1. Types of ion channels in the nerve cell membranes?

Ligand-gated and Voltage-gated ion channels

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

• Voltage-gated ion channels open due to voltage difference across the membrane. Ligand- gated channels open due to neurotransmitter/ligand binding.
• Voltage-gated channels are ion specific and do not directly bind to neurotransmitters. Ligand-gated channels bind to neurotransmitters and are non-specific.
• Voltage-gated ion channels that allow for the movement of sodium, potassium, and calcium. Ligand-gated ion channels respond to gamma aminobutyric acid (GABA), acetylcholine, glutamate and serotonin.

3. Compare ionotropic and metabotropic receptors.

• Ionotropic receptors are responsible for opening ion channels. Metabotropic receptors are responsible for metabolic changes.
• Ionotropic receptors transduction signal is a brief action. Metabotropic receptors transduction signal lasts for seconds to minutes.
• Ionotropic receptors have no secondary-messengers. Metabotropic receptors have secondary-messengers.
• Ionotropic receptor channels are weakly sensitive to any membrane potential. Metabotropic are sensitive to the activation of indirect voltage-gated ion channel regulation.
• Ionotropic receptors have multiple subunits per receptor. Metabotropic receptors have seven transmembrane G protein-coupled receptors.
• Ionotropic receptors directly open channels due to neurotransmitter/ligand receptor binding. Metabotropic receptors do not directly open channels by binding. A second-messenger has to mediate intracellular signalling cascades.

4. Classify CNS receptors.

5. Difference between EPSP and IPSP and an example of each.

EPSP (Excitatory Postsynaptic Potential) the activation of an additional AP (action potential) due to depolarization. An example would be when acetylcholine binds to a nicotinic receptor. Sodium channels open up which results in depolarization.

IPSP (Inhibitory Postsynaptic Potential) is the suppression of an additional AP (action potential) due to hyperpolarization. An example would be when gamma-butyric amino acid binds to a GABA receptor. Chloride channels open up which results in hyperpolarization.

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

Depolarization is caused when an AP (action potential) reaches the axon terminal of a presynaptic neuron. Voltage-gated calcium channels allows for an influx of calcium into the presynaptic membrane. A fusion is caused between the synaptic vesicles and the presynaptic membrane. Synaptic vesicles release neurotransmitters into the synaptic cleft. Neurotransmitters diffuse across the synaptic cleft to bind to the receptors on the postsynaptic membrane in order to elicit an effect. Calcium is essential for the release of neurotransmitters, which then elicits an effect.