Ch. 12 Vocabulary

Front 1

absolute refractory period

Back 1

time during an action period when another action potential cannot be generated because the voltage-gated sodium channel is inactivated

Front 2

action potential

Back 2

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

Front 3

activation gate

Back 3

part of the voltage-gated sodium channel that opens when the membrane voltage reaches threshold

Front 4

astrocyte

Back 4

glial cell type of the CNS that provides support for neurons and maintains the blood-brain barrier

Front 5

autonomic nervous system (ANS)

Back 5

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

Front 6

axon

Back 6

single process of the neuron that carries an electrical signal (action potential) away from the cell body toward a target cell

Front 7

axon hillock

Back 7

tapering of the neuron cell body that gives rise to the axon

Front 8

axon segment

Back 8

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)

Front 9

axon terminal

Back 9

end of the axon, where there are usually several branches extending toward the target cell

Front 10

axoplasm

Back 10

cytoplasm of an axon, which is different in composition than the cytoplasm of the neuronal cell body

Front 11

biogenic amine

Back 11

class of neurotransmitters that are enzymatically derived from amino acids but no longer contain a carboxyl group

Front 12

bipolar

Back 12

shape of a neuron with two processes extending form the neuron cell body -- the axon and one dendrite

Front 13

blood-brain barrier (BBB)

Back 13

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

Front 14

brain

Back 14

the large organ of the central nervous system composed of white and gray matter, contained within the cranium and continuous with the spinal cord

Front 15

central nervous system (CNS)

Back 15

anatomical division of the nervous system located within the cranial and vertebral cavities, namely the brain and the spinal cord

Front 16

cerebral cortex

Back 16

outermost layer of gray matter in the brain, where conscious perception takes place

Front 17

cerebrospinal fluid (CSF)

Back 17

circulatory medium within the CNS that is produced by ependymal cells in the choroid plexus filtering the blood

Front 18

chemical synapse

Back 18

connection between two neurons, or between a neuron and its target, where a neurotransmitter diffuses across a very short distance

Front 19

cholinergic system

Back 19

neurotransmitter system of acetylcholine, which includes its receptors and the enzyme acetylcholinesterase

Front 20

choroid plexus

Back 20

specialized structure containing ependymal cells that line blood capillaries and filter blood to produce CSF in the four ventricles of the brain

Front 21

continuous conduction

Back 21

slow propagation of an action potential along an unmyelinated axon owing to voltage-gated sodium channels located along the entire length of the cell membrane

Front 22

dendrite

Back 22

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

Front 23

depolarization

Back 23

change in a cell membrane potential from rest toward zero

Front 24

effector protein

Back 24

enzyme that catalyzes the generation of a new molecule, which acts as the intracellular mediator of the signal that binds to the receptor

Front 25

electrical synapse

Back 25

connection between two neurons, or any two electrically active cells, where ions flow directly through channels spanning their adjacent cell membranes

Front 26

electrochemical exclusion

Back 26

principle of selectively allowing ions through a channel on the basis of their charge

Front 27

enteric nervous system (ENS)

Back 27

neural tissue associated with the digestive system that is responsible for nervous control through autonomic connections

Front 28

ependymal cell

Back 28

glial cell type in the CNS responsible for producing cerebrospinal fluid

Front 29

excitable membrane

Back 29

cell membrane that regulates the movement of ions so that an electrical signal can be generated

Front 30

excitatory postsynaptic potential (EPSP)

Back 30

graded potential in the postsynaptic membrane that is the result of depolarization and makes an action potential more likely to occur

Front 31

G protein

Back 31

guanosine triphosphate (GTP) hydrolase that physically moves from the receptor protein to the effector protein to activate the latter

Front 32

ganglion

Back 32

localized collection of neuron cell bodies in the peripheral nervous system

Front 33

gated

Back 33

property of a channel that determines how it opens under specific conditions, such as voltage change or physical deformation

Front 34

generator potential

Back 34

graded potential from dendrites of a unipolar cell which generates the action potential in the initial segment of that cell's axon

Front 35

glial cell

Back 35

one of the various types of neural tissue cells responsible for maintenance of the tissue, and largely responsible for supporting neurons

