Chapter 12: Nervous Tissue Flashcards
absolute refractory period
time during an action period when another action potential cannot be generated because the voltage-gated Na+ channel is inactivated
action potential
change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal; unique to neurons and muscle fibers
activation gate
part of the voltage-gated Na+ channel that opens when the membrane voltage reaches threshold
astrocyte
glial cell type of the CNS that provides support for neurons and maintains the blood-brain barrier
autonomic nervous system (ANS)
functional division of the nervous system that is responsible for homeostatic reflexes that coordinate control of cardiac and smooth muscle, as well as glandular tissue
axon
single process of the neuron that carries an electrical signal (action potential) away from the cell body toward a target cell
axon hillock
tapering of the neuron cell body that gives rise to the axon
axon segment
single stretch of the axon insulated by myelin and bounded by nodes of Ranvier at either end (except for the first, which is after the initial segment, and the last, which is followed by the axon terminal)
axon terminal
end of the axon, where there are usually several branches extending toward the target cell
axoplasm
cytoplasm of an axon, which is different in composition than the cytoplasm of the neuronal cell body
biogenic amine
class of neurotransmitters that are enzymatically derived from amino acids but no longer contain a carboxyl group
bipolar
shape of a neuron with two processes extending from the neuron cell body—the axon and one dendrite
blood-brain barrier
physiological barrier between the circulatory system and the central nervous system that establishes a privileged blood supply, restricting the flow of substances into the CNS
brain
the large organ of the central nervous system composed of white and gray matter, contained within the cranium and continuous with the spinal cord
central nervous system
anatomical division of the nervous system located within the cranial and vertebral cavities, namely the brain and spinal cord
cerebral cortex
outermost layer of gray matter in the brain, where conscious perception takes place
cerebrospinal fluid (CSF)
circulatory medium within the CNS that is produced by ependymal cells in the choroid plexus filtering the blood
chemical synapse
connection between two neurons, or between a neuron and its target, where a neurotransmitter diffuses across a very short distance
cholinergic system
neurotransmitter system of acetylcholine, which includes its receptors and the enzyme acetylcholinesterase
choroid plexus
specialized structure containing ependymal cells that line blood capillaries and filter blood to produce CSF in the four ventricles of the brain
continous conduction
slow propagation of an action potential along an unmyelinated axon owing to voltage-gated Na+ channels located along the entire length of the cell membrane
dendrite
one of many branchlike processes that extends from the neuron cell body and functions as a contact for incoming signals (synapses) from other neurons or sensory cells
depolarization
change in a cell membrane potential from rest toward zero
effector protein
enzyme that catalyzes the generation of a new molecule, which acts as the intracellular mediator of the signal that binds to the receptor
electrical synapse
connection between two neurons, or any two electrically active cells, where ions flow directly through channels spanning their adjacent cell membranes
electrochemical exclusion
principle of selectively allowing ions through a channel on the basis of their charge
enteric nervous system
neural tissue associated with the digestive system that is responsible for nervous control through autonomic connections
ependymal cell
glial cell type in the CNS responsible for producing cerebrospinal fluid
excitable membrane
cell membrane that regulates the movement of ions so that an electrical signal can be generated
excitatory postsynaptic potential
graded potential in the postsynaptic membrane that is the result of depolarization and makes an action potential more likely to occur
G protein
guanosine triphosphate (GTP) hydrolase that physically moves from the receptor protein to the effector protein to activate the latter
ganglion
localized collection of neuron cell bodies in the peripheral nervous system
gated
property of a channel that determines how it opens under specific conditions, such as voltage change or physical deformation
generator potential
graded potential from dendrites of a unipolar cell which generates the action potential in the initial segment of that cell’s axon
glial cell
one of the various types of neural tissue cells responsible for maintenance of the tissue, and largely responsible for supporting neurons
graded potential
change in the membrane potential that varies in size, depending on the size of the stimulus that elicits it
gray matter
regions of the nervous system containing cell bodies of neurons with few or no myelinated axons; actually may be more pink or tan in color, but called gray in contrast to white matter
inactivation gate
part of a voltage-gated Na+ channel that closes when the membrane potential reaches +30 mV
inhibitory postsynaptic potential
graded potential in the postsynaptic membrane that is the result of hyperpolarization and makes an action potential less likely to occur