Question

1a. Explain the significance of glutamate in the brain and of NMDA receptors.

1b. Describe the mechanism of action of glycine and GABA as neurotransmitters, and discuss their significance.

1c. Explain how nitric acid is produced in the body, and describe its functions.

1d. Define spatial summation and temporal summation, and explain their functional importance.

1e. Explain how postsynaptic inhibition is produced and how IPSPs and EPSPs can interact.

1f. Describe the mechanism of presynaptic inhibition.produced.

Answer 1

1.a. Glutamate is a neurotransmitter used in the brain. It helps in transmission of excitatory impulses through binding to its receptors. It increases permeability of cell for sodium, potassium and calcium ions. It also inhibits adenylate cyclase by decreasing intracellular levels of cAMP.
NMDA are a type of voltage gated receptors present on the cell membrane of neurons that binds to glutamate. They increase calcium and sodium influx into the cell and potassium out of the cell. Thus resulting in transmission of excitatory impulses.
1b. GABA is a neurotransmitter of central nervous system. GABA helps in transmission of inhibitory impulses in the brain. It increases influx of chloride ions into the cell and potassium out of the cell which causes release of inhibitory synpases.
Glycine also acts as a neurotransmitter in the nervous system. It increases entry of chloride into the cells which causes generation of inhibitory impulses.
1.c. The nitric oxide is produced by many cells of the body including endothelial cells. These cells converts the amino acid L arginine into nitric oxide in the presence of nitric oxide synthase enzyme.
Nitric oxide diffuses from the vessel wall into the smooth muscle cells causing activation of guanylyl cyclase. Guanylyl cyclase causes conversion of GTP into cGMP which inhibits muscle contaction and thus relaxes the smooth muscles.
1.d. Spatial summation is the adding up of action potential from different presynaptic inputs which causes generation of an action potential. When action potential containing excitatory impulses is added up it results in excitation of cells whereas summation of inhibitory action potential results in inhibition of cellular activity.
Temporal summation is the summation of amplitude of presynaptic action potential with the postsynaptic action potential resulting in generation of large action potential.