anatomy exam 2 chapter 7
Each myofibril consists of approximately ________ sarcomeres.
10,000
Myofibrils are made primarily of
actin and myosin
The striated appearance of skeletal muscle results from
actin and myosin arrangement.
A resting muscle generates most of its ATP by
aerobic respiration
The stiffness that occurs at death, when actin and myosin molecules stay linked to each other in a contracted state, is due to a lack of
ATP
Which of the following is one of the steps that ends a contraction?
Acetylcholine is broken down by acetylcholinesterase
The ________ contains vesicles filled with acetylcholine.
axon terminal
The enzyme acetylcholinesterase causes acetylcholine to
break down.
Which statement regarding "heat loss" is true?
Muscle contractions play an important role in the maintenance of normal body temperature.
Which statement regarding isometric contractions is true?
The tension produced never exceeds the load
Upon the nerve impulse arriving at the axon terminal
acetylcholine is released
Muscle cells
can only contract
During which phase is the stimulus frequency so high that the relaxation phase is eliminated?
complete tetanus
Exhaustion of energy reserves or decline in pH due to production and dissociation of lactic acid causes
muscle fatigue
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
The additional oxygen required during the recovery period to restore the normal pre-exertion levels is called the
oxygen debt.
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(n)
twitch
The active sites on actin molecules are usually covered up by other molecules. What is the critical material required to uncover the active sites on the actin molecules that will then bind to myosin heads?
calcium
The specialized sarcolemma that contains acetylcholine receptors is the
motor end plate.
In response to action potentials arriving from the transverse tubules, the sarcoplasmic reticulum releases
calcium ions
Neurotransmitters that cause skeletal muscle contraction are normally stored in
motor neuron axon terminals.
After death, rigor mortis lasts until
myofilaments are broken down
Place these steps of muscle contraction in the correct order. 1. Action potential is generated along the sarcolemma 2. Nerve impulse arrives at synapse 3. Calcium is released into muscle cell cytoplasm 4. Acetylcholine is produced 5. Actin and myosin molecules continuously cross-link, with actin molecules being pulled inward
2, 4, 1, 3, 5
The region of a sarcomere containing myosin, going from one end of the myosin molecules to the other end of the myosin molecules, is the
A band
Choose the correct statement regarding motor units
A motor neuron may control only two or three muscle fibers of the eye muscle(s)
During moderate activity, which of the following is true regarding muscle metabolism?
Glucose and fatty acids are catabolized.
The area of the sarcomere that is the light region between two successive A-bands is the
I band
Which of the following occurs when glycolysis produces pyruvate faster than it can be used by the mitochondria?
Lactic acid is produced
Why do individual muscle twitches have to be added together, as in summation or tetanus?
Multiple twitches add up to an increase in muscle fiber tension, which increases the strength of the muscle.
Which statement regarding the relaxation phase of a muscle twitch is true?
Muscle tension falls to resting levels
Which of the following statements describes how muscles help maintain homeostasis?
Skeletal muscle contractions help maintain body temperature.
Which statement regarding skeletal muscle is true?
Skeletal muscles contain blood vessels.
A layer of collagen fibers that surrounds an entire muscle is called?
epimysium.
A muscle ________ contains a sarcolemma, sarcoplasm, myofilaments, and myofibrils.
fiber
Regarding muscle fiber elongation
gravity may help lengthen a muscle fiber after elongation
Skeletal muscle fibers differ from "typical cells" in that these muscle fibers
have many nuclei.
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
Calcium ions are released from the sarcoplasmic reticulum during the ________ phase of contraction.
latent
Regarding lactic acid regulation, which cells in the body consume extra oxygen and produce ATP for the conversion of excess lactate absorbed from the blood back to glucose?
liver cells
A sheath of connective tissue surrounding a bundle of striated muscle fibers is called?
perimysium
Muscle fascicles are separated by
perimysium.
Botulism
results from a bacterial toxin that prevents the release of acetylcholine at the axon terminals
The area between Z lines is the
sarcomere.
The terminal cisternae are structural features of the
sarcoplasmic reticula.
The skeletal muscles store calcium ions in the terminal cisternae of the
sarcoplasmic reticulum
As a skeletal muscle contraction is initiated, acetylcholine binding alters the motor end plate membrane's permeability to
sodium ions
Creatine phosphate serves to
supply energy to synthesize ATP
Acetylcholinesterase is found within the
synaptic cleft.
Regarding a skeletal muscle fiber, wherever a T-tubule encircles a myofibril, the tubule is tightly bound to
the sarcoplasmic reticulum.
What is the function of the transverse tubule?
to transmit electrical impulses to the cell's interior