SCSA Human Biology Science as a Human Endeavour

It is secreted from the anterior lobe. Communication between the hypothalamus and the anterior pituitary occurs through chemicals through the infundibulum. The hypothalamus stimulates the anterior pituitary to release hormones via releasing factors. The hormones are released into a capillary network and transported through veins. The hypothalamus also produces inhibiting factors to inhibit the activity of the pituitary.

The hormone dissolves in water, not fats, so it cannot pass through the cell membrane. Instead, the hormone molecule attaches to a receptor molecule found on the surface of the target cell, and the receptor molecule must match the shape of the signalling molecule.

The binding of the hormone to the receptor triggers a response inside the cell. This secondary messenger activates enzymes inside the cytoplasm, which adjust the chemical activity of the cell, causing the speed of reactions to either increase or decrease.

The gene for hGH is located on a human chromosome and is treated with a restriction enzyme, which cuts DNA at specific sites. A plasmid is cut with the same restriction enzyme, and the gene is inserted into the plasmid using ligase. The plasmid acts as a vector and produces a transgenic organism. The recombinant plasmid enters into a host bacterial cell, which clones. The bacteria express the gene to synthesize the human protein, which produces large-scale amounts of hGH.

They attach to receptor proteins in the membrane of the target cell, forming a hormone-receptor complex. This activates a secondary messenger inside the cytoplasm or cell, activating particular enzymes, and having a short-lived response.

Low blood glucose levels are detected by chemoreceptors, and the alpha cells are stimulated. Glucagon is secreted, stimulating glycogenolysis, which is the breakdown of glycogen to glucose, and gluconeogenesis, which is the production of glucose from amino acids and fats. Both of these processes primarily occur in the liver. It also stimulates lipolysis, the breakdown of fats, which occurs in most body cells or adipose tissue.

The adrenal medulla secretes adrenaline/noradrenaline, and the adrenal cortex secretes cortisol. This further enhances the rate of glucose production, increasing blood glucose by gluconeogenesis/glycogenolysis.

Type 1 diabetes is the inability to produce insulin. The drug works to enhance insulin activity, so if there is no insulin being produced, the drug will have no effect.

Hypothyroidism is a disorder where low levels of thyroxine lead to a decrease in metabolic rate. This causes symptoms such as decreased heart rate and decreased blood pressure. Treatments include increasing iodine in the diet, taking synthetic hormone tablets, or surgery.

Conversely, hyperthyroidism is a disorder where high levels of thyroxine lead to overstimulation of body cells. This causes symptoms such as increased heart rate and high blood pressure. Treatments include taking drugs to block the thyroid's use of iodine, surgery to remove all or part of the gland, or radioactive iodine.

Glucose is removed from blood to provide energy for liver functioning.

Glucose also converted to glycogen by the process of glycogenesis controlled by insulin, and glycogen is stored in the liver.

When blood sugar levels fall glycogen is converted back to glucose by the process of glycogenolysis, which is controlled by glucagon