final exam ch 7

38) Which of the following is one of the steps that ends a contraction? A) Sarcoplasmic reticulum absorbs sodium ions. B) Acetylcholine binds to receptors on the sarcolemma. C) Calcium ions bind to troponin. D) Acetylcholine is broken down by acetylcholinesterase. E) An action potential spreads across the entire surface of the muscle fiber.

) Acetylcholine is broken down by acetylcholinesterase.

The ________ contains vesicles filled with acetylcholine. A) axon terminal B) motor end plate C) neuromuscular junction D) synaptic cleft E) transverse tubule

) axon terminal

Upon the nerve impulse arriving at the axon terminal, A) active sites on actin are exposed. B) active sites on myosin are exposed. C) actin heads will bind to myosin. D) muscle relaxation occurs. E) acetylcholine is released.

acetylcholine is released.

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 A) cAMP. B) DNA. C) RNA. D) ATP. E) tRNA.

ATP

Creatine phosphate serves to A) cause the decomposition of ATP. B) supply energy to synthesize ATP. C) decompose ADP. D) synthesize ADP. E) synthesize glucose.

B

Which of the following occurs when glycolysis produces pyruvate faster than it can be used by the mitochondria? A) Pyruvate levels drop in the cytoplasm. B) Lactic acid is produced. C) Pyruvate is converted to sucrose. D) Lactic acid dissociates into a water molecule and hydrogen. E) Oxygen is produced.

B

31) The enzyme acetylcholinesterase causes acetylcholine to A) break down. B) synthesize. C) bond to actin. D) be secreted. E) form cross-bridges.

break down.

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? A) treppe B) tetany C) muscle tone D) fatigue E) a twitc

C

In response to action potentials arriving from the transverse tubules, the sarcoplasmic reticulum releases A) acetylcholine. B) sodium ions. C) potassium ions. D) calcium ions. E) acetylcholinesterase.

calcium ions.

The specialized sarcolemma that contains acetylcholine receptors is the A) synaptic knob. B) motor end plate. C) motor unit. D) synaptic cleft. E) I band

motor end plate.

Neurotransmitters that cause skeletal muscle contraction are normally stored in A) myofibrils. B) motor neuron axon terminals. C) motor units. D) motor end plates. E) actin.

motor neuron axon terminals.

After death, rigor mortis lasts until A) ATP is produced. B) T-tubules recapture calcium ions. C) sodium ions are released by the sarcoplasmic reticulum. D) sarcomeres lengthen. E) myofilaments are broken down.

myofilaments are broken down.

Calcium ions are released from the sarcoplasmic reticulum during the ________ phase of contraction. A) latent B) contraction C) twitch D) relaxation E) recovery

A

During which phase is the stimulus frequency so high that the relaxation phase is eliminated? A) complete tetanus B) a twitch C) incomplete tetanus D) recovery E) recruitment

A

Glycolysis A) is an anaerobic process. B) is the breakdown of pyruvate to glucose. C) acts as the only source of ATP in muscle tissue. D) is only active during rest. E) occurs in the nucleus.

A

The additional oxygen required during the recovery period to restore the normal pre-exertion levels is called the A) oxygen debt. B) refractory oxygen amount. C) anaerobic oxygen threshold. D) aerobic oxygen threshold. E) aerobic oxygen conversion.

A

Which statement regarding the relaxation phase of a muscle twitch is true? A) The phase begins at stimulation and typically lasts about two milliseconds. B) Muscle tension falls to resting levels. C) The action potential sweeps across the sarcomere during this period. D) Tension rises to a peak. E) Cross-bridges are interacting with active sites on actin filaments throughout this period.

B

A resting muscle generates most of its ATP by A) conversion of creatine phosphate. B) anaerobic respiration. C) aerobic respiration. D) glycolysis. E) heat loss.

