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Homeostasis Flashcards

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1
Q

What Is Homeostasis?

A

Homeostasis is the ability to return to an optimum point so that internal environment within organisms can be maintained.

It involves trying to maintain the chemical make-up, volume and other features of blood and tissue fluid.

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2
Q

Importance Of Homeostasis?

A
  • Enzymes that control the biochemical reactions within proteins (e.g. channel) operate best at optimum pH and temperature,
  • Changes from optimum can cause a reduction in the rate of reaction because of reduced kinetic energy or denaturation,
  • Changes in water potential can change glucose concentration of tissue fluid and blood can cause cells to shirk or burst,
  • Glucose concentration also effects the supply of glucose for respiration.
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3
Q

Homeostasis Helps Control?

A

Helps control the fluctuations around the optimum of:

Water potential,

pH,

Temperature.

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4
Q

Control Mechanism For Homeostasis?

A

The control of any self-regulating system involves a mechanism:

  1. The optimum point is monitored by a receptor which detects any deviation from the optimum point.
  2. If a change occurs, the receptor signals the coordinator which coordinated information from receptor to an appropriate effector.
  3. An effector is an muscle or gland, which brings about the changes needed to return the system to the optimum point.
  4. The return to the optimum point is a feedback mechanism - a receptor responds to a stimulus.
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5
Q

Positive Feedback?

A

System deviates from the optimum.

  1. A change is detected by the receptor.
  2. A change is then produced which causes a even greater deviation from the optimum.
    • E.g. more sodium channels open in a membrane to allow even more sodium ions to move.
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6
Q

Negative Feedback?

A

System deviates from the optimum.

  1. Change is detected by the receptor.
  2. A change is then produced which returns the system back closer to the optimum.
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7
Q

Adaptations Of Control Systems?

A

Control systems are negative and positive feedback systems.

They are adapted because:
- they have many receptors and effectors which allows them to control and act quickly on a change in environment,

  • positive and negative feedback systems have separate mechanisms (receptors and effectors) which allows them to control from different directions.
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8
Q

Why Is Information Analysed By Coordinate?

A

The coordinate analyses information from all receptors before making action.

For example, it analyses information from skin receptors and hypothalamus.

Skin receptors may indicate skin is cold because of sweating but hypothalamus may indicate the blood temp is above normal. This may be due to exercise.

The coordinator would then not raise the body temperature despite disputing receptor indications.

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9
Q

What Happens When Glucose Levels Fall - Steps?

A

Fall in blood glucose in blood:

  1. Pancreas is mostly made up of cells that produce digestive enzymes but these are scattered with groups of hormone producing cells.
    These are called islets of Langerhans.
  2. A fall in concentration stimulates receptors ‘a cells’ (alpha cells - coordinator) in islets of Langerhans in pancreas.
  3. a cells secrete glucagon into blood plasma.
  4. Glucagon attaches to receptors on liver cells which activates enzymes.
  5. This causes enzymes to convert glycogen to glucose (glycogenolysis) which is released into blood, raising blood concentration.
  6. Some amino acids may also be converted to glucose (gluconeogenesis).
  7. This raises the concentration of glucose in the blood and return it to its optimum concentration. This raising of the blood glucose concentration causes a cells to reduce the secretion of glucagon (negative feedback).
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10
Q

What Happens When Glucose Levels Rise - Steps?

A

Glucose levels rise:

  1. Pancreas is mostly made up of cells that produce digestive enzymes but these are scattered with groups of hormone producing cells.
    These are called islets of Langerhans.
  2. A rise in concentration stimulates receptors ‘b cells’ (beta cells - coordinator) in islets of Langerhans in pancreas.
  3. B cells secrete insulin into blood plasma.
  4. Insulin binds to glycoprotein receptors on cell-surface of liver cells,
    5: The binding of insulin changes the tertiary structure of glucose carrier proteins, causing them to open.
  5. This opening of glucose carrier protiens allows glucose to move into cells via faciliatated diffusion.
  6. The binding increases the number of carrier proteins in the cell-surface membrane.
  7. The binding activates the enzymes that convert glucose to glycogen (glycogenesis) and fat.
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11
Q

How Does The Binding Of Insulin Increase The Number Of Carrier Proteins?

A

The binding of insulin onto the glycoproteins of the liver increases the number of carrier proteins in the cell-surface membrane.

This is because:

At low levels of insulin, the channel protein is part of vesicle membranes.

When insulin rises, the vesicles fuse with the membrane, which increases the number of transport channels.

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12
Q

Glycogenolysis?

A

Conversion of glycogen (store of glucose) to glucose,

When blood glucose concentration is lower than normal, this happens,

The liver converts stored glycogen back into glucose which diffuses into the blood to restore the normal blood glucose concentration.

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13
Q

Gluconeogenesis?

A

Production of glucose from non-carbohydrates.

E.g. aminos acids and glycerol are non-carb.

This occurs when glycogen is used up.

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14
Q

Where Does Glucose Come From?

