M SLABBERT
Blog #1
24 Feb 2021, 14:09
- What type of ion channels are found on nerve cell membranes?
Voltage-gated ion channels
Ligand-gated ion channels
- Name 3 differences between voltage-gated and ligand-gated ion channels.
| Voltage-gated : | Ligand-gated : |
| Voltage channels respond to changes in membrane potential, which allows them to open and close. | Ligand ion channels open when a chemical ligand such as a neurotransmitter binds to the protein. |
| Voltage channels include potassium, calcium and sodium channels. | Ligand ion channels consists of ACh, glycine, GABA, nicotinic and AMPA receptors. |
|
Voltage channels specifically bind to a certain ion and they do not bind directly to neurotransmitters. |
Ligand ion channels are not specific for any ions and they bind directly to neurotransmitters |
- Compare ionotropic and metabotropic receptors.
Ionotropic :
- Directly bind to the receptor to open ion channels.
- Responsible for opening of ion channels.
- Activation lasts for milliseconds.
Metabotropic :
- Does not bind to receptor, but is involves the use of 7-transmembrane G-protein receptors, that releases secondary messengers to therefore open the ion channels.
- Responsible for metabolic changes.
- Activation lasts from seconds to minutes.
- Classify the CNS receptors into ionotropic and metabotropic and know the transduction mechanism of each receptor.
Ionotropic :
- GABAᴀ
- Nicotinic (Acetyl choline)
- EAA (Glutamate)
- Serotonin (5-HT3)
Metabotropic :
Has two transduction systems namely; the Adenyl cyclase system and the Phospholipase system.
Adenyl cyclase system :
- Beta (β1+2)
- Dopamine (D1+2)
- Alpha (α2)
- Serotonin (5-HT1A+B)
- Cholineergic Muscarine (M2)
Phospholipase system :
- Alpha (α1)
- Serotonin (5-HT2)
- Cholineergic Muscarine (M1)
- Histamine (H1)
- Explain the difference between an EPSP and an IPSP and give examples of each.
EPSP : Excitatory Post Synaptic Potential, is the change in membrane voltage of a postsynaptic cell following the influx of positively charged ions into a cell as a result of the activation of ligand-sensitive channels.
EPSP Example : Na+
IPSP : Inhibitory Post Synaptic Potential, is an electrical charge in the membrane of a postsynaptic neuron caused by the binding of an inhibitory neurotransmitter from a presynaptic cell to a postsynaptic receptor. It makes it more difficult for a postsynaptic neuron to generate an action potential.
IPSP example : Cl-
- What is the role of calcium in the development of a synaptic potential?
Calcium ions entering the cell through voltage gated ions causes and action potential which stimulates the axon terminal to release neurotransmitters, which then creates a synaptic potential. Therefore, calcium is important in the formation of neurotransmitters.