Chapter 48 and 49: Neurons and Nervous System Flashcards
neurons
cells that conduct and store information in the nervous system
cell body
part of the neuron that houses most of the cytoplasm, nucleus, etc.
dendrites
branched extensions at receiving end
axon
extends from neuron to cell it acts on
synapse
connection between neurons; excitement passed chemically
presynaptic cells
cell that releases neurotransmitters
neurotransmitters
chemical messages between neurons
postsynaptic cell
cell that receives neurotransmitters
membrane potential
voltage difference across cell membrane; difference in charge between inside and outside
resting potential
membrane potential of a neuron that isn’t excited
ATP-powered sodium-potassium pump
brings K+ in, sends Na+ out
ion channels
let ions move down their gradients
potassium ion channels
K+ always leaking out
sodium ion channels
Na+ builds up outside
voltage potential
created by net movement of charge
equilibrium potential
chemical and electrical gradients balanced
gated ion channels
neuron channels that respond to some stimulus by opening/closing
voltage-gated ion channels
respond to change in membrane potential
depolarization
membrane potential becomes less negative and activates voltage-gated Na+ channels
action potential
massive, rapid depolarization; once potential exceeds threshold of -55mV; all or nothing response
hyperpolarization
a change in a cell’s membrane potential that makes it more negative
action potential steps
gated Na+ channels only active for a short time, rapid depolarization opens voltage-gated K+ channels resulting in hyperpolarization, undershoots normal resting rate
refractory period
time between action potentials; sets maximum frequency of action potentials
myelin sheath
protective membrane around axon, made up of glial cells
oligodendrocytes
glial cells in CNS
schwann cells
glial cells in PNS
factors that increase speed of propagation
axon diameter and insulation
nodes of Ranvier
gaps in myelin sheath; voltage gated Na+ channels limited to
synaptic cleft
space between presynaptic and postsynaptic cells
ligand-gated ion channel
bind neurotransmitter on postsynaptic membrane
excitatory postsynaptic potentials
depolarize membrane
inhibitory postsynaptic potentials
hyperpolarize membrane
temporal summation
series of potentials from same synapse (graded)
spatial summation
potentials from different synapse (graded)
nerve net
nervous system of cnidarians
nerves
multiple neurons; found in more complex animals
central nervous system (CNS)
brain + nerve cords running body length
cephalization
concentration of nervous system into the brain
peripheral nervous system (PNS)
ganglia and nerves outside CNS
ganglia
cell bodies; groups of nerves or brain cells that are closely related
brain
where all stimulus, voluntary and involuntary behavior is processed
spinal cord
carries impulses to and from brain
reflexes
involuntary movement
gray matter
non-myelin matter, outside of brain
white matter
myelin matter, inside of brain, outside of spinal cord
derived from hollow dorsal nerve cord
central canal (spinal cord) and ventricles (brain); filled with cerebrospinal fluid for diffusion of resources and waste
blood-brain barrier
selective, semi-permeable membrane between the blood and the interstitium of the brain
glia
nourish, support, and regulate the functioning of neurons in the vertebrate brain and spinal cord
radial glia
embryonic glia that form tracks along which newly formed neurons migrate from the neural tube, the structure that gives rise to the CNS
astrocytes
facilitate information transfer at synapses and sometimes release neurotransmitters; initiates formation of the blood-brain barrier during embryonic development
radial glia and astrocytes
can act as stem cells, generating new neurons in glia
microglia
immune cells that protect against pathogens
ependymal cells
line ventricles and promote circulation of cerebrospinal fluid
cranial nerves
connect brain with head
spinal nerves
connect spinal cord to rest of body
afferent neurons
bring information to the CNS (sensory)
efferent neurons
carry information from CNS
motor system
skeletal muscles; voluntary and reflex motion
autonomic nervous system
involuntary; smooth and cardiac muscle, glands, etc.
sympathetic division
arousal, “fight or flight”
parasympathetic division
calming, “rest and digest”
enteric division
digestion
brainstem
midbrain + pons + medulla; homeostasis, coordination of movement, attention, alertness, motivation
cerebellum
coordinates movement, hand-eye coordination
forebrain
diencephalon and cerebrum
diencephalon
thalamus, hypothalamus and epithalamus; homeostasis, sensory info, circadian rhythms
cerebrum
center for information processing in mammals
corpus callosum
connect the left and right hemispheres
reticular formation
controls sleep and arousal; filters incoming information and determines what reaches the cerebral cortex
biological clock
regulates sleep cycles
limbic system
responsible for emotions; amygdala, hippocampus, and thalamus
cortex
frontal, parietal, occipital and temporal lobes (each with different functions)
laterilization
two hemispheres not identical in function
neural plasticity
learning and memory formed by strengthening or weakening of synaptic connections
hippocampus
form memories by rearranging connections
short term memories
store stimuli for a short time
long-term memories
rearrangements in the cerebral cortex
long term potentiation
frequent excitation of a synapse can make the postsynaptic neuron more sensitive to the presynaptic neuron
