mastering a&p- chapter 11 (part of 12) EXAM 5

Although it plays a role, it is not a primary determinant of the resting membrane potential

Na+ permeability

How is an action potential propagated along an axon? A. An efflux of potassium from the current action potential depolarizes the adjacent area. B. An influx of sodium ions from the current action potential depolarizes the adjacent area. C. Stimuli from the graded (local) potentials from the soma and dendrites depolarize the entire axon.

An influx of sodium ions from the current action potential depolarizes the adjacent area.

Arrange the parts in order, from left to right, of a successful direct depolarization path within one neuron.

Dendrite > Cell body > Axon hillock > Axon > Presynaptic terminal

The primary determinant of the resting membrane potential

K+ permeability

Which statement best describes exocytosis? A. Membrane organelles fuse together and mix neurotransmitter. B. Membrane organelles fuse with the membrane and release contents out of the cell. C. Membrane organelles fuse with the membrane and release contents inside the cell D. Sodium from the action potential fuses with the membrane vesicle and releases the neurotransmitter in the cytoplasm, which can then diffuse out to the extracellular fluid.

Membrane organelles fuse with the membrane and release contents out of the cell.

The resting membrane potential of the cell

Membrane potential of −70 mV

The point at which there is no net movement of K+ into or out of the cell

Membrane potential of −90 mV

The concentrations of which two ions are highest outside the cell? View Available Hint(s) a. K+ and protein anions (A−) b. Na+ and protein anions (A−) c.Na+ and Cl− d. K+ and Cl−

Na+ and Cl−

How do neurofibrils differ from nerve fibers? a. Neurofibrils are cytoskeletal intermediate filaments maintaining cell shape, but they do not conduct impulses. b. Neurofibrils are confined to dendrite receptor areas and are consequently not found in nerve fibers. c. Neurofibrils are axon subunits that are bundled together to make up a single nerve fiber. d. There is no real difference, since they are both capable of impulse conduction away from a neuron.

Neurofibrils are cytoskeletal intermediate filaments maintaining cell shape, but they do not conduct impulses.

Why does the action potential only move away from the cell body? The flow of the sodium ions only goes in one direction—away from the cell body The areas that have had the action potential are refractory to a new action potential.

The areas that have had the action potential are refractory to a new action potential.

When an action potential arrives at the end of the axon terminal, a series of events take place that result in the release of neurotransmitter from the presynaptic axon. Select the answer that correctly describes the primary stimulus for vesicles to move toward the cell membrane and eventually release their contents. A. Axonal Ca+2 is increased because endoplasmic reticulum voltage-gated calcium channels open and Ca+2 enters the cytoplasm. B. Voltage-gated channels open, and K+ exits to the extracellular fluid, decreasing intracellular K+. C. Voltage-gated membrane channels open, and multiple types of ions enter the cytoplasm, increasing the intracellular positive charge. D. Voltage-gated membrane channels open, and Ca+2 enters the cytoplasm, increasing intracellular calcium.

Voltage-gated membrane channels open, and Ca+2 enters the cytoplasm, increasing intracellular calcium.

The velocity of the action potential is fastest in which of the following axons? a large unmyelinated axon a small unmyelinated axon a small myelinated axon

a small myelinated axon

The neuron cannot respond to a second stimulus, no matter how strong

absolute refractory peirod

Also called a nerve impulse transmitted by axons.

action potential

What condition will increase the diffusion of molecules, such as neurotransmitters? an increased viscosity of the fluid between neurons an increase in number of postsynaptic receptors an increase in the distance between the neurons an increase in the amount of neurotransmitter exocytized by the presynaptic axon

an increase in the amount of neurotransmitter exocytized by the presynaptic axon

If the membrane of a postsynaptic dendrite is setting up a graded potential, what must have happened after neurotransmitter was released by the presynaptic terminal? The neurotransmitter __________.

bound at postsynaptic receptors to open postsynaptic ion channels

The interior of the cell becomes less negative due to an influx of sodium ions.

depolarization

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron, a. the receiving neuron becomes more positive inside. b. the receiving neuron becomes more negative inside. c. vesicles in the synaptic terminal fuse to the plasma membrane of the sending neuron. d. ion channels in the plasma membrane of the sending neuron open. e. ion channels in the plasma membrane of the receiving neuron open.

ion channels in the plasma membrane of the receiving neuron open.

A molecule that carries information across a synaptic cleft is a... neurotransmitter. sending neuron. receiving neuron. synapse. synaptic cleft.

neurotransmitter

Let's consider a scenario in which the resting membrane potential changes from −70 mV to +70 mV, but the concentrations of all ions in the intracellular and extracellular fluids are unchanged. Predict how this change in membrane potential affects the movement of Na+. The electrical gradient for Na+ would tend to move Na+ __________ while the chemical gradient for Na+ would tend to move Na+ __________. a. out; in b. in; in c. out; out d. in; out

out, in

Which of the following choices best represents synaptic transmission? presynaptic cell body to dendrite to synapse presynaptic axon to presynaptic cell body to dendrite presynaptic axon to synapse to postsynaptic axon presynaptic axon to synapse to dendrite or postsynaptic cell body

presynaptic axon to synapse to dendrite or postsynaptic cell body

An exceptionally strong stimulus can trigger a response.

relative refractory peirod

The specific period during which potassium ions diffuse out of the neuron due to a change in membrane permeability.

repolarization

Which of the following best characterizes depolarization? a. small, consecutive steps of K+ entering the cytoplasm b. small, consecutive steps of Na+ exiting from the cytoplasm into the extracellular fluid c. small, consecutive steps of Na+ penetration into the axon along its length d. mass movement of Na+ into the axon cytoplasm from the cell body to the terminal

small, consecutive steps of Na+ penetration into the axon along its length

Stimulation of a postsynaptic neuron by many terminals at the same time.

spatial summation

An insufficient stimulus to reach an action potential

subthreshold stimulus

The small space between the sending neuron and the receiving neuron is the vesicle. synaptic cleft. neurotransmitter. calcium channel. synaptic terminal.

synaptic cleft.

Numerous nerve impulses arriving at a synapse at closely timed intervals exert a cumulative effect.

temporal summation

If a signal from a sending neuron makes the receiving neuron more negative inside, a. the sending neuron becomes more positive inside. b. the receiving neuron is less likely to generate an action potential. c. the receiving neuron immediately generates an action potential. d. the sending neuron becomes more negative inside. e. the receiving neuron is more likely to generate an action potential.

the receiving neuron is less likely to generate an action potential.

When calcium ions enter the synaptic terminal, neurotransmitter molecules are quickly removed from the synaptic cleft. they cause an action potential in the sending neuron. the inside of the receiving neuron becomes more positive. they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron. the inside of the receiving neuron becomes more negative.

they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

Any stimulus at or above this level will result in action potential.

threshold stimulus

The generation of an action potential in a neuron requires the presence what type of membrane channels leakage channels voltage-gated channels chemically gated channels membrane channels are not required

voltage-gated channels