anatomy chapter 10

The action potential is conducted into a skeletal muscle fiber by

transverse tubules.

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

triads

In a sarcomere, thick filaments are linked laterally by proteins of the

M line

Myosin molecules form cross-bridges when they attach to __________.

actin

not found in both skeletal and cardiac muscle fibers

intercalated disks

Which of the following is involved in the power stroke?

myosin

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

repeated, exhaustive stimulation.

Which type of muscle tissue has the greatest effect on the body's heat production?

skeletal

Which of the following is not characteristic of smooth muscle?

Smooth muscle connective tissue forms tendons and aponeuroses.

After heavy exercise, if energy reserves in a muscle are depleted, ________ occurs.

an oxygen debt

Synaptic vesicles contain neurotransmitters that are released by ________ when the action potential arrives.

exocytosis

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

plasticity

What is the synaptic cleft?

the space between the synaptic terminal and the motor end plate

The muscle action potential penetrates into a fiber along the __________.

transverse tubules

How would the loss of acetylcholinesterase from the motor end plate affect skeletal muscle?

It would cause spastic paralysis (muscles are contracted and unable to relax).

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

T tubules

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

a motor unit.

Sarcomere is best defined as ___________.

a repeating unit of striated muscle

The rapid rise and fall in force produced by a muscle fiber after a single action potential is

a twitch.

During neuromuscular transmission, the axon terminals release __________.

acetylcholine

Triggering of the muscle action potential occurs after

acetylcholine binds to chemically-gated channels in the end plate membrane.

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

acetylcholine.

Which of the following proteins contains the active site involved in cross-bridge formation?

actin

The biochemical reaction that consumes the majority of a muscle's ATP is the __________.

actin myosin cross-bridge cycle

The most important factor in decreasing the intracellular concentration of calcium ion after contraction is

active transport of calcium into the sarcoplasmic reticulum.

Creatine phosphate

acts as an energy reserve in muscle tissue.

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.

What causes the vesicles inside a neuron to fuse with the plasma membrane?

an action potential in the neuron

Muscles are attached to bones by tendons or __________.

aponeuroses

The sarcoplasmic reticulum contains __________.

calcium

Active sites on the actin become available for binding after

calcium binds to troponin.

During anaerobic glycolysis

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

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

epimysium

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

fascicles

The __________ type of muscle fiber has relatively few mitochondria.

fast

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

forcing blood from the heart into the major arteries

During the Cori cycle, in the liver

glucose is produced from lactic acid.

Fast fibers

have low resistance to fatigue and have quick twitches.

Muscle fibers differ from "typical cells" in that muscle fibers

have many nuclei.

Which of these would lead to increased oxygen consumption?

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

When a muscle contraction develops tension but doesn't shorten the muscle, the contraction is called __________.

isometric

Muscle fatigue occurs due to a buildup of __________ and __________ in pH.

lactic acid; decrease

The muscle weakness of myasthenia gravis results from

loss of acetylcholine receptors in the end-plate membrane.

Myofibrils are __________.

made of a series of sarcomeres

When acetylcholine binds to receptors at the motor end plate, the end plate membrane becomes

more permeable to sodium ions.

Receptors for acetylcholine are located on the

motor end plate.

The neuromuscular junction is a connection between a neuron and a __________.

muscle fiber

In an isotonic contraction,

muscle tension exceeds the load and the muscle lifts the load.

Skeletal muscle fibers are formed from embryonic cells called

myoblasts

Which thick filament binds to actin once its active binding sites are exposed?

myosin

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

neuromuscular junction.

Acetylcholine receptors are primarily located __________.

on the motor end plate

Anaerobic glycolysis provides energy for muscle contraction when the supply of __________ is limited.

oxygen

A thin layer of connective tissue that surrounds a muscle fascicle is called the __________.

perimysium

Skeletal muscle does each of these except __________.

pump blood

To increase muscle tension, the nervous system can __________.

recruit larger motor units, increase the number of active motor units, increase the stimulation frequency

A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction?

reduces the muscle's ability for contraction

The role of acetylcholinesterase in the neuromuscular junction is to __________.

remove acetylcholine from the synaptic cleft

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 plasma membrane of a skeletal muscle fiber is called the

sarcolemma

Z lines define the edges of which of the following?

sarcomeres

In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm.

sarcoplasmic reticulum

Which organelle completely surrounds each myofibril inside a muscle fiber?

sarcoplasmic reticulum

The series of membranous channels that surround each myofibril is the

sarcoplasmic reticulum.

Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber

shortens

The type of muscle fiber that is most resistant to fatigue is the ________ fiber.

slow

The narrow space between the synaptic terminal and the muscle fiber is the

synaptic cleft.

The end of a neuron, where acetylcholine-filled vesicles are located, is called the __________.

synaptic terminal

When a skeletal muscle fiber contracts,

the H bands and I bands get smaller, the zones of overlap get larger, the width of the A band remains constant, the Z lines get closer together.

The advantage of having many nuclei in a skeletal muscle fiber is

the ability to produce large amounts of the muscle proteins needed for growth and repair.

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

An action potential in the muscle fiber causes __________.

the muscle fiber to contract

Which arrangement of the sarcomere gives rise to the structure (band or line) indicated by the arrow?

the region of the sarcomere that contains only thin filaments

Myosin molecules form what part of the sarcomere?

thick filament

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

through calcium release from the sarcoplasmic reticulum

When the sarcomere is at rest, what is covering the active sites on actin?

tropomyosin

At rest, active sites on the actin are blocked by

tropomyosin molecules.

When calcium ion binds to troponin,

tropomyosin moves into the groove between the helical actin strands.

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

tropomyosin shifting position

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

troponin

When calcium is released inside a muscle cell, what does it bind to?

troponin

At rest, the tropomyosin molecule is held in place by

troponin molecules.

Inside a neuron, acetylcholine is contained within __________.

vesicles

In a sarcomere, cross-bridge attachment occurs specifically in the

zone of overlap.