Which types of ion channels are found on the nerve cell membranes?

- Voltage gated & Ligand-gated channels

Name 3 differences between voltage-gated and ligand-gated ion channels

Voltage gated channels: 

1. Changes in the membrane potential opens/closes the ion channel.

2. Specific for a certain ion. 

3. Sodium, Potassium and Calcium channels. 

Ligand-gated channels: 

1. Binding of a ligand (neurotransmitter) opens/closes the ion channel. 

2. Not specific.

3. Aceytl-choline, y-amino butyric acid, glutamate and serotonin receptors. 

Compare ionotropic and metabotropic receptors

Ionotropic receptors change shape when they are bound by a ligand, and this change of shape makes a channel that allows ions to flow through. This has a short duration of action. 

Metabotropic receptors do not have channels. They have a G-active protein that will activate a secondary messenger that will activate something else. This has a long duration of action (up to minutes).

Classify the CNS receptors into ionotropic and metabotropic and know the transduction mechanism of each receptor

There are only four ionotrpic receptors known. They are: 

- GABAa 

-Nicotinic 

-EEA

-5-HT3 

The metabotropic receptors include: 

- The adenylyl cylase system; B1+2, D1 = stimulates the formation of 2nd messengers (c-AMP)

; D2, a2, 5-HT1 A+B, M2, GABAb = formation of 2nd messengers is suppressed. 

- Phospholipase C system; a1, 5-HT2, M1 and H1 = stimulates the formation of 2nd messengers (IP3 and DAG)

 

Explain the difference between an EPSP and an IPSP and give examples of each

EPSP  (Excitatory Post Synaptic Potential) - An electrical change (depolarisation) in the post synaptic membrane caused by the binding of an excitatory neurotransmitter from a presynaptic membrane will make it more likely for the post synaptic neuron to generate an action potential. An example of this would be when a neurotransmitter binds to Nicotinic receptor, Na+ channels open which causes depolarisation and has an activating effect. 

IPSP (Inhibitory Post Synaptic Potential) - An electrical charge (hyper polarisation) in the post synaptic membrane cause by the binding of an inhibitory neurotransmitter from the presynaptic membrane will make it less likely for the post synaptic neuron to generate an action potential. An example of this would be when neurotrasmitter binds to GABAa, Cl- channels open and causes hyper polarisation which has an inhibiting effect. 

What is the role of calcium in the development of a synaptic potential?

Calcium ions trigger the release of neurotransmitters from the synaptic vessicle into the synaptic cleft. The synaptic vessicles fuse with the presynaptic membrane and exocytosis of the neurotransmitters occurs.