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36 Cards in this Set

  • Front
  • Back

Which of the following is CORRECTLY paired?

C. skeletal muscle: voluntary control

What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?

B. arrival of an action potential

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

troponin

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

A. actin

What causes the myosin head to disconnect from actin?

D. binding of ATP

What energizes the power stroke?

C. hydrolysis of ATP

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?

D. acetylcholine (ACh)

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?

A. voltage-gated calcium channels

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?

A. exocytosis

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?

C. Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.

How is acetylcholine (ACh) removed from the synaptic cleft?

C. acetylcholinesterase (AChE; an enzyme)

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?

A. terminal cisternae of the sarcoplasmic reticulum

Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?

D. Excitation refers to the propagation of action potentials along the axon of a motor neuron.

Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?

B. Calcium release from the sarcoplasmic reticulum initiates the contraction.

A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?

D. A series of proteins that control calcium release.

What is name given to the regularly spaced infoldings of the sarcolemma?

B. transverse or T tubules

Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?

A. Calcium ions.

What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?

A. Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.

Excitation-contraction coupling includes all EXCEPT which of the following events?

C. release of acetylcholine from axon terminals at the neuromuscular junction

What is a cross bridge cycle?

D. It is the cycle in which an energized myosin head binds to actin and performs a power stroke, then binds to ATP in order to detach and re-energize.

Muscle tissue does NOT ________.

C. produce blood cells

Which type of muscle CANNOT contract without being stimulated by the nervous system?

A. skeletal

Which muscle characteristic describes the ability of muscle to respond to a stimulus?

A. excitability

Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?

D. Acetylcholine is degraded by acetylcholinesterase.

The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?

A. Acetylcholine is released by axon terminals of the motor neuron.

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.

B. extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

Calcium entry into the axon terminal triggers which of the following events?

C. Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.

Acetylcholine binds to its receptor in the sarcolemma and triggers __________.

C. the opening of ligand-gated cation channels

Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?

A. The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?

D. A myosin head bound to actin

What structure is the functional unit of contraction in a skeletal muscle fiber?

B. The sarcomere

Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?

C. Calcium ions are stored in the sarcoplasmic reticulum.

After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?

D. ATP binds to the myosin head.

How does the myosin head obtain the energy required for activation?

B. The energy comes from the hydrolysis of ATP.

What specific event triggers the uncovering of the myosin binding site on actin?

C. Calcium ions bind to troponin and change its shape.

When does cross bridge cycling end?

C. Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.