W4 - Additional Slides Flashcards
What is a synapse (electrical/chemical)?
A junction between 2 neurons that permits transmission of a signal from one nerve to another
Electrical synapses are very fast, what are used to ‘connect’ the two neurons?
Gap junctions consisting of connexons
How do NTMs cross a chemical synapse?
Vesicles of NTM fuse to membrane due to increase in cytosolic Ca2+ conc caused by depolarisation of axon terminal and release via exocytosis, diffuse across synaptic cleft and bind to post-syn memb-bound receptors
What happens once NTM bind to post-syn receptors?
Triggers an electrophysiological response in post-syn cell (excitatory/inhibitory)
What two things can happen to the NTM once it’s been used?
Recycled into the pre-syn neuron or degraded (e.g. by acetylcholinesterase)
What happens to cause excitatory NTMs to cause depolarisation in the post-syn neuron?
Excitatory Post Synaptic Potential (EPSP) is triggered by binding to ligand gated ion channels for SODIUM IONS
What happens to cause inhibitory NTMs to cause hyperpolarisation in the post-syn neuron?
Inhibitory Post-Synaptic Potential (IPSP) is triggered by binding to ligand gated ion channels for CHLORIDE IONS
What is the main excitatory NTM in vertebrates and what is it in the brain?
Vertebrates - ACh, brain - glutamate
What is the main inhibitory NTM in the brain and the main one in the SC?
Brain - GABA, SC - glycine
Describe spatial summation
Stimulating multiple axons at the same time increase the likelihood of AP in the one neuron it is acting on, individually the threshold isn’t reached
Describe temporal summation
If you stimulate the same axon twice this increases the likelihood of an AP in the post syn cell, just one stimulation may only generate a very small EPSP
What is the difference between what sodium channels are working during the EPSP and then the AP?
EPSP - ligand gated cause change in memb potential, once threshold is reached - voltage gated take over to create AP
