chapter 12 homeostasis

Question 1

what is homeostasis

Answer 1

homeostasis is the maintenance of a constant internal environment = allows organisms to be independent from changes in the external environment (where the organism lives)
Always brought about by internal changes - even if external changes occur but internal conditions remain the same, homeostatic mechanisms will not occur

Question 2

what happens when we eat too much

Answer 2

BGC is above normal level
Islets of Langerhans in the pancreas serve as both the receptor and control centre which detects and responds to the increase in blood glucose concentration
The Islets of Langerhans secrete insulin into the bloodstream, which is transported to the liver and muscles;
Insulin increases the permeability of cell surface membrane of liver and muscle cells to glucose= increases the rate of glucose absorption + stimulates liver and muscles to convert excess glucose into glycogen = glycogen is stored in muscles/liver
Blood glucose concentration is decreased back to normal
Negative feedback to Islets of Langerhans to reduce insulin secretion;

Question 3

what happens when we are fasting

Answer 3

BGC is below normal level
Islets of Langerhans in the pancreas serve as both the receptor and control centre = detects and responds to the decrease in blood glucose concentration
The Islets of Langerhans secrete glucagon into the bloodstream, which is transported to the liver and muscles;
Glucagon stimulates conversion of stored glycogen in liver and muscles into glucose= glucose enters bloodstream = BGC increases
Blood glucose concentration is increased back to normal,
Negative feedback to Islets of Langerhans to reduce glucagon secretion;

Question 4

what happens when we drink too much water

Answer 4

when BWP is above normal,
Hypothalamus detects the increase in blood water potential;
Pituiary gland responds to the signal from the hypothalamus
PG releases less anti-diuretic hormone (ADH) into the bloodstream, which is transported to the kidneys;
Less ADH decreases the permeability of the cells in the wall of the collecting ducts to water = less water to be reabsorbed into the bloodstream
Blood water potential is decreased back to normal
Negative feedback to hypothalamus to increase ADH secretion to normal levels
More water is excreted = more urine produced = more diluted urine

Question 5

what happens when we are dehydated

Answer 5

BWP is below normal,
Hypothalamus detects the decrease in blood water potential;
Pituiary gland responds to the signal from the hypothalamus
PG releases more anti-diuretic hormone (ADH) into the bloodstream, which is transported to the kidneys;
More ADH increases the permeability of the cells in the wall of the collecting ducts to water = more water to be reabsorbed into the bloodstream
Blood water potential is increased back to normal
Negative feedback to hypothalamus to decrease ADH secretion to normal levels
Less water is excreted = less urine produced = more concentrated urine

Question 6

what happens when we are cold

Answer 6

thermoreceptor detects the decrease in body temperature below normal level
hypothalamus in the brain sends nerve impulses to relevant body parts
Arterioles in the skin constrict, shunt vessels dilate = less blood flows to blood capillaries in the skin = decrease heat loss through RCC
Sweat glands become less active = less sweat produced = less water evaporated from sweat = decrease latent heat loss;
Metabolic rate increases = increase heat released within the body
(when main CMs are not enough to bring up body temp) Shivering which is a reflex spasmodic contraction of skeletal muscles occurs = increases amount of heat released
Body temperature is increased back to normal
Providing negative feedback to various body parts which stop the corrective mechanisms

Question 7

what happens when we are too warm

Answer 7

temperature receptors detects the increase in body temperature;
hypothalamus in the brain sends nerve impulses to relevant body parts;
Arterioles in the skin dilate, shunt vessels constrict = more blood flows to blood capillaries in the skin = increase heat loss through RCC
Sweat glands become more active = more sweat produced = more water evaporated from sweat = increase latent heat of vaporisation lost
Metabolic rate decreases to decrease heat released in body
Body temperature is decreased back to normal
Providing negative feedback to various body parts which stop the corrective mechanisms;