Neuronal communication Flashcards
Pacinian corpuscle
-pressure sensor in skin
-when pressure is applied, the rings of connective tissue deform, pushing against the nerve ending
Depolarisation
the inside of the cell becomes less negative compared to the outside
Motor neurone
-carry action potential from CNS to effectors
-long axon with cell body at one end
-cell body has dendrites attached
-action potential travels from the dendrites to the axon
Sensory neurone
-carry action potential from sensory receptor to CNS
-long dendron, short axon
-cell body in middle of axon/dendron (axon after cell body)
-action potential travels from dendron to axon to synaptic endings
Relay neurone
-connect sensory and motor neurones
-short axon
-action potential travels from dendrites to synaptic endings
Myelinated neurones + advantages
-schawnn cells wrapped around axon
-small gaps in the sheath called nodes of ranvier
-prevents movements of ions across neurone memebranes
-ions can only move at nodes of ranvier
-this makes conduction much quicker
Neurones at rest
-sodium potassium pumps pump 3Na+ out for every 2K+ into the cell
-Na+ channels closed, some K+ channels open, so some K+ diffuse out of neurone
-negative anions inside the neurone make inside negative compared to outside
-potential difference of -60mV
Stages of action potential
-starts at resting state -60mV
-sodium channels open, so Na+ diffuse into cell
-This depolarises the membrane and reaches threshold value= -50mV
-positive feedback causes nearby voltage gated sodium channels to open, so more Na+ diffuse in
-the potential difference across the membrane reaches +40mV. inside positive compared to outside
-sodium channels close, potassium channels open
-K+ diffuse out of cell, repolarising the cell (becoming more negative)
-potential difference overshoots slightly making it hyperpolarised
-original potential difference is restored and neurone returns to rest
Refractory period
-after AP, neurone can’t reach another immediately
-this allows the cell to recover
-ensures action potential only flows in one direction
Local currents
-when Na+ flood into neurone causing depolarisation, this creates local currents
-Na+ begin to diffuse along the neurone
-these local currents cause slight depolarisation and cause Na+ ion channels to open further along the membrane
Saltatory conduction
-ionic movements that create an action potential can only occur at the nodes of ranvier
-local currents are elongated and Na+ diffuse along the neurone from one node of ranvier to the next
-this speed up the action potential
All or nothing rule
-all action potentials are the same intensity= +40mV
-once the threshold value is reached, there is no stopping the action potential
Transmission across a synapse
-action potential arrives at pre synaptic bulb
-this opens voltage gated Ca2+ channels
-Ca2+ diffuse into cell
-this causes vesicles containing acetylcholine to fuse with presynaptic membrane and release neurotransmitter via exocytosis
-acetylcholine diffuses across the gap
-binds to post synaptic receptors on Na+ channels
-this opens Na+ channels so Na+ diffuses in
-this creates a generator potential
-if sufficient generator potentials combine, the threshold value will be reached and action potential created
-acetylcholinesterase hydrolyses acetylcholine into acetic acid and choline
-these diffuse back into the pre-synaptic bulb
-this closes the Na+ channels
-acetic acid and choline recombine using ATP from mitochondria in pre synaptic bulb
Summation
-effects of several excitatory post-synaptic potentials are added together
-just one EPSP alone isn’t enough to cause an action potential in post synaptic neurone, therefore several EPSPs are needed
Temporal summation- result from several action potentials in the same pre-synaptic neurone
Spatial summation- action potentials arriving from multiple pre-synaptic neurones
IPSPs
-inhibitory post-synaptic potential
-reduce the effect of summation and prevent an action potential in post-synaptic neurone
-open Cl- channels so Cl- flood in
-this hyperpolarises the neurone
-this makes it difficult to generate an action potential
