Nerves 5 Flashcards
What is a synapse?
the connection where one neurone modulates the activity of a target
What does the action potential cause in the presynaptic terminal of the NMJ?
opens voltage gated calcium channels
What does the release of calcium cause in the presynaptic terminal?
triggers fusion of neurotransmitter contain vesicles
What neurotransmitter is released at the NMJ?
acetylcholine
What happens to acetylcholine?
It diffuses across synaptic cleft and binds to acetylcholine receptors (nicotinic)
What does the acetylcholine do?
opens ligand gated sodium/ potassium channels and evokes a graded (Local) potential called the end plate potential
What is significant about the endplate potential?
it always depolarises the adjacent membrane to threshold which opens voltage gated sodium channels to generate a new AP
What removes ACh?
anticholinesterase
What does tetrodotoxin do?
blocks sodium channels and so blocks the action potential
What does joro spider toxin do?
blocks calcium channels and so stops transmitter release
What does botulinum toxin do?
prevents vesicle fusion
What does curare do?
blocks ACh receptors and so prevents endplate potential
What do anticholinesterases do?
prevent breakdown of ACh and so increase transmission at NMJ
What 4 qualities of CNS synapses makes them more complex than the neuromuscular junction?
- complicated synaptic connectivity
- variety of anatomical arrangement of synapse
- range of postsynaptic potentials
- range of neurotransmitters
What kind of postsynaptic potentials does the CNS have compared to the NMJ?
NMJ only has the big endplate potential CNS can have: -Fast EPSPs (ionotropic) -Slow EPSPs (metabotropic) -Fast IPSPs -Slow IPSPs
What does the range of postsynaptic potentials in the CNS allow?
complex synaptic integration
What 3 anatomical arrangements can synapses in the CNS have compared to the NMJ.
NMJ anatomical arrangement does not change CNS can have: -axo-somatic -axo-dendritic -axo-axonal
What is meant by ‘synaptic connectivity’ in the CNS?
the different numbers and functions of neurones in a pathway to elicit an effect
NMJ is very simple and generally is just motor neurone-muscle cell but the CNS can involve lots of converging and diverging neurones and interneurones
