Describe the two control mechanisms which enable the body to maintain optimum health?

Answer 1

Homeostasis is brought about by negative feedback control. When a change from the norm/set point is detected a counteractive set of measures occur to return the body's internal environment to the set point;

eg.1. Osmoregulation . The norm/ set point is the normal blood water level.

If the blood water level increases eg after drinking, this is detected by osmoreceptors in the hypothalamus. The hypothalamus responds by sending impulses to the pituitary gland to reduce Antidiuretic hormone (ADH) release. Reduced levels of ADH cause the kidney tubules to reabsorb less water leading to excretion of large volumes of dilute urine and returning the blood water levels to the set point.

If the blood water level decreases eg after exercise or eating salty foods, this is detected by osmoreceptors in the hypothalamus. The hypothalamus responds by sending impulses to the pituitary gland to increase ADH release. Increased levels of ADH cause the kidney tubules to reabsorb more water leading to excretion of small volumes of concentrated urine and returning the blood water levels to the set point.

eg 2. Blood glucose level. Receptors in the pancreas detect a rise / fall in glucose level in the bloodstream.

If blood glucose is too low eg after exercise or a prolonged fast, the pancreas releases the hormone glucose which promotes the conversion of glycogen in the liver to glucose to raise the blood glucose level to the set point.

If blood glucose level is too high eg after a meal, the pancreas releases a different hormone, insulin, to promote the conversion of excess glucose to glycogen to be stored in the liver. this has the effect of lowering blood glucose level to the set point.

Answer 2

These are the negative control mechanism and the positive control mechanism that are part of keeping the body's homeostasis (overall balance).

Negative control mechanisms are those that decrease or stop a certain function (as in the reduction of urine production during dehydration). These keep the balance in our everyday functions.

Positive control mechanisms work in reverse - that is, they speed up or increase a certain function. These are used in rare occurrences as in childbirth, where certain hormones are released to induce birth contractions.

Answer 3

Endocrine and Nervous systems

Answer 4

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