Front 36

graded potential

Back 36

change in the membrane potential that varies in size, depending on the size of the stimulus that elicits it

Front 37

gray matter

Back 37

regions of the nervous system containing cell bodies of neurons with few or no myelinated axons

Front 38

inactivation gate

Back 38

part of a voltage-gated sodium channel that closes when the membrane potential reaches +30 mV

Front 39

inhibitory postsynaptic potential (IPSP)

Back 39

graded potential in the postsynaptic membrane that is the result of hyperpolarization and makes an action potential less likely to occur

Front 40

initial segment

Back 40

first part of the axon as it emerges from the axon hillock, where the electrical signals known as action potentials are generated

Front 41

integration

Back 41

nervous system function that combines sensory perceptions and higher cognitive functions (memories, learning, emotion, etc.) to produce a response

Front 42

ionotropic receptor

Back 42

neurotransmitter receptor that acts as an ion channel gate, and opens by the binding of the neurotransmitter

Front 43

leakage channel

Back 43

ion channel that opens randomly and is not gated to a specific event, also known as a non-gated channel

Front 44

ligand-gated channels

Back 44

another name for ionotropic receptor for which a neurotransmitter is the ligand

Front 45

lower motor neuron

Back 45

second neuron in the motor command pathway that is directly connected to the skeletal muscle

Front 46

mechanically gated channel

Back 46

ion channel that opens when a physical event directly affects the structure of the protein

Front 47

membrane potential

Back 47

distribution of charge across the cell membrane, based on the charges of ions

Front 48

metabotropic receptor

Back 48

neurotransmitter receptor that involves a complex of proteins that cause metabolic changes in a cell

Front 49

microglia

Back 49

glial cell type in the CNS that serves as the resident component of the immune system

Front 50

multipolar

Back 50

shape of a neuron that has multiple processes -- the axon and two or more dendrites

Front 51

muscarinic receptor

Back 51

type of acetylcholine receptor protein that is characterized by also binding to muscarine and is a metabotropic receptor

Front 52

myelin

Back 52

lipid-rich insulating substance surrounding the axons of many neurons, allowing for faster transmission of electrical signals

Front 53

myelin sheath

Back 53

lipid-rich layer of insulation that surrounds an axon, formed by oligodendrocytes in the CNS and Schwann cells in the PNS; facilitates the transmission of electrical signals

Front 54

nerve

Back 54

cord-like bundle of axons located in the peripheral nervous system that transmits sensory input and response output to and from the CNS

Front 55

neuron

Back 55

neural tissue cell that is primarily responsible for generating and propagating electrical signals into, within, and out of the nervous system

Front 56

neuropeptide

Back 56

neurotransmitter type that includes protein molecules and shorter chains of amino acids

Front 57

neurotransmitter

Back 57

chemical signal that is released from the synaptic end bulb of a neuron to cause a change in the target cell

Front 58

nicotinic receptor

Back 58

type of acetylcholine receptor protein that is characterized by also binding to nicotine and is an ionotropic receptor

Front 59

node of Ranvier

Back 59

gap between two myelinated regions of an axon, allowing for strengthening of the electrical signal as it propagates down the axon

Front 60

nonspecific channel

Back 60

channel that is not specific to one ion over another, such as a nonspecific cation channel that allows any positively charged ion across the membrane

Front 61

nucleus

Back 61

in the nervous system, a localized collection of neuron cell bodies that are functionally related; a "center" of neural functions

Front 62

oligodendrocyte

Back 62

glial cell type in the CNS that provides the myelin insulation for axons in tracts

Front 63

peripheral nervous system (PNS)

Back 63

anatomical division of the nervous system that is largely outside the cranial and vertebral cavities, namely all parts except the brain and spinal cord

Front 64

postsynaptic potential (PSP)

Back 64

graded potential in the postsynaptic membrane caused by the binding of neurotransmitter to protein receptors

Front 65

percentral gyrus of the frontal cortex

Back 65

region of the cerebral cortex responsible for generating motor commands, wehre the upper motor neuron cell body is located

