Lesson 3 - Synaptic Transmission

Question 1

Synaptic Transmission
Neurons

Answer 1

Neurons transmit electrical impulses => action potentials
Transmitted between pre-synaptic neuron (neuron transferring action potential) and post-synaptic neuron (neuron receiving action potential)

Question 2

Synaptic Transmission
Action Potential

Answer 2

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

Question 3

Synaptic Transmission
Re-Uptake

Answer 3

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

Question 4

Synaptic Transmission
Neurotransmitters

Answer 4

Can be excitatory or inhibitory (most can be both but GABA is purely inhibitory)
Excitatory causes an electrical charge in membrane of post synaptic neuron resulting in excitatory post synaptic potential (EPSP), meaning post synaptic neuron is more likely to fire an impulse
Inhibitory cause an inhibitory post synaptic potential (IPSP), making it less likely neuron fires an impulse

Question 5

Synaptic Transmission
Summation

Answer 5

Neuron can receive both EPSPs and IPSPs at same time
Likelihood that neuron will fire an impulse is determined by adding up the excitatory and inhibitory synaptic input
Net result of calculation, known as summation, determines whether or not neuron fires an impulse
If net effect is inhibitory, neuron will not fire
If net effect is exhibitory, neuron will fire

Question 6

Direction of Synaptic Transmission

Answer 6

Information can only travel in one direction at a synapse
Vesicles containing neurotransmitters are only present on the pre-synaptic membrane
Receptors for neurotransmitters are only present on post synaptic membrane
It is the binding of the neurotransmitter to receptor which enables information to be transmitted to next neuron
Diffusion of neurotransmitters mean they only go from high to low contraction, so only travel from pre to post

Question 7

Synaptic Transmission Medication

Answer 7

Psychoactive drugs, such as SSRIs, work by affecting transmission of neurotransmitters across synapse
Some pain medications mimic effects of inhib neurotransmitters
Stimulation of post synaptic receptors by inhib neurotransmitters result in inhibition of post synaptic membrane
When inhib neurotransmitter binds to post synaptic receptors, it makes post synaptic neuron less likely to fire
Due to summation, if inhib neurotransmitters are higher then excit, they can inhibit an action potential from occurring => pain medications decrease activity and reduce brain activity => less pain

Question 8

Synapse Diagram

Answer 8