Muscles

Given these events: 1. action potential travels along the sarcolemma 2. T tubules undergo depolarization 3. voltage-gated Ca2+ ion channels in sarcoplasmic reticulum open 4. Ca2+ ions diffuse into the sarcoplasm 5. Ca2+ ions bind to troponin molecules Choose the arrangement that lists these events in the order they occur following a single stimulation of a skeletal muscle cell. . A) 1,2,3,4,5 B) 1,3,5,4,2 C) 2,1,3,4,5 D) 3,1,5,2,4 E) 4,5,12,3

A) 1,2,3,4,5 The sequence of events occurring after a single stimulation of a skeletal muscle includes: 1,2,3,4,5.

Which of these units contains overlapping actin and myosin myofilaments? A) A band B) H zone C) I band D) M line E) Z disk

A) A band The A band consists of overlapping actin and myosin myofilaments. The H zone consists of myosin myofilaments only.

Unlike neurons, muscle fibers have no A) absolute refractory period. B) action potentials. C) resting membrane potential. D) cell membrane. E) mitochondria.

A) absolute refractory period. Muscle fibers have no absolute refractory period; relaxation is not required before a second action potential can stimulate a second contraction.

Fatty acids can be used as an energy source for muscle contraction during A) aerobic exercise. B) fast, intense exercise. C) anaerobic respiration. D) breakdown of glycogen to glucose. E) the time of oxygen debt.

A) aerobic exercise. The utilization of fatty acids to produce ATP is seen in aerobic respiration and is used by muscles to fuel contraction.

Muscle cells that are cylindrical and branched, each with a single, centrally located nucleus, and that contract spontaneously are A) cardiac muscle. B) skeletal muscle. C) smooth muscle. D) unknown: not enough characteristics to determine the type of muscle

A) cardiac muscle. Cardiac muscle cells are cylindrical and branched, each with a single, centrally located nucleus, and they contract spontaneously. Skeletal muscle cells are not branched, they are multinucleated and under voluntary control.

If the permeability of the plasma membrane to Na+ ions increases, the result is A) depolarization of the plasma membrane. B) repolarization of the plasma membrane. C) little, if any, change in the resting membrane potential of the plasma membrane.

A) depolarization of the plasma membrane. The influx of Na+ ions makes the inside of the cell membrane less negative, depolarizing the cell membrane.

The drug atropine blocks neurotransmitter receptors on the postsynaptic terminal of the neuromuscular junction. This causes . A) flaccid paralysis. B) spastic paralysis. C) no change in muscle function.

A) flaccid paralysis. Atropine causes flaccid paralysis by binding with the acetylcholine receptors on the postsynaptic terminal of the neuromuscular junction. Because acetylcholine cannot bind with the receptors, ligand gated Na+ ion channels are not opened, there is no action potential generated, and no subsequent muscle contraction.

A muscle contraction in which the muscle produces an increasing tension, but the length remains constant is a(n) A) isometric contraction. B) isotonic contraction. C) concentric contraction. D) eccentric contraction.

A) isometric contraction. Isometric contraction occurs when a contracting muscle produces tension with the length remaining constant.

Which of these characteristics is typical of a slow-twitch muscle fiber? A) large number of mitochondria B) few capillaries C) low myoglobin content D) largely anaerobic E) b, c, and d

A) large number of mitochondria Only choice A is correct; slow-twitch muscle fibers do have a large number of mitochondria that are utilized in aerobic respiration.

Given these events: 1. acetylcholine binds to receptors on the postsynaptic membrane 2. acetylcholinesterase breaks down acetylcholine 3. choline is reabsorbed by presynaptic membrane 4. depolarization of postsynaptic membrane occurs 5. ligand-gated Na+ ion channels open Choose the arrangement that lists the events in the order they occur when an action potential travels through the axon of a motor neuron. A) 1,2,3,4,5 B) 1,5,4,2,3 C) 2,1,3,4,5 D) 4,3,2,1,5 E) 5,4,1,2,3

B) 1,5,4,2,3 The sequence of events occurring as an action potential travels through the axon of a motor neuron include: 1,5,4,2,3.

Given these events: 1. active sites on actin myofilament are exposed 2. actin myofilament slides over myosin myofilament 3. Ca2+ ion binds to troponin 4. myosin heads move 5. cross bridges form Choose the arrangement that lists the correct order in which they occurduring a single stimulation of a skeletal muscle. A) 4,3,2,1,5 B) 3,1,5,4,2 C) 3,2,5,4,1 D) 2,4,3,5,1 E) 1,2,3,4,5

B) 3,1,5,4,2 In sequence, the events that occur during a single stimulation of skeletal muscle include: 3,1,5,4,2.

For cross bridge release, it is necessary for __________ to attach to the myosin head. A) a tropomyosin molecule B) ATP C) Ca2+ ions D) a troponin molecule E) the sarcolemma

B) ATP ATP must attach to the myosin head for cross bridges to release from actin.

