Muscle Tissue

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Anatomy and Physiology Chapter 10

Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for

contraction

The dense layer of connective tissue that surrounds an entire skeletal muscle is the

epimysium.

The delicate connective tissue that surrounds the skeletal muscle fibers and ties adjacent muscle fibers together is the

endomysium

An ________ can be described as a broad tendinous sheet.

aponeurosis

The repeating unit of a skeletal muscle fiber is the

sarcomere

The region of the sarcomere containing the thick filaments is the

A band

At rest, the tropomyosin molecule is held in place by

troponin molecules

The area in the center of the A band that contains no thin filaments is the

H band

Each thin filament consists of

two actin protein strands coiled helically around each other

At rest, active sites on the actin are blocked by

tropomyosin molecules

The thin filaments of striated muscle are made primarily of which protein(s)?

tropomyosin, actin, troponin, nebulin

The protein that regulates muscle contraction by controlling the availability of active sites on actin is called ________.

tropomyosin

The protein that is found in the Z line of a sarcomere is called ________.

actinin

Thin filaments are mostly made of the protein ______.

actin

Thick filaments are made of the protein ________.

myosin

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?

acetylcholine (ACh)

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?

voltage-gated calcium channels

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?

exocytosis

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?

Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.

How is acetylcholine (ACh) removed from the synaptic cleft?

acetylcholinesterase (AChE; an enzyme)

The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?

terminal cisternae of the sarcoplasmic reticulum

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

neuromuscular junction

Receptors for acetylcholine are located on the

motor end plate

The action potential is conducted into a skeletal muscle fiber by

transverse tubules

When calcium ion binds to troponin,

tropomyosin moves into the groove between the helical actin strands

After death, muscle fibers run out of ATP and calcium begins to leak from the sarcoplasmic reticulum into the sarcoplasm. This results in a condition known as

rigor mortis

The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter

acetylcholine

Which statement about excitation-contraction coupling is incorrect?

Calcium ion is released from the transverse tubule

A single motor neuron together with all the muscle fibers it innervates is called

motor unit

The type of contraction in which the muscle fibers do not shorten is called

isometric

Suppose that you try to pick up an object and discover that it is much heavier than you expected. Which process must occur in the muscle to increase tension so you can pick up the object?

recruitment

A muscle produces its highest tension when in complete ________.

tetanus

A single contraction-relaxation cycle in a muscle fiber produces a ________.

twitch

During the Cori cycle, in the liver

glucose is produced from lactic acid.

During the recovery period the body's need for oxygen is increased because

additional oxygen is required to restore energy reserves consumed during exercise.

A resting muscle generates most of its ATP by

aerobic metabolism of fatty acids

Creatine phosphate

acts as an energy reserve in muscle tissue

During anaerobic glycolysis

ATP is produced, carbohydrate is metabolized, oxygen is not consumed, pyruvic acid is produced.

Aerobic metabolism normally provides ________ percent of the ATP demands of a resting muscle cell.

95

Which of these would lead to increased oxygen consumption?

increased muscle activity, increased conversion of lactic acid to glucose, increased heat production, increased aerobic respiration by muscle cells.

During activities requiring aerobic endurance

most of the muscle's energy is produced in mitochondria

Fast muscle fibers can adapt to aerobic metabolism by generating more mitochondria in response to

repeated, exhaustive stimulation

Which of the following statements is (are) true regarding human muscles?

most have slow and fast fibers, eye muscles are composed entirely of fast fibers, slow fibers are abundant in the calf muscles, slow fibers are abundant in the back muscles.

The ability of smooth muscle to function over a wide range of lengths is called

plasticity

Which of the following is not a function of smooth muscle tissue?

forcing blood from the heart into the major arteries

Inside a muscle, bundles of single muscle fibers form __________.

fascicles

The muscle action potentials that initiate contraction are transmitted from the sarcolemma into the interior of the muscle fiber by __________.

T tubules

T tubules and the terminal cisternae are clustered into structures called __________.

triads

The sarcoplasmic reticulum contains __________.

calcium

Which organelle completely surrounds each myofibril inside a muscle fiber?

sarcoplasmic reticulum

To what regulatory protein does calcium bind during the initiation of the contraction cycle in skeletal muscle fibers?

troponin

Which of the following causes the active site on actin to be exposed or uncovered?

tropomyosin shifting position

Which of the following most correctly describes excitation in the context of excitation-contraction coupling in skeletal muscle?

the generation of an action potential in the sarcolemma

Which of the following phrases best describes how excitation is coupled to contraction in skeletal muscle fibers?

through calcium release from the sarcoplasmic reticulum

Malignant hyperthermia (MH) is a rare genetic disease in which the sarcoplasmic reticulum leaks calcium when the patient is put under general anesthesia. Which of the following best describes how anesthesia would affect the skeletal muscles of a patient with MH?

The muscles would contract because of calcium binding to troponin.

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?

arrival of an action potential

The binding of calcium to which molecule causes the myosin binding sites to be exposed?

troponin

A myosin head binds to which molecule to form a cross bridge?

actin

What causes the myosin head to disconnect from actin?

binding of ATP

What energizes the power stroke?

hydrolysis of ATP

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