L3- Synaptic Transmission

Question 1

What are the stages of synaptic transmission?

Answer 1

1. Neurons transmit action potentials between the pre-synaptic and post-synaptic neurons.
2. When the action potential reaches pre-synaptic terminal, it triggers release of neurotransmitters from vesicles via exocytosis.
3. Neurotransmitter diffuses across the synaptic cleft, where it binds to post-synaptic receptor sites.
4. Neurotransmitter taken back by vesicles on the pre-synaptic neuron via re-uptake.
   They are stored for later release.

Question 2

what are action potentials and neurotransmitters?

Answer 2

action potentials- electrical impulses.

neurotransmitters- chemical messengers.

Question 3

what is the pre-synaptic and post-synaptic neuron?

Answer 3

pre-synaptic = the neuron transferring the action potential.
post-synaptic = the neuron recieving the action potential.

Question 4

what are vesicles

Answer 4

sacs on the pre-synaptic membrane.

Question 5

what is the synaptic cleft?

Answer 5

the physical gap between the pre-synaptic and post-synaptic membranes.

Question 6

what is re-uptake?

Answer 6

the process which terminates the effects of synaptic transmission.
- the quicker the neurotransmitter is taken back, the shorter the effects.

Question 7

why can information only travel in one direction at the synapse?

Answer 7

• the vesicles containing neurotransmitters are only present on the pre-synaptic membrane.
• the receptors for the nt are only present on the post-synaptic membrane.
• it is the binding of the receptor which enables information to be transmitted to the next neuron.
• Diffusion of the nt’s mean they can only go from high to low conc. so can only travel from the pre-synaptic to post-synaptic membrane.

Question 8

what are psychoactive drugs and how do they work?

Answer 8

medication that affects brain function to alter perception, mood or behaviour. (eg.SSRIs)
- work by affecting (increasing or inhibiting) the transmission of nt’s across the synapse.

Question 9

what are the two types of neurotransmitters?

Answer 9

Excitatory or inhibitory.

most can be both but GABA are purely inhibitory.

Question 10

excitation?

Answer 10

Excitatory neurotransmitters cause 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 11

Inhibition?

Answer 11

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

Question 12

what is summation

Answer 12

A neuron can recieve 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 inhibitatory synaptic input.
• the net result of this calculation= summation.
• if net effect is inhibitory it wont fire. if excitatory it will fire an impulse.