homeostasis Flashcards
definition of homeostasis
-maintenance of a relatively constant internal environment within a narrow range in an organism even when the external environment change significantly
definition of negative feedback
-a form of regulation in which accumulation of an end product slows down the process
-a primary mechanism of homeostasis, whereby a change in variable triggers a response that counteracts the initial change
what happens when blood glucose concentration rises
-Islets of Langerhans in pancreas is stimulated
-IoL secretes more insulin that is transported to liver and muscles via blood
-permeability of cells surface membrane to glucose increase
-liver and muscles convert excess -glucose into glycogen that is stored in the liver and muscles
-blood glucose concentration decrease and insulin production falls
-BGC returns to normal
what happens when blood glucose concentration falls
-Islets of Langerhans in pancreas stimulated
-IoL secrete more glucagon that is transported to liver and muscle via blood
-glucagon stimulates the conversion of stored glycogen back into glucose, and glucose enters the bloodstream from the liver
-BGC rises and glucagon production decrease
-BGC returns to normal
what happens when blood water potential falls
-osmoreceptors in hypothalamus is stimulated
-posterior pituitary gland secretes more anti-diuretic hormone that increases the permeability of collecting duct to water
-more water reabsorbed by kidney tubules
-less water excreted, urine is more concentrated, less urine produced
-BWP rises, BWP returns to normal
what happens when blood water potential rises
-osmoreceptors in hypothalamus stimulated
-posterior pituitary secretes less ADH
-less water reabsorbed by kidney tubules
-more water excreted, urine is less concentrated, more urine produced
-BWP falls, BWP returns to normal
movement of ions and water in marine and freshwater fish
Freshwater
-water through diffusion in skin and gills, out through urine
-ions through active uptake, out through diffusion in skin and gills and urine
Marine
-water through mouth, out through diffusion in skin and gills, and urine
-ions in through diffusion in skin and gills, out through active secretion and urine
how does marine vertebrates overcome losing water through skin and gills
-little urine production
-drink large amount of water
-active transport at gills to remove excess salt
how does freshwater organism overcome taking too much water and losing salt
-lots of dilute urine
-active transport at gills to take in salt
properties of outer cornified layer
-layer of dead, dry and flat cells
-cells continually rubbed off and replaced by new cells
-keratin proteins
-water resistant to prevent entryt of microrganisms, uncontrolled water loss by evaporation, protective layer to prevent mechanical injury
why is outer cornified layer water resistant
-prevents uncontrolled loss of water by evaporation and entry of microorganism into body
-protective layer, prevent mechanical injury
properties of granular layer
-living cells
-cells move up from malpighian layer
-becomes dry and dead to form cornified layer
properties of malpighian layer
-contains pigment for skin colour
-protect skin from harmful ultra violet rays from the skin
-continual cell division to form upper cell layers
propose of arteriole dilation and constriction
-dilation allows more blood flow to capillaries in skin, skin turns red while blushing
-constriction reduces blood flow to capillaries in skin, skin turns pale
hair papilla, hair follicle, hair erector muscles
-a mass of tissue containing blood capillaries and nerves, epidermal cells constantly divide, die and harden to form hair
-hollow tube through epidermis and dermis
-attached to hair follicle that contracts to make hair stand, skin around the hair raises to form goose bumps and pimples
