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support cells

nonexcitable cells that provide structural support or that serve important physiological and immunological functions in the nervous system. also called Glial cells.


an atom or small molecule with a positive or negative electric charge

central nervous sytem

the brain and spinal cord

peripheral nervous sytem

portion of the nervous system that lies outside the brain and spinal cord; includes nerves and ganglia


refers to a cell that responds to stimuli by generating an electrical signal at the cell membrane.


neurons and muscle cells are ____________

target cell

cell that receives signals from a neuron or hormone

multipolar neuron

a neuron with a central cell body that gives rise to multiple dendrites and a single axon. The most common type of neuron in humans.

cell body

portion of nueron contain nucleus and organelles; also called the soma


cytoplasmic process that extends from a neurons cell body; usually shorter and thicker than axons and highly branched


receive signals from other neurons


long, thin cytoplasmic process that extends from a neurons cell body; may be insulated with myelin


transmits action potentials

cell body

main nutrional and metabolic region of neuron; receives signals from other cells and sends them towards the axon

cell body and dendrites

receptive and integrative regions of neuron

action potential

long-distance regenerative electrical signal transmitted along an axon; an all-or-none event; also called a nerve impulse, spike, or discharge


transmitting, or conductive, region of neuron


generates an action potential and conducts it to the next cell


junction between a neuron and its target cell (another neuron, muscle, or gland)

axon hillock

first portion, or initial segment, of axon

axon collateral

branch of an axon

axon terminal

bulbous ending of a branch of an axon; also called synaptic ending or synaptic bouton


insulation surrounding axons

myelin sheath

formed by support cells that wrap repeatedly around an axon, forming a thick layer of insulation


insulating material produced by the support cells of the nervous system

Schwann cells

type of support cell in peripheral nervous sytem that forms myelin sheath around axons

nodes of ranvier

tiny areas of bare axon between neighboring segments of myelin sheath


the distribution of ions across the cell membrane causes the inside of a cell to be slighlty _______ compared to the outside

Integral proteins

proteins embedded in the lipid bilayer of the neuronal cell membrane

ion channels

integral proteins containing watery pores through which ions pass to cross the cell membrane

Gated channels

Ion channels controlled by chemicals or by membrane voltage

nongated channels

ion channels, also called leakage channels, that are always open

voltage-gated channels

ion channels with gates that are opened or closed by changes in membrane voltage

membrane potential

the electrical potential, or voltage, across a cell membrane that results from the separation of charged particles across the membrane


chemical that is released at synapses

chemically-gated channels

ion channels with gates that open or close when a neurotransmitter binds to them


channels located in the cell membrane of dendrites, cell body and axon

chemically - gated

channels located on the dendrites and cell body


channels located on axon hillock, along unmyelinated axons, and at nodes of ranvier of myelinated axons

non-gated channels

responsible for resting membrane potential

chemically gated channels

responsible for synaptic potentials, the incoming signals to the neuron

synaptic potential

short-distance electrical signal that can vary in amplitude

voltage-gated channels

responsible for the generation and propagation of the action potential, the outgoing signal of the neuron

voltage -gated

channels located on axon only


channels located everywhere on neuron except axon


channels located over entire axon


the movement of molecules from one location to another because of random thermal motion;


negatively charged ion


positively charged ion

membrane potential

the difference in charge between the inside of the nerve cell membrane and the outside


the change in the sodium and potassium ions caused by a stimulus


chemicals that propagate the message across the synapse


most abundant neurotransmitter in the body

Effector Organ

organ innervated by the nervous system

gap junction

a small tube or channel between adjacent cells formed by transmembrane proteins. Found at electrical synapses.

central nervous system

the brain and spinal cord

somatic nervous system

that portion of the peripheral nervous system whichy innervates skeletal muscle

autonomic nervous system

the efferent portion of the peripheral nervous system which innervates smooth muscle, cardiac muscle and glands.

neuromuscular junction

synapse between a motor neuron and skeletal muscle fiber

axodendritic synapse

synapse between an axon terminal and a dendrite; carry input signals to neurons

axosomatic synapse

synapse between an axon terminal and the cell body of a neuron; carry input signals to neurons

axoaxonic synapes

synapse between two axon terminals; do not provide input signals to neurons; can regulate the amount of chemical transmitter released by another axon terminal thus inhibiting or facilitating the signal from another neuron

electrical synapse

synapse formed by gap junctions between two neurons; always excitatory; fast

chemical synapse

synapse formed by an axon terminal and neuronal cell membrane; a neurotransmitter conveys the signal from the axon terminal to the neuronal cell membrane; either excitatory or inhibitory; slow

chemical synapse

most common type of synapse; associated with complex human behaviours such as learning and memory

synaptic potential

incoming signal to neuron; short distance electrical signal which can vary in amplitude

electrochemical gradient

combined electrical and chemical forces on an ion. this force determines the net movement of charged particles.


