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

• Voltage-gated ion channels
• Ligand-gated ion channels

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

Voltage-gated Respond to change in membrane potential Na+, k+, Ca2+ channels

Ligand-gated Respond to a neurotransmitter binding to a receptor on an ion channel Called ionotropic receptors

Compare ionotropic and metabotropic receptors.

Ionotropic receptors

• They respond to chemical NTs that bind to receptor subunits present in structure.
• Binding to this receptor causes direct opening of a channel
• Important for fast synaptic transmission, thus effects do not last long

Metabotropic receptors

• They are G-protein coupled receptors that acts when there is direct action of G-proteins on the ion channel or when there is G-protein-enzyme activation that leads to formation of second messengers.
• There are 7 transmembrane G-proteins
• When a neurotransmitter binds to the metabotropic receptor it does not lead to direct gating of a channel
• Effects of activation lasts longer.

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

Ionotropic

• GABA_A
• Nicotinic
• Glutamate

• NMDA
• Kainate
• AMPA

• 5-HT₃

Metabotropic

• Adrenergic

• α₁                                                                          (Phospholipase C)
• α₂                                             (Adenyl cyclase)
• ß₁₊₂                                                                     (Adenyl cyclase)

• Dopaminergic

• D₁                                                                         (Adenyl cyclase)
• D₂

• Serotonergic

• 5-HT₁ (A B C D)                      (adenyl cyclase)
• 5-HT₂                                                                (Phospholipase C)
• 5-HT_4-7

• Cholinergic

• Muscarine(M_2-4)                      (Adenyl cyclase)
• M₁₊₃₊₅                                                               (Phospholipase C)

• GABA_B
• EXCIT AA R

• MGluR1 (adenyl cyclase)       - mGluR8 (Phospholipase C)            

• BD
• H₁                                                                                   (Phospholipase C)

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

EPSP (Excitatory postsynaptic potential)

• Membrane potential is depolarized
• Produced by the opening of Na and Ca channels and the closing of some K channels
• When Nicotinic receptor is stimulated by Ach the membrane potential is depolarized, sodium channels open and excitatory postsynaptic potential originates.

IPSP (Inhibitory postsynaptic potential)

• Membrane potential is hyperpolarized
• Produced by the opening of Cl and K channels
• When GABA-A is stimulated the membrane-potential is hyperpolarized chloride channels open.

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

Calcium plays an important role in developing a synaptic potential, because the influx of calcium into the post-synaptic terminal triggers the release of NO from the vesicles for example so it can move back to the presynaptic membrane so the process can start again, thus it will exert an influence on the release of the neurotransmitter.