Synapses Flashcards
What are synapses?
Specialised junctions between 2 neurones at which electrical activity in a presynaptic neurone influences electrical activity of a post synaptic neurone
What are the 2 types of synapses?
Electrical
Chemical
Electrical synapses Rare or common? What type of junction? Speed? Found?
Rare
Gap junction joins pre and post synaptic cells
Very rapid adjacent depolarization
Found in brainstem (eg, breathing & hypothalamus, hormone secretion)
Chemical synapses
Rare or common?
What type of junction?
Common
Pre and post synaptic neurones joined by the synaptic cleft
What are transmitted across the synaptic cleft in chemical synapses?
Neurotransmitters are transmitted across cleft from pre to post synaptoc axons
Is it only 1 neurotransmitter that is released from an axon in a chemical synapse?
Occasionally, more than 1 neurotransmitter may be simultaneously released from an axon, cotransmitter
What are synapses at a chemical synapse covered in? What are they used for?
Astrocytes (glial cells), reuptake of excess neurotransmitter
What happens when neurotransmitters are released?
Ca2+ channels open when AP reaches pre synaptic terminal
Ca2+ cause vesicles (containing neurotransmitter) to move to pre cell membrane and fuse and release their contents
N diffuses across cleft & attaches to receptor on post membrane
What are the 5 processes of synaptic transmission?
Manufacture - intracellular biochemical processes
Storage - vesicles
Release - action potential
Interact with post synaptic receptors - diffusion across synapse
Inactivation - breakdown or reuptake
When neurotransmitters bind to postsynaptic receptors on CSM, what are the 2 responses?
Depolarization
Hyperpolarisation
What will depolarisation occus in?
What will happen?
Depolarization will occur in excitatory channels (excitatory post synaptic potential- EPSP)
Many Na+ leave and few K+ enter
What will hyperpolarisation occus in?
What will happen?
Occur in inhibitory channels (IPSP)
Many K+ leave or many Cl- enter
Is 1 excitatory synaptic event enoughto reach threshold level?
No
AP generated by combined effect of many excitatory synapses
What are the 2 types of summation?
Temporal
Spatial
What is temporal summation?
N from same presynaptic cell at diff times
