CH 10 HBOD MUSCLE TISSUE

True or false: A single myofibril runs the length of the muscle fiber.

True

True or false: In the absence of calcium, troponin attaches to tropomyosin to hold it in place on the surface of the F actin strand.

True

True or false: Playing the piano with your fingers uses very small motor units.

True

True or false: Smooth muscle cells lack transverse tubules.

True

When a muscle fiber contracts, which parts of the sarcomere maintain a constant length throughout contraction?

A band

What muscle type(s) would you expect to find in the cardiovascular system?

Cardiac & smooth

True or false: After diffusing across the synaptic cleft, ACh binds to receptors on the synaptic knob.

False

True or false: In smooth muscle contraction the thick and thin filaments slide past one another causing the Z lines to move closer together.

False

light band containing thin filaments only

I band

appears as a dark protein disc in center of H zone

M line

When calcium ions bind to troponin, which of the following then occurs?

The myosin-binding sites on actin are exposed.

After being generated, the muscle impulse continues to spread throughout the muscle fiber as long as ______ keeps the motor end plate receptors open.

acetylcholine

The motor end plate has large numbers of ______ receptors.

acetylcholine

Contraction of a muscle fiber requires that the myosin heads in the thick filament bind to active sites on ______ molecules within the thin filaments

actin

Each myosin head in a thick filament can bind to the protein in a thin filament called

actin

Which of the following proteins are found in a thin filament?

actin

binding site for myosin to shorten a sarcomere

actin

double-stranded contractile protein

actin

Which of the following proteins are found within a sarcomere?

actin connectin

Cardiac muscle cells use _________ respiration almost exclusively.

aerobic

For longer contractions, muscle cells obtain ATP by which process?

aerobic respiration

Smooth muscle cells generally generate ATP through which mechanism?

aerobic respiration

The endomysium is composed of what type of connective tissue?

areolar

The superficial fascia, composed of ______ and adipose connective tissue, separates muscle from skin.

areolar

Smooth muscle is found where in the respiratory system?

around the bronchioles

The connective tissue layers in muscle provide protection, distribution sites for blood vessels and nerves, and a means of ______ to the skeleton.

attachment

Cardiac muscle cells are ______.

autorhythmic

The ______ feature of cardiac muscle cells is responsible for the repetitious, rhythmic heartbeat.

autorhythmic

thick filament

bind to thin filaments and cause contraction

Cardiac muscle cells are ______ and contain ______ nuclei.

branched; 1-2

Which can cause muscle fatigue?

build up of intracellular Pi insufficient Ca2+ Na+ or K+ imbalances

At an NMJ, the influx of ______ ions into the synaptic knob causes the exocytosis of ACh into the synaptic cleft.

calcium

Functionally, troponin provides a binding site for ______ ions.

calcium

When an action potential travels down T-tubules to the terminal cisternae of the SR, what ion is released into the sarcoplasm?

calcium

When a nerve signal arrives at a synaptic knob, what type of channels open in the membrane?

calcium voltage-gated

During contraction of smooth muscle, ______ binds to calcium and activates myosin light chain kinase.

calmodulin

The sarcolemma of smooth muscle cells has small invaginations called ______.

caveolae

A muscle fiber is what level of organization in the body?

cellular

The long tails of the myosin molecules in the thick filaments point toward the ______ of the filament.

center

The shortening of muscle cells is called _______, a property that allows muscle cells to cause body movement.

contraction

The expansive sheet of dense irregular connective tissue that separates individual muscles is called the ______.

deep fascia

In an isometric contraction, the muscle ______ body movement.

does not produce

Muscle tissue demonstrates the property of _____ when it is done contracting and returns to its resting length.

elasticity

The motor neuron axon travels through the epimysium and perimysium and enters the ______, where it delivers a nerve impulse to an individual ______.

endomysium; muscle fiber

The synaptic knob of the neuron is a(n) ______ of an axon.

expanded tip

There is a(n) ______ network of blood vessels delivering blood to muscle tissue.

