A&P Chapter 9 Questions

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell? calcium ion pump troponin ATP arrival of an action potential

The binding of calcium to which molecule causes the myosin binding sites to be exposed? actin troponin tropomyosin myosin

A myosin head binds to which molecule to form a cross bridge? troponin tropomyosin actin

What causes the myosin head to disconnect from actin? binding of ATP binding of calcium hydrolysis of ATP binding of troponin

What causes the power stroke? calcium release of ADP and Pi hydrolysis of ATP binding of ATP

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter? acetylcholine (ACh) serotonin dopamine norepinephrine

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open? voltage-gated calcium channels voltage-gated potassium channels chemically gated calcium channels voltage-gated sodium channels

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft? a channel exocytosis a protein carrier

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur? Binding causes chemically gated potassium channels to open in the motor end plate. Binding causes potassium voltage-gated channels to open in the motor endplate. Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate. Binding causes voltage-gated sodium channels to open in the motor endplate.

How is acetylcholine (ACh) removed from the synaptic cleft? a reuptake pump on the axon terminal diffusion away from the synaptic cleft acetylcholinesterase (AChE; an enzyme) All of the above.

The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell? cytosol T tubule terminal cisternae of the sarcoplasmic reticulum sarcolemma

Myofilament with a knob-like head

Myofilament stiffened and stabilized by tropomyosin

The cytoplasm of a skeletal muscle fiber

Bundle of skeletal muscle fibers enclosed by connective tissue called perimysium

Membrane of muscle cell

Blocks myosin-binding sites on actin

Long cylindrical cells

Contractile unit

Made up of several sarcomeres

What is the role of calcium in the cross bridge cycle? Calcium binds to active sites on actin, forming the cross bridge. Calcium binds to myosin, causing the myosin head to release from the actin myofilament. Calcium binds to troponin, altering its shape. Calcium binds to troponin, exposing the active site on troponin.

What role does tropomyosin play in the cross bridge cycle? Tropomyosin pushes the myosin head away, causing cross bridge detachment. Tropomyosin binds to calcium, causing muscle relaxation. The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form. Tropomyosin moves the actin filament relative to the myosin filament

How does troponin facilitate cross bridge formation? Troponin controls the position of tropomyosin on the thin filament, enabling myosin heads to bind to the active sites on actin. Troponin hydrolyzes ATP, which provides the energy necessary for cross bridges to form. Troponin gathers excess calcium that might otherwise block actin's progress. Troponin moves away from the active sites on actin, permitting cross bridge formation.

What, specifically, is a cross bridge? myosin binding to actin tropomyosin covering the active sites on actin calcium binding to troponin ATP binding to the myosin head

Which event causes cross bridge detachment? ATP binding to the myosin head release of ADP and inorganic phosphate from the myosin head release of calcium from troponin nervous input ends

Where in the cross bridge cycle does ATP hydrolysis occur? during the cocking of the myosin head during the power stroke during the movement of tropomyosin to expose the active sites on actin during the removal of calcium from troponin

How/when does the myosin head cock back to store energy for the next cycle? when ADP is released from the myosin head The power stroke cocks the myosin head. The sliding of the actin myofilament during the power stroke re-cocks myosin heads that have previously delivered their power stroke. After the myosin head detaches, energy from ATP hydrolysis is used to re-cock the myosin head.

BMD (2,3-butanedione 2-monoximime) inhibits myosin, such that ATP can bind to myosin but myosin is unable to hydrolyze the bound ATP. What effect would BMD have on the cross bridge cycle? Myosin heads would remain detached, unable to cock. Tropomyosin would not move, and the active sites on actin would not be exposed. Myosin heads would remain attached to actin, unable to detach. Myosin heads would remain attached to actin, unable to perform the power stroke.

During contraction, what prevents actin myofilaments from sliding backward when a myosin head releases? There are always some myosin heads attached to the actin myofilament when other myosin heads are detaching. The cross bridge remains in place, preventing the actin myofilament from sliding. The actin myofilament can only move in one direction relative to the myosin filament. Calcium blocks the active sites on actin.

