The Synpase

Question 1

What is electrophysiology done?

Answer 1

Using a glass electrode to measure the membrane potential

Question 2

Where do action potentials occur?

Answer 2

Only in axons, in the nodes of ranveir

Question 3

What is a synapse?

Answer 3

A specalised region between the axon of a neuron and another cell.

Question 4

Describe the structural features found in a synpase

Answer 4

Presynaptic membrane (at the axon end bulb/bouton), Postsynaptic membrane (membrane with the receptors) and synaptic cleft between the two membranes.

Question 5

What allows for the movement of synaptic vesicles along an axon? And what are found in these synaptic vesicles?

Answer 5

Microtubules allow synaptic vesicles to travel along the axon. These vesicles contain neurotransmitters.

Question 6

What is a bouton?

Answer 6

It is the terminal of a presynaptic cell that has become swollen.

Question 7

Where can axon terminals synapse on?

Answer 7

Dendrites, dendritic spines or cell body

Question 8

What are the knob like structures on dendrites and what are they used for?

Answer 8

They dendritic spines which are used for building synapses and reception of signals.

Question 9

Describe the process of exocytosis in a neuron

Answer 9

• The vesicle and presynaptic membrane recognise each other via two proteins which are paired together. v-SNARE and t-SNARE.
• The v-SNARE and t-SNARE under go a conformation change and folds strongly, drawing the membranes close.
• The vesicle docks on the membrane but exocytosis is block by complexin.
• Action potential triggers a calcium influx at the end bulb which induces synaptotagmin to displace complexin and exocytosis proceeds

Question 10

What are the major classes of neurotransmitters?

Answer 10

Monoamines - e.g. dopamine, noradrenaline, adrenaline, and serotonin.
Amino acids - glutamate, GABA and glycine
Peptides -Opioids, endorphins, somatostatin and oxytoxin.

Question 11

How are peptide hormones made?

Answer 11

They are made in the RER. Packaged into vesicles in the Golgi and then transported along mircrotubules to the axon terminal.

Question 12

Describe how small molecule neurotransmitters are made

Answer 12

Vesicles are generated from endosomes and they then take up the neurotransmitters.

Question 13

what are small molecule neurotransmitters?

Answer 13

Monoamines and amino acids

Question 14

What are the two classes of receptors for neurotransmitters

Answer 14

Ionotropic receptors (fast signals)
Metabotropic (slow signals)

Question 15

Describe how ionotropic receptors work?

Answer 15

They bind directly to the receptor, causing a conformation change that open the pores, allowing an flow of ions through. And the voltage of the cell changes.

Question 16

Describe how metabotropic receptors work?

Answer 16

• Neurotransmitter binds to receptor and binds the G-protein. The G-protein becomes activated by replacing GDP with GTP.
• Active G-protein leaves the receptor and binds to the target enzyme.
• Enzyme generates messenger molecules which bind to the channel causing them to open.
• GDP-ase removes P from GTP and therefore inactivating the G-protein
• Inactive G-protein leaves enzyme, inactivating the enzyme.

Question 17

Describe the differences in the speeds between ionotropic and metabotropic

Answer 17

Ionotropic is much faster while metabotropic is slower as it involves many more components.

Question 18

What is quanta release?

Answer 18

The release of a single vesicle at the presynaptic membrane, However the more vesicles released, the stronger the signal.

Question 19

What are post synaptics potentials?

Answer 19

These are a change in the membrane potential caused by the passage of ions through channels that have been opened after the binding of a neurotransmitter to the postsynaptic membrane.

Question 20

What is an excitatory post synaptic potential?

Answer 20

A net flow of positive ions into the cell that depolarises the membrane.

Question 21

What is an inhibitory post synaptic potential?

Answer 21

A net flow of negative ions that flow into the cell and hyperpolarise the membrane.

Question 22

What is summation and what does summation determine?

Answer 22

It is when several post synaptic potential occur and together can generate an action potential. Summation therefore determines if an action potential is generated.

Question 23

What are the differences between EPSP and action potentials?

Answer 23

EPSP do not propagate along the axon and they can be caused by ionotropic or metabotropic gating.
EPSP do not have a refractory period, thus a serious of EPSP can summate.