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96 terms

Ch 48 Nervous System

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sensory input
when sensory organs send info from the environment to the brain
CNS
Central Nervous System, the portion of the vertebrate nervous system consisting of the brain and spinal cord
effector cells
the muscle cells or gland cells that actually carry out the body's responses to stimuli.
PNS
Peripheral Nervous System is everything besides the brain and spinal cord
CELL BODY
largest part of a typical neuron; contains the nucleus and much of the cytoplasm
AXON
long nerve fiber that conducts away from the cell body of the neuron
DENDRITES
branching extensions of neuron that receives messages from neighboring neurons
axon hillock
specialized region of the axon, which connects the inital segment of the axon to the cell body
myelin sheath
a layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next
synaptic terminals
Ends of axons that form one side of the synaptic cleft; the location where neurotransmitters are stored.
neurotransmitters
chemical messengers that traverse the synaptic gaps between neurons
synapse
the junction between two neurons (axon-to-dendrite) or between a neuron and a muscle
postsynaptic cell
Cell recieveing the neurotransmitter, so that sodium ions can go in and Action potenital may occur
presynaptic cell
the transmitting cell at a synapse
reflex arc
the neural path of a reflex
reflex
an automatic instinctive unlearned reaction to a stimulus
sensory neuron
a neuron conducting impulses inwards to the brain or spinal cord
motor neuron
a neuron conducting impulses outwards from the brain or spinal cord
effector cell
A muscle cell or gland cell that performs the body's responses to stimuli; responds to signals from the brain or other processing center of the nervous system.
ganglia
clusters of cell bodies in the PNS
nuclei
clusters of cell bodies in the CNS
glia
sustentacular tissue that surrounds and supports neurons in the central nervous system
astrocytes
largest, most numerous glial cells; maintain blood-brain barrier to isolate CNS from general circulation; provide structural support for CNS; regulate ion and nutrient concentrations; perform repairs to stabilize tissue and prevent further injury
blood brain barrier
Blood vessels (capillaries) that selectively let certain substances enter the brain tissue and keep other substances out
oligodendrocytes
type of neuroglial cell that produces myelin in the CNS
Schwann cells
Supporting cells of the peripheral nervous system responsible for the formation of myelin.
membrane potential
The charge difference between a cell's cytoplasm and the extracellular fluid, due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances.
resting potential
electrical charge across the cell membrane of a resting neuron
excitable cells
have the ability to generate changes in their membrane potentials.
chemically gated ion channels
Ion channels that are opened or closed by a neurotransmitter
voltage gated ion channels
A specialized ion channel that opens or closes in response to changes in membrane potential
action potential
the local voltage change across the cell wall as a nerve impulse is transmitted
depolarization
sodium rushes into neuron through membrane, potassium ruses out; results in a change in charge cell becomes less negative
hyperpolarization
The movement of the membrane potential of a cell away from rest potential in a more negative direction.
graded potential
a shift in the electrical charge in a tiny area of a neuron
threshold potential
the electrical charge or potential difference at which an action potential will occur
refractory period
(neurology) the time after a neuron fires or a muscle fiber contracts during which a stimulus will not evoke a response
saltatory conduction
Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.
synaptic cleft
space between two connecting neurons where neurotransmitters are released
synaptic vesicles
tiny sacs in a terminal button that release chemicals into the synapse
neurotransmitter
transmits nerve impulses across a synapse
EPSP
Excitatory postsynaptic potential; a slight depolarization of a postsynaptic cell, bringing the membrane potential of that cell closer to the threshold for an action potential.
IPSP
Inhibitory postsynaptic potential; a slight hyperpolarization of the postysynaptic cell, moving the membrane potential of that cell further from threshold.
summation
(physiology) the process whereby multiple stimuli can produce a response (in a muscle or nerve or other part) that one stimulus alone does not produce
acetylcholine
a neurotransmitter that enables learning and memory and also triggers muscle contraction
biogenic amines
Neurotransmitter derived from amino acids, and include catecholamines (dopamine, epinephrine & norepinephrine) & indolamines (histamine & serotonin)ä
epinephrine
adrenaline; activates a sympathetic nervous system by making the heart beat faster, stopping digestion, enlarging pupils, sending sugar into the bloodstream, preparing a blood clot faster
norepinephrine
neurotransmitter that is involved in arousal and the fight-or-flight system (also mood, sleep, and learning)
dopamine
a monoamine neurotransmitter found in the brain and essential for the normal functioning of the central nervous system
serotonin
a neurotransmitter involved in e.g. sleep and depression and memory
glycine
An amino acid; an important inhibitory neurotransmitter in the lower brain stem and spinal cord.
glutamate
a major excitatory neurotransmitter; involved in memory
aspartate
an amino acid transmitter that is excitatory at many synapses
GABA
gamma-aminobutyric acid, major inhibitory neurotransmitter of the CNS
neuropeptides
relatively short chains of amino acids, serve as neurotransmitters.
