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137 terms

Ch 11 Anatomy Test 3

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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.
ion
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
excitable
refers to a cell that responds to stimuli by generating an electrical signal at the cell membrane.
excitable
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
dendrite
cytoplasmic process that extends from a neurons cell body; usually shorter and thicker than axons and highly branched
dendrite
receive signals from other neurons
axon
long, thin cytoplasmic process that extends from a neurons cell body; may be insulated with myelin
axon
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
axon
transmitting, or conductive, region of neuron
axon
generates an action potential and conducts it to the next cell
synapse
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
myelin
insulation surrounding axons
myelin sheath
formed by support cells that wrap repeatedly around an axon, forming a thick layer of insulation
myelin
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
negative
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
neurotransmitter
chemical that is released at synapses
chemically-gated channels
ion channels with gates that open or close when a neurotransmitter binds to them
nongated
channels located in the cell membrane of dendrites, cell body and axon
chemically - gated
channels located on the dendrites and cell body
voltage-gated
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
chemically-gated
channels located everywhere on neuron except axon
nongated
channels located over entire axon
diffusion
the movement of molecules from one location to another because of random thermal motion;
anion
negatively charged ion
cation
positively charged ion
membrane potential
the difference in charge between the inside of the nerve cell membrane and the outside
depolarization
the change in the sodium and potassium ions caused by a stimulus
neurotransmitters
chemicals that propagate the message across the synapse
acetylcholine
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.
receptors
a molecule, usually a protein, that binds specifically to other molecules such as neurotransmitters and hormones
depolarize
to change the membrane potential of a cell to a value that is more positive than its resting membrane potential
hyperpolarize
to change the membrane potential of a cell to a value that is more negative than its resting membrane potential
threshhold
a critical level of membrane potential at which the depolarization process becomes regenerative and the cell generates an action potential
neurotransmitter
a chemical that is released at synapses and acts at a receptor on the postsynaptic cell
enzyme
protein that catalyses a biochemical reaction
phosphorylation
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.
potentiation
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
Reflexes
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
Receptor/channel
A. Triggers voltage change in postsynaptic neuron
Neurotransmitter
B. Binds to postsynaptic receptor/channel
Acetylcholine
B. Excites skeletal muscle
Norepinephrine
F. Main neurotransmitter of sympathetic nervous system
Dopamine
D. "Feel good" transmitter; deficient in Parkinson's disease
Serotonin
A. "Mood" transmitter; target of Prozac to relieve depression
GABA
E. Generally inhibitory; found throughout CNS
Endorphins
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
Multipolar
Which is the most common neuron type in humans?
skin
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?
resting
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
unmyelinated
Conduction of impulses is very slow in fibers.
faster
The larger the diameter of the axon, the ________ it conducts impulses.
repolarization
During repolarization, only K+ ion channels are open.
Endorphins
act as naturally occurring opiates and reduce the perception of pain under certain stressful conditions.
Astrocytes
neuroglia is most responsible for the blood-brain barrier
bipolar
neurons are generally associated with the special senses
retrograde movement
Organelles for degradation in the axon are moved by
saltatory
Impulses move along a myelinated axon by ____________ movement
From the nodes of Ranvier
Where do axon collaterals emerge on a myelinated nerve?
Leakage
channels that do not respond to any signals and are always open.
Potassium
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
ATP
is thought to be the most primitive neurotransmitter.
PNS
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.
Astrocytes
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.
nuclei
clusters of cell bodies in the CNS
ganglia
clusters of cell bodies in the PNS
tracts
bundles of neuron processes in the CNS
nerves
bundles of neuron processes in the PNS
Voltage-gated channels
open and close in response to changes in the membrane potential