysium is a layer of dense collagenous connective tissue that surrounds a muscle.

Skeletal muscle is described as striated. What does that mean?

The tissue exhibits alternating dark and light bands.

The ability of a muscle cell to respond to stimuli is called .

excitability

Another name for a skeletal muscle cell is a muscle ______.

fiber

Another name for a single skeletal muscle cell is a skeletal muscle .

fiber or myocyte

Myosin heads bind to ______.

globular actin

The round purple structures in the figure are ______.

globular actin

Enlargement of muscles in children and adults that results from an increase in the size of each muscle fiber is called .

hypertrophy

Energy from the breakdown of ATP is used to ______.

move the myosin heads during contraction release the cross-bridges move calcium ions into the sarcoplasmic reticulum

Muscle fibers develop from less mature, multinucleated cells called _____.

myoblasts

Each _____ is a threadlike structure, approximately 1-3 micrometers in diameter, that extends from one end of the muscle fiber to the other.

myofibril

The actin and myosin ______ form highly ordered units called sarcomeres which are joined end to end to form the ______.

myofilaments, myofibrils

The golf club shaped contractile molecule which includes an ATPase enzyme is called ______.

myosin

The voltage of a repolarizing neuron or muscle fiber is becoming more ______ with respect to the extracellular fluid around it.

negative

When a cell is in the repolarizing phase of an action potential, its intracellular environment is becoming more ______ when compared with the extracellular environment.

negative

The nerve fiber innervates the muscle fiber at the ______.

neuromuscular junction

A chemical released at the distal end of an axon that either stimulates or inhibits an adjacent cell is called a(n) ______.

neurotransmitter

Substances that are released from a presynaptic membrane and inhibit or stimulate the activity of an adjacent cell are called ______.

neurotransmitters

Each fasciculus is surrounded by a thick connective tissue layer called the ______.

perimysium

Myoblast(s) are ______.

the precursors of muscle fibers

Muscle excitability is defined as the ability ______.

to respond to a stimulus

Tube-like invaginations of the sarcolemma that conduct action potentials toward the center of the muscle fiber are called _____.

transverse tubules

The molecule that inhibits the binding of myosin to actin by blocking the binding site is _____.

tropomyosin

The portion of the sarcomere that binds calcium is _____.

troponin

Within a myofibril, calcium-binding sites are found on ______.

troponin

The organelles that are located within the presynaptic terminals and contain neurotransmitter are called synaptic _________

vesicles

The organelles that are located within the presynaptic terminals and contain neurotransmitter are called synaptic ________________

vesicles