information conducting unit of the nervous system
the neuron
dendrites
collect info from other cells
increase cell’s surface area
dendritic spines: small protrusions that cover the dendrites
axon
extends out from the cell body
teleodendria - smaller branches toward the end
terminal button
‘End foot’ at the end of each teleodendrion
Sits close to the dendritic spine of another neuron (forms synapse)
synapse
space between the terminal button of one neuron and dendritic spine of another
NT
chemical released from terminal buttons that carries the message across the synapse
flow of info within neurons
1 - info from other neurons is collected at dendrites
2 - info is processed in the cell body
3 - info passed on to the axon
4 - info passed on to terminal, where it is passed on to its target
dendritic spine
small protrusion on dendrites that increase surface area
nucleus of neurons
contain chromosomes made of DNA
genes - segments of DNA that contains code or blueprint for producing a specific protein. functional units that control the transmission and expression of traits from one generation to the next
the cell membrane overview
extracellular fluid is outside the cell (cushions the cell)
intracellular fluid or cytoplasm inside
concentration between these 2 are different
specifics about the cell membrane
lipid bilayer
membrane is impermeable
substances cross via embedded proteins (channels, gates, or pumps)
sodium potassium pump
in cell membrane of neurons, is 3 Na+ in, 2 k+ out
action potential in 5 steps
1 - resting potential = 70mV
2 - the action potential, depolarization phase
3 - repolarization phase
4 - hyperpolarization
5 - restoration of resting potential
what was used to study AP’s
squid axons bc they’re very like ours and they’re so big
resting potential phase
neuron at rest
- cell membrane is polarized
- intracellular fluid has a negative charge relative to extracellular fluid
- about -70mV
- maintained by efflux of Na+ and influx of K+
- 3 Na out, 2 K in
action potential - depolarization phase
- external or internal stimuli, if it reaches -50 mV threshold, an AP is triggered, extremely large flip n polarity of membrane (depolarization)
- voltage sensitive Na+ channels open, rapid influx of Na+
- intracellular fluid develops a positive charge, reaches 30 mV
repolarization phase
- Na+ channels close
- voltage gated K+ channels open -> rapid efflux of K+
- intracellular fluid develops a more negative charge (repolarization)
hyperpolarization
K+ efflux overshoots, even more negative intracellular fluid than in resting state
restoration of resting potential
sodium-potassium pump reactivated
cell membrane back to polarized (-70 mV)
absolute refractory periods
neuron can absolutely not conduct another signal
- during depolarization and repolarization
relative refractory period
during hyperpolarization
- just needs A LOT more stimulation, and Na+, to get to threshold
what are refractory periods for
to limit AP frequency so not over-firing
prevents backward flow of signal
typical rate of AP’s per second
30 per second
flow of AP along axon
one point on the membrane excites the adjacent area on the membrane, AP propagates down the axon membrane.
- causes current to flow toward axon terminal
- larger axon diameter, quicker transmisson of AP
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Lab video2
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Org. of the NS 167
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Org. of the NS 299
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Neurons58
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Cranial Nerves14
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Tricky topics - test 1109
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Sensory Systems - General & Visual75
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Sensory Systems - Auditory37
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Somatosensory27
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Motor System86
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Test 3 - Clinical Techniques84
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Test 3 - Etiologies Pt 184
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Test 3 - Etiologies Part 259
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MRI cue cards11
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Test 4 - general & aphasia77
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Test 4 - memory34
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Test 4 - Frontal lobe function113
