HW 7

Which of the following occurs when an action potential arrives at the presynaptic terminal? a) Synaptic vessels migrate to the plasma membrane and release acetylcholine. b) Acetylcholine is actively transported from the presynaptic neuron. c) Acetylcholine is actively transported to the postsynaptic neuron. d) Ligand-gated sodium channels open. e) Sodium ions diffuse into the cell

a) Synaptic vessels migrate to the plasma membrane and release acetylcholine.

Successive EPSPs from a presynaptic terminal to a postsynaptic neuron is called ________. a) Temporal summation b) Synaptic plasticity c) Spatial summation d) Divergence

a) Temporal summation

Repolarization occurs because __________. a) potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close b) the extra efflux of potassium ions causes the membrane potential to become slightly more positive than the resting value c) the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level d) more sodium ions diffuse into the cell than potassium ions diffuse out of it e) the inactivation gates of the voltage-gated sodium ion channels begin to open and the diffusion of sodium ions decreases

a) potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close

When threshold is reached in a neuron, depolarization occurs with the same amplitude of potential change. This is known as ____ a) the All-or-None principle b) Cable properties of axons c) A graded response d) Salutatory conduction

a) the All-or-None principle

What structures are involved in electrical synapses? a) Tight junctions b) Gap junctions c) Desmosomes d) Microvilli

b) Gap junctions

Acetylcholine has which effect on the postsynaptic neuron? a) Ligand-gated calcium ion channels open and calcium diffuses inward. b) Ligand-gated sodium ion channels open and sodium diffuses inward. c) Terminal vessels migrate to the plasma membrane d) Voltage-gated calcium ion channels open and calcium diffuses inward. e) Voltage-gated sodium ion channels open and sodium diffuses inward.

b) Ligand-gated sodium ion channels open and sodium diffuses inward.

During depolarization, which of the following statements about voltage-gated ion channels is TRUE? a) K+ gates open before Na+ gates. b) Na+ gates open before K+ gates. c) Na+ and K+ gates open at the same time. d) Na+ gates open while K+ gates remain closed. e) K+ gates open while Na+ gates remain closed.

b) Na+ gates open before K+ gates.

Depolarization of a cell membrane occurs because _____________. a) sodium ions are blocked from entering the cell b) more sodium ions diffuse into the cell than potassium ions diffuse out of it c) the concentration of sodium and potassium ions in the extracellular fluid is at equilibrium d) the concentration of sodium and potassium ions in the cell is at equilibrium

b) more sodium ions diffuse into the cell than potassium ions diffuse out of it

A neuron that has just propagated an action potential is quickly stimulated again, but no response occurs. This neuron must have been in the __________when the second stimulus arrived. a) Relative refractory period b) All-or-None period c) Absolute refractory period d) After- potential period

c) Absolute refractory period

What type of cells produce the myelin sheath in the central nervous system (CNS)? a) Schwann cells b) Microglia c) Oligodendrocytes d) Astrocytes

c) Oligodendrocytes

Which of the following statements about the resting membrane potential is TRUE? a) The exterior of the cell has a net negative charge and the interior has a net positive charge. b) The exterior of the cell has a net negative charge and the interior is neutral. c) The exterior of the cell has a net positive charge and the interior has a net negative charge. d) The exterior of the cell has a net positive charge and the interior is neutral. e) The exterior of the cell is neutral and the interior has a net negative charge.

c) The exterior of the cell has a net positive charge and the interior has a net negative charge.

Depolarization occurs because __________. a) more K+ diffuses into the cell than Na+ diffuses out of it b) more K+ diffuses out of the cell than Na+ diffuses into it c) more Na+ diffuses into the cell than K+ diffuses out of it d) more Na+ diffuses out of the cell than K+ diffuses into it e) both Na+ and K+ diffuse into the cell

c) more Na+ diffuses into the cell than K+ diffuses out of it

Hyperpolarization, or after potential occurs because __________. a) potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close b) the extra efflux of potassium ions causes the membrane potential to become slightly more positive than the resting value c) the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level d) more sodium ions diffuse into the cell than potassium ions diffuse out of it e) the inactivation gates of the voltage-gated sodium ion channels begin to open and the diffusion of sodium ions decreases

c) the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level

An action potential arriving at the presynaptic terminal causes _____. a) voltage-gated sodium ion channels to open, and sodium ions to diffuse into the cell b) voltage-gated sodium ion channels to open, and sodium ions to diffuse out of the cell c) voltage-gated calcium ion channels to open, and calcium ions to diffuse into the cell d) acetylcholine to diffuse into the cell e) ligand-gated sodium channels to open, and sodium ions to diffuse out of the cell

c) voltage-gated calcium ion channels to open, and calcium ions to diffuse into the cell

Which of the following is/are a location of nicotinic ACh receptors? a) Autonomic ganglia b) Specific regions of the brain c) Skeletal muscle d) All of the choices are correct

d) All of the choices are correct

Hyperpolarization that leads to postsynaptic inhibition is a/an ____. a) NMDA b) LTP c) EPSP d) IPSP

d) IPSP

A recently depolarized area of a cell membrane cannot generate an action potential because of the ______________. a)high concentration of potassium ions in the cytoplasm b) presence of receptor sites on the membrane c) high concentration of sodium ions in the extracellular fluid d) absolute refractory period

d) absolute refractory period

Depolarization occurs because __________. a) potassium ions continue to diffuse out of the cell after the inactivation gates of the voltage-gated sodium ion channels begin to close b) the extra efflux of potassium ions causes the membrane potential to become slightly more positive than the resting value c) the increased potassium ion permeability lasts slightly longer than the time required to bring the membrane potential back to its resting level d) more sodium ions diffuse into the cell than potassium ions diffuse out of it e) the inactivation gates of the voltage-gated sodium ion channels begin to open and the diffusion of sodium ions decreases

d) more sodium ions diffuse into the cell than potassium ions diffuse out of it

What structure(s) are present exclusively within the myelin sheath of the PNS? a) Neurilemma b) Nodes of Ranvier c) Myelin d) Sheath of Schwann e) Both neurilemma and sheath of shwann

e) Both neurilemma and sheath of schwann