Central Nervous System Synapses Flashcards
Structure of events in CNS synapse?
Action potential coming down axon and reaching terminal
leading to opening of voltage gated calcium channels
calcium floods into cell and leads to calcium dependent exocytosis
Why is calcium important?
really important intracellular messenger
affects activity of a number of proteins involved in vessicle trafficking
vessicles get pulled to membrane and fuse with it
releases neurotransmitter into synaptic cleft where it will diffuse across and bind to its receptors on postsynaptic cell membrane
leads to opening or closing of ion channels and a potential being evoked
What are the classes of neurotransmitters in central nervous system synapses?
Amines- derived from a single AA
Amino Acids (most common)
Peptides
Purines
Gases
What are the amine neurotransmitters?
adrenaline
noradrenaline
dopamine
serotonin (5HT)
histamine
What are the amino acid neurotransmitters?
Glutamate- most common excitatory neurotransmitter
GABA- most common inhibitory neurotransmitter (brain)
Glycine- most fast inhibition in spinal cord
What are the peptides neurotransmitters?
endorphins
cholecystokinin
substance P
What are the purines neurotransmitters?
ATP
Adenosine
Why are gas neurotransmitters different to the rest?
nitric oxide , really lipophillic mol so if you were to put in vesicle- would diffuse out
Instead, produced on demand and then it freely diffuses out of the nerve terminal
What are the range of postsynaptic potentials in the central nervous system?
Fast EPSPs (ionotropic)
Slow EPSPs (metabotropic)
Fast IPSPs (ionotropic)
Slow IPSPs (metabotropic)
What are the degree of volts of postsynaptic potential in CNS?
1mV- need complex synaptic integration
What are the different CNS Synapses ?
axo-dendritic - pre synaptic terminal synapses onto dendrite (excitatory)
axo-somatic- pre synaptic terminal synapsing onto soma or cell body (inhibitory)
axo-axonal- one presynaptic terminal synapsing onto another presynaptic terminal (inhibitory or excitatory)
What are the diff synaptic connectivity in CNS?
Divergent pathways- one cell that synapses onto a number of others and influences their activity directly
(and in neuromuscular)
Convergence- one cell at bottom influenced by a number of others (not in neuromuscular)
Describe feedback inhibition in the CNS?
(not in neuromuscular junction)
When action potential fired, collateral (branch) activates an inhibitory interneuron
Inhibitory neurotransmitter released
neuron hyperpolarises
prevents repeated firing
What are the different kinds of pathways in the CNS?
monosynaptic reflex- sensory neuron detects stimuli of interest out in periphery, fire an action potential and then synapse directly onto motor neuron- tell it to fire and muscle contraction
Polysynaptic reflexes- sensory neuron influences behaviour of interneuron and so on and then influences motor neuron.
Three synapses in inter neurons where there is potential for synaptic integration and therefore three neurons where their behaviour could be influenced by convergent pathways.
Describe inhibitory reflex pathways?
If sub out grey interneuron for inhibitory interneuron that releases an inhibitory neurotransmitter like GABA that would then lead to this motor neuron being inhibited and not causing muscle contraction .
