Question

1a. Explain how chemically regulated channels differ from voltage-regulated channels and the nature of excitatory and inhibitory postsynaptic potentials.

1b. Explain how ligand-gated channels are opened, using nicotinic ACh receptors as an example.

1c. Explain how ligand-gated channels operate, using muscarinic ACh receptors as an example.

1d. Describe where stimulatory and inhibitory effects of muscarinic ACh receptors occur and how these effects are produced.

1e. Compare the properties of EPSPs and action potentials, identify where in a neuron these are

Answer 1

1a)...

chemically regulated channels- they open and close in response to chemicals binding to them ... Like neurotransmitters such as AcetylCholine when released post synaptically bind to ACh receptor causing opening of sodium channels . Other eg are hormones etc..

Voltage regulated channels - open and close in repsonse to change in membrane potential as seen in neuronal membrane and neuromuscular junction...

excitatory postsynaptic potentials (EPSP) - the rapid influx of positively charged sodium ions to the interior neutralises part of negativity of RMP. For eg THe RMP increases in positive direction from -65 to -45mV . This positive increase is called EPSP because if this potential reises high enough in positive direction , it will elicit an action potential in post synaptic neuron thus exciting it . Eg this is done by neurotransmitter like serotonin, GABA etc...

inhibitory postsynaptic potentials (IPSP).- Opening potassium channels will allow positively charged potassium ions to move to the exterior and this will also make the interior membrane potential more negative than usual.. thus, both chloride influx and potassium efflux increase the degree of intracellular negativity which is called hyperpolarisation.. this inhibits the neuron because the membrane potential is even more negative than normal intracellular potential therefore, an increase negativity beyind the normal RMP levels is called IPSP... Eg inhibitory neurotransmitter like Glutamate and glycine facilitates IPSP...

1b). Nicotinic receptors enclose membrane channels and open when ACh binds to the receptor. This causes a depolarization called an excitatory postsynaptic potential (EPSP) ..

1c ). Dear student ligand gated channels are basically means as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as Na⁺, K⁺, Ca²⁺, and/or Cl⁻ to pass through the membrane... But muscarinic ACh receptors are metabotropic receptor that means they are G coupled receptor ... And whether it will create EPSP or IPSP depends on the type of G couoled recptor with which it is linked. So olease recheck the question

1d).

1e is already answered in above questions... Thank you..