Which of the following is CORRECTLY paired? cardiac muscle: nonstriated smooth muscle: striated cardiac muscle: voluntary control skeletal muscle: voluntary control

Muscle tissue does NOT ________. generate heat maintain posture produce blood cells produce movement stabilize joints

Which muscle characteristic describes the ability of muscle to respond to a stimulus? contractility elasticity excitability extensibility

Skeletal muscle cells are grouped into bundles called __________. myofilaments fascicles muscle fibers myofibrils

Synaptic vesicles at the neuromuscular junction contain __________. synaptic potentials ACh receptors calcium acetylcholine

ACh receptors are found mainly in the __________. synaptic vesicles axon terminal terminal cisternae sarcolemma

What most directly causes synaptic vesicles to release acetylcholine into the synaptic cleft? calcium entering the axon terminal an action potential arriving at the axon terminal sodium entering the muscle fiber depolarization of the sarcolemma

Acetylcholine receptors are best characterized as what type of channel? voltage-gated Na+-K+ channels chemically gated Ca2+ channels chemically gated Na+-K+ channels voltage-gated Ca2+ channels

When the chemically gated ion channels open, which ion is mainly responsible for depolarizing the sarcolemma? calcium potassium ACh sodium

What is the primary mechanism by which ACh is cleared from the synaptic cleft? endocytosis by synaptic vesicles diffusion away from the synaptic cleft broken down by acetylcholinesterase reuptake into the synaptic terminal

What would happen if acetylcholine was not removed from the synaptic cleft? Multiple action potentials would occur in the muscle fiber. Multiple action potentials would occur in the motor neuron. The acetylcholine receptors would not open. Voltage-gated Ca2+ channels would remain open.

Which of the following is true concerning the anatomy of a skeletal muscle fiber? Myofibrils contain thick and thin filaments. A triad consists of a T tubule and the nearby sarcolemma. T tubules are extensions of the sarcoplasmic reticulum. The sarcolemma is the muscle fiber's cytoplasm.

The calcium that initiates skeletal muscle contraction is released from what structure(s)? sarcolemma terminal cisternae T tubules sarcomeres

Which of the following are composed of myosin? tropomyosin intermediate filaments thick filaments thin filaments

In muscle fibers, which regulatory protein blocks the attachment of myosin heads to actin? tropomyosin thick filaments calcium acetylcholinesterase

What event most directly triggers the release of calcium from the terminal cisternae? movement of tropomyosin away from the active sites on actin cross bridge formation between the thick and thin filaments action potential propagating toward the axon terminal action potential propagating down the T tubule

How do calcium ions initiate contraction in skeletal muscle fibers? Calcium ions bind to troponin, changing troponin's shape. Calcium ions provide the energy necessary for the myosin head power stroke. Calcium ion movement depolarizes the sarcolemma at the synaptic cleft. Calcium ions bind to tropomyosin, exposing the active sites on actin.

Which of the following best describes the events of "excitation" in "excitation-contraction coupling"? movement of tropomyosin away from the active sites on actin propagation of the action potential along the sarcolemma release of calcium from the terminal cisternae cross bridge formation

Which of the following best describes the events of "contraction" in "excitation-contraction coupling"? cross bridge formation sliding of myofilaments release of calcium from the terminal cisternae propagation of the action potential along the sarcolemma of the muscle fiber

What is the type of chemical reaction used to rebuild ADP into ATP? hydrolysis rehydration synthesis dehydration synthesis

Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products? Krebs cycle and oxidative phosphorylation glycolysis hydrolysis of creatine phosphate

Which of the following processes produces 36 ATP? glycolysis Krebs cycle and oxidative phosphorylation hydrolysis of creatine phosphate

The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________. ATP is used to rephosphorylate creatine into creatine phosphate. Oxygen rebinds to myoglobin. Pyruvic acid is converted back to lactic acid. Glycogen is synthesized from glucose molecules.

Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP? white fast twitch fibers red slow twitch fibers

What is the actin status to begin cross bridge formation?