1) Which types of ion channels are found on the nerve cell membrane?

Voltage-gated ion channels (Potential dependant) and Ligand-gated ion channels.

2) Name 3 differences between voltage-gated and ligand-gated ion channels.

• Voltage-gated ion channels open and close as respond to changes in the membrane potential of the cell, where Ligand-gated ion channels open and closes when a ligand (Neurotransmitter) binds directly to the ion channel.
• Voltage-gated ion channels are ion specific and Ligand-gated ion channels are notion specific.
• Voltage-gated ion channels consist mainly of Ca+ and K+, whilst Ligand-gated ion channels consist of acetylcholine and nicotine.

3) Compare ionotropic and Metabotropic receptors.

Ionotropic	Metabotropic
Activation of a receptor leads to a quick stimulation. No second messenger will be formed due to direct receptor binding. Accountable for the opening and closing of ion channels.	Activation of a receptor leads to prolonged activation. A second messenger will be formed due to G-protein formation. Responsible for the changes in metabolism.

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

Ionotropic receptors:

1.  GABA A
2. Nicotanic
3. EAA
4. Seratonin (5-HT 3)

Metabotropic receptor (according to 2 systems)

1.  Adenylyl cyclase:  Beta 1+2, Alpha 2, D1+2, 5-HT 1A+B, M2 and GABA B. Positively as well as negatively bound receptors. If the Positively bound receptors are stimulated it causes the formation of a second messenger, which then leads to ATP to convert to Camp. If the negatively bound receptors are stimulated it leads inhibition of Camp.
2. Phospholipase: Alpha 1, M1, H1 and 5-HT 2. Positively bound receptors only and when stimulated it leads to the conversion of PIP2 to DAG as well as IP3.

5) Explain the difference between an EPSP and an IPSP and give an example of each.

EPSP (excitatory postsynaptic potential) is the cause of depolarization when an excitatory pathway is stimulated. It serves as an excitatory postsynaptic potential which will lead to the activation of an action potential. E.g. Seratonin receptors. IPSP (inhibitory postsynaptic potential) is produced by the stimulation of an inhibitory pathway, causing the postsynaptic membrane to be hyperpolarized leading to the selective opening of chloride channels. The IPSP will cause suppression of further action potentials, e.g. GABA receptors.

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

Calcium plays a role when the glutamate or aspartate binds to the glutamate receptor, opening the Ca+ channels opening leading to an influx of Ca+ ions into the terminal of the nerve. Then the vesicles will cause depolarization on the synaptic membrane leading to the development of an EPSP which will cause the release of ligands (neurotransmitters) into the synaptic cleft. Therefore Calcium is necessary for the release of neurotransmitters.

IPSP