C

Choose the correct statement regarding motor units. A) Muscle fibers of each motor unit are not mingled with those of other motor units. B) During a sustained contraction, all motor units are activated simultaneously. C) A motor neuron may control only two or three muscle fibers of the eye muscle(s). D) When muscles contract for sustained periods, maximal tension is maintained. E) Most motor neurons control fewer than five muscle fibers.

C

During moderate activity, which of the following is true regarding muscle metabolism? A) The ATP produced is used to build energy reserves of ATP and glycogen. B) Most ATP is produced through glycolysis, with lactate and hydrogen ions as byproducts. C) Glucose and fatty acids are catabolized. D) Mitochondrial activity provides about one-third of the ATP consumed. E) Mitochondria are not involved.

C

Which statement regarding isometric contractions is true? A) Tension rises during a contraction. B) The skeletal muscle's length changes. C) The tension produced never exceeds the load. D) Tension remains at a constant level until relaxation occurs. E) Examples are walking and running.

C

Which of the following occurs when tension production rises to a peak and very brief periods of relaxation occur? A) resting period B) latency C) tension plateau D) incomplete tetanus E) complete tetanus

D

53) Why do individual muscle twitches have to be added together, as in summation or tetanus? A) Only added twitches produce any muscle contraction: A fiber undergoing a muscle twitch does not contract at all. B) There has to be a critical mass of muscle twitches for calcium to be released into the muscle cell. C) Not enough acetylcholine will be produced for contraction without multiple twitches. D) Multiple twitches add up to an increase in muscle fiber tension, which increases the strength of the muscle. E) Not enough ATP is generated by one muscle twitch.

D

Exhaustion of energy reserves or decline in pH due to production and dissociation of lactic acid causes A) muscle contraction. B) the conduction of neural information to the muscle fiber. C) muscle relaxation. D) muscle fatigue. E) the striated appearance of skeletal muscle.

D

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? A) neurons B) cardiac muscle cells C) skeletal muscle fibers D) liver cells E) erythrocytes

D

Regarding muscle fiber elongation, A) many active mechanisms exist for muscle fiber elongation. B) muscle contraction is passive; whereas, elongation is active. C) opposing muscle movements are not a factor. D) gravity may help lengthen a muscle fiber after elongation. E) elastic forces are generated where a muscle fiber elongates.

D

34) 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 A) 2, 3, 4, 1, 5 B) 4, 2, 1, 5, 3 C) 1, 2, 4, 3, 5 D) 2, 4, 1, 3, 5 E) 1, 2, 4, 5, 3

D) 2, 4, 1, 3, 5

) A single stimulus-contraction-relaxation sequence in a muscle fiber is known as a(n) A) incomplete tetanus. B) latent period. C) complete tetanus. D) summation. E) twitch.

E

Botulism A) is the result of an attack on acetylcholine receptors by the immune system. B) is usually tied to a genetic predisposition. C) is a viral illness. D) results from the loss of acetylcholine receptors at the motor end plate. E) results from a bacterial toxin that prevents the release of acetylcholine at the axon terminals.

E

Muscle cells A) actively lengthen. B) generate compression. C) possess a mechanism that regulates the tension amount by changing the number of contracting sarcomeres. D) vary tension production based on the amount of sodium ions bound to actin. E) can only contract.

E

Which statement regarding "heat loss" is true? A) Muscle activity does not generate heat. B) Shivering in a cold environment results in higher levels of heat loss. C) When skeletal muscles are contracting at peak levels, body temperature drops. D) Heat loss is reduced when blood flow to the skin increases. E) Muscle contractions play an important role in the maintenance of normal body temperature.

E

As a skeletal muscle contraction is initiated, acetylcholine binding alters the motor end plate membrane's permeability to A) acetylcholinesterase. B) sodium ions. C) calcium ions. D) chloride ions. E) potassium ions.

sodium ions.

Acetylcholinesterase is found within the A) nucleus. B) sarcolemma. C) myofibril. D) sarcomere. E) synaptic cleft.

synaptic cleft.