Front 66

process

Back 66

in the cells, an extension of a cell body; in the case of neurons, this includes the axon and dendrites

Front 67

propagation

Back 67

movement of an action potential along the length of an axon

Front 68

receptor potential

Back 68

graded potential in a specialized sensory cell that directly causes the release of neurotransmitter without an intervening action potential

Front 69

refractory period

Back 69

time after the initiation of an action potential when another action potential cannot be generated

Front 70

relative refractory period

Back 70

time during the refractory period when a new action potential can only be initiated by a stronger stimulus than the current action potential because voltage-gated K+ channels are not closed

Front 71

repolarization

Back 71

return of the membrane potential to its normally negative voltage at the end of the action potential

Front 72

resistance

Back 72

property of an axon that relates to the ability of particles to diffuse through the cytoplasm; this is inversely proportional to the fiber diameter

Front 73

response

Back 73

nervous system function that causes a target issue (muscle or gland) to produce an event as a consequence to stimuli

Front 74

resting membrane potential

Back 74

the difference in voltage measured across a cell membrane under steady-state conditions, typically -70mV

Front 75

saltatory conduction

Back 75

quick propagation of the action potential along a myelinated axon owing to voltage-gated sodium channels being present only at the nodes of Ranvier

Front 76

satellite cell

Back 76

glial cell type in the PNS that provides support for neurons in the ganglia

Front 77

Schwann cell

Back 77

glial cell type in the PNS that provides the myelin insulation for axons in nerves

Front 78

sensation

Back 78

nervous system function that receives information from the environment and translates it into the electrical signals of nervous tissue

Front 79

size exclusion

Back 79

principle of selectively allowing ions through a channel on the basis of their relative size

Front 80

soma

Back 80

in neurons, that portion of the cell that contains the nucleus; the cell body, as opposed to the cell processes (axons and dendrites)

Front 81

somatic nervous system (SNS)

Back 81

functional division of the nervous system that is concerned with conscious perception, voluntary movement, and skeletal muscle reflexes

Front 82

spatial summation

Back 82

combination of graded potentials across the neuronal cell membrane caused by signals from separate presynaptic elements that add up to initiate an action potential

Front 83

spinal cord

Back 83

organ of the CNS found within the vertebral cavity and connected with the periphery through spinal nerves; mediates reflex behaviors

Front 84

stimulus

Back 84

an event in the external or internal environment that registers as activity in a sensory neuron

Front 85

summate

Back 85

to add together, as in the cumulative change in postsynaptic potentials toward reaching threshold in the membrane, either across a span of the membrane or over a certain amount of time

Front 86

synapse

Back 86

narrow junction across which a chemical signal passes from neuron to the next, initiating a new electrical signal in the target cell

Front 87

synaptic cleft

Back 87

small gap between cells in a chemical synapse where neurotransmitter diffuses from the presynaptic element to the postsynaptic element

Front 88

synaptic end bulb

Back 88

swelling at the end of an axon where neurotransmitter molecules are released onto a target cell across a synapse

Front 89

temporal summation

Back 89

combination of graded potentials at the same location on a neuron resulting in a strong signal from one input

Front 90

thalamus

Back 90

region of the CNS that acts as a relay for sensory pathways

Front 91

thermoreceptor

Back 91

type of sensory receptor capable of transducing temperature stimuli into neural action potentials

Front 92

threshold

Back 92

membrane voltage at which an ation potential is initiated

Front 93

tract

Back 93

bundle of axons in the central nervous system having the same function and point of origin

Front 94

unipolar

Back 94

shape of a neuron which has only one process that includes both the axon and dendrite

Front 95

upper motor neuron

Back 95

first neuron in the motor command pathway with its cell body in the cerebral cortex that synapses on the lower motor neuron in the spinal cord

Front 96

ventricle

Back 96

central cavity within the brain where CSF is produced and circulates

Front 97

voltage-gated channel

Back 97

ion channel that opens because of a change in the charge distributed across the membrane where it is located

Front 98

white matter

Back 98

regions of the nervous system containing mostly myelinated axons, making the tissue appear white because of the high lipid content of myelin