homeostasis and hormonal control Flashcards
purpose of homeostasis?
maintain a constant internal environment so an organism is independent of changes in the external
environment
negative feedback process?
1) normal that must be maintained
2) stimulus
3) receptor
4) corrective mechanism
5) effector
6) feedback (to receptors that condition has been restored back to normal, corrective mechanism decrease)
regulating blood water potential
1) stimulus: water potential increase/ decrease above/ below normal
2) receptor: hypothalamus in brain detects stimulus
3) corrective mechanism: pituitary gland secretes less/ more ADH, cells in walls of collecting ducts become less/more permeable to water, less/more water reabsorbed by kidney tubules back into bloodstream
4) effector: more/less water excreted, urine produced less/more diluted, water potential increase/ decrease back to normal. Feedback sent to hypothalamus and ADH production increases/ decreases
conc of blood glucose above normal?
1) stimulus: blood glucose conc increases above normal
2) receptor: islets of langerhans stimulated
3) corrective mechanism: islets of langerhans secrete more insulin which is transported by blood to liver and muscles. Permeability of cell surface membrane to glucose increases, causing increased glucose uptake by cells. Insulin stimulates liver and muscles cells to convert excess glucose to glycogen for storage in liver and muscles, increasing the oxidation of glucose during tissue respiration
4) effects: conc of blood glucose decreases back to normal, feedback sent to pancreas and insulin production falls.
conc of blood glucose below normal?
1) stimulus: blood glucose conc decreases below normal
2) receptor: islets of langerhans stimulated
3) corrective mechanism: islets of langerhans secrete more glucagon which is transported by blood to liver and muscles. Glucagon stimulates liver and muscle cells to convert stored glycogen into glucose and fats and amino acids to glucose that is released by the liver into the blood
4) effects: conc of blood glucose increases back to normal, feedback sent to pancreas and glucagon production decreases.
what are hormones?
chemical substances produced in minute quantities by an endocrine gland, transported in the bloodstream to target organ(s) where it exerts its effect(s)
(endocrine glands are ductless, eg pancreas and pituitary gland)
effects of insulin?
1) islets of langerhans increase secretion of insulin when blood glucose conc is high
2) insulin increases utilisation of glucose by body cells
3) insuline decreases blood glucose conc by increasing rate of glucose uptake by cells, making cell membranes more permeable to glucose, stimulating the liver and muscles cells to convert excess glucose into glycogen for storage in liver and muscles, also increases the oxidation of glucose during tissue respiration
effects of glucagon?
1) islets of langerhans increase secretion of glucagon when blood glucose is low
2) glucagon increases blood glucose conc by stimulating liver and muscles to convert stored glycogen to glucose and converting fats and amino acids to glucose
what is diabetes mellitus?
blood glucose conc cannot be regulated
what causes diabetes mellitus?
resistance to insulin or insufficient production of insulin
risk factors for diabetes mellitus
obesity, sedentary lifestyle, family history
ways to reduce risks of diabetes mellitus
1)maintain healthy body weight
2)engage in more physical activities that enable excess glucose to be used up. Glucose provides energy for muscular contractions and make the liver and muscles cells more sensitive to insulin
treatment for diabetes mellitus?
1) type one: insulin injections
2) type two: oral medication, changes to diet or lifestyle
function of blood vessels?
1) constriction and dilation of muscles at the arteriole help regulate body temperature
2) shunt vessels connect skin arterioles with skin venules. When shunt vessels constrict, skin arterioles dilate (vice versa)
process of blood vessels maintaining body temperature?
1) vasodilation: when arterioles dilate, shunt vessels constrict, more blood flows to blood capillaries at skin surface. More heat lost from skin by CCR
2) vasoconstriction: when arterioles constrict, shunt vessels dilate, less blood flows from blood capillaries at skin surface. Less heat lost from skin by CCR
how to sweat glands help maintain constant body temperature?
secretes sweat which flows through sweat duct and sweat pore to skin surface. When water in sweat evaporates from body surface, latent heat of vaporisation is lost from the body, removing heat from the body
what happens on a hot day?
1) stimulus: blood and skin temperature increase above normal
2) receptor: thermoreceptors in skin send information about temperature changes in external environment to the brain. Thermoreceptors in hypothalamus detects changes in temperature of blood flowing through the brain
3) corrective mechanism: arterioles in skin dilate, shun vessels constrict. more blood flows to capillaries in skin. Sweat glands become more active and production of sweat increased. Rate of metabolic activities decrease.
4) effector: more heat loss at skin surface by CCR, more latent heat of vaporisation lost as water in sweat evaporates and reduced heat production leading to less heat released in body from metabolic activities
what happens on a cold day?
1) stimulus: blood and skin temperature decrease below normal
2) receptor: thermoreceptors in skin send information about temperature changes in external environment to the brain. Thermoreceptors in hypothalamus detects changes in temperature of blood flowing through the brain
3) corrective mechanism: arterioles in skin constrict, shun vessels dilate, less blood flows to capillaries in skin. Sweat glands become
less active, production of sweat decreases. Rate of metabolic activities increase. Shivering (spasmodic contraction of muscles occur when above reactions are jot enough to prevent drop in temperature). Hair erector muscles contract, layer of air trapped on skin
4) effect: less heat lost at skin surface and body. less latent heat of vaporisation lost due to evaporation of sweat. More heat released into body
