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
properties of sweat glands
-coiled tube in the dermis and surrounded by blood capillaries
-sweat flows through sweat duct to sweat pore
-excretory organ that removes urea
-sweat regulates body temperature
properties of sensory receptors
-detect changes in environment and stimuli
-thermoreceptors found in epidermis and dermis
-touch receptors found just below dermis
-pressure receptors found deep in epidermis
properties of adipose tissue
-fat storage
-insulating layer that prevents heat loss
how does the body gain heat
-aerobic respiration
-eating, exercising
-shivering on a cold day
-sun’s radiation
-warm air on hot day
-heat distributed by blood to the whole body
-liver and muscle
how does the body lose heat
-radiation, convection from skin, shunt vessels that connects skin arterioles with venules, when constrict, more blood to skin capillaries, increase heat loss
-evaporation of sweat from skin surface
-exhalation of air
-through faeces and urine
definition of radiation
-loss of heat down a concentration gradient to the surrounding, refers to the transfer of heat through from a warm body to a cooler body through air
definition of convection
-movement of air in which warmer air is replaced by colder air due to difference in density, speed up heat loss by evaporation and radiation
definition of evaporation and conduction
-transfer of heat from hot solid to cooler solid when they come into contact
-involves change of state from liquid to gas, evaporation of sweat removes latent heat and is accomplished by cooling
how does body regulate increase in temperature
-blood and skin temperature rises
-temperature receptors detect change and send nerve impulses to brain
-hypothalamus stimulated and sends nerve impulses to relevant body parts
-skin arterioles dilate, more blood flow to skin capillaries, shunt vessel constrict, greater heat loss
-sweat glands more active, sweat production increases, more latent heat loss as sweat evaporates, hair erector muscles in skin relaxes
increase in heat loss, decrease in heat production, decreased metabolic rate reduces heat production, BT returns to normal
how does body regulate decrease in temperature
-blood and skin temperature falls
-temperature receptors detect changes and sends nerve impulses to brain
-hypothalamus stimulated and send nerve impulses to relevant body parts, … vice versa
-hair erector muscle contracts, hair follicle stand up, layer of air is trapped, since air is a good insulator of heat, helps reduce heat loss to environment
what is shivering
-reflex that occurs when skeletal muscle contracts in small movements to generate heat by expending energy
