Lesson 3

Question 1

Action Potential

Answer 1

Neurons transmit electrical impulses, known as action potentials, between the pre-synaptic neuron (the neuron transferring the action potential) and the post-synaptic neuron (the neuron receiving the action potential).

Question 2

Synaptic Transmission

Answer 2

• When the action potential reaches the pre-synaptic terminal it triggers the release of neurotransmitters (chemical messengers) from sacs on the pre-synaptic membrane known as vesicles in a process called exocytosis.
• The released neurotransmitter diffuses across the synaptic cleft (physical gap between the pre-synaptic membrane and post-synaptic membrane) where it binds to specialised post-synaptic receptor sites.

Question 3

Re-uptake

Answer 3

• Synaptic transmission takes only a fraction of a second, with the effects terminated by a process called re-uptake.
• The neurotransmitter is taken back by the vesicles on the pre-synaptic neuron where they are stored for later release.
• The quicker the neurotransmitter is taken back the shorter the effects.

Question 4

Psychoactive drugs

Answer 4

Psychoactive drugs (medication that affects brain function to alter perception, mood or behaviour), such as SSRIs, work by affecting (increasing or inhibiting) the transmission of neurotransmitters across the synapse.

Question 5

Excitatory Neurotransmitters

Answer 5

Excitatory neurotransmitters causes an electrical charge in the membrane of the post-synaptic neuron resulting in an excitatory post-synaptic potential (EPSP), meaning that the post-synaptic cell is more likely to fire an impulse.

Question 6

Inhibitory Neurotransmitters

Answer 6

• Inhibitory neurotransmitters cause an inhibitory post-synaptic potential (IPSP), making it less likely that the neuron will fire an impulse.

Question 7

Summation

Answer 7

• A neuron can receive both EPSPs and IPSPs at the same time.
• The likelihood that the cell will fire an impulse is determined by adding up the excitatory and the inhibitory synaptic input.
• The net result of this calculation, known as summation, determines whether or not the cell will fire an impulse.
• If the net effect is inhibitory the neuron will not fire, and if the net effect is excitatory, the neuron will fire.