Human Anatomy 6

Smooth muscle cells

are spindle-shaped

The enzyme acetylcholinesterase causes acetylcholine to

break down

In response to action potentials arriving from the transverse tubules, the sarcoplasmic reticulum releases

calcium ions

Muscle cells

can only contract

Which of the following is characteristic of cardiac muscle?

cardiac muscle cells are striated

During which phase is the stimulus frequency so high that the relaxation phase is eliminated?

complete tetanus

A layer of collagen fibers that surrounds an entire muscle is called

epimysium

Which statement regarding isometric contractions is true?

examples are walking and running

A muscle ______ contains a sarcolemma, sarcoplasm, myofilaments, and myofibrils.

fiber

During moderated activity, which of the following is true regarding muscle metabolism?

glucose and fatty acids are catabolized

Regarding muscle fiber elongation

gravity may help lengthen a muscle fiber after elongation

Fast fibers

have high glycogen reserves

Skeletal muscle fibers differ from "typical cells" in that these muscle fibers

have many nuclei

The term used to describe muscular growth in response to usage is

hypertrophy

Which of the following occurs when tension production rises to a peak and very brief periods of relaxation occur?

incomplete tetanus

Glycolysis

is an anaerobic process

Anaerobic endurance

is exemplified by contractions of fast muscle fibers

Which of the following occurs when glycolysis produces pyruvate faster than it can be used by the mitochondria?

lactic acid is produced

Calcium ions are released from the sarcoplasmic reticulum during the _____ phase of contraction

latent

During activities requiring aerobic endurance

most of the muscle's energy is produced in mitochondria.

The specialized sarcolemma that contains acetylcholine receptors is the

motor end plate

Neurotransmitters that cause skeletal muscle contraction are normally stored in

motor neuron axon terminals

Exhaustion of energy reserves or decline in pH to production and dissociation of lactic acid causes

muscle fatigue

Which statement regarding the relaxation phase of a muscle twitch is true?

muscle tension falls to resting levels

Which of the following occurs as a result of motor units in a particular muscle being always active, even though their contractions do not produce enough movement to cause contraction?

muscle tone

Muscle fascicles are separated by

perimysium

The skeletal muscle structures that actively shorten and are responsible for muscle fiber contraction are called

sarcomeres

The skeletal muscles store calcium ions in the terminal cisternae of the

sarcoplasmic reticulum

Which of the following statements describes how muscles help maintain homeostasis?

skeletal muscle contractions help maintain body temperature

Which type of scenario is most likely?

small motor units are recruited first

Nonstriated, involuntary muscle is

smooth

What is the function of the transverse tubule?

to transmit electrical impulses to the cell's interior

During active-site exposure, calcium ions bind to which of the following?

troponin

Tropomyosin strands are held in position by which of the following?

troponin molecules

A single stimulus-contraction-relaxation sequence in a muscle fiber is known as a

twitch

Myofibrils are made primarily of

actin and myosin

The striated appearance of skeletal muscle results from

actin and myosin arrangement

When a calcium ion binds to troponin

active sites on actin are exposed

Which of the following sarcomere components is made up of proteins that connect the central portions of each thick filament to its neighbors?

M line

Which statement regarding skeletal muscle is true?

Skeletal muscles contain blood vessels