a molecule, usually a protein, that binds specifically to other molecules such as neurotransmitters and hormones


to change the membrane potential of a cell to a value that is more positive than its resting membrane potential


to change the membrane potential of a cell to a value that is more negative than its resting membrane potential


a critical level of membrane potential at which the depolarization process becomes regenerative and the cell generates an action potential


a chemical that is released at synapses and acts at a receptor on the postsynaptic cell


protein that catalyses a biochemical reaction


biochemical process of adding a phosphate group to a molecule

somatic motor system

the efferent portion of the peripheral nervous system which innervates skeletal muscle

glial cells

nonexcitable cells that provide structural support or that serve important physiological and immunological functions in the nervous sytem. also called support cells.


when the postsynaptic potential is enhanced following repeated or continous activity at that synapse

temporal summation

the integration of synaptic potentials occuring at the same location but sequentially in time

spatial summation

the integration of synaptic potentials occuring at the same time at multiple locations

The resting state of a neuron

All voltage-gated Na+ and K+ channels are closed

Depolarization phase in the generation of an action potential

Opening of potassium gates and the rushing out of K+

Multiple sclerosis

The autoimmune disease that leads to destruction of the myelin sheaths in the CNS

Saltatory conduction

C. The unique propagation process which occurs in myelinated axons

The all-or-none phenomenon

A. The situation where an action potential either happens completely or NOT at all

G-protein-linked receptors

B. Indirect synaptic responses which are complex, prolonged, and often diffuse, as a result of the production of intracellular second messenger molecules


E. Rapid automatic responses to a stimulus in which the particular stimulus always produces the same motor response

A. Temporal summation

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

C. Spatial summation

Simultaneous stimulation of many terminals, distributed widely over the surface of a postsynaptic neuron

B. Subthreshold stimulus

An insufficient stimulus

D. Threshold stimulus

Any stimulus above this intensity will result in an action potential in a neuron

Somatic nervous system

A. Conducts impulses from CNS to skeletal muscles

Autonomic nervous system

C. Conducts impulses from CNS to internal organ muscles

Central nervous system

B. Consists of brain and spinal cord

Peripheral nervous system

D. Consists of nerves carrying impulses to and from brain and spinal cord

Presynaptic calcium influx

D. Triggers neurotransmitter release

Synaptic cleft

C. Separates presynaptic terminal from postsynaptic membrane


A. Triggers voltage change in postsynaptic neuron


B. Binds to postsynaptic receptor/channel


B. Excites skeletal muscle


F. Main neurotransmitter of sympathetic nervous system


D. "Feel good" transmitter; deficient in Parkinson's disease


A. "Mood" transmitter; target of Prozac to relieve depression


E. Generally inhibitory; found throughout CNS


C. Peptides with inhibitory, opiate-like actions

Somatic afferent fibers

B. Skin, skeletal muscles, and joints to CNS

Visceral afferent fibers

A. Organs in the ventral body cavity to CNS

Somatic motor fibers

C. CNS to skeletal muscles

Visceral motor fibers

D. CNS to smooth muscles, cardiac muscles, and glands


Which is the most common neuron type in humans?


The sensory, or afferent, division of the peripheral nervous system transmits information from the _____ to the CNS

potassium diffuses out of the cell

The interior of a nerve cell has a slight excess of negative charge because:

Rough endoplasmic reticulum

The Nissl bodies seen in the neuron cell body represents which cellular organelle?


In the ________ state virtually all the voltage-gated Na+ and K channels are closed.

Ependymal cells

lines the central cavities of the brain and spinal cord and provide a barrier between the CSF and nervous tissue


Conduction of impulses is very slow in fibers.


The larger the diameter of the axon, the ________ it conducts impulses.


During repolarization, only K+ ion channels are open.


act as naturally occurring opiates and reduce the perception of pain under certain stressful conditions.


neuroglia is most responsible for the blood-brain barrier


neurons are generally associated with the special senses

retrograde movement

Organelles for degradation in the axon are moved by


Impulses move along a myelinated axon by ____________ movement

From the nodes of Ranvier

Where do axon collaterals emerge on a myelinated nerve?


channels that do not respond to any signals and are always open.


plays the most important role in generating the membrane potential.

pump three sodium ions out of the cell for every two ions of potassium it brings into the cell.

The sodium-potassium ion pump will:

absolute refractory period

When the neuron is in the______________________ and all its voltage-gated sodium channels are open, it cannot respond to another stimulus, no matter how strong, until the channels are reset.

Synaptic potentiation

associated with an influx of calcium into the cell


is thought to be the most primitive neurotransmitter.


Schwann cells myelnate axons only in the

Ependymal cells

line the central cavities of the brain and spinal cord, where they form a fairly permeable barrier between the cerebrospinal fluid that fills those cavities and the tissue fluid bathing the cells of the CNS. The beating of their cilia helps to circulate the cerebrospinal fluid that cushions the brain and spinal cord.


are the most abundant and most versatile glial cells. Their numerous radiating processes cling to neurons and their synaptic endings, and cover nearby capillaries, supporting and bracing the neurons and anchoring them to their nutrient supply lines, the blood capillaries; have a role in making exchanges between capillaries and neurons, in helping to determine capillary permeability, in guiding the migration of young neurons, and in synapse formation.


clusters of cell bodies in the CNS


clusters of cell bodies in the PNS


bundles of neuron processes in the CNS


bundles of neuron processes in the PNS

Voltage-gated channels

open and close in response to changes in the membrane potential

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