Homeostasis (Topic 6C) Flashcards
what effect does increasing the tempertaure have on metabolic reactions?
when temperature increases rate of metabolic reaction increases
why does increasing the tempertaure increase rate of metabolic reaction?
more heat means more kinetic energy so molecules move faster and are more likely to collide with enzymes active sites which means each collision is more likely to result in a reaction
why does the reaction stop if tempertaure gets too high?
the enzyme is denatured
if pH is too high or low enzymes become…
denatured
pH =
-log10 [H+]
if blood glucose concentration is too high the water potential of blood is…
reduced to a point where water molecules move out the cell via osmosis
if blood glucose concentration is too low…
cellsare unable to carry out normal acitivities
define negative feedback
the mechanism that restores the level to normal in the body
what are the steps in the negative feedback loop?
- normal level
- level changes above normal
- receptors detect change
- communication via nervous system or hormonal system
- effectors respond
- level brought back to normal
define positive feedback
the mechanism that amplifies change away from the normal level
what are the steps of the positive feedback mechanism?
- normal level
- normal level changes
- receptors detect change
- communication via nervous or hormonal system
- effectors respons
- level brought back to normal
blood glucose is monitored by cells in the…..
pancreas
the 2 horomes involved in contolling blood glucose concentration are…
insulin
glucagon
insulin and glucagon are screted by…
the islets of langerhans
the islets of langerhans contain __ cells and __ cells
alpha
beta
which hormone do alpha cells secrete?
glucagon
which hormone do beta cells secrete?
insulin
when blood glucose is too high which hormone is released?
insulin
insulin activates…
glycogenesis
glycogenesis is…
the conversion of glucose to glycogen that’s activated by insulin
when blood glucose concentration is too low which hormone is released?
glucagon
glucagon activates….
glucogenesis
glycogenolysis
gluconeogenesis is….
the conversion of glycerol to glucose
glucogenolysis is….
the conversion of glycogen to glucose
when the blood glucose concentration gets too high what happens?
- normal blood glucose concentartion
- rise in blood glucose concentration
- pancreas detects change
- pancreas secretes insulin & glucgaon secretion stops
- liver and muscle cells respond
how do the liver and muscle cells respond when insulin is secreted?
- cells take up more glucose
- glycogenesis is activated
- cells respire more glucose
when the blood glucose concentration gets too low what happens?
- normal blood glucose concentration
- fall in blood glucose concentration
- pancreas detects change
- pancreas secretes glucagon & stops insulin secretion
- liver cells respond
how do liver cells respond when glucagon is secreted?
- glucogenesis is activated
- gluconeognesis is avtivated
- cells respire less glucose
glucose transporters are _____ proteins
channel
glucose transporters allow glucose to be transported across….
cell membranes
where is adrenaline secreted from?
adrenal glands
when is adrenaline secreted?
when there’s a low concentration of glucose, when you’re stressed or during exercise
when adrenaline binds to receptors in the cell membrane of liver cells what happens?
it activates glycogenolysis
it inhibits glycogenesis
activates glucose secretion
inhibits insulin secretion
step 1 of second messenger model
hormone is secreted and acts as a first messenger
step 2 of second messenger model
hormone binds to receptor on surface membrane of target cells
step 3 of second messenger model
hormone- receptor complex activates enzyme inside of cells
step 4 of second messenger model
activated enzyme produces large amounts of cyclic AMP the second messenger
step 5 of the second messenger model
the second messenger (cAMP) actiavtes enzymes such as those involved by glycogenolysis `
step 6 of the second messenger model
many molecules of glycogen are hydrolysed releasing glucose molecules
the two types of diabetes are:
type 1 diabetes
type 2 diabetes
what is type 1 diabetes?
an autoimmune condition where the B cells are attacked and they can’t produce insulin
what is hyperglycaemia?
insulin not produced by beta cells
what causes hyperglycaemia?
insulin not produced by beta cells
type 1 diabetes
why is there some glucose found in the urine of people with type 1 diabetes?
the kidneys can’t absorb all the excess glucose in the blood
how is type 1 diabetes treated?
insulin injections
eating regular meals
avoiding too much simple carbohydrates
why should simple carbohydrates be avoided for diabetics?
simple carbohydrates are more easily broken down
the blood glucose concentration increases rapidly
causes hyperglyceamia
what do scientists think is causing type 1 diabetes?
genetics
virus
what is type 2 diabetes?