extensive

True or false: A muscle fiber that is partially shortened can produce a contraction stronger than the contraction it can produce when at its resting length.

false

perimysium covers the

fascicle

The majority of skeletal muscle fibers in the body are ______ fibers.

fast glycolytic

Which of the three skeletal muscle fiber types has the largest diameter and provides both power and speed?

fast glycolytic

If used repeatedly for endurance events, ______ fibers can develop the appearance and functional capabilities of ______ fibers.

fast; intermediate

In a normally functioning muscle, the inability to contract and produce tension is called muscle

fatigue

Type IIa fibers have a high resistance to ______.

fatigue

A skeletal muscle cell is also called a muscle

fiber

Smooth muscle is composed of short cells that have a ______ shape.

fusiform

With endurance training, it is possible for fast ______ fibers to take on characteristics of fast ______ fibers.

glycolytic; oxidative

Which are characteristics of oxidative fibers?

good for endurance red high concentration of myoglobin use aerobic respiration

lighter region in the middle of an A band

h zone

Each myosin strand has a free ______ and an attached tail.

head

What part of a myosin molecule does ATP bind to?

head

The diameter of a muscle fiber will predict ______.

how much power it will produce

The mechanism that allows smooth muscle to maintain muscle contraction without the use of additional ATP is the

latchbridge

muscle fiber

metabolic activities; contraction

Because muscle cells require a huge amount of ATP in order to contract, they have a large number of which organelle?

mitochondria

Slow fibers have a relatively large number of ______. This permits slow muscle fibers to produce a greater amount of ______ than fast muscle fibers while contractions are underway.

mitochondria; ATP

Upon release from the synaptic knob, acetylcholine attaches to receptors on the ______.

motor end plate

Skeletal muscle contraction is controlled by

motor neurons

Muscle tissue is distributed almost everywhere in the body; it is responsible for the _____ of materials within and throughout the body.

movement

Epimysium covers the

muscle

endomysium covers the

muscle cell

The sarcoplasm of a skeletal muscle fiber contains hundreds to thousands of long, cylindrical structures called _________that extend the length of the cell.

myofibrils

contain myofilaments that are responsible for muscle contraction

myofibrils

An extensive network of blood vessels and nerve fibers extends through both the epimysium and the _____ of a muscle.

perimysium

The connective tissue layer that surrounds each muscle fascicle is called ______.

perimysium

After stimulation of ACh receptors, a muscle impulse spreads quickly along the _________and into the muscle fiber along T-tubules.

sarcolemma

The motor end plate is a specialized region of the ______.

sarcolemma

The plasma membrane of a skeletal muscle fiber is called the

sarcolemma

regulates entry and exit of materials

sarcolemma

Within a myofibril, each ______ shortens as the muscle fiber contracts.

sarcomere

Within a myofibril, Z discs separate the functional contractile units known as

sarcomeres

The cytoplasm of a skeletal muscle cell has a specific name and is known as

sarcoplasm

site of metabolic processes for normal muscle fiber activities

sarcoplasm

At the end of muscle contraction, calcium ions are moved back into the _______reticulum by ATP-driven ion pumps.

sarcoplasmic

At the end of contraction, when the stimulation from the nerve impulse ceases, calcium ions are pumped back into the ______.

sarcoplasmic reticulum

According to the sliding filament theory, when a muscle contracts, thick and thin filaments_______ past each other, and the ______ shortens

slide sarcomere

the ______-filament theory explains how muscle fibers shorten during contraction.

sliding

An individual has better proficiency in performing repeated contractions under aerobic conditions if he or she has a greater percentage of ______ fibers in specific muscles.

slow

Smooth muscle contraction is ________ , resistant to_________, and usually sustained for an extended period of time.

slow fatigue

Over longer distances, runners who have higher proportions of ______ muscle fibers in their leg muscles are able to outperform runners who have a greater number of ______ muscle fibers in their leg muscles.

slow; fast

Type I muscle fibers contract more ______ than type IIa and IIb muscle fibers.

