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EPSP: Excitatory post-synaptic potential
depolarization of the neuron
IPSP: inhibitory post-synaptic potential
hyperpolarization of the neuron
Where does summation take place?
summation takes place at the axon hillock
2 ways to reestablish the resting potential
-when both voltage gated channels close, Na and K flow through the alwasy opened channels due to concentration gradient and electrostatic pressure
-sodium potassium pump also goes at work
During hyperpolarization period, the neuron is...
another action potential cannot be generated for time being
2 types of refractory periods
-absolute refractory period and relative refractory period
Absolute refractory period
time period during which no additional action potential can be generated
Relative refractory period
the neuron is resistant to another action potential, but stronger EPSPs can still evoke an action potential
*very strong situmli can evoke A.Ps
Where is the action potential generated from?
- axon hillock
- *neighboring areas adjacnet to local changes will be influenced to to trigger the opening of voltage gated Na channels
- **this is how it is moved across the lenght of the axon to axon terminals
Action potential moves along the axon towards the terminal leaving behind...
membrane that is refractory for a few milliseconds
As action potential travels through myelinated axon, they
- become passive and decrease in magnitude
- *but they speed up
Are there channels underneath the myelin?
gaps on the myelinated axons
nodes of ranvier
nodes of ranvier
voltaged-gated channels regenerate the action potential
*travels much faster than unmyelinated
- action potential is propagated in a manner called saltatory conduction.
Motor neuron speed
how does Tetrodotoxin affect the generating of A.P?
- -blocks Na+ channels
- *thats how it is lethal
How does information pass from one cell to the next?
- Chemical transmission, Neurotransmitters
- * they then act on the next cell to initiate either EPSP or IPSP and the cycle starts over
What happens when action potentials reach axon terminals?
they casue to release neurotransmitters
- space between the axon terminal and the membrane of the next cell
terminal that releases neurotransmitter
membrane that receives the nuerotransmitter on the other side of the synaptic cleft
Where are the neurotransmitters held?
Nuerotransmitters come in two types
large and small molecules
Where are the small molecule neurotrasnmitters made?
- -cytoplasm of axon terminal or buton.
- *packaged by golgi complex on terminal
-smaller than vesicles that contain larger neurotransmitters
description of large molecuels of nuerotransmitters
-peptides, small proteins
-made in cytoplasm of the soma, packaged there by golgi complex into vesicles
-then they are trasnported to the terminal along microtubules
As A.P reaches terminals, voltage change opens anohter type of voltage gated channel...
- voltage-gated calcium channels
- *concentrated near the synapse
Influx of Ca causes vesicles to move to...
- presynaptic membrane
- * w/o a.p no nuerotransmitter is released