The _________ within the CNS support neurons and anchor them to their nutrient source.
astrocytes
what are the most abundant CNS neuroglia
astrocytes
What cells are defensive cells in the CNS
Microglial
Cold sores on the skin of the mouth occur when herpes simplex viruses that are dormant in neural ganglia become active and travel to the skin of the mouth. What is the mechanism by which these viruses travel from the ganglia (located within the head) to the skin of the mouth?
anterograde transport
Where in the neuron is an action potential initially generated?
axon hillock
The depolarization phase of an action potential results from the opening of which channels?
voltage-gated Na+ channels
The repolarization phase of an action potential results from __________
the opening of voltage-gated K+ channels
Hyperpolarization results from __________.
slow closing of voltage-gated K+ channels
What type of conduction takes place in unmyelinated axons?
Continuous conduction
An action potential is self-regenerating because __________.
depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment
Why does regeneration of the action potential occur in one direction, rather than in two directions?
The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential.
What is the function of the myelin sheath?
The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?
Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.
In which type of axon will velocity of action potential conduction be the fastest?
Myelinated axons with the largest diameter
The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.
The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.
During depolarization, which gradient(s) move(s) Na+ into the cell?
both the electrical and chemical gradients
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.
The concentrations of which two ions are highest outside the cell.
Na+ and Cl–
Local anesthetics block voltage-gated Na+ channels, but they do not block mechanically gated ion channels. Sensory receptors for touch (and pressure) respond to physical deformation of the receptors, resulting in the opening of specific mechanically gated ion channels. Why does injection of a local anesthetic into a finger still cause a loss of the sensation of touch from the finger?
Touch stimulation of this sensory receptor will open the mechanically gated ion channels, but action potentials are still not initiated because propagation of an action potential requires the opening of voltage-gated Na+ channels.
The small space between the sending neuron and the receiving neuron is the
synaptic cleft
A molecule that carries information across a synaptic cleft is a
neurotransmitter.
When calcium ions enter the synaptic terminal they cause
they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.
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.
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.
Which membrane potential occurs because of the influx of Na+ through chemically gated channels in the receptive region of a neuron?
excitatory postsynaptic potential
An excitatory postsynaptic potential, a type of graded potential, occurs because of the influx of Na+ through chemically gated channels in the receptive region, or postsynaptic membrane, of a neuron. Graded potentials are generated by chemically gated channels, whereas action potentials are produced by voltage-gated channels.
Which neurotransmitter(s) is/are the body's natural pain killer?
endorphins
Which neuron circuit pattern is involved in the control of rhythmic activities such as breathing?
reverberating circuit
What component of the reflex arc determines the response to a stimulus?
integration center