Exam 6: Neuronal Signaling and the Structure of the Nervous System

A) takes place in the axon terminals of neurons.
B) takes place in the cell bodies of neurons.
C) takes place on ribosomes in the postsynaptic cell's membrane.
D) uses amino acids as precursor molecules.
E) only takes place at synapses outside the central nervous system.

Correct Answer

verified

Show Answer

A) Acetylcholine is broken down by enzymes present on postsynaptic cell membranes.
B) Acetylcholine that is released at synapses binds to adrenergic receptors in the postsynaptic cell membrane.
C) Catecholamines are the most abundant neurotransmitters in the central nervous system.
D) Opiate drugs, such as morphine, are antagonists of a class of neurotransmitters called endorphins.
E) Gamma-aminobutyric acid (GABA) is a major excitatory transmitter in the central nervous system.

Correct Answer

verified

Show Answer

A) Dopamine
B) Acetylcholine
C) Morphine
D) Glutamate
E) Substance P

Correct Answer

verified

Show Answer

A) The rate of propagation of an action potential down an axon is independent of stimulus strength.
B) They are associated with an absolute refractory period.
C) A supra-threshold stimulus is required to stimulate an action potential during the relative refractory period.
D) An action potential occurs whenever a suprathreshold stimulus occurs, and its amplitude does not vary with the size of a stimulus, as long as the membrane is not in the refractory period.
E) Action potentials are always the same size, even when ion gradients vary in size.

Correct Answer

verified

Show Answer

Correct Answer

verified

Show Answer

A) The absolute refractory period refers to the period of time during which another action potential cannot be initiated in that part of the membrane that is undergoing an action potential, no matter how great the strength of the stimulus.
B) The relative refractory period refers to the period of time during which another action potential can be initiated in that part of the membrane that has just undergone an action potential if a stronger than normal stimulus is applied.
C) The refractory period prevents the action potential from spreading back over the part of the membrane that just underwent an action potential.
D) The refractory period places an upper limit on the frequency with which a nerve cell can conduct action potentials.
E) All of the above choices are correct.

Correct Answer

verified

Show Answer

A) It refers to the passage of materials from the cell body of a neuron to the axon terminals.
B) It refers to the passage of materials from axon terminals to the cell body of a neuron.
C) It refers to the transport of materials from the inside to the outside across the axonal membrane.
D) It is especially important for maintaining the integrity of neurons with long axons.

Correct Answer

verified

Show Answer

A) afferent nervous system.
B) sympathetic nervous system.
C) parasympathetic nervous system.
D) somatic motor nervous system.
E) autonomic nervous system.

Correct Answer

verified

Show Answer

A) diencephalon
B) cerebrum
C) limbic system
D) reticular formation
E) cerebellum

Correct Answer

verified

Show Answer

A) The permeability to Na⁺ is much greater than the permeability to K⁺.
B) All of the K⁺ channels in the membrane are open.
C) The voltage-gated Na⁺ channels are in the inactivated state.
D) Most of the voltage-gated Na⁺ channels are in the closed state.
E) There is equal permeability to Na⁺ and K⁺.

Correct Answer

verified

Show Answer

Correct Answer

verified

Show Answer

A) The membrane potential must be at the Na⁺ equilibrium potential.
B) Na⁺ influx must exceed K⁺ efflux.
C) The membrane must be out of the relative refractory period.
D) Na⁺ channels must all be inactivated.
E) Multiple inhibitory postsynaptic potentials (IPSPs) must summate.

Correct Answer

verified

Show Answer

Correct Answer

verified

Show Answer

A) It is faster in small-diameter axons than in large-diameter axons.
B) It is faster for a strong stimulus than for a weak one.
C) It is faster in myelinated axons than in nonmyelinated axons.
D) It is faster in the dendrites than in the axon.
E) It occurs at the same rate in all axons, regardless of their diameter.

Correct Answer

verified

Show Answer

A) is called the potential difference between those points.
B) is called the diffusion potential between those points.
C) is called the current, and is expressed in the units of millimoles.
D) is the same for all ions.

Correct Answer

verified

Show Answer

A) Voltage-gated Na⁺ channels are opened.
B) The Na⁺, K⁺ pump restores the ions to their original locations inside and outside of the cell.
C) The permeability to Na⁺ increases greatly.
D) ATPase destroys the energy supply that was maintaining the action potential at its peak.
E) The permeability to K⁺ increases greatly while that to Na⁺ decreases.

Correct Answer

verified

Show Answer

A) It is a function of the concentration of that ion on both sides of the membrane.
B) It is the potential at which there is no net movement of that ion across the membrane.
C) It is the potential difference across the membrane at which an electric force favoring movement of the ion in one direction is equal in magnitude and opposite in direction to the diffusion force provided by the concentration difference of the ion across the membrane.
D) A permeable ion will move in the direction that will tend to bring the membrane potential toward that ion's equilibrium potential.
E) An anion that is in higher concentration inside the cell than outside the cell will have a negative eqilibrium potential.

Correct Answer

verified

Show Answer

Correct Answer

verified

Show Answer