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65 terms

Chapter 12 Nervous Tissue

STUDY
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False
The nervous system employs exclusively electrical means to send messages, whereas the endocrine system communicates by means of chemical messengers.
True
Most neurons have multiple dendrites
False
Neurons move material away from the soma by retrograde transport.
True
Unipolar neurons have only a single process leading away from the soma.
False
Oligodendrocytes serve the same purpose in the CNS that satellite cells do in the PNS
True
Ependymal cells line the inner cavities of the CNS.
False
In the brain, neurons are more abundant than neuroglia.
True
Action potential never occurs in dendrites.
False
When a neuron is stimulated, Na+ gates open and allow Na+ to exit the cell.
False
In a myelinated fiber only the initial segment in the trigger zone have voltage-regulated channels.
True
Norepinephrine is a monoamine.
False
Acetylcholine triggers the synthesis of the second messenger cAMP only in neurons of the PNS.
True
Nitric oxide (NO) acts as a neuromodulator by altering synaptic function.
...
Any two EPSPs will override one IPSP.
...
Memories are formed by neural pathways of modified synapses.
Visceral motor
____ division carries signals to the smooth muscle in the large intestine.
sympathetic
The ___ division tends to prepare the body for action
Glands
___ are examples of effectors of the nervous system.
visceral motor division.
The autonomic nervous system is also called the
cells
Nerves are ___ of the nervous system.
afferent; efferent
Some ___ neurons are specialized to detect stimuli, whereas ____ neurons send signals to the effectors of the nervous system.
association
About 90% of the neurons in the nervous system are ___ neurons.
Multipolar
___ neurons are the most common type of neurons.
an axon.
Nerve fiber refers to
soma
Most metabolic and regulatory functions in a neuron happen at the
Schwann cells
This image shows a representative neuron. What does "5" represent?
dendrites
This image shows a representative neuron. What does "1" represent?
Dendrites
____ are the primary site for receiving signals from other neurons.
Oligodendrocytes
___ form myelin in the spinal cord.
lipids
Most of the myelin sheath is composed of
cells
The myelin sheath is formed by
large myelinated fiber
Conduction speed of a nerve fiber would be the fastest in a
the soma and at least some neurilemma intact.
In order for a peripheral nerve fiber to regenerate it must have
Potassium
___ has the greatest influence on the resting membrane potential
dendrites
Most local potentials happen at the
depolarization of the plasma membrane.
Opening of sodium gates typically leads to
inflow of chloride
Which of the following will cause the plasma membrane to hyperpolarize when at its RMP?
graded
Local potentials are _____, meaning they vary in magnitude according to the strength of the stimulus.
hyperpolarizes the plasma membrane.
An inhibitory local potential
sodium gates are fully open
While the membrane is depolarizing its
a rising local potential
This image shows an action potential. What does "1" represent?
hyperpolarization of the membrane
This image shows an action potential. What does "6" represent?
nondecremental; decremental
Local potentials are ___, whereas action potential are ___.
potassium ions are leaving the cell.
During hyperpolarization (or afterpotential
repolarizing
When the voltage of a plasma membrane shifts from +35mV towards 0 mV, we say the cell is
no stimulus of any strength will trigger a new action potential.
During the absolute refractory period
a nerve signal.
A traveling wave of excitation is what we know as
There are no internodes in unmyelinated fibers.
What would be the best explanation for why myelinated fibers conduct signals faster than unmyelinated fibers?
they are released into the bloodstream before reaching the postsynaptic cell.
All of the following are typical characteristics of neurotransmitters except
acetylcholine
A cholinergic synapse employs ___ as its neurotransmitter.
-aminobutyric acid (GABA)
___ binds to ligand-regulated gates, and is the most common inhibitory neurotransmitter in the brain.
synaptic vesicles release ACh
Which of these happens first in an cholinergic synaptic transmission?
G protein dissociates from the NE receptor
Which of these happens first in an adrenergic synaptic transmission?
that breaks down monoamines.
Some antidepressant drugs act by inhibiting monoamine oxidase (MAO), which is an enzyme
synaptic vesicles secrete neurotransmitter by exocytosis
All of these contribute to the cessation of the signal in a synaptic transmission except
Acetylcholine
___ excites skeletal muscle and inhibits cardiac muscle.
hyperpolarization of the cell membrane.
Inhibitory postsynaptic potentials (IPSPs) are associated with
chloride; IPSP
Opening of __ gates produces an ___.
a voltage change from -70 mV to -69.5 mV
Which of these is an example of an EPSP in a typical neuron?
spatial summation
A neuron can receive thousands of EPSPs from different neurons, and responds by triggering or not triggering an action potential. This addition and response to the net effect of postsynaptic potentials is called
facilitation
Presynaptic inhibition is the opposite of
a reverberating circuit
The best type of neural pool for producing a prolonged output is
coding
Even though all action potentials are the same, the brain can differentiate a variety of stimuli by source and intensity. The mechanism by which the nervous system converts these action potentials into meaningful information is called neural
dopamine
Parkinson disease is a progressive loss of motor function due to the degeneration of specific neurons. These neurons secrete an inhibitory neurotransmitter that prevents excessive activity in motor centers of the brain. This neurotransmitter is
synaptic facilitation; short-term memory
Accumulation of Ca2+ in the synaptic knob is called ___, and probably plays an important role in ___.