slowly

A "step-wise" increase in the force of contraction of a single muscle fiber or single motor unit due to repeated stimulation is called

summation

The narrow space separating the synaptic knob and the motor end plate is called the ______.

synaptic cleft

A nerve impulse travels through an axon to its ______.

synaptic knob

A thick cordlike structure that attaches a muscle to a bone is called a(n) ______.

tendon

The force generated when a skeletal muscle is stimulated to contract is muscle

tension

As a result of ACh stimulation, calcium ions are released from the ______ of the sarcoplasmic reticulum.

terminal cisternae

T-tubules are located adjacent to ______, which are reservoirs storing the calcium ions required for muscle contraction.

terminal cisternae

Slow-twitch and fast-twitch muscle fibers differ primarily in ______.

their ATPase which splits ATP

The H band (or H zone) is more lightly shaded because only ________filaments are present.

thick

in a sarcomere, the M line serves as an attachment site for the ______ filaments and keeps them aligned during contraction and relaxation.

thick

A cross section of a myofibril through the A band contains which myofilaments?

thick and thin

A cross section of a myofibril through the H zone contains which myofilaments?

thick only

In a sarcomere, Z discs serve as anchors for ______.

thin filaments

Single unit muscle cells contract ______.

together

As you sit there reading this your muscles, even your relaxed ones are not completely relaxed and soft. This is because they have some background tension called resting muscle ______.

tone

As the troponin changes shape (due to binding calcium), it moves the ______ molecule to which it is attached, thus exposing the active sites on the G-actin molecules.

tropomyosin

When a muscle fiber is in a relaxed state, the ______ molecules cover the G-actin active sites, preventing interaction between thick filaments and thin filaments.

tropomyosin

covers the active sites on actin when muscle cell is at rest

tropomyosin

double-stranded regulatory protein

tropomyosin

Thin filaments in smooth muscle cells contain which proteins?

tropomyosin actin

The two regulatory proteins associated with thin myofilaments are ______.

tropomyosin and troponin

Calcium ions bind to what protein in a thin myofilament?

troponin

Smooth muscle thin filaments do not contain ______ as in skeletal muscle.

troponin

Upon release from the terminal cisternae, some calcium ions bind to ______ causing it to change shape.

troponin

A single contraction and relaxation of a muscle fiber is referred to as a muscle

twitch

Each myosin protein molecule in a thick filament consists of ______ strands.

two

Thick filaments are about ______ the diameter of thin filaments.

two times

Skeletal muscle fibers are classified into three types based on what two characteristics?

type of contraction and ATP supply

Autonomic motor neurons that control smooth muscle contraction have bulbous swellings called ______ that contain synaptic vesicles.

varicosities

within a synaptic knob, synaptic ______ contain the neurotransmitter ACh

vesicles

Individual cardiac muscle cells can be stimulated to generate a muscle impulse ______ stimulation.

without nervous

The ______ line is a thin, transverse, protein meshwork structure in the center of the H zone of a sarcomere.

M

True or false: Most muscles contain a combination of all three muscle types, slow oxidative, fast oxidative, and fast glycolytic.

True

True or false: Postural muscles contract continuously when a person is awake to prevent collapse of the body.

True

True or false: Skeletal muscle is usually attached to the skeleton, but it is also found at the openings between the digestive tract and the external environment and the urinary tract and the opening to the external environment.

True

True or false: Your biceps brachii muscle in your arm is an organ.

