Synaptic Events

Question 1

What is a synapse?

Answer 1

Point of communication between a neuron and another cell

Question 2

What is axon (presynaptic) terminal?

Answer 2

Voltage-gated channels Ca2+ channels

-Postsynaptic cell = receptors (proteins)

Question 3

What is a synaptic cleft?

Answer 3

Space between the presynaptic and postsynaptic cells

Question 4

Sequence of events?

Answer 4

1) AP reaches axon terminal
2) open of voltage gated Ca2+ channels
3) influx Ca2+
4) triggers sequence of chemical reactions in the axon terminal
5) synaptic vesicles bind to presynaptic membrane
6) neurotransmitter is released into the synaptic cleft = exocytosis

Question 5

Where does the neurotransmitter diffuse?

Answer 5

Across synaptic cleft - neurotransmitter binds to postsynaptic cell receptor

Question 6

What does a neurotransmitter bind to?

Answer 6

the receptor a small change in the membrane potential occurs = postsynaptic potential

• Excitatory PSP = EPSP
• Inhibitory PSP = IPSP

Question 7

EPSP

Answer 7

Binding of neurotransmitter to postsynaptic cell becoming less negative on the inside

• Example: Na+ or Ca2+ influx
• More likely to generate an action potential in the postsynaptic cell

Question 8

IPSP

Answer 8

Binding of neurotransmitter to postsynaptic cell becoming more negative on the inside (hyperpolarization)

• Example: K+ efflux or Chloride influx
• More difficult to generate an action potential in the postsynaptic cell

Question 9

PSP

Answer 9

Balance of + to - changes from moment to moment

• If more EPSP than IPSP, enough that the net is greater than +15mV, then an AP is generated
• If the sum of IPSP and EPSP is less than +15mV, no AP is created