BIOL 2401 Ch 10 Skeletal Muscle

Multiunit smooth muscle cells are stimulated ______.

individually

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

intercalated disks

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

Smooth muscle contraction is under control of the nervous system.

involuntary

If you strain to push on a wall that does not move, your muscles are in a type of

isometric

A graph of a muscle twitch contains three periods. The period during which there is no change in external muscle tension (and no change in muscle length) is the ________ period.

latent

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

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

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

more

Neurons that stimulate muscle contraction are called ______ neurons.

motor

A motor unit is composed of a single ______ and all of the muscle fibers it controls.

motor neuron

Skeletal muscle contraction is controlled by

motor neurons

The iris of the eye is composed of nonstriated muscle that is involuntarily controlled. Therefore, it must contain

multiunit smooth muscle.

What is the force generated when a skeletal muscle is stimulated to contract called?

muscle tension

After the age of 30, the number of ______ in existing muscle fibers decreases.

myofibrils

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

myofibrils

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

myofilaments

Myofibrils are made of ______.

myofilaments

Myofibrils consist of bundles of short ______.

myofilaments

Termination of the nerve impulse at an NMJ results in the passive sliding of ______ back to their original state.

myofilaments

Muscle cells store oxygen bound to a ___ molecule.

myoglobin

Thick filaments are assembled from bundles of the protein called

myosin

Thick myofilaments are composed of ___ bundles of protein molecules.

myosin

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

myosin heads

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

Myoglobin is a molecule within muscle cells that can bind

oxygen

After you stop running, you notice that you keep breathing heavily for some time. This is because your body is in ______.

oxygen debt

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 a

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

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

reticulum

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

sarcolemma

The plasma membrane of a skeletal muscle fiber is called the

sarcolemma

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

sarcomere

A contracting skeletal muscle fiber typically shortens as all of its ______ shorten in length.

sarcomeres

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

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

sarcoplasmic

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 or stem

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

shorter; 1-2

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

The ___ filament theory explains how muscle fibers shorten during contraction.

sliding

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

slow fatigue

The type of fibers specialized to continue contracting for extended periods of time, as would be required in running a marathon, for example, are _____ fibers.

slow-twitch

A circular muscle band that contracts at an orifice is also known as a _______________.

sphincter

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

A neuromuscular junction contains a(n) ______.

synaptic knob, motor end plate, synaptic cleft

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

Which are the reservoirs that store the calcium 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

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

The deep invaginations of the sarcolemma that extend into the sarcoplasm of skeletal muscle fibers as a network of narrow membranous tubules are called ______.

transverse tubules

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

Calcium ions bind to what protein in a thin myofilament?

troponin

If the sarcoplasm of a muscle cell is flooded with calcium ions, to which protein will they bind?

troponin

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

troponin

Smooth muscle cells retains their mitotic ability.

true

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

true

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

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: Smooth muscle cells lack transverse tubules.

true

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

twitch

Thick filaments are about ______ the diameter of thin filaments.

two times

A sarcomere is defined as the distance from one _____ to the next adjacent ____ . (The same answer fills in both spaces.)

z disc

Which can cause muscle fatigue?

-build up of intracellular P1 - insufficient Ca2+ - Na+ or K+ imbalances (357)

The enzyme _____________ resides in the synaptic cleft and breaks down molecules of ACh.

Acetylcholinesterase

Which may occur as a result of muscle atrophy?

All of the choices are correct.

In a muscle there are concentric layers of connective tissues. From deep to superficial these connective tissue layers are the

Blank 1: endomysium Blank 2: perimysium Blank 3: epimysium

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

Blank 1: epimysium Blank 2: perimysium Blank 3: endomysium

The act of shivering is an example of skeletal muscle performing what function?

Heat production

When viewed under a light microscope, the light bands, called ______ bands, contain only ______ filaments.

I; thin

During which phase of the crossbridge cycle is ATP split into ADP and Pi?

Immediately preceding the resetting of the myosin head.

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

M

______________ muscle fibers have large myoglobin stores, slow contraction velocity, and the highest resistance to fatigue.

