Studied by 41 people
synapse
very small gap bwtn one neuron & the next
how large is a synaptic space?
~ 20 nm
presynaptic cell aka…
axon
postsynaptic cell aka…
dendrite
how are electrical signals of an impulse transmitted?
by gap junctions (small tubes of cytoplasm)
how do impulses normally travel across synapses?
by chemical signals thru diffusion
neurotransmitter
chemical that crosses synapse
what occurs when the nerve impulse reaches the end of the axon?
membrane depolarizes
gated channels open → Ca+2 enters cell by facilitated diffusion
influx of Ca+2 into terminal end of axon causes…
synaptic vesicles to merge with presynaptic membrane
where are neurotransmitters stored?
in vesicles
vesicle
small membrane-bound structure used to transport material w/i cell
exocytosis
merging of membrane & release of materials
after exocytosis…
neurotransmitters are released & forced into synapse
where do neurotransmitters bind to after being released into synapse?
postsynaptic receptors on dendrites
depending on kind of neurotransmitters & kind of membrane…
postsynaptic neuron is either excited or inhibited
when the postsynaptic neuron is excited…
Na+ enters
when the postsynaptic neuron is inhibited…
K+ enters (neuron tries not to have action potential; no stimulus)
what happens to neurotransmitters at end of chem impulse?
neurotransmitters are degraded & recycled
if there is a stimulus…
gain Na+
lose K+
if there is no stimulus…
neuron less likely to depolarize
lose Na+
gain K+
what are the two colors of neuron matter?
white & gray
why do nerves look white in white matter?
b/c myelin sheath contains type of white fat
what does myelin sheath surround?
surrounds axon
white matter neurons transmit impulses ____
very fast (~ 100 m/sec)
white matter neurons aka
long distance neurons (> 2 cm)
long distance neurons
longest nerves; single cells from base of spine to tips of toes (peripheral NS)
why do long distance neurons need myelin sheath?
b/c myelin sheath speeds impulses to travel long distances
gray matter neurons are ___
unmyelinated
gray matter neurons aka
short distance neurons
location of short distance neurons
brain & spinal cord (central NS)
gray matter neurons transmit impulses ____
moderately fast (~ 30 m/sec)
nervous system divided into…
central & peripheral NS
central NS consists of…
brain & spinal cord
peripheral NS consists of…
all other neurons besides brain & spinal cord
in peripheral NS, nerve fibers carry info…
to (afferent division) & from (efferent division)
peripheral NS divided into…
somatic & autonomic NS
what does somatic NS control?
voluntary action
what does autonomic NS control?
involuntary action
autonomic NS divided into…
sympathetic & parasympathetic NS
neurotransmitter in sympathetic NS =
adrenalin aka epinephrine
when does sympathetic NS function?
functions when person is under stress & need to prep for fight or flight
where do sympathetic nerves exit?
exits spinal cord from central position (cervical, thoracic, & lumbar regions)
what does sympathetic NS tend to do?
tends to awaken body in morning
neurotransmitter in parasympathetic NS =
acetycholine
what does parasympathetic NS regulate?
regulates internal organ function when body is at rest (cranial & sacral regions)
what does parasympathetic NS tend to do?
tends to relax body to prep for sleep (every 90 min)
both sets of nerves (sympathetic & parasympathetic)
enter each organ to accelerate or decelerate organ function
final reaction depends on which signals are stronger
work antagonistic (against) to each other
Note
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