Nervous System Flashcards
central nervous system
brain and spinal cord
peripheral nervous system
nerves of the body
somatic nervous system
controls voluntary actions
autonomic nervous system
controls involuntary actions
sympathetic nervous system
fight or flight response (part of autonomic)
parasympathetic
calms down body after fight or flight (part of autonomic)
astrocytes
▫bring a neuron nutrients and take away waste
▫connect capillaries and neurons
microglia
carry out phagocytosis on neurons and microorganisms
what forms the blood-brain barrier
asteocytes
ependymal cells
produce cerebrospinal fluid
oligodendrocytes
produce myelin sheaths around axons
schwann cells
▫wrap itself around the axon to create myelin sheath
▫found only in peripheral nervous system
satellite cell
supports cell bodies of neurons in ganglia
steps of action potential
- stimulus
- depolarization
- repolarization
- hyperpolarization
- returning to rest
step 1: stimulus
stimulus excites neuron and opens some mechanically gated sodium channels. may or may not cause action potential
what is the cells resting voltage
-70mV
cell’s threshold
-55mV
step 2: depolarization
of threshold is reached, voltage gated sodium channels open and sodium ions enter, depolarizing the axon
step 3: repolarization
when membrane is depolarized to 30mV voltage gated potassium channels open. reestablishes membrane potential
step 4: hyperpolarization
too much potassium flows out and axon becomes slightly more negative
step 5: returning to rest
sodium potassium pump reestablishes original gradient and returns axon to resting potential
propagation
movement of an action potential down an axon
refractory period
the period during an action potential when an axon cannot respond to any other stimuli
absolute refractory
when sodium channels are already open (can’t open more)
relative refractory period
during hyperpolarization, when sodium channels are normal, requires larger stimulus to reach action potential
layers of a nerve, including membranes
neuron (nerve fiber) endoneurium fascicle perineurium nerve epinerium
endoneurium
around each individual neuron
perineurium
around each fascicle
epineurium
around entire nerve
electrical synapse
▫direct contact between neurons via gap junctions
▫impulse travels directly from one neuron to the next
chemical synapse
▫separated by synaptic cleft
▫electrical impulse turned into chemical signal via neurotransmitter release
excitatory chemical signal
cause depolarization, promote new action potential
inhibitory chemical signal
cause hyperpolarization, suppresses new action potentials
cholinergic synapses
release acytlecholine
steps of acetylcholine release
▫impulse reaches terminal bulb
▫calcium enters terminal bulb
▫ACh is released from vesicles via exocytosis
▫ACh binds to receptors to cause depolarization in next neuron
▫ACh is broken down by AChE into acetate and choline
▫choline pumped back into terminal bulb to create more ACh
synaptic delay
braid period of delay between conversion of electrical signal to chemical signal and back
synaptic fatigue
running out of neurotransmitter
direct effect
neurotransmitter releases and binds with receptors, this causes opening of ligand gated channels
indirect effect via g protein
neurotransmitter binds and causes activation of a g protein, this causes opening of ion channels
indirect effect via enzymes
neurotransmitters diffuse across membrane and activate enzymes with produce other compounds which open ion channels
axoaxonic synapses
axon connects to the axon terminal of another neuron
neurolemma
part of schwann cell where cytoplasm gets squeezed to the perimeter
afferent
carry info to the CNS
efferent
carry info from the CNS
functions of the nervous system
▫gathers info
▫info is integrated (brought together)
▫responds to signals
▫maintains homeostasis
number of cranial nerves
12 pairs
number of spinal nerves
31 pairs
interneurons
connect sensory neurons with motor neurons and brain and spinal cord
afferent and efferent are part of the ______ nervous system
peripheral
are large or small diameter neurons faster
large