Substance P
A neurotransmitter that is involved in the transmission of pain messages to the brain.
endorphins
natural, opiate like neurotransmitters linked to pain control and to pleasure
nerve net
loosely organized network of nerve cells that together allow cnidarians to detect stimuli
cephalization
concentration of sense organs and nerve cells at the front of an animal's body
nerve cords
a bundle of long extensions of nerve cell bodies, lead away from the brain
ventricles
the two lower chambers of the heart, and they pump blood out to the lungs and body., series of interconnected cavities within the cerebral hemispheres and brainstem filled with cerebrospinal fluid
central canal
The narrow cavity in the center of the spinal cord that is continuous with the fluid-filled ventricles of the brain.
CSF
cerebrospinal fluid, surrounds the brain and spinal cord
white matter
whitish nervous tissue of the CNS consisting of neurons and their myelin sheaths
gray matter
Brain and spinal cord tissue that appears gray with the naked eye; consists mainly of neuronal cell bodies (nuclei) and lacks myelinated axons.
cranial nerves
12 pairs of nerves arising from the brain
spinal nerves
31 pairs of nerves arising from the spinal cord
sensory division
of the PNS of made up of sensory, or afferent, neurons that convey information to the CNS from sensory receptors that monitor the external and internal environment.
motor division
Transmits impulses from the CNS to effector organs
autonomic nervous system
the part of the nervous system of vertebrates that controls involuntary actions of the smooth muscles and heart and glands
sympathetic division
The branch of the autonomic nervous system that mobilizes the body's resources for emergencies.
parasympathetic division
The branch of the autonomic nervous system that generally conserves bodily resources.
forebrain
top of the brain which includes the thalamus, hypothalamus, and cerebral cortex; responsible for emotional regulation, complex thought, memory aspect of personality
hindbrain
the posterior portion of the brain including cerebellum and brainstem
cerebrum
anterior portion of the brain consisting of two hemispheres
cerebral cortex
the layer of unmyelinated neurons (the gray matter) forming the cortex of the cerebrum
medulla oblongata
lower or hindmost part of the brain
midbrain
the middle division of brain responsible for hearing and sight; location where pain is registered; includes temporal lobe, occipital lobe, and most of the parietal lobe
reticular formation
a nerve network in the brainstem that plays an important role in controlling arousal
EEG
electroencephalogram, a graphical record of electrical activity of the brain
cerebellum
the "little brain" attached to the rear of the brainstem; it helps coordinate voluntary movement and balance
epithalamus
contains the hormone-secreting pineal gland; forms the roof of the diencephalons
thalamus
the brain's sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla
hypothalamus
a neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion
biologic clock
The theory of aging that suggests that our cells are pre-programmed genetically to divide a specific number of times and then cells lose their ability to repair themselves
SCN
suprachaiasmatic nucleus, regulates circadian rhythyms
light=cortisol release (alert)
dark=melatonin (sleep)
cerebral hemispheres
the right and left halves of the cerebrum
basal nuclei
important centers for motor coordination, acting as switches for impulses from other motor systems.
neocortex
the more recently evolved portions of the cortex of the brain that are involved with higher mental functions and composed of areas that integrate incoming information from different sensory organs.
corpus callosum
a broad transverse nerve tract connecting the two cerebral hemispheres
limbic system
a system of functionally related neural structures in the brain that are involved in emotional behavior
short term memory
activated memory that holds a few items briefly, such as the seven digits of a phone number while dialing, before the information is stored or forgotten
long term memory
the relatively permanent and limitless storehouse of the memory system. Includes knowledge, skills, and experiences
LTD
Long term depression, a reduction in the efficiency of a neuronal synapse that can last an hour or more. occurs in cerebellum and is input specific. decreased response in glutamate poss due to internalization of its recpetors
LTP
Long Term Potentiation, An increase in a synapse's firing potential after brief, rapid stimulation. Believed to be a neural basis for learning and memory.
growth cone
A distinctive structure at the growing end of most axons. It is the site where new material is added to the axon.