Physiology 3: Excitatory and Inhibitory Neurotransmission in the CNS Flashcards
normal resting mP of a neuron?
-70mV
depolarisation or excitation will cause what effect on the resting mP of a neuron?
will increase
normal resting mP of a depolarised neuron (more + ions)?
-40mV
hyperpolarisation will have what effect on the neuron’s restign mP?
will decrease
what would cause hyperpolarisation?
exit of + ions
entry of - ions
which is the only main ion in which its external conc is lower than its intracellular conc? as a result of this, what effect will it have on a neuron’s mP?
K+
will cause hyperpolarisation as the high intracellular conc will flow outwards out of the cell rather than the low extracellular conc moving in
what effect will a Cl- influx have on the cell/
will cause hyperpolarisation as you are adding a negative ion
what effect does a K agonist have?
opens K channel to let K+ OUT causing inhibition
what effect will a K+ antagonist have?
closes K channel to retain K+ in the cell, increasing cell mP
a synapse is made up of what 3 components?
presynaptic axon terminal
synaptic cleft
postsynaptic dendrite
what happens at a neuron’s axon terminal?
an AP depolarises
what happens after a neuron depolarises?
- voltage gated Ca channels open and Ca enters the cell
2. triggers exocytosis of synaptic vesicle contents
once neurotransmitter is released from the synaptic vesicle where does it go?
diffuses across the synaptic cleft and binds to receptors on the postsynaptic dendrite causing a response
name 4 ways in which neurotransmitters can be switched off
- by enzymes
- returned to axon terminals for reuse
- transported into glial cells
- by diffusing out of synaptic cleft
direct gating is done by which receptors?
ionotropic
indirect gating is mediated by activation of which receptors?
metabotropic
give examples of receptors that are ligand gated
GABAa
glycine
ACh
glutamate
glutamate receptor channels are __mers
tetra
GABAa, glycine and Ach channels are __mers
penta
name the major excitatory neurotransmitter
glutamate
name the 2 kinds of ionotropic glutamate receptors
non-NMDA
NMDA
which ionotropic glutamate receptor mediates fast excitatory synaptic transmission in the CNS?
non-NMDA
which ionotropic glutamate receptor mediates the slow component of the excitator AP
NMDA
what kind of glutamate receptor is particularly permeable to Ca? why is this problematic?
NMDA receptors
promotes neurotoxicity
how do metabotropic glutamate receptors work?
activate a secondary messenger cascade
main inhibitory neurotransmitter in the CNS?
GABA
ionotropic GABA receptors operate what channel?
Cl
GABAb activates a _ channel
K+
what drugs enhance inhibition of neurotransmitters by allosterically binding to GABAa
benzodiazepines
barbiturates
are ionotropic or metabotropic receptors faster?
ionotropic
____ receptors can close as well as open ion channels
metabotropic
how do metabotropic receptors trigger an AP if they’re too slow to do so?
have modulatory synaptic actions that can trigger it
nicotinic Ach receptors follow the metabotropic pathway T or F
F, follow the ionotropic pathway so are fast
muscarinic (aka g-protein coupled) Ach receptors follow the metabotropic pathway T or F
T
what branch of receptors follow the metabotropic pathway as a rule
G protein coupled receptors
afferent input to a neurons can also be called the…
EPSP (excitatory postsynaptic potential)
define the EPSP
a depolarising (+) change in the rmp caused by the actions of excitatory neurotransmission
excitatory should make you think…
positive
inhibitory should make you think…
negative
define the IPSP
negative change in the rmp cause by the release of an inhibitory neurotransmitter -> inhibits the AP
what is the graded potential?
a change in the rmp of a neuron caused by either an EPSP or an IPSP which is too small to reach threshold
amplitude of a graded potential increases as more __ enters
Na
what is an interneurone?
a locally acting neurone that releases GABA and thus causes inhibition
what is a projection neuron? does it bring about an EPSP or IPSP?
a neuron responsible for conveying signals to other parts of the brain
EPSP as releases glutamate
the influence of a synapse depends on..
the DISTANCE the current has to travel to the neuron’s trigger zone
what is a quanta?
a secretory vesicle filled with neurotransmitter
is there a pattern to which a neurone discharges its charge?
yes, it does so rhythmically unless it is under the influence of an IPSP
