Zusammenfassung der Ressource
negative feedback and its
importance in biology
- control of blood glucose concentration
- pancreas detects blood glucose
concentration is too high
- 1. beta cells secrete insulin and
alpha cells stop secreting glucagon
- 2. insulin binds to
receptors on liver and
muscle cells
- 3. cells take up
more glucose,
glycogenesis is
activated, cells
respire more
glucose
- 4. less glucose in the
blood
- pancreas detects blood glucose
concentration is too low
- 4. cells release
glucose into
the blood
- 3. glycogenolysis is
activated,
gluconeogenesis is
activated, cells
respire less glucose
- 1. alpha cells secrete glucagon and beta cells stop secreting
insulin
- 2. glucagon binds to receptors on
liver cells
- control of blood water potential
- low water potential in the blood
- 1. the drop in water content
is detected by osmoreceptors
in the hypothalamus
- 2. the posterior pituitary gland
releases more ADH into the blood
- 3. the DCT and collecting duct then become
more permeable so more water is
reabsorbed into the blood by osmosis
- 4. a small amount of highly
concentrated urine is produced and less
water is lost
- high water potential in the
blood
- 1. the rise in water content
is detected by
osmoreceptors in the
hypothalamus
- 2. the posterior pituitary gland
releases less ADH into the blood
- 3. less ADH means that the DCT and collecting duct become less
permeable so less water is reabsorbed into the blood by osmosis
- 4. a large
amount of
dilute urine
is produced
and more
water is lost
- control of heart rate and blood
pressure
- high blood pressure, O2 and pH
levels and low CO2 levels
- 1. baroreceptors detect high blood
pressure and chemoreceptors
detect chemical change in the blood
- 2. impulses are sent to the
medulla which sends impulses
along parasympathetic
neurones which secrete
acetylcholine which binds to
receptors on the SAN
- 3. heart rate slows down and
decreases, reducing blood
pressure and returning O2, CO2
and pH levels back to normal
- negative
feedback
prevents
damage to
artery walls,
atheromas,
blood clots and
myocardial
infarctions
- low blood pressure, O2 and pH
levels and high CO2 levels
- 1. baroreceptors detect low
blood pressure and
chemoreceptors detect
chemical change in the blood
- 2. impulses are sent to the medulla which
sends impulses along sympathetic neurones
which secrete noradrenaline which binds to
receptors on the SAN
- 3. heart rate speeds up and increases, increasing blood
pressure and returning O2, CO2 and pH levels back to
normal
- negative feedback prevents damage to artery walls,
atheromas, blood clots and myocardial infarctions
- homeostasis
- the maintenance of a constant internal environment despite fluctuations
- receptors to
detect when
levels are not
at the normal
level
- the info is then
communicated via
the nervous or
hormonal system
- effectors then respond to counteract the
change to bring the level back to normal
- the mechanism that restores
the level to normal is negative
feedback
- this is vital for cells to function noramlly
and stop them being damaged