Homeostasis

Question 1

What is homeostasis?

Answer 1

The maintainance of a stable internal enviroment in response to external and internal changes.

Question 2

What is the importance of maintaining a stable body temperature?

Answer 2

If the temperature is too low enzyme activity decreases and metabolic reactions become less effective. If the temperature is optimum then the particles have more energy meaning they more faster meaning there are more frequent and sucessfull collisions which forms enzyme-substrate complexes meaning metabolic reactions are at their most effective. However, if the temperature is too high the active site of enzyme changes shape meaning an enzyme-substrate complex can’t form and metabolic reactions become less effective.

Question 3

What is the importance of maintaining a stable body pH?

Answer 3

If the pH is too low or high the shape of the active site changes meaning an enzyme-substrate complex can no longer form and metabolic reactions become less effective. At optimum pH enzyme activity is at its highest so metabolic reactions are at their most effective.

Question 4

What is the importance of maintaining a stable blood glucose concentration?

Answer 4

If the blood concentration is too high then water will move into cells which will cause them to expand and eventually burst and die. If it is too low water moves out the cell which causes it to shrivel up and die. Also cell can’t carry out normal activites like respiration.

Question 5

What is negative feedback?

Answer 5

The mechanism brings about an effect that opposes the change and brings the levels back to normal

Question 6

What is positive feedback?

Answer 6

The mechanism brings about a change that amplifies the change and brings levels away from normal.

Question 7

How is heat lost in organisms?

Answer 7

Sweating

Question 8

How do ectotherms control their body temperatures?

Answer 8

They use outside sources like heated rocks.

Question 9

How do endotherms control their body temperature?

Answer 9

They use internal systems.

Question 10

What happens when temperatures are too low in mammals?

Answer 10

Vasoconstriction which means the capillaries become narrower meaning less blood can pass through and less heat can be lost from the surface of the skin. The hair muscles contract causing them the to stand on end and shivering.

Question 11

What happens when temperatures are too high in mammals?

Answer 11

Vasodilation where the capillaries become wider meaning more blood can pass through them and more heat can be lost through the surface of the skin. The hair muscles relax causing them to stand down and the sweat glands release water which removes heat.

Question 12

What is the role of the pancreas in regulating blood glucose levels?

Answer 12

The cells in the islet of hanglets detect whether the levels are too high and too low.

Question 13

What causes blood glucose levels to increase?

Answer 13

Eating something that contains carbohydrates.

Question 14

What causes blood glucose levels to decrease?

Answer 14

Excersise

Question 15

What happens when the blood glucose levels are too high?

Answer 15

The alpha cells in the islet of hanglets detect this and release insulin. The insulin binds to their specific receptors on the cell membrane which triggers GLUT4 to move out of the vesicles to the cell membrane and those allow glucose into the cell and active enzymes convert glucose into glycogen in a process called glycogenesis.

Question 16

What happens with glucagon when the blood glucose levels are too high?

Answer 16

The beta cells detect thus and release glucagon which binds to their specific receptors on the membranes of liver cells which activates active enzymes to break down glycogen into glucose in a process called glycogenolysis.

Question 17

What happens with adrenaline when the blood glucose levels are too high?

Answer 17

It activates glycogenlysis and inhibits glucogenesis. It also activates glucagon secretion and inhibits insulin secretion.

Question 18

How do adrenaline and glucagon activate glycogenolysis inside the cell?

Answer 18

via a second messenger.

Question 19

How do second messengers work?

Answer 19

1. When glucagon binds to specific receptors on the cell surface membrane it activates an enzyme called adenylate cyclase which converts ATP into a chemical called cAMP.
2. The cAMP then activates an enzyme called protein kinase A which activates a cascade of reactions that lead to glycogen’s conversion into glucose.

Question 20

What is diabetes Type 1?

Answer 20

When the beta cells don’t produce enough insulin.
, blood glucose levels remain high which can eventually lead to death.

Question 21

What causes diabetes Type 1?

Answer 21

the immune system attacks the beta cells of the pancreas meaning they no longer produce insulin.

Question 22

What is the treatment for diabetes Type 1?

Answer 22

regular insulin injections.

Question 23

Why must insulin injections be monitored?

Answer 23

Too much insulin causes the blood glucose levels to decrease too much which can lead to fainting and comas.

Question 24

What is diabetes Type 2?

Answer 24

When the liver cells no longer react to insulin

Question 25

What causes diabetes Type 2?

Answer 25

to the fact that the receptors are damaged.

Question 26

What are the treatments for diabetes Type 2??

Answer 26

eating a healthy and balanced diet, more exercise and losing weight in certain cases.

Question 27

What is the role of the kidneys?

Answer 27

To filter waste products out of the blood and reabsorb useful solutes.

Question 28

Where does ultrafiltration and selective reabsorption happen?

Answer 28

the nephrons

Question 29

How does the glomerular filtrate form?

Answer 29

As the blood enters the arterioles in the cortex because the pressure in the efferent arteriole is higher compared to the afferent arteriole when the blood goes into the glomerulus the pressure is high so smaller molecules like water and glucose are forced out into the Bowman’s Capsule and form the glomerular filtrate. Larger substances like proteins and red blood cells stay in the blood.

Question 30

What does PCT stand for?

Answer 30

proximal convoluted tubule.

Question 31

What happens in the PCT?

Answer 31

useful substances like glucose are reabsorbed via active transport and facilitated diffusion.

Question 32

What does DCT stand for?

Answer 32

distal convoluted tubule.

Question 33

How does the water potential in the blood decrease?

Answer 33

sweating, excretion and if there is a lot of salt in the blood.

Question 34

How does the water potential in the blood increase?

Answer 34

drinking water.

Question 35

What is the role of the loop of Henle in the reabsorption of water?

Answer 35

1. At the top of the ascending limb sodium ions are pumped out as it is permeable to sodium ions and since the limb is impermeable to water the water does not move out of it.
2. This lowers the water potential of the medulla.
3. Because the water potential in the medulla is lower compared to the descending limb water moves out of it via osmosis and since the descending limb is not permeable to sodium ions it means the concentration of the glomerular filtrate is high.
4. The water in the medulla is reabsorbed via a capillary network and goes back into the blood.
5. Water also moves out of the DCT via osmosis and is reabsorbed by these capillaries.

Question 36

How is the release of ADH controlled?

Answer 36

osmoreceptors in the hypothalamus detect a change in the water potential and they send a message to the posterior pituitary gland which releases ADH.

Question 37

What is the role of ADH?

Answer 37

It makes the walls of the kidneys more permeable.

Question 38

How does ADH make the walls of the DCT and collecting ducts more permeable?

Answer 38

When the ADH binds to receptors in the cell membrane, proteins called aquaporins are imbedded into the cell membrane and they allow water to move into the cells via osmosis.

Question 39

What happens when the blood water potential is too high?

Answer 39

1. The osmoreceptors in the hypothalamus detect this and send a message to the posterior pituitary gland which releases less ADH.
2. This means the walls of the DCT and the collecting duct become less permeable to water and less of it is reabsorbed into the blood so the levels decrease.

Question 40

What happens when the blood water potential is too low?

Answer 40

1. The osmoreceptors in the hypothalamus detect this and send a message to the posterior pituitary gland which releases more ADH.
2. This means the walls of the DCT and the collecting duct become more permeable to water and more of it is reabsorbed into the blood so the levels increase.