Neurotransmission Flashcards
Define neurotransmission:
transmission of nerve impulses across a synapse
Define neuroconduction:
movement of nerve impulses down neurons; also called propogation of nerve impulses
What is the term of an axon meeting a dendrite
axodendritic synapse
What is the term of an axon meeting a soma
axosomatic synapse
What is the term of an axon meeting a axon hillock
axoaxonic synapse
In axons, where is the wave of depol iniated?
axon hilock
Define axon hillock
a smol area in cell where axon meets soma, this area is the most sensitive to electrical stimulation
Which area is the most sensitive to electrical stimulation?
axon hillock
Only a short section of axon is _____ at any one time, but AP still moves alon axon
depolarizing
Why doesnt reverse conduction occur?
area behind depol membrane is in refractory period
What are the three reasons for refractory period?
asures transmission is one way, APs are separate events, and allows cells to recover to the resting state
How is AP transmission ensured to be one way
K+ channels open behind signal so it can only go one way bc of open voltage gates
Why do AP need to be separate events
so coding of message is possible
What contributes to strength of stimulus
AP frequency and NOT amplitude bc all APs are the same
what would happen to neurons in terms of recovery if refractory period was removed?
neurons might run down due to loss of ions/energy shortages due to large use of energy to shift ions back to re-establish RMP
Does wave of depol always occur?
nope, could be saltatory conduction
where does wave of depol occur?
unmyelinated neurons
in saltatory conduction, AP jumps btw what?
node de ranvier
Does more square meter of axon have to depol in salt conduction or wave of depol?
wave of depol
Mylein speeds up process how?
only a short section of axon has to depol
Mylinated speed vs unmyelinated?
150ms vs 50 ms
What is myelin
fatty insulation for neurons
What is an alternative to myelin that speeds up AP?
thick axons sped up process bc less resistance to current flow (i.e. ion movement) with a larger membrane
Myelinated axons are used for what?
skeletal muscle and SOMATIC pain
what is a somatic pain
sharp and quick
what happens in demyelinated disease
message is unpredicrable, cant control muscle, dont get normal sensory msg
What is the patholgy of unmyelinated disease?
als
Depole of one node means the node behind it is in which period?
refractatory period
What are the two ways of communicating btw neurons?
electrical and chemical synapse
Define electrical synapse
The electrical signal is transmitted across synapse by inducing ionic movement in adjact cell, thus allowing neurotransmission ; voltage change in one cell causes voltage change in adjacent cell
Where can you find electrical synapses?
myocardium and uterus
Why are electrical synapses useful?
allows cells to stay synchronized
what muscle uses electrical synapse?
smooth muscle, i.e GI tract, heart, uterus, bronchioles
What are gap junctions?
a hole btw 2 adjacent cells allowing electrical synapse
What flows through gap junction?
anything can flow through!
What flows through gap junction and causes depolarization?
ions flow through causing depol in postsynaptic membrane
What channels are present at axon terminal?
voltage-sensitive CA channels
What does CA influx stimulate?
vesicles containing NT to fuse with presynaptic membrane and release contents into synaptic cleft via exocytosis
How do NT travel across synapse?
down concentration gradient
NT-receptor is bound to what channel?
ligand gated sodium channel
When does sodium channel close in respect to NT?
when NT broken down by enzymes and taken back to presynaptic neuron
_______ _____ can occur from one or more neurons
temporal summation
define post synaptic potential
the voltage change (all the graded potentials) occuring in post synapse