Slow

Smooth muscle tissue in which cells are individually sent signals to contract (rather than contracting in unison) is referred to as

Smooth muscle tissue in which cells are individually sent signals to contract (rather than contracting in unison) is referred to as

Which structures are reservoirs that store acetylcholine?

Synaptic vesicles

Deep invaginations of sarcolemma are called ______.

T-tubules

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

The myosin-binding sites on actin are exposed.

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

Which letter is associated with the line that is a thin protein structure that serves as an attachment site for thin filament ends?

Z

With increased age, skeletal muscles show:

a decrease in the number of myofibrils.

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

Slow and intermediate fibers require oxygen to produce ATP, so the metabolic reactions within these fibers are termed ______.

aerobic

The presence of mitochondria and myoglobin facilitate _________ respiration in muscle cells.

aerobic

Fibers from one motor unit

are dispersed throughout most of the muscle.

Smooth muscle is found in which of the following locations?

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

Smooth muscle is found where in the respiratory system?

around the bronchioles

After breaking your arm, you have a cast on it for three months. When the cast is removed, your arm looks much smaller than it did before. The process called ______ caused this to happen.

atrophy

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

attachment

Contractile proteins in smooth muscle are arranged ______.

between dense bodies and dense plaques

Acetylcholine exerts its effect by

binding to receptors at the motor end plate.

Functionally, troponin provides a binding site for ______ ions.

calcium

The cyclic events of "attach, pivot, detach, return" continue as long as ____ ions remain bound to the troponin.

calcium

The type of muscle fibers that are striated, form Y-shaped branches, and are joined by intercalated discs are

cardiac

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

caveolae

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

cellular

When smooth muscle is stretched, it responds by ______.

contracting then relaxing

When a muscle relaxes,

crossbridges stop forming and muscle elasticity returns the muscle to rest length.

The amount of additional oxygen that must be inhaled in order to restore pre-exercise levels is called oxygen

debt

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

dense irregular

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 connective tissue layer that surrounds an entire muscle is called ______.

epimysium

Match each muscle unit with the connective tissue layer that surrounds it. Instructions

epimysium - whole muscle fascicle - perimysium muscle cell - endomysium

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

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

A piano player uses her hands for brief quick movements. Which muscle fiber type would you therefore predict to be predominant in these muscles?

fast glycolytic

The most prevalent of skeletal muscle fibers in the body are _____ fibers.

fast-twitch

A reduced ability to generate tension due to recent exertion of force is known as muscle ________.

fatigue

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

fatigue

Overall, as aging progresses, muscle strength and endurance are impaired, and the individual has a tendency to

fatigue

A skeletal muscle cell is also called a muscle

fiber

In a lab, wave summation is demonstrated by increasing the _________ of the stimulus.

frequency

One of the reasons you might struggle to lift a heavy object with your arm fully extended is because

full extension results in decreased overlap between thick and thin filaments in the muscle.

Smooth muscle cells are ______ in shape.

fusiform

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

head

What part of a myosin molecule does ATP bind to?

head

If a muscle cell is stimulated to contract, allowed to partially relax, then stimulated again, its force of contraction the second time will be ______.

higher

The diameter of a muscle fiber will predict ______.

how much power it will produce

An increase in the number of mitochondria can be observed in ______.

hypertrophy

An increase in the size of a muscle fiber is called _________________.

hypertrophy

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

H

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

2

Each thick filament contains about ______ protein molecules (each molecule has two heads and two braided tails).

2

The net energy yield from one glucose molecule through the process of glycolysis is

2 ATP

Area B of the sarcomere represents the ______ band.

A

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

A band

Glycolysis and aerobic respiration are used to generate ______ in muscle fibers.

ATP

__________ is a protein that anchors myofibrils that are adjacent to the sarcolemma to proteins in the sarcolemma.

Dystrophin

When an impulse arrives at the knob of the motor neuron, calcium

Enters through voltage gated channels and triggers the release of transmitter.

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

Excitability

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

The electron transport system refers to oxidative phophorylation using the coenzymes FADH2 and _______.

NADH