Lecture 11

Question 1

When was the electron microscope invented and what did it allow for?

Answer 1

Developed in the 30s, allowed us to work at a much higher resolution than a light microscope. Revealed the structure of the synapse for the first time in the 50s (we didn’t look at neurons until then).

Question 2

What cells are the key regulators of the synapse

Answer 2

Glial cells.

Question 3

Where are neurotransmitters stored in the presynaptic neuron?

Answer 3

Synaptic vesicles. May be stored in larger pockets called storage granules (longer storage).

Question 4

Where is the neurotransmitter released?

Answer 4

On the presynaptic side of the membrane.

Question 5

What is a gap junction?

Answer 5

Different type of synapse (electrical)- area of contact between adjacent cells in which connexin proteins in each cell form connecting hemichannels-around 5ms faster than the chemical synapse-good for when cells need to fire simultaneously.

Question 6

Why have a chemical synapse?

Answer 6

Multple neurotransmitters and connections, plasticity, can be modified easier (type of receptor and neurotransmitter).

Question 7

What are the 4 steps of neurotransmission?

Answer 7

1) Synthesis and storage in axon terminal 2) Transported to the presynaptic membrane and released in response to an action potential. 3) Activation of receptors on target cell membrane. 4) Shut it down.

Question 8

What are the 2 ways that neurotransmitters are derived? (Step 1).

Answer 8

1) Synthesized in the axon terminal- using building blocks from food that are pumped into cells via transporters (protein molecules embedded in cell membrane).
2) Synthesized in cell body- According to instructions contained in DNA, transported on microtubules to the axon terminal.

Question 9

What are some of the foods that create different neurotransmitters?

Answer 9

Acidic foods and fats (acetylcholine) and Tryptophan (precursor for serotonin-most protein based foods.

Question 10

What are the 3 locations in which neurotransmitters are stored?

Answer 10

1) Attached to microfilaments, 2) stored in granules 3) attached to presynaptic membrane (immediate release)

Question 11

How are neurotransmitters released? (Step 2)

Answer 11

At the terminal, the action potential opens voltage-sensitvie Ca+ channels-enters terminal and binds to protein calmodulin, forming a complex. Calmodulin causes some of the vesicles to empty/get ready to (via exocytosis) contents.

Question 12

What is an activity dependent release?

Answer 12

Changes signal from electrical to chemical.

Question 13

What happens in step 3 (receptor site activation)

Answer 13

Neurotransmitter diffuses across the synapse and activates post-synaptic neuron (chemical to electrical). T

Question 14

What are transmitter activated receptors?

Answer 14

Proteins embedded in the membrane of a cell that has a binding site for a specific neurotransmitter.

Question 15

What would happen if a neurotransmitter wasn’t deactivated? (step 4).

Answer 15

Constant firing of the cell which kills a neuron- can use this to create programmed cell death which is one way of creating lesions.

Question 16

What happens to information propogation if the neuron isn’t deactivated?

Answer 16

Constant information flow, cannot alter the signal.

Question 17

What are the 4 different ways that deactivation is accomplished?

Answer 17

1) Diffusion (away from the synaptic cleft)
2) Degradation by enzymes in the synaptic cleft-neurotransmitter broken down into constituent parts.
3) Reuptake into presynaptic neuron for reuse
4) Glial reuptake- taken up by neighbouring glial cells where it can be modified or exported to the presynaptic neuron

Question 18

What is one neurotransmitter that glial cells help with?

Answer 18

Glutamate-it is actually toxic but the glial cell modifies it so it is not.

Question 19

Where is the excitatory synapse?

Answer 19

Typically on the dendrites, larger active zone, round vesicles

Question 20

Where is the inhibitory synapse?

Answer 20

Typically located on the cell body, small active zones, flat vesicles.

Question 21

What happens when there is a loss of excitation/inhibition respectively?

Answer 21

Loss of excitation=less behaviour. Loss of inhibition=more behaviour.

Question 22

What are Ionotropic receptors?

Answer 22

Binding site for a neurotransmitter, pore that regulates ion flow-effects of neurotransmitter on this receptor is typically very simple and very quick. Change in ion flow, and thus membrane voltage.

Question 23

What are metabotropic receptors?

Answer 23

Binding site for neurotransmitter, no pores, linked to a G protein. G protein opens ion channel and alters protein synthesis (plasticity)-modification: learning and memory.

Question 24

What are autoreceptors?

Answer 24

Responds to neurotransmitter released by a neuron-sits on presynaptic cleft. Creates a negative feedback loop- tells presynaptic cleft that we don’t need to relase anymore, keeps signal in check.

Question 25

How many different receptors are there for dopamine and serotonin respectively?

Answer 25

Dopamine=5

Serotonin=14