Synaptic transmission Flashcards
What is the resting membrane potential of an average neurone?
-70mV
What maintains the resting membrane potential?
Na+/K+ pump
pumps 3Na+ out and 2K+ in
What is an action potential?
momentary reversal of membrane potential
How does an action potential travel down an axon?
in response to a signal, the soma end of the axon becomes depolarised
depolarisation spreads down the axon. the 1st part of the membrane repolarised. because sodium channels are inactivated and more potassium channels have opened, the membrane cannot depolarise again
action potential continues to move down the axon
Describe how an action potential crosses a synapse
action potential depolarises the axon terminal
depolarisation opens voltage-gated calcium ion channels, and calcium ions enter the cell
calcium entry triggers exocytosis of synaptic vesicle contents
neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell
neurotransmitter binding initiates a response in the postsynaptic cell
Describe the recycling of acetylcholine in the synaptic cleft
ACh is made from choline and acetyl CoA
in the synaptic cleft, ACh is rapidly broken down by the enzyme acetylcholinesterase
choline is transported back into the axon terminal by cotransport with sodium ions
recycled choline is used to make more ACh
How is synaptic transmission terminated?
diffusion + absorption:
- neurotransmitters diffuse away from the synaptic cleft and are returned to the presynaptic neuron
degradation:
- neurotransmitters are degraded by enzymatic reactions in the synaptic cleft
reuptake:
- neurotransmitters are taken back into the presynaptic neuron
Where is dopamine found in the brain?
substantia nigra
ventral tegmental area (VTA)
hypothalamus
What is the chief inhibitory transmitter in the brain?
Gamma-aminobutyric acid (GABA)