True

In a neuromuscular junction, the enzyme _________ breaks down acetylcholine.

acetylcholinesterase

To stop motor end plate stimulation, usually acetylcholine is quickly broken down and removed from the receptor by ______.

acetylcholinesterase

A tropomyosin molecule is a short, thin, twisted filament that covers small sections of the ______ strands.

actin

Contractile proteins in smooth muscle are arranged ______.

between dense bodies and dense plaques

thin filament

bind to thick filaments and cause contraction

The ACh receptors on the motor end plate are ______ ion channels.

chemically

The enzyme acetylcholinesterase resides in the synaptic

cleft

The type of tetany in which a muscle cell is stimulated so frequently that it is not allowed to relax at all between stimuli is called _________ tetany

complete

A (An) _______ contraction of the arm muscles allows you to lift a book from the table, whereas a (an) ______ contraction of the arm muscles allows you to lower the book back down to the table.

concentric; eccentric

Muscles are considered organs because they are composed not only of muscle tissue but also ______ tissue and nervous tissue

connective

When smooth muscle is stretched, it responds by ______.

contracting then relaxing

In smooth muscle cells, thin filaments are attached to ______.

dense bodies

In a muscle, the perimysium is composed of what type of connective tissue?

dense irregular

The epimysium of a muscle is composed of ______ connective tissue.

dense irregular

Acetylcholine moves across the synaptic cleft by ______.

diffusion

Muscular dystrophy results from the lack of or an abnormal structure of which protein?

dystrophin

The epimysium of a muscle surrounds ______.

entire skeletal muscle

The three connective tissue layers surrounding the individual components of a muscle are the

epimysium perimysium endomysium

In a transverse section of a muscle, you can see that each skeletal muscle is actually composed of many __________, which are bundles of muscle fibers.

fascicles

Which of the following structures anchors adjacent cardiac muscle cells together?

intercalated disc

Cardiac muscle cells form Y-shaped branches and join to adjacent muscle cells at junctions called

intercalated discs

The calcium needed to activate smooth muscle contraction originates in the ______ around the cell.

interstitial fluid

When a nerve impulse reaches the end of an axon of a neuromuscular junction, calcium flows ______ the synaptic knob.

into

Smooth muscle contraction is under ______ control

involuntary

Multiunit smooth muscle is found in which of the following locations?

iris of the eye arrector pili muscles in the skin

Curare is a plant toxin used by indigenous people of South America in their blowguns to paralyze prey. What is a feasible mechanism of action for this drug?

it binds to and blocks ACh receptors on the motor end plate

Smooth muscle shows a different length-tension relationship than skeletal muscle because ______.

it lacks Z discs but has dense bodies the arrangement of the thick and thin filaments allows for contraction even when stretched

Big muscles like the "quads," which are used for power, have ______ motor units.

large

In order to predict how much tension a muscle can produce when contracting, it is important to consider the ______ relationship of thick and thin filaments.

length-tension

Eccentric contractions actively ______ a muscle.

lengthen

Athletes have more defined muscles than non-athletes even while at rest because they have ______ motor units contracting all the time.

more

The vascular supply to slow muscle fibers is ______ than the network of capillaries around fast muscle fibers.

more extensive

Where a motor neuron axon terminal and a muscle cell meet is called a ________ junction

neuromuscular

Synaptic knob, motor end plate, and synaptic cleft are parts of a ______.

neuromuscular junction

While observing skeletal muscle tissue under the microscope you note that it appears striated. You tell your lab partner this is because ______.

of the arrangement of myofilaments in each sarcomere

Contraction of specific skeletal muscles stabilizes joints and helps maintain the body's ________by holding the head and truck erect.

posture

As you hold a barbell and begin to flex your arm in a curl, your biceps brachii slowly lifts the weight by using more and more motor units. This phenomenon, which increases the strength of the contraction, is referred to as

recruitment

As you struggle to twist open a jar, more motor units are called into action until you finally generate enough force to open it. This is an example of ______.

recruitment

The endomysium contains ______ fibers to help bind together neighboring muscle fibers.

reticular

An internal membrane complex in skeletal muscle cells that is similar to the smooth endoplasmic reticulum of other cells is called the sarcoplasmic

reticulum

stores calcium ions needed for muscle contraction

sarcoplasmic reticulum

During the development of skeletal muscle cells, some myoblasts do not fuse and instead become ______ cells.

satellite

If a skeletal muscle is injured, surrounding _____ cells may be stimulated to differentiate and assist in its repair and regeneration.

