Homeostasis Flashcards
what is homeostasis
the maintenance of the internal environment within an optimum range
changes to the water potential of the blood and tissue fluids cause cells to
shrink and expands as a result of water leaving or entering by osmosis
what is negative feedback
a change is counteracted to return back to normal
what is positive feedback
change is amplified so level moves further away from normal
what happens to enzyme activity when temperature falls below optimum range
enzyme activity decreases and causes rate of important reactions to slow down
in terms of bonds and enzymes what happens when body temperature rises above optimum range
enzymes denature at higher temperature causes the hydrogen bonds that maintain enzyme structure to break this alters active site so the enzyme can no longer catalyse reactions
in terms of respiration what will happens if the blood glucose levels are too low
respiration will slow and the amount of ATP will fall
how does carbohydrates affect blood glucose level
causes an increase In blood glucose concentration
which organ maintains the blood glucose levels
pancreas
how does exercise cause a decrease in blood glucose concentration (glucose)
glucose is being used in respiration to power muscle contractions
what occurs if there is a fall in blood glucose concentration (5M)
stimulus is detected by receptors
alpha cells in pancreas will secrete glucagon
glucagon will cause liver cells to convert glycogen into glucose
which raises BGC which is circulated back to the pancreas reducing alpha cell stimulation therefore reducing glucose production
what occurs if there is a rise in blood glucose concentration
insulin will be produced from beta cells in pancreas
insulin increases uptake of glucose by cells and its conversion to glycogen and fat
the fall in BGC reduced insulin production
what is glycogenesis
when BGC too high
glucose —->glycogen
glycogenolysis
BGC too low
glycogen—->glucose
glyconeogenesis
BGC too low
glycerol+amino acid. —–> glucose
what hormone do beta cells secrete when there is high blood glucose concentration
insulin
where are the beta cells located
islet of langerhans
in terms of insulin, enzymes, muscle cells, respiration explain how insulin lowers blood glucose concentration
insulin binds to the receptors in the muscle cell
causes a change in the tertiary structure of the glucose allowing more glucose into cells by facilitated diffusion
activation of the enzymes that convert glucose to glycogen and fat
the rate uptake of glucose by muscle cells increase
rate of respiration in muscle cells increase
what is the importance of insulin (2M)
lowering BGC
maintaining an optimum blood water potential
what do alpha cells detect
fall in BGC
what do alpha cells secrete when detecting a fall in blood glucose concentration
hormone glucagon
does glucagon increase or decrease blood glucose concentration
increases BGC
if blood glucose concentration were not increased by glucagon how would this affect respiration
there would not be enough glucose available for respiration then there would be energy for survival
is adrenaline secreted at low or high blood glucose concentration
low BGC
where is adrenaline secreted
adrenal gland
how does adrenaline raise blood glucose concentration
by attaching to protein receptors on the cell-surface membrane of target cells
activating enzymes that causes the breakdown of glycogen to glucose in the liver
what is osmoregulation
control of water potential in the blood
what occurs if the blood water potential is too high(3M)
more water may be lost by excretion to return normal water potential levels
the blood reabsorbs less water from kidney
urine is more dilute water potential in blood decreases
what occurs if the blood WATER potential is too low
less water lost by excretion the blood reabsorbs more water from kidney
urine is more concentrated and water potential in blood increases
the first step of filtration of the blood to form urine takes place in the bowmans capsule this produces a
glomerular filtrate
blood flows into the glomerulus through which arteriole
afferent arteriole
is the afferent arteriole much wider or narrower than the efferent arteriole and how does this affect the blood pressure in capillaries
afferent arteriole is much wider
blood pressure in capillaries is very high
after the glomerular filtrate has been produced in the bowmans capsule which two substances are reabsorbed into the bloodstream and through which tube
glucose and water
through the PCT
does the loop of henle produce a low or high water potential
low water potenial
is the ascending limb impermeable or permeable to water
impermeable
is the descending limb impermeable or permeable to water
permeable
when Na ions are actively pumped out of the ascending limb where are they pumped into and how does this affect water potential
into the medulla
decreasing water potential
what is the effect of the descending and ascending limb in terms of concentration and water potential
creates a high solute concentration
low water potential in tissue fluid
what effect does a high solute concentration and water potential in tissue fluid have on collecting duct
water inside the collecting duct to diffuse into the surrounding tissue fluid by osmosis
water is then reabsorbed into the blood stream
what does ADH control
controls osmoregulation
how does ADH affect permeability on the distal convoluted tubule and collecting duct
influences permeability
controls how much water is reabsorbed from the kidney into the blood
when ADH bind….
vesicles containing aquaporins fuse with cells membrane
aquaporins are proteins channels for water
aquaporins increase permeability of the distal convoluted tube and collecting duct
more water is then reabsorbed into the blood by osmosis
how ultrafiltration occurs in a glomerulus
high blood/ hydrostatic pressure
water, glucose, ions, urea through small gaps/pores in capillary endothelium
and through capillary basement membrane
the thicker medulla will lead to a longer or shorter loop of henle
longer loop of henle
how ultrafiltration produces a glomerular filtrate
high blood pressure/ hydrostatic pressure
small molecules pass through basement membranes
proteins too large to go through so stay behind
presence of pores in the capillaries
some desert mammals have long loop of henle and secrete large amounts of ADH explain how these two features are adaptation to living in desert conditions
For loop of henle:
Sodium/chloride ions absorbed from filtrate in ascending limb
gradient established in medulla
For ADH:
act on collecting duct/ distal convoluted tubule
make cells more permeable
location of osmoreceptors in the body
hypothalamus
describe how the secretion of ADH affect urine produced in kidneys
membrane
aquaporins are proteins channels for water
aquaporins increase permeability of the distal convoluted tube and collecting duct
more water is then reabsorbed into the blood by osmosis
making the urine more concentrated and in smaller volume
explain the role of the loop of henle in the absorption of water from the filtrate
in the ascending limb sodium ion actively transported
ascending limb impermeable to water
in descending limb sodium ion diffuse in
descending limb permeable to water so water moves out
low water potential In the medulla
the longer the loop of henle the lower the water potential in the medulla
water leaves collecting duct by osmosis sown water potential gradient
role of ADH in the production of concentrated urine
when water potential of blood is too low
detected by receptors in the hypothalamus
pituitary secretes more ADH
ADH increases permeability
opens channels for water in the distal convoluted tubule
more water reabsorbed by osmosis down the water potential gradient
in a diabetic person lack on insulin will lead to reduced….
uptake of glucose by cells/liver/muscles
reduced conversion of glucose to glycogen
two substances that will be present in the glomerular filtrate
urea
amino acids
two ways in which the cells of the proximal convoluted tubule are adapted to reabsorption
microvilli provide large SA
carrier protein in membrane for active transport
channel protein for facilitated diffusion
many mitochondria for active transport
how urea is removed from the blood
high hydrostatic pressure causes ultrafiltration at bowman’s capsule through basement membrane enabled by small size urea molecules
how urea is concentrated in the filtrate
reabsorption of water by osmosis at proximal convoluted tubule
active transport if ions/ glucose creates gradient
where does ultrafiltration occur
bowman’s capsule
part of the brain which acts as the coordinator in the control of water
hypothalamus
