b11&12 Flashcards
how is body temperature managed?
controlled by the thermoregulatory centre in the brain.
the skin contains receptors sensitive to the temperature of the blood and sends nervous impulses to the thermoregulatory center
what happens at high body temp?
vasodilation - blood vessels dilate and sweat is produced from sweat glands. both these mechanisms cause a transfer of energy from the skin to environment.
what happens at low body temp?
vasoconstriction - blood vessels constrict and blood flows further away from surface of skin, the sweating stops and the skeletal muscles contract to shiver.
what is the endocrine system?
it is composed of glands which secrete chemicals called hormones directly into the bloodstream which carries the hormone to a target organ where it produces an effect
how is the endocrine system different to the nervous system?
the effects are slower but they act for longer
what is the pituitary gland?
it is in the brain and is the master gland. it secretes many hormones in response to body conditions.
what happens when blood glucose concentration is too high?
the pancreas produces hormone insuline which causes glucose to move from the blood into the cells. in the liver and muscle cells, excess glucose is converted to glycogen for storage.
what happens when blood glucose concentration is too low?
the pancreas produces the hormone glucagon which causes glycogen to be converted into glucose and released into the blood.
cause effect and treatment of type one diabeties
when the pancreas fails to produce sufficient insulin. It is characterised by uncontrolled high blood glucose
levels and is normally treated with insulin injections.
cause effect and treatment of type 2 diabeties
when the body cells no longer respond to insulin produced by the pancreas. a carbohydrate controlled diet and an exercise regime are common treatments. obesity is a risk factor for Type 2 diabetes.
how is water normally lost from the body?
water leaves the body via the lungs during exhalation. water, ions and urea are lost from the skin in sweat
what happens to excess water?
it is removed via the kidney in the urine. if body cells lose or gain too much water by osmosis, they do not function efficiently.
how does the kidney remove ammonia and produce urine?
when the blood enters the kidneys, it is filtered by the nephrons. the nephrons filter all small substances like glucose, water, some ions and ammonia. then, as glucose, some ions and water is needed by the body, it is selectivley reabsorbed back into the blood - all the glucose, but only some water is reabsorbed. no ammonia is absorbed because it is toxic and needs to be removed.
this is then passed through the nephrons into the bladder and released as urine.
what does ADH do?
ADH is a hormone produced by the pituitary gland that helps control the water levels in the body.
- it acts on the kidney tubules.
- when the blood is too concentrated, and there is not enough water, ADH is stimulated
- so that the kidney tubules are more permeable meaning more water is reabsorbed back into the blood.
- this is controlled by negative feedback.
how does dialysis work?
- it acts as an artificial kidney to remove most of the urea and maintain the water and salt balance of the blood.
- unfiltered blood is taken from an artery in the arm, pumped into the dialysis machine and then returned to a vein in the arm.
- inside the machine, the blood and dialysis fluid is seperated by a partially permeable membrane.
- the blood flows in the opposite direction to dialysis fluid allowing exchange to occur where a concentration gradient exists.
what does a dialysis fluid contain?
the fluid contains glucose concentration similar to blood. salt concentration similar to blood and no urea so that the urea in the blood can diffuse out.
