Nervous System
Where in the neuron is an action potential initially generated?
Axon Hillock
During depolarization, which gradient(s) move(s) Na+ into the cell?
Both the electrical and chemical gradients
Binding of a neurotransmitter to its receptors opens _________ channels on the __________ membrane.
Chemically gated; postsynaptic
Binding of the neurotransmitter to its receptor causes the membrane to __________
Either depolarize or hyperpolarize
_______ of the membrane is negative resting membrane potential of a typical neuron
Inside
When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,
Ion channels in the plasma membrane of the receiving neuron open
The concentration of _____ is higher inside than outside the cell
K+
The membrane is more permeable to ______
K+
The membranes of neurons at rest are very permeable to _______ but only slightly permeable to ________.
K+; Na+
The resting membrane potential maintained by Na+ -K+ pumps that actively transport ________ into and _______ out of the cell
K+; Na+
Saltatory propagation occurs in _______ axons, in which action potentials ___________
Myelinated, move from one node of Ranvier to another
The concentration of ______ is higher outside than inside the cell
Na+
The concentrations of which two ions are highest outside the cell?
Na+ and Cl-
The Na+ -K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?
Na+ is pumped out of the cell and K+ is pumped into the cell
A molecule that carries information across a synaptic cleft is a _______
Neurotransmitter
________ of the membrane is positive resting membrane potential of a typical neuron
Outside
In a synapse, neurotransmitters are stored in vesicles located in the __________
Presynaptic neuron
Hyperpolarization results from ______________.
Slow closing of voltage-gated K+ channels
The small space between the sending neuron and the receiving neuron is the __________
Synaptic cleft
Why does the action potential only move away from the cell body?
The areas that have had the action potential are refractory to a new action potential
The re-polarization phase of an action potential results from _____________.
The opening of voltage-gated K+ channels
If a signal from a sending neuron makes the receiving neuron more negative inside,
The receiving neuron is less likely to generate an action potential
When calcium ions enter the synaptic terminal
They cause vesicles containing neurotransmitters molecules to fuse to the plasma membrane of the sending neuron
An action potential releases neurotransmitter from a neuron by opening which of the following channels?
Voltage-gated Ca+2 channels
The depolarization phase of an action potential results from the opening of which channels?
Voltage-gated Na+ channels
The generation of an action potential in a neuron requires the presence of what type of membrane channels?
Voltage-gated channels
What is the value for the resting membrane potential for most neurons?
-70 mV
Place the events involved in generation of an action potential in the correct order of occurrence from left to right a. Na+ influx depolarization b. K+ efflux repolarization c. threshold stimulus Na+ channels open d. hyperpolarization K+ channels close e.Na+ channels close, K+ channels open
1. Threshold stimulus Na+ channels open 2. Na+ influx depolarization 3. Na+ channels close; K+ channels open 4. K+ efflux repolarization 5. Hyperpolarization K+ channels close
What is the magnitude (amplitude) of an action potential?
100 mV
The velocity of the action potential is fastest in which of the following axons?
A small myelinated axon
The mechanism by which the neurotransmitter is returned to a presynaptic neuron's axon terminal is specific for each neurotransmitter. What neurotransmitter is broken down by an enzyme before being returned?
Acetylcholine
How is an action potential propagated along an axon?
An influx of sodium ions from the current action potential depolarizes the adjacent area