Question

Describe in detail chemical synapses, transmitter-gate (ligand-gated) channels and GPCRs. Diagrams and pictures can be included but also text descriptions.

Answer 1

Chemical Synapse: These specialized junctions which help the cells of the nervous system to send signal to another cells of the nervous system and to non-neural cells such as muscles or glands. A chemical synapse between a motor neuron and a muscle cell is known as neuromuscular junction. These synapses allow the neurons of the central nervous system to form interconnected neural circuits. They are thus crucial to the biological computations that underlie perception and thought. They also provide the means through which the nervous system connects to and controls the other systems of the body.

Transmitter-gate (ligand-gated): Ligand-gated ion channels are membrane proteins which are fundamental signaling molecules in neurons. These molecules are located the plasmalemma and on the intracellular organelles. These are gated by both intracellular and extracellular ligands. A central, water-filled pore opens and conducts ions at very high rates of up to 10⁷ ions per second. When the channel closes or when it enters a non-conducting (desensitized) state, channel activity is terminated.

G Protein Coupled Receptor (GPCRs): GPCR constitute a large protein family of receptors that detect molecules outside the cell and activate internal signal transduction pathways and, ultimately, cellular responses. Coupling with G proteins, they are called seven-transmembrane receptors because they pass through the cell membrane seven times. These are the largest family and most diverse group of membrane receptors in eukaryotes. GPCRs are distributed in intracellular compounds including the endoplasmic reticulum, Golgi apparatus, nuclear membrane and even inside the nucleus itself in addition to cell surface.