Synaptic Transmission

Question 1

what is Synaptic Transmission

Answer 1

synaptic transmission is the process for transmitting messages from neuron to neuron

Question 2

label/draw a synapse

Question 3

outline process of synaptic transmission

Answer 3

1. action potential (electrical signal) created in pre-synaptic neuron. it travels from the dendrites down the axon until it reaches the presynaptic terminal (end of the neuron). All signals within the neuron are electrical.
2. each neuron is separated from the next by a tiny gap called a synapse. electrical signal can’t cross the synapse so must become chemical. to do this it stimulates vesicles (sacs containing neurotransmitters) to release neurotransmitters (chemical messengers) into the synapse.
3. neurotransmitters crosses gap, binds with receptors on the dendrites of the postsynaptic neuron. this enables the signal/info to be transmitted. the effect will depend on the neurotransmitter being excitatory or inhibitory.
4. neurotransmitters can travel back ti the presynaptic neuron. This process is known as ‘reuptake’ which allows the neurotransmitter to be stored and made available for later use (recycling programme)

Question 4

neurotransmitters

Answer 4

several types of neurotransmitters (chemical messengers) have been identified in the brain.

each NT has its own specific structure that fits perfecting into a post-synaptic receptor site (lock and key).

NTs have specialist functions
- eg. acetylcholine (ACh) is found at each point where a motor neurons meets a muscle. and units release it causes muscles to contract.
- eg. dopamine affects the NS including emotional arousal, pleasure, voluntary movement.

Question 5

excitation and inhibition

Answer 5

NTs have either an excitatory or inhibitory effect on the neighbouring neuron.

Inhibitory NTs (eg seratonin) cause inhibition in the receiving neuron, resulting in the neuron becoming more negatively charged and less likely to fire.
If the message is likely to be stopped at the post synaptic neuron, it is an inhibitory synapse.

Excitatory NTs (eg. adrenaline) cause excitation of the post synaptic neuron by increasing its positive charge and making it more likely to fire.
If a synapse is more likely to cause the post-synaptic neuron to fire, its is an excitatory synapse.

excitatory potential like the accelerator and an inhibitory potential is like the brake.

normal brain function depending regulated balance between excitatory and inhibitory influence.

Question 6

summation

Answer 6

a neuron can receive both excitatory and inhibitory NTs at the same time.

the likelihood of the cell firing is therefore determined by adding up the excitatory and inhibitory synaptic input. known as summation.

if the net effect on the postsynaptic neuron is inhibitory, the neuron will be less likely to fire.

if the net effect is excitatory, the neuron will be more likely to fire.

if more excitatory NTs bind with receptors, the overall net effect will be positive and the neuron will be more likely to fire

if more inhibitory NTs bind with receptors, the overall net effect will be negative and the neuron will be less likely to fire

Question 7

summation

Answer 7

a neuron can receive both excitatory and inhibitory NTs at the same time.

the likelihood of the cell firing is therefore determined by adding up the excitatory and inhibitory synaptic input. known as summation.

if the net effect on the postsynaptic neuron is inhibitory, the neuron will be less likely to fire.

if the net effect is excitatory, the neuron will be more likely to fire.

if more excitatory NTs bind with receptors, the overall net effect will be positive and the neuron will be more likely to fire

if more inhibitory NTs bind with receptors, the overall net effect will be negative and the neuron will be less likely to fire