B cells do not produce enough insulin
body cells don’t respond to insulin as receptors don’t function properly
body cells don’t take up enough glucose
what are the 5 risk factors of type 2 diabetes?
family history
lack of exercise
age
poor diet
obesity
when is type 2 diabetes usually aquired?
later in life
when is type 1 diabetes usaully aquired?
earlier in life
how can type 2 diabetes be treated?
healthy, balanced life
regular exercise
losing weight
if a healthy lifestyle does not treat type 2 diabetes, what treatment is used?
glucose lowering drugs
insulin injections
how does blood enter the kidney?
through the renal arterty
what is the function of the kidney?
filter out urea/excess ions from the blood
osmoregulation is….
the regulation of water potential in the blood
ultrafitration is….
the filtering of substances out of the blood
selective reabsorption is….
the reabsorption of useful substances and the right volume of water into the blood
a nephron is…
long tubules with bundles of capillaries where the blood is filtered
what happens during ultrafiltartion?
4 steps
- Blood enters from the renal artery into smaller arterioles
- The afferent arteriole takes blood to the glomerulus
- High pressure forces out liquid and small molecules into the Bowman’s capsule
- The efferent arteriole transports the blood away which now contains only large proteins/blood cells
why is there a high pressure in the glomerulus?
The efferent arteriole is smaller in diameter than the afferent arteriole
what is the glomerular filtrate?
the substances from the blood that enter the Bowerman’s capsule
which substances are not filtered out of the blood any why?
blood cells
proteins
too large to pass through
what happens during reabsorption in the proximal convultued tubule?
- Glucose and solutes are reabsorbed into the blood by active transport
- Water moves into the blood by osmosis down the water potential gradient
How are the cells in the proximal convoluted tubule adapted for reabsorption?
Microvilli provide large surface area
What are the two parts of the loop of Henle?
Descending limb
Ascending limb
Explain how the loop of Henle works
- At the top of the ascending limb, Na+ ions are actively transported into the medulla
- The water potential of the medulla is lowered
- Water moves out of the descending limb, into the medulla by osmosis
- The glomerular filtrate is more concentrated
- At the bottom of the ascending limb, Na+ ions diffuse into the medulla
- The water potential in the medulla is lowered
Why is it important that the ascending limb is impermeable to water?
So that water does not move out of the ascending limb and into the medulla and increase the water potential
What is the whole point of the loop of Henle?
To make the water potential of the medulla very low
So water moves out of the DESCENDING LIMB
How are the distal convoluted tubule, medulla, loop of Henle and collecting duct linked ?
The loop of henle lowers the water potential of the medulla
Water moves out of the DCT and collecting duct into the medulla
How is the water that enters the medulla reabsorbed into the blood?
Through the capillary network
Why is the countercurrent of the loop of Henle important?
Maintains a concentration gradient in the medulla across the whole length of the loop
More water can move into the medulla
How is the volume of water which is reabsorbed into the capillaries controlled?
Changing the water permeability of the DCT and collecting duct
What happens when the water potential of the blood is too low?
- Osmoreceptors in the hypothalamus detect the decrease in water potential
- Posterior pituitary gland releases ADH
- ADH binds to receptors on cell membranes of DCT and collecting duct cells
- Aquaporins move to and fuse with cell membrane
- More water can pass out and into the medulla so more water is reabsorbed
What happens to the urine when the water potential of the blood is too low?
Very concentrated and little volume
as more water has been reabsorbed
What happens when the water potential of the blood is too high?
- Osmoreceptors in hypothalamus detect increase in water potential
- Posterior pituitary gland releases less ADH
- DCT and collecting tube are less permeable to water
- Less water moves out and into the medulla so less is reabsorbed
What happens to urine when the water potential of the blood is too high?
Large volume and very dilute
as less water reabsorbed
What is ADH?
Anti-diuretic hormone