__________ surrounds each muscle fasciculus, whereas __________ surrounds each muscle fiber. A) Epimysium, perimysium B) Perimysium, endomysium C) Epimysium, endomysium D) Endomysium, perimysium E) Endomysium, epimysium

B) Perimysium, endomysium Perimysium surrounds each muscle fasciculus and endomysium surrounds each muscle fiber.

Which of these is NOT a part of the actin myofilament? A) actin B) cisternae C) tropomyosin D) troponin

B) cisternae Cisternae are not part of the actin myofilament. Actin myofilaments consist of tropomyosin, troponin, and actin.

During contraction, muscles shorten __________ , and lengthen __________ . A) forcefully, forcefully B) forcefully, passively C) passively, forcefully D) passively, passively

B) forcefully, passively During contraction, muscles shorten forcefully and lengthen passively.

Visceral smooth muscle A) responds in an all-or-none fashion to action potentials. B) has slow waves of depolarization and repolarization. C) has depolarization occur when the cell becomes more permeable to Na+ ions and K+ ions. D) requires a stimulus from a neuron or hormone. E) produces strong contractions that only last for a few milliseconds.

B) has slow waves of depolarization and repolarization. Visceral smooth muscle does not respond in a all-or-none fashion to action potentials, a series of action potentials may result in only one contraction.

Which of these locations has the ability to break down ATP, which releases energy? A) globular actin molecule B) head of myosin molecule C) troponin molecule D) tropomyosin molecule E) troponin-tropomyosin complex

B) head of myosin molecule The head of the myosin molecule has ATPase activity that breaks down ATP, releasing energy.

Most of the interior of muscle fibers is filled with A) fasciculi. B) myofibrils. C) nuclei. D) sarcoplasm. E) sarcoplasmic reticulum

B) myofibrils. Most of the interior of muscle fibers is filled with myofibrils, the contractile proteins composed of myofilaments.

In the neuromuscular junction, the axon is also called the A) postsynaptic membrane. B) presynaptic terminal. C) synaptic cleft. D) synaptic vesicle.

B) presynaptic terminal. The axon is also called the presynaptic terminal in the neuromuscular junction. The synaptic cleft is the space between the axon terminal and the muscle fiber.

Anaerobic respiration A) produces 38 ATPs per glucose molecule. B) produces an oxygen debt. C) occurs in resting muscles or muscles undergoing long-term exercise. D) can use fatty acid to produce ATP. E) all of these

B) produces an oxygen debt. Aerobic, not anaerobic, respiration occurs in resting muscles or muscles undergoing long-term exercise. Anaerobic respiration occurs during short periods of intense exercise.

The most common type of fatigue is: A) muscular fatigue. B) psychological fatigue. C) synaptic fatigue. D) sarcoplasmic reticulum fatigue. E) army fatigue.

B) psychological fatigue. Psychological fatigue is the most common type of fatigue, where a person perceives that additional muscular work is not possible. Muscular fatigue occurs when there is ATP depletion, and physiologically, the ability to generate muscle tension declines.

Which of these is correctly matched? A) multiunit smooth muscle -- spontaneous contractions B) visceral smooth muscle -- contracts when stretched C) skeletal muscle -- slower, longer lasting contractions than smooth muscle D) multiunit smooth muscle -- numerous gap junctions; autorhythmic E) all of these

B) visceral smooth muscle -- contracts when stretched Visceral smooth muscle tends to contract in response to a sudden stretch.

Which of these units contains the Z disk? A) A band B) H zone C) I band D) M line

C) I band The I band contains the Z disk.

A motor unit is A) all the fibers in one muscle. B) all the fibers in one fasciculus. C) all the muscle fibers innervated by a single motor neuron. D) all the nerves that innervate one muscle fiber.

C) all the muscle fibers innervated by a single motor neuron A motor unit is all the muscle fibers innervated by a single motor neuron.

Each muscle cell is a A) fasciculus. B) sarcomere. C) fiber. D) myofibril.

C) fiber. Each muscle cell is a fiber. Myofibrils are the protein structures composed of myofilaments found inside the muscle fibers (cells).

Fast-twitch muscle fibers A) are more resistant to fatigue than slow-twitch fibers. B) have a richer blood supply than slow-twitch fibers. C) have a larger amount of stored glycogen than slow-twitch fibers. D) have more mitochondria than slow-twitch fibers. E) have more myoglobin than slow-twitch fibers.

C) have a larger amount of stored glycogen than slow-twitch fibers. Slow-twitch muscle fibers have a richer blood supply than fast-twitch fibers.

Multiple-wave summation is caused by A) stimuli of increasing size. B) increasing number of nerves stimulated. C) increasing frequency of stimuli. D) complete relaxation between stimuli. E) a subthreshold stimulus.

