FKLG312 SU 1.1

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

Voltage-gated channels (examples include Na⁺, K⁺ and Ca²⁺ channels)

Ligand gated channels (has ionotropic and metabotropic receptors) Ligands = neurotransmitters.

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

Voltage gated	Ligand gated
Usually has an all or nothing action potential, is specific to certain ion, until it is depleted. (Changes in membrane potential of the cell)	Binding of ligands or neurotransmitters to ion channel
Transmits signal from cell to nerve terminals.	Consists out of ionotropic and metabotropic receptors and transmembrane G-protein coupled receptors.
Ion specific	Not ion specific

3. Compare ionotropic and metabotropic receptors.

Ionotropic R’s	Metabotropic R’s
Responsible for opening of ion channels	Responsible for metabolic changes
Only four different receptors are ionotropic	All the other receptors found in the body are metabotropic.
No second messengers formed.	Binding of neurotransmitters to these receptors may lead to the formation of second messengers.
An ESPS or ISPS will be the result of the binding to Ionotropic R’s	Due to the second messengers, there are to transduction systems (Adenylyl cyclase and Phospholipase C system) that can be followed to activate various enzymes.

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

Ionotropic R’s	Metabotropic R’s
GABAA	Adrenergic (α and β)
Nicotinic	Dopaminergic
EAA – such as NMDA, AMPA, Kainate	EAA – mGluR1- mGluR8
5-HT3	GABAB
BD	Serotonergic
	Muscarine (M1-3)

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

- An electrical charge (hyperpolarisation) in the membrane of a postsynaptic neuron caused by the binding of an inhibitory neurotransmitter from a presynaptic cell to a postsynaptic receptor; makes it more difficult for a postsynaptic neuron to generate an action potential.

- An electrical (depolarisation) in the membrane of a postsynaptic neuron caused by the binding of an excitatory neurotransmitter from a presynaptic cell to a postsynaptic receptor; makes it more likely for a postsynaptic neuron to generate an action potential.

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

An action potential reaches the axon terminal and depolarization takes place on the membrane, this will lead to the opening of the voltage-gated Ca²⁺ channel, leading to an influx of Ca²⁺ ions. Due to these extra ions the synaptic vesicles releases neurotransmitters. These neurotransmitters will bind to specific receptors.