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73 terms

Anatomy and Physiology Ch.12

Test#3
STUDY
PLAY
Opioids relieve pain by blocking the release of
Substance P
The afferent division of the PNS _____________.
carries sensory information
Neuroglia perform all of these functions except __________.
release neurotransmitters
If a nerve cell receives many IPSPs at the same time, __________.
it will show spatial summation
The neuroglial cells that participate in maintaining the blood-brain barrier are the
astrocytes
The ________ nervous system is composed of the brain and spinal cord.
central
The ________ nervous system controls the skeletal muscles.
somatic
The efferent division of the peripheral nervous system innervates: smooth muscle cells
skeletal muscle cells
heart muscle cells
glandular cells
All of the answers are correct.
All of the answers are correct
The axon hillock connects the axon with the __________.
cell body (soma)
Most CNS neurons fall into which structural category?
multipolar
The most abundant class of neuron in the central nervous system is
multipolar
Clusters of RER and free ribosomes in neurons are called
Nissl bodies
Branches that may occur along an axon are called
collaterals
Axons terminate in a series of fine extensions known as
telodendria
Neurons that have one axon and one dendrite, with the soma in between, are called
bipolar
________ neurons are small and have no anatomical features that distinguish dendrites from axons.
Anaxonic
Most CNS neurons lack centrioles. This observation explains
why CNS neurons cannot divide to regenerate damaged tissue
The largest and most numerous of the glial cells in the central nervous system are the
astrocytes
Functions of astrocytes include all of the following, except
maintaining the blood-brain barrier.
forming a three-dimensional framework for the CNS.
conducting action potentials.
responding to neural tissue damage.
guiding neuron development.
conducting action potentials
What are the functions of astrocytes in the CNS?
Guiding neuron development
repairing damaged neural tissue
adjusting the composition of the interstitial fluid
maintaining the blood brain- barrier
________ line the brain ventricles and spinal canal.
Ependymal cells
The site of intercellular communication between a neuron and another cell is the
synapse
Sensory neurons of the PNS are
unipolar
Small, wandering cells that engulf cell debris and pathogens in the CNS are called
microglia
The neurilemma of axons in the peripheral nervous system is formed by
Schwann cells
Glial cells that surround the neurons in ganglia are
satellite cells
Many medications introduced into the bloodstream cannot directly affect the neurons of the CNS because
the endothelium of CNS capillaries forms a blood-brain barrier
Extensive damage to oligodendrocytes in the CNS could result in
loss of sensation and motor control
Damage to ependymal cells would most likely affect the
formation of cerebrospinal fluid
In the peripheral nervous system, Schwann cells participate in the repair of damaged nerves by
forming a cellular cord that directs axonal re-growth
After a stroke, what type of glial cell accumulates within the affected brain region?
microglia
Which type of ion channel is always open?
passive
At the normal resting potential of a typical neuron, its sodium-potassium exchange pump transports
3 intracellular sodium ions for 2 extracellular potassium ions.
Opening of sodium channels in the axon membrane causes
depolarization
Voltage-gated channels are present
in the membrane that covers axons
Voltage-gated channels are present
moves sodium and potassium opposite to the direction of their electrochemical gradients.
________ open or close in response to binding specific molecules.
Chemically gated channels
________ channels open or close in response to physical distortion of the membrane surface.
Mechanically gated
If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur, except
the intracellular concentration of potassium ions will increase
Graded potentials
may be either a depolarization or hyper-polarization
Voltage-gated sodium channels have both an activation gate and a(n) ________ gate.
inactivation
If acetylcholine (ACh) causes inhibition of a postsynaptic neuron, to what type of membrane channel did the ACh bind?
chemically-regulated potassium channel
If the axolemma becomes more permeable to potassium ion:
a stronger stimulus will be required to cause an action potential
In what part of the neuron does the action potential typically initiate?
initial segment of the axon
During an action potential of a neuron, what directly causes the different channels to open and close?
the transmembrane potential (voltage)
What is the typical duration of a nerve action potential?
2 ms
Around what transmembrane potential does threshold commonly occur?
-60 mV
What ion is responsible for the depolarization of the neuron during an action potential?
Na+ (sodium)
What type of membrane transport causes the depolarization phase of the action potential in neurons?
diffusion
Where are action potentials regenerated as they propagate along an unmyelinated axon?
at every segment of the axon
The movement of what ion is responsible for the local currents that depolarize other regions of the axon to threshold?
sodium (, sodium (Na+)
Approximately how fast do action potentials propagate in unmyelinated axons in humans?
1 meter per second
In contrast to the internodes of a myelinated axon, the nodes __________.
have lower membrane resistance to ion movement.
Where are action potentials regenerated as they propagate along a myelinated axon?
at the nodes
The node-to-node "jumping" regeneration of an action potential along a myelinated axon is called __________.
saltatory propagation
How do action potential propagation speeds in myelinated and unmyelinated axons compare?
Propagation is faster in myelinated axons.
What happens just after an axon is depolarized to threshold?
Some sodium channels are open
The all-or-none principle states that
all stimuli great enough to bring the membrane to threshold will produce identical action potentials.
During repolarization of a neuron
potassium ions move out of the cell.
A threshold stimulus is the
depolarization necessary to cause an action potential.
Rapid impulse conduction from "node" to "node" is called
Saltatory propagation
Which of the following is an example of a presynaptic cell?
neuron
What separates the presynaptic and postsynaptic cells at a chemical synapse?
synaptic cleft
What mechanism releases neurotransmitter from presynaptic neurons?
exocytosis
What type of channel in the postsynaptic membrane binds neurotransmitter?
chemically gated
What separates the presynaptic and postsynaptic cells at a chemical synapse?
synaptic cleft
A neuron that receives neurotransmitter from another neuron is called
the post-synaptic neuron
Which type of synapse is most common in the nervous system?
chemical
The ion that triggers the release of acetylcholine into the synaptic cleft is
Calcium
Cholinergic synapses release the neurotransmitter
Acetylcholine
If the chemically-gated sodium channels in the postsynaptic membrane were completely blocked,
Synaptic transmission would fail
Which of the following is not a possible drug effect on synaptic function?
change the type or receptor found in the postsynaptic membrane
Presynaptic facilitation by serotonin is caused by
calcium channels in the presynaptic membrane remaining open longer