Homeostasis Flashcards
what is a hormone?
chemical substance produced in minute amounts by glands, carried by the blood, which alters the activity of one or more specific target organs and is broken down by the liver
what are endocrine glands?
produce hormones that secrete them directly to the bloodstream without ducts
(Islet of Langerhans)
what are exocrine glands?
produce secretions that is carried by a duct
(pancreatic duct)
what is the definition of homeostasis?
maintenance of a constant internal environment
what does homeostasis do?
ensure a stable internal environment with optimal conditions so cells can function efficiently
what is the receptor?
it detects the stimulus and relays information to the control center
what is the control center?
it controls information to the reference point and sends a signal to the effector
what is the effector?
carries out appropriate response to counteract the change
what hormones does the islet of Langerhans secrete?
- glucagon secreted from alpha cells to increase blood glucose concentration
- insulin secreted from beta cells to decrease blood glucose concentration
what happens when blood glucose levels rise higher than reference point?
- detected by islet of Langerhans
- secretion of insulin from beta cells
- insulin transported to liver and muscles by blood
- blood glucose returns to normal and detected by beta cells
- insulin secretion decreased
- insulin sent to and broken down by the liver
what does insulin do?
- increases permeability of cell membranes to glucose, increasing cells’ rate of uptake of glucose
- increases rate of cellular respiration; oxidation of glucose
- stimulates liver and muscle cells to convert glucose to glycogen
- decreased breakdown of glycogen to glucose
what happens when blood glucose levels drop lower than reference point?
- detected by islet of Langerhans
- secretion of glucagon from alpha cells
- glucagon transported to liver by blood
- blood glucose returns to normal and detected by alpha cells
- glucagon secretion decreased
- glucagon sent to and broken down by the liver
what does glucagon do?
- stimulates conversion of stored glycogen to glucose in liver
- conversion on non-carbohydrate sources to glucose
what is type 1 diabetes?
the body does not produce enough insulin
what is type 2 diabetes?
the body is not sensitive to insulin
what happens when bodily temperature is lower and higher than reference point?
- thermoreceptor detects
- information sent to the hypothalamus
- nerve impulses sent to relevant body parts
- temperature returns to reference point
- stimulus is removed
what are the effects of a higher than reference point body temperature?
- arterioles go through vasodilation while shunt vessels constrict for more blood to flow to the skin and lose heat
- sweat glands are more active to produce more sweat for more sweat evaporation and latent heat of vaporisation to be removed from the body
- metabolic rate is slowed down to produce less heat
what are the effects of a lower than reference point body temperature?
- arterioles go through vasoconstriction while shunt vessels dilate for less blood to flow to the skin and lose heat
- sweat glands are less active to produce less sweat for less sweat evaporation and latent heat of vaporisation to be removed from the body
- metabolic rate is increased to produce more heat
- shivering, contraction of muscles produce heat
what is the ADH?
anti-diuretic hormone that increases water reabsorption in kidney tubules
what happens when the water potential of blood plasma falls or rises higher than the reference point?
- osmoreceptors in hypothalamus detect change
- pituitary gland is stimulated
- ADH is released in larger/lesser amounts
- water potential returns to normal
- secretion of ADH returns to normal
how does ADH work?
- kidney tubules absorb more water
- less and more concentrated urine is produced
