week 1 anatomy nervous system

what is the central nervous system divided into?

brain and spinal cord

what is the peripheral nervous system divided into

somatic (conscious) and visceral (unconscious)

what is somatic divided into?

somatic sensory and somatic motor

what is visceral divided into?

visceral motor and sensory

what is visceral motor divided into?

sympathetic (fight or flight) and parasympathetic (rest and digest)

nervous system functions

sensory, integrative, and motor

sensory function of the nervous system

intake info about internal and external conditions

integrative function of the nervous system

make decisions based on previously lived experiences (brain)

motor function of the nervous system

execute desired outcome based on integrated sensations (muscle)

what are the two families of nervous system cells?

neurons and neuroglia

neurons consist of …

dendrites, cell body (neurosoma), axon hillock, myelin, nodes of rainvier, and axon terminals (terminal buttons)

anatomical classification of neurons

multipolar, bipolar, and unipolar

multipolar

1 axon body with more than one dendrites

bipolar

one axon with 2 ends/sides

unipolar

one axon, one end

functional classifications of neurons

sensory (afferent), motor (efferent), interneuron

sensory (afferent) neurons

bring info into the CNS

motor (efferent)

exert function by innervating some kind of muscle

interneuron

“go between” cell which helps connect sensory and motor neurons

neuroglia

basically supporting cells in nervous system; different in PNS and CNS

what are the neuroglia in the CNS

astrocytes, oligodentrocytes, microglia, and ependymal cells

astrocytes

care for neuron, provide all nutrients and carry waste

oligodentrocytes

provide myelin to several nearby axons - no neurilemma

microglia

help to defend neurons against pathogens, clean debris

ependymal cells

produce cerebrospinal fluid

neuroglia in the PNS

Schwann cells and satellite cells

Schwann cells

myelinating cells in the PNS

satellite cells

every other cell but Schwann cells

myelination

the process in which myelin is made around the axon; provided by oligodendrocytes in the CNS and Schwann cells in the PNS

myelin

a multilayered sheath of lipids and proteins which wrap around the axolemma of the axons of neurons; increases speed of axons

neurilemma

outermost layer of myelin that contains the nucleus

myelin sheath

fatty insulation surrounding an axon

_____ and ______ determine the speed of the axon

size of axon, if it is myelinated

grey matter

made of neuronal cell bodies, dendrites, and synapses; where processing, thinking, and integration of information happen

white matter

made of myelinated axons, like wires connecting different grey matter areas

where is white matter found?

in the spinal cord, white matter surrounds grey matter. in the brain, grey surrounds white

sodium potassium pump maintains _____ of the cell membrane

polarity

the sodium potassium ATPase pump sends ____ out of the cell and brings ______ into the cell

3 Na +, 2 K +

what is resting membrane potential?

-70 mV

graded potential

in dendrites or cell body; small, local, result from small deviations from RMP, when added together make an action potential

depolarization

a positive deviation in the voltage of the cell membrane

excitatory post-synaptic potential (EPSP)

a small depolarization event that occurs when a ligand binds to and opens a Na+ channel, resulting in Na+ influx into the cell

hyperpolarization

a negative deviation in the voltage of the cell membrane

inhibitory post-synaptic potential (IPSP)

a small hyperpolarization event that occurs response to an inhibitory ligand binding to and opening a ligand-gated Cl- channel, resulting in Cl- influx into the cell

because Cl - is negatively charged, an influx of Cl into the cell causes voltage across the membrane to become more ______

negative

summation

he process by which EPSPs and IPSPs add together to “decide” whether or not the neuron will continue the nervous signal by sending an impulse

temporal summation

a single neuron fires several EPSPs over a short span of time in order to push the axon hillock to its action potential threshold

spatial summation

several different axons provide simultaneous EPSPs in different areas of the dendrites or cell body in order to push the axon hillock to action potential threshold

action potential threshold

-55 mV

1st step of action potential

stimuli summate @ axon hillock to threshold

2nd step of action potential

voltage gated sodium channels open, causing depolarization

3rd step of AP

voltage gated sodium channels inactivate, potassium channels open, causing repolarization

4th step of AP

voltage gated sodium channels close, potassium channels still open, causing hyper polarization

5th step of AP

all channels close and ATPase pump returns cell to RMP

continuous propagation

occurs in unmyelinated axons, goes across each adjacent segment of neurilemma

saltatory propagation

occurs in myelinated axons, electrical potential jumps from node to node bc that is where voltage gated channels are located

axodentritic synapses are axon to

dendrite

axosomatic synapses are axon to

cell body

axoaxonic synapses are axon to

axon hillock

chemical synapses

uses neurotransmitters to communicate a graded potential across the synapse

step 1 of the chemical synapse

action potential arrives @ synaptic end bulb

step 2 of the chemical synapse

voltage change opens Ca2+ channels

step 3 of the chemical synapse

Ca2+ diffuses into the neuron and binds to ACh vesicle

step 4 of the chemical synapse

vesicles empty ACh into the synapse

step 5 of the chemical synapse

ACh diffuses across synaptic cleft and binds to receptors on postsynaptic neuron

step 6 of the chemical synapse

receptor/channels open and Na+ diffuses into the cell (graded potential)

step 7 of the chemical synapse

if graded potential summate to at least -55 mV, new AP is generated

a neurotransmitter can be removed from the synapse by…

diffusion, enzymatic degradation, (re)uptake by cells