Neuronal Communication Flashcards
CNS
brain and spinal cord
PNS
all nerves and sense organs which feed into CNS
spinal fibres
sensory neurones
carry ap from a sensory receptors to CNS
motor neurones
carry an action potential from the CNS to the effectors
nerve impulse
electrical signals produced by movement of ions across cell membranes
sensory receptors
specialised cells that can detect changes in surroundings and create action potentials
pacinian corpuscles
pressure sensor that detects changes in pressure on the skin
potential gradient
cell negatively charged inside compared to outside and negative potential enhanced by negatively charged ions already inside the cell
relay neurones
connect sensory and motor neurones
why are neurones very long
transmit action potentials over a long distance
dendrites
carry impulse towards cell body
axon
carries impulse away from cell body
advantages of myelination
transmit ap much faster
carry ap over long distances
more rapid response to a stimulus
neurones at rest
when not transmitting an ap
refractory period
time that allows the cell to recover after an ap and ensure they’re only transmitted in one direction
saltatory conduction
process which the ap appears to jump from one node to the next to speed up transmission
synaptic cleft
small gap between neurones as the ap cannot bridge the gap between 2 neurones
role of a synapse
ap in pre-synaptic neurones release a neurotransmitter that diffused across the cleft to generate a new ap in the post-synaptic neurone and bridge the gap
cholinergic synapse
synapses that use acetylcholine as the neurotransmitter
if acetylcholine is left in the synaptic cleft…
it will continue to open sodium ion channels in the post-synaptic membrane and continue to cause ap
role of acetylcholinerase
prevent acetylcholine causing an ap
2 ways nerve junctions involve several neurones
several neurones from different places converging on one neurone
or
one neurone sending signals out to several neurones that diverge to different effectors
temporal summation
several ap’s in the same pre-synaptic neurone
spatial summation
ap’s arriving from several different pre-synaptic neurones
excitatory post-synaptic potential (EPSP)
one ap passes down an axon to the synapse and causes vesicles to move and fuse with pre-synaptic membrane
the small number of acetylcholine diffusing produces a small depolarisation
summation
may take several EPSPs to reach the threshold so they combine together to increase membrane depolarisation until it reaches
inhibitory post-synaptic potentials (IPSPs)
produced by some pre-synaptic neurones reducing the effect of summation and prevent an ap in the post-synaptic neurone
transducer
a cell that converts one form of energy into another (electrical impulse)
myelinated neurones
has an individual layer of myelin around it
action potential
a brief reversal of the potential across the membrane of a neurone causing a peak of -40mV
resting potential
the potential difference across the membrane while the neurone is at rest -60mV
neurotransmitter
a chemical used as a signalling molecule between two neurones at a synapse
habituated
when the synapse is fatigued after repeated stimulation so the nervous system no longer responds to the stimulus
local currents
movement of ions along a neurone close to the membrane caused by an influx of sodium ions
nodes of Ranvier
gaps in the myelin sheath
