Biopsych: Synpatic Transmission

Question 1

What are neurotransmitters?

Answer 1

Chemical messengers in the body, found in the brain, spinal cord (as well as some glands). Chemicals that transmit signals across the synaptic cleft - communications between neurons. Works like a key and opens specific locks (the post synaptic receptor).
- only certain neurotransmitters fit into certain receptors
- has specialised functions (e.g. acetylcholine is found in the synaptic clefts between the motor neurons and muscles, when these are transmitted, the muscles will contract)

Question 2

What are synapses?

Answer 2

A junction between 2 nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter.

Question 3

How do chemical impulses pass from one neuron to another?

Answer 3

1. Vesicles release neurotransmitter into synaptic cleft
2. Neurotransmitter binds to receptors and activates them
3. Excess neurotransmitter is taken up by the presynaptic neuron
4. Enzymes are released to break down the remaining neurotransmitter
5. Vesicles are replenished with new and reused neurotransmitter

Question 4

What is summation?

Answer 4

The effect of a neurotransmitter at a synapse depends on many factors, including how much neurotransmitter is released and the action of the neurotransmitter on the postsynaptic neuron.
- these postsynaptic potentials may be excitatory or inhibitory depending on whether they bring the post synaptic neuron closer to, or further from the threshold required to produce an action potential.
- when a neuron receives excitatory and/or inhibitory inputs at the same time, it ‘adds’ the inputs together.
- if the number of excitatory inputs overall are sufficiently great, it will result in the generation of an action potential and the transmission of a nerve impulse
- this addition of ‘inputs’ is called summation.
—> neurons can either have an excitatory or inhibitory effect on a neighbouring neuron.

Question 5

What is Excitation?

Answer 5

• more likely to fire the action potential
• increases the liklihood of something happening
• e.g. adrenaline causes excitation by increasing a neurons positive charge and makes it more likely to fire

Question 6

What is inhibitation?

Answer 6

• decreases the likelihood for something to happen
• e.g. serotonin causes inhibitation in the neighbouring neuron, causing it to be negatively charged and thus less likely to fire

Question 7

What is Spatial summation?

Answer 7

2 or more inputs arrive from different pre-synaptic cells to the same synapse at the same time. These post synaptic potentials add together

Question 8

What is Temporal summation?

Answer 8

2 or more action potentials (nerve impulses) arrive in rapid succession along a single pre-synaptic neuron. These post synaptic potentials add together.