Lesson 3 - Synaptic transmission

Question 1

What is synaptic transmission?

Answer 1

It refers to the process by which a nerve impulse (action potentials) passes across the synaptic cleft from the presynaptic neuron to the post synaptic neurone

Question 2

How do neurons cause an action potential?

Answer 2

When a neuron is in a resting state, the inside of the cell is negatively charged compared to the outside, and neurons must transmit information both within the neuron and from one neuron to another. Neurons get activated by a stimulus which turns the inside of a cell positive for a split second causing an action potential to occur - creating an electrical impulse that travels down the axon to the end of the neuron

Question 3

What happens when action potential reaches the pre synaptic terminal?

Answer 3

When the action potential reaches the presynaptic terminal, it triggers the release of neurotransmitters from the sacs within the presynaptic neruon known as vesicles in a process called exocytosis. These neurotransmitters then diffuse across the synaptic cleft where they bind to the specialised postsynaptic receptor sites

Question 4

How long is synaptic transmission

Answer 4

It only takes 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 presynaptic neuron where they are stored for later release. The quicker the neurotransmitters are taken back, the shorter the effects

Question 5

What are excitatory and inhibitory neurotransmitter

Answer 5

Neurotransmitters can either be excitatory and inhibitory. Excitatory neurotransmitters cause an electrical charge in the membrane of the post synaptic neuron, resulting in an excitatory post synaptic potential, meaning that the post synaptic neuron is more likely to fire an impulse . Inhibitory neurotransmitters cause an inhibitory post synaptic potential, making it less likely the postsynaptic neuron will fire

Question 6

What is direction of synaptic transmission?

Answer 6

At a synapse, info can only travel in one direction. The vesicles containing the neurotransmitters are only present in the presynaptic membrane. It is the binding of the neurotransmitter to the receptor that enables the information to be transmitted to the next neuron. Diffusion also means that neurotransmitters can only go from an area of high concentration to an area of low concentration, so can only travel from pre synaptic membrane to post synaptic membrane

Question 7

What is summation

Answer 7

Nerve cell receives both EPSP and IPSP. The likely hood that the cell will fire is determined by adding up the total synaptic input. The net result of this calculation is summation and determines weather the neuron will fire or not

Question 8

Medication

Answer 8

Psychoactive drugs, such as SSRIs work by affecting the transmission of neurotransmitters across the synapse

Pain medications act as inhibitory neurotransmitters, making the Post - SN less likely to fire and therefore inhibiting an action potential, decreasing brain activity and less pain