Neurotransmission W1 Flashcards
voltage across membrane at rest?
-70mV
which side of membrane is positive/negative?
+ extracellular
- intracellular
3 ways to stimulate a resting neuron?
ligand gated ion channels
voltage gated ion channels
propagation of current
effect of a stimulus on membrane potential
increase or decrease membrane potential
threshold for membrane depolarization? what occurs when this is met?
-55mV
voltage gated Na channels open
which channels open/close in depolarization/repolarization
depolarization - voltage gated Na channels open
repolarization - voltage gated K channels open, voltage gated Na channels close
what triggers repolarisation
voltage reaches +40mV
what occurs in the refractory period?
neuron is hyperpolarized and an action potential cannot be generated
what does myelination facilitate
saltatory conduction
how does saltatory conduction occur?
ions can’t pass across the fatty myelin layer, impulse jumps between nodes of Ranvier between myelin sheaths
problems of unmyelinated axons
slow process
high energy requirement
what conditions cause loss of myelin therefore impairing conduction?
Multiple Sclerosis (CNS)
Guillain Barre Syndrome (PNS)
description of chemical transmission at a synapse?
action potential arrives, voltage gated Ca2+ channels open allowing Ca2+ to enter cell, this allows vesicle docking and neurotransmitter release. neurotransmitters bind to receptors, channels open/close. Vesicular membrane retrieved from plasma membrane, neurotransmitter removed by glial uptake (for enzyme degredation)
inhibitory neurotransmitters?
GABA
serotonin
glycine
excitatory neurotransmitters?
glutamate
adrenaline
noradrenaline
inhibitory/excitatory synapse - what occurs in post synaptic cell
inhibitory - hyperpolarisation
excitatory - depolarisation
example of neurotransmitter that can be both excitatory and inhibitory? what does this depend on?
dopamine
depends on type of post synaptic receptor it binds to
2 types of summation?
spatial and temporal
spatial summation description
simultaneous signals from multiple presynaptic neurons received by a single postsynaptic neuron
temporal summation description
single presynaptic neuron rapid-firing signals to a postsynaptic neuron
what does diazepam do in the nervous system
enhances GABA channel opening (inhibitory transmission)
effects of overdose of diazepam
lethargy
slurred speech
poor co-ordination
bradycardia
hypotension
apnoea
what is lethargy
pathological state of sleepiness or deep unresponsiveness and inactivity
what does the resting state of a neuron require
energy!
