Lecture 4: Synaptic Transmission Flashcards
information is passed between cells at the __
synapse
synaptic transmission involves ___ signalling between cells
chemical
an action potential in a presynaptic cell triggers transmitter release that is dependent on ___ (ion type)
calcium
transmitters interact with __ and ___ receptors to alter the function of postsynaptic cell
inotropic and metabotropic
activation of ionotropic receptors initiates a ___ response in the postsynaptic cell
electrical
postsynaptic cells integrate synaptic inputs by the process of __ and __ summation
temporal and spatial
miniature endplate potentials demonstrate the ___ nature of transmitter release at synapses
quantal
t/f neuromuscular transmission can be affected by drugs and toxins
true
from the axon to the synapse, __ energy is converted to __ energy
electrical; chemical
list 4 types of circuits for synaptic transmission
- diverging
- converging
- reverberating
- parallel
explain the reasoning for the small size of a synapse
want neurotransmitter to effectively and quickly get to receptors on postsynaptic cell so information can travel quickly
outline the steps of synaptic transmission
- there is an action potential in the presynaptic cell
- voltage-gated Ca2+ channels open and it rushed in
- the Ca2+ causes vesicles containing neurotransmitter to travel to membrane and fuse to release neurotransmitters across synapse
- neurotransmitter binds to receptor on post synaptic cell
- receptor undergoes conformational change, opening channels
- there is a change in postsynaptic membrane potential
- postsynaptic response
there are ___ on both vessicle and cell membrane that allow for vesicle docking
proteins
what proteins are involved in vesicle docking?
- synaptotagmin
2. SNAREs: synaptobrevin, SNAP-25, and syntaxin
what is the role of Ca2+ wrt to vesicle docking proteins?
binds to them and stimulates for them to bind to each other
what are 3 methods of removal of neurotransmitter from synapse?
- diffusion
- enzymatic degradation
- uptake by cells
why is removal of neurotransmitter from synapse important?
must turn off transmission quickly so information can reach the next steps and be transmitted faster
if neurotransmitter is not recycled by the presynaptic cell, what other type of cells uptake them?
glial astrocytes in CNS
the ability of a neurotransmitter to simply diffuse away from the synapse is based on the __ of the synapse
shape
when might it be beneficial to prevent removal of neurotransmitter>
in treatment of diseases that results in weak transmission
what type of receptor is an inotropic receptor?
ligand-gated
activation of inotropic receptors involves the change in membrane ___
permeability to certain ion
inotropic receptors generate a ___, ___ response
fast; electrical
what type of receptors are metabotropic receptors?
g-protein coupled receptors
metabotropic receptors function by activating___
intracellular secondo messaggero pathways
the response caused by metabotropic receptors is ___(faster/slower) than that os inotropic receptors
slower
explain the action of EPSP
they bring the membrane potential closer to threshold
nicotinic receptors are permeable to both __ and __ ions when acetylcholine is bound
na and K
give 2 examples of events that can cause an EPSP
- acetylcholine activation of nicotinic acetylcholine receptors
- glutamte activation of ionotrpoic glutamate receptor (cation channels)
an EPSP can be classed as a __ potential
local graded
explain IPSP
hyper polarization that brings membrane potential further from threshold
give an example of IPSP
GABA activation of inotropic GABAa receptor that allows passage of chloride into cell
what is spatial summation of synaptic inputs?
postsynaptic cell integrates inputs coming from different locations (different presynaptic). can be added together to reach threshold
what is temporal summation of synaptic inputs?
postsynaptic cell integrates frequency of inputs coming from the same location/cell. can be added together to reach treshold
list 5 ways drugs can work as inhibitors at the synapse
- cause leakage of transmitter into cytoplasm instead of into synapse
- block transmitter release
- inhibit transmitter synthesis
- block (act as antagonist)
- block transmitter reuptake by presynaptic cell, possibly causing the cell to run out
list 4 ways drugs can act as facilitators at the synapse
- increase transmitter release
- block transmitter repupatke
- block transmitter degradation
- mimic (act as agonist)
what element of the membrane of muscle cell makes it more responsive?
folds that house more receptors
are there EPSP / IPSP in neuromuscular transmission?
no, if theres an action potential in neutron, theres an action potential in muscle
describe the steps of neuromuscular transmission
- nerve action potential generated
- calcium rushes in and causes vessicle fusion
- acetycholine is released into synapse
- acetylcholine is bound to receptor causing channel to allow more passage of ions
- end plate potential is reached
- EPP spreads to adjacent membrane
- EPP leads to acscle action potential and propagation of AP
- acetylcholinesterase breaks down excess actylocholene
t/f miniature end plate potentials happen randomly, even at rest
true
what causes mini end plate potentials
the occasional Ache molecules slipping out without being activated ny ca2+
BoTX impairs the ___
release of vesicle contents (permanently)
4-AP inhibits __ resulting in ___ action potentials
K channels; prolonged
wCTX inhibits ___ leading to ___
ca2+ channels; muscle paralysis
hemicholinium prevents __ , causing __
recycling of choline; presynaptic cell to run out
neostigmine /endrophonium inhibit ___ ,allowing __
acetylcholinesterase; longer ache presence (longer ap)
d-tubocuranine, a-bungarotoxin, and gall amine are __ products that inhibit __-. they can be found in __ and __
plant; endplate potential’ poisonous animal venom and muscle relaxant for surgery