C) increasing frequency of stimuli. Increasing frequency of stimuli causes multiple-wave summation, increased tension due to the stimulation of muscle in rapid succession resulting in an increased rate of contraction, as well as a decreased rate, then absence of relaxation.

Even though each muscle fiber responds in all-or-none fashion, a whole muscle can contract with varying force because of A) different threshold values of each fiber. B) total tetanus of the muscle. C) multiple motor unit summation. D) rigor mortis. E) the lag phase of contraction.

C) multiple motor unit summation. A whole muscle can contract with varying force because of multiple motor unit summation. Stimuli of increasing strength can stimulate a greater number of motor units, causing a greater force of contraction.

The enlarged areas of the sarcoplasmic reticulum near the T tubules are the A) sarcolemma. B) sarcomeres. C) terminal cisternae. D) troponin molecules. E) tropomyosin molecules.

C) terminal cisternae. Terminal cisternae are the enlarged areas of the sarcoplasmic reticulum near the T tubules. Sarcomeres are the functional units of skeletal muscle.

Given these events: 1. acetylcholine is released from synaptic vesicles 2. an action potential reaches the presynaptic terminal 3. Ca2+ ions diffuse into the cell 4. acetylcholine is secreted from the presynaptic terminal by exocytosis Choose the arrangement that lists the events in the order they occur when an action potential travels through the axon of a motor neuron. A) 1,2,3,4 B) 1,3,4,2 C) 2,1,3,4 D) 2,3,1,4 E) 3,2,1,4

D) 2,3,1,4 The sequence of events occurring as an action potential travels through the axon of a motor neuron include: 2,3,1,4.

Which of these is part of the contraction process of smooth muscle? A) Calcium ions bind to troponin. B) Caveolae bind with calcium to produce cross bridges. C) Troponin and tropomyosin are moved. D) Calcium ions bind to calmodulin, which activates an enzyme.

D) Calcium ions bind to calmodulin, which activates an enzyme. Calcium binding to calmodulin activates the enzyme myosin kinase, which allows the transfer of a phosphate group from ATP to the head of the myosin and results in the formation of a cross bridge.

Troponin binds to A) actin. B) calcium ions. C) tropomyosin. D) all of these

D) all of these

Which of these processes results in an increase in the force of contraction of a whole muscle? A) multiple motor unit summation B) multiple wave summation C) treppe D) all of these

D) all of these Multiple motor unit summation, multiple wave summation, and treppe all cause an increase in the force of contraction of a whole muscle.

Which of these layers of a skeletal muscle is the same as the fascia? A) sarcolemma B) perimysium C) fasciculus (bundle) D) epimysium E) endomysium

D) epimysium The epimysium, consisting of dense collagenous connective tissue, is the same as the fascia. The fasciculus is surrounded by a perimysium.

The resting membrane potential occurs when A) sodium ions diffuse into the cell. B) sodium ions diffuse out of the cell. C) potassium ions diffuse into the cell. D) potassium ions diffuse out of the cell. E) large negative molecules diffuse out of the cell

D) potassium ions diffuse out of the cell. The resting membrane potential occurs when potassium ions diffuse out of the cell polarizing the plasma membrane.

Given these sources of energy during exercise: 1. anaerobic respiration 2. aerobic respiration 3. ATP and creatine phosphate in the cell The correct sequence for the use of these energy sources by muscle cells when an individual starts exercising is A) 1,2,3. B) 1,3,2. C) 2,1,3. D) 3,2,1. E) 3,1,2.

E) 3,1,2. The correct sequence of energy sources used by muscle cells during exercise is: 3,1,2.

Cross bridges form during muscle contraction when myosin comes in contact with active sites on A) troponin molecules. B) tropomyosin molecules. C) calcium ions. D) acetylcholine molecules. E) actin molecules.

E) actin molecules. Myosin comes in contact with actin molecules by the formation of cross bridges during muscle contraction.

Which of these is (are) required for the relaxation of a muscle fiber? A) ATP B) Ca2+ ion uptake into the sarcoplasmic reticulum C) acetylcholinesterase activity D) no additional stimulation of the neuron E) all of these

E) all of these ATP, Ca2+ ion uptake into the sarcoplasmic reticulum, acetylcholinesterase activity, and no additional stimulation of the neuron, are all required for the relaxation of skeletal muscle fiber.

During muscle contraction, which of these processes requires ATP? A) transport of calcium ions into the sarcoplasmic reticulum B) release of cross-bridges C) formation of cross-bridges D) active transport of Na+ and K+ ions E) all of these

E) all of these During muscle contraction, ATP is required for the transport of calcium ions into the sarcoplasmic reticulum, but also for the release of cross-bridges, the formation of cross-bridges, and the active transport of Na+ and K+ ions.

Which of these regions shorten(s) during skeletal muscle contraction? A) A band B) I band C) H zone D) both a and b E) both b and c

E) both b and c The I band and the H zone both shorten during skeletal muscle contraction.