satellite

Concentric isotonic contractions actively ______ a muscle.

shorten

Cardiac muscle cells are ______ and thicker than skeletal muscle cells, and they have only ______ nuclei.

shorter; 1-2

In which activities are muscles in an isometric contraction?

sitting up very straight pushing on a locked door holding a yoga pose

Approximately 40-50% of your body weight is _____ muscle.

skeletal

Attached to the skeleton and surrounding the openings of the urinary and gastrointestinal traces are locations of ______ muscle.

skeletal

Maintenance of posture and production of heat are functions of ______ muscle.

skeletal

Somatic motor neurons innervate ______ muscle.

skeletal

The length-tension relationship of ________ muscle cells is limited by the Z discs that are lacking in________ muscle cells.

skeletal smooth

The attachment of ACh to the receptor on the motor end plate causes the receptor to open, allowing _______ions to enter the muscle fiber.

sodium

The motor end plate has folds and indentations to increase the membrane surface area adjacent to the ______.

synaptic knob

In a muscle cell at rest, the myosin heads of a thick filament point ______ the sarcomere.

toward the ends of

You have hooked a frog calf muscle up to a myogram that records muscle tension. You notice that when you stimulate the muscle to contract, then stimulate it again before it can fully relax, the amount of tension generated in the second contraction is greater than the first contraction. This phenomenon is called ______.

wave summation

According to the sliding filament theory, the length of the ______ band remains constant, but the ______ zone disappears.

A; H

Acetylcholinesterase in the synaptic cleft is needed so that ______ will not continuously stimulate the cell to contract.

ACh

Muscle cells are said to have what characteristic because they can respond to stimulation from the nervous system?

Excitability

In a thin filament, individual G-actin molecules are strung together to form ______.

F-actin

In each helical strand of F-actin, many small, spherical molecules are connected to form a long filament resembling a string of beads. Each spherical molecule is called ______.

G-actin

At maximal contraction of a muscle fiber, the thin filaments are pulled into the ______ zone which disappears.

H

In a relaxed muscle fiber there are no thin filaments overlapping the thick filaments in the ______ zone.

H

In a sarcomere, the ______ zone (or band) is the light, central region of the A band.

H

The Z disc is a thin transverse protein structure in the center of the ______ band in a sarcomere.

I

Muscle cells store oxygen bound to a _________ molecule

Myoglobin

The muscle that surrounds the opening to your esophagus and opens reflexively to allow you to swallow food is what type of muscle?

Sphincter

The skeletal muscles arranged in layers along the walls of the abdominal cavity and the floor of the pelvic cavity perform what function?

Support Contraction Protection

transports the action potential from the sarcolemma throughout the entire muscle fiber

T-tubule

Deep invaginations of sarcolemma are called ______.

T-tubules

Once started, a muscle impulse will travel along the sarcolemma and into the muscle fiber via the ______.

T-tubules

______ distribute the muscle impulse throughout the inside of the muscle fiber.

T-tubules

Smooth muscle cells retains their mitotic ability.

True

made of dark proteins that create a zig-zag line

Z disc

As cross-bridges form, the myosin heads pivot toward the center of the sarcomere. This action pulls the thin filaments toward the sarcomere center, causing the ______ to move closer together as the sarcomere shortens.

Z discs

Smooth muscle cells have a ______ mechanism that allows them to contract with more power and use less ATP than a skeletal muscle cell.

latch bridge

Smooth muscle is found in which of the following locations?

in wall of the uterus around blood vessels in the wall of the small intestine

Multiunit smooth muscle cells are stimulated ______.

individually

Muscle fibers contain cylindrical structures called myofibrils, which are composed of ______.

myofilaments

Muscle fibers that rely on aerobic respiration for ATP synthesis contain a high concentration of _______, which gives them a reddish appearance.

myoglobin

Thick filaments are assembled from bundles of the protein called

myosin

After the cross bridges are formed, ATP is required to detach the ______ and complete the sequence of cyclic events.

myosin heads