action potentials 2 Flashcards
how are messages transmitted from neuron to neuron
synaptic transmissions from axo-dendritic synapses
messages transmission from neuron to muscle
cell body of motorneuron to end plate of neuromuscular junction
Neuromuscular junction as a model
of (excitatory) synaptic transmission
action potential causes Ca2+ to come in and allow vesicles to be released. gets released onto synaptic cleft and can now bind onto LGIC on post synaptic cleft
Two main types of chemical synapses in the CNS
excitatory and inhibitory
excitatory
Depolarisation.
* Neurotransmitters:
mainly glutamic acid (glutamate) or acetylcholine (Ach)
* Ionic mechanisms of EPSPs:
Transient opening of channels permeable to Na+, K+ and
sometimes Ca2+
inhibitory
Hyperpolarisation.
Neurotransmitters:
mainly gamma-aminobutyric acid (GABA) or glycine
* Ionic mechanisms of IPSPs:
Usually transient opening of K+ channels
small molecule neurotransmitters
Usually fast action (~millisecs) and direct on postsynaptic receptors
- Amino acids: glutamate, GABA, glycine
- Acetylcholine (ACh)
- Amines: serotonin (5-HT), noradrenaline, dopamine
neuropeptides
large molecules that are slow
Have an indirect (‘metabotropic’) action on postsynaptic receptors
e.g. Neuropeptide Y (NPY), Substance P, Kisspeptin, Enkephalin
Factors determining synaptic action
type of receptor and neurotransmitter
amount of neurotransmitter receptor present
Neurotransmitter inactivation
diffusion away from synapse
enzymes degrading it
re-uptake and recycling
temporal summation
stimulated many times in short amount of time to get it to have an impulse
spatial summation
multiple neurons contribute to an impulse
what happens if there was no inhibitory excitation
too much calcium released and kills cells.
