CB31 Neurotransmission 1

Question 1

Define the term synapse

Answer 1

Synapses are junction between two excitable cells

Question 2

Define the term neuromuscular junction

Answer 2

Communication between nerve to skeletal muscle

Question 3

Define the term neuroeffector junction

Answer 3

Communication between nerve to gland/cardial/smooth muscle

Question 4

Compare the properties of electrical & chemical synapses

Answer 4

Electrical synapses are low resistance pathways from pre- to post- synaptic cell with cytoplasmic continuity; there’s virtually no delay in transmission. Found in the brain but move common in cells that are electrically synchronous ( cardiac tissue, smooth muscle)
Action potential causes wave of depolarisation in presynaptic junction → rapidly transmitted through connections to postsynaptic

Chemical synapses involve neurotransmitters stored in presynaptic vesicles & a
Wider synaptic cleft.
Action potential triggers their release into synaptic cleft
Action potential must be regenerated in postsynaptic cell

Question 5

Describe the structure & physiology of the neuromuscular junction

Answer 5

Motor neuron has multiple terminal boutons, where the contact is made with the end plate
Terminal bouton is the presynapse → skeletal muscle postsynapse

Question 6

Describe the processes & mechanisms of neurotransmitter release

Answer 6

• Incoming action potentials depolarise the presynaptic cell which activates voltage gated calcium ion channels
• huge influx of Ca2+ into cell triggering vesicle fusion with presynaptic membrane
• vesicles release neurotransmitters via exocytosis
• ACh binds & opens nicolinic receptors (ligand-gated ion channels)
• causes an influx in Na+ ions into muscle cell
• localised depolarisation of muscle endplate (endplate potential)
• muscle membrane surrounding endplate depolarises
• activation of na+ & k+ voltage gated ion channels
• regeneration & propagation of action potential