Jeff Kerr; Week 6 MED1011; Anatomy
Receptors are proteins capable of recognising a stimulus, can be on cell surface membrane or inside nucleus, when activated a biological response is formed. Signalling can be through secreted molecules or binding if signal is on the plasma membrane of a cell. Cell surface receptors cannot cross membrane so bind, intracellular receptors diffuse into the cell and bind to receptors in the cytoplasm or nucleus, can also be transported through by a carrier protein.
Theca cells have LH signals to produce androgens, granulosa respond ot FSH to convert androgens to estrogen. Sense of smell occurs via interaction with membrane receptors.
Hormones are transported through the blood. Endocrine secretion is from the pituitary gland. Hormones reach distant targets. Endocrine signals only act on recognised receptors on selected target cells. Insulin dimerises, phosphorylates response substrate inside the cell to allow glucose to enter the cell at target.
Autocrine targets the same cell, paracrine to adjacent cells. Can signal by diffusion. Columns of cartilage secrete factors acting over a distance, morphogen is often a growth factor to control cell development. A group of cells creates stronger autocrine signalling than does a single cell.
Neurotransmitters connect with synapses, electrical signal which converts to chemical which causes electrical stimulation. Specificity is due to direct contact between nerves and their targets. There can be synapses between nerves and muscles (NMJ).
Gap junctions allow cell to cell communication. They coordinate contraction and movements of heart and GIT. Cardiac muscle cells have intercalated discs and desomsomes in sections. Cells have electrical and metabolic coupling.