A

The normal concentration of blood glucose is 5mmol dm-3.

Blood glucose comes from three sources:

  • Diet (glucose is absorbed from hydrolysis of other carbohydrates such as starch, maltose, lactose and sucrose),
  • Hydrolysis in small intestine (glycogenolysis - glycogen to glucose) stored in liver and muscle cells,
  • Glucogenoegenesis - production of glucose from sources other than carbohydrates.

Glucose levels then decrease when a person exercises or by hormones which cause a break down of glucose.

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15
Q

What Hormones Do Pancrease Produce?

A

Insulin and glucagon.

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16
Q

Glycogenesis?

A

Conversion of glucose to glycogen.

Occurs when there is an excess of glucose and the liver removes glucose from the blood and converts it to glycogen.

This way, it can store 75-100g of glycogen, which is sufficient to maintain the humans blood glucose concentration for about 12 hours when at rest, in absence of other sources.

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17
Q

Second Messenger Model - Steps?

A

A mechanism of hormone action - used by two hormones (adrenaline and glucagon) involved in the regulation of blood glucose concentration

  1. Adrenaline binds to the protein receptor on the cell-surface membrane of liver cell.
  2. The binding causes a shape change on the inside of the membrane.
  3. This activates an enzyme called adenyl cyclase which converts ATP to cyclic AMP (cAMP).
  4. The cAMP acts as a second messenger that binds to protein kinase (enzyme) and activates it.
  5. This enzyme catalyses the conversion of glycogen to glucose.
  6. The glucose will move out of the liver cell by facilitated diffusion through channel proteins.
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18
Q

Pancreas?

A

The pancreas is a large, pale-coloured gland, situated in the upper abdomen, behind the stomach.

It produces digestive enzymes (lipase, amylase and protease) for digestion and hormones (insulin and glucagon) for regulating blood glucose concentration.

Pancreas has many cells together called Islets of Langerhans - contains beta and alpha cells.

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19
Q

Alpha Cells?

A

In the islets of Langerhans,

Larger,

Produce hormone glucagon.

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20
Q

Beta Cells?

A

Islets of Langerhans,

Smaller,

Produce insulin (a globular protein made up of 51 amino acids).

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21
Q

Hormones Are?

A

The hormonal system communicates more slowly than the nervous system,

Hormones are different chemically but they all have certain characteristics:

  • produced in glands which secrete hormones into directly into blood (endocrine glands - glands that produce hormones),
  • carried in blood plasma to the cells on which they act - known as target cells - which have specific receptors on their cell-surface membrane that are complementary to a specific hormone,
  • are effective in very low concentrations, but often have widespread and long-lasting effects.
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22
Q

Why Is Glucose Concentration Important For Brain?

A

Glucose is used for respiration by all cells, therefore, glucose concentration in the body must be at optimum so mammals can contain relatively constant respiration.

If the concentration levels fall too low, cells will be deprived of energy (for respiration) and die.

Brain cells cannot respire anything except glucose (can’t respire lipids, etc).

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23
Q

If Glucose Concentration Rises Too High, What Happens?

A

If glucose concentration rises too high, it lowers the water potential of blood,

This creates osmotic problems and can cause dehydration and be dangerous.

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24
Q

Insulin?

A

A globular protein made up of 51 amino acids,

Binds specifically to glycoprotein receptors on cell-surface membranes,

All cells in body (except red blood cells) have glycoproteins receptors for insulin but we usually talk about the binding to liver cells.

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25
Q

Acting Antagonistically?

A

The two hormones insulin and glucagon act in opposite ways - increasing concentration and decreasing concentration.

Therefore, they act antagonistically through a negative feedback system.

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26
Q

Optimum Blood Glucose Concentration Is?

A

5mmol dm-3 in blood.

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27
Q

Diabetes Definition?

A

Def: Diabetes is a metabolic disorder caused by an inability to control blood glucose concentration due to a lack of the hormone insulin or loss of responsiveness to insulin.

Diabetes is a disease in which a person is unable to metabolise carbohydrate, especially glucose, properly.

350million people worldwide with diabetes.

Two types of sugar diabetes - ‘diabetes mellitus’ - type 1 and type 2.

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28
Q

Type 1 Diabetes?

A

Body is unable to produce insulin,

Insulin-dependent (juvenile-onset diabetes),

Body also cannot store excess glucose as glycogen,

Genetic so usually begins in childhood,

Result of autoimmune response whereby the body’s immune system attacks its own cells (b cells are attacked by other body cells),

Signs of diabetes include; 
high blood glucose concentration, 
glucose in urine, 
need to urinate excessively, 
weight loss, 
blurred vision,

Symptoms of diabetes include;
Tiredness,
Increased thirst and hunger,

Develops quickly (weeks) and symptoms are usually more severe than type 2 and mor obvious.

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29
Q

Type 2 Diabetes?

A

Happens because glycoprotein receptors (target cells) on body cells are lost or lose responsiveness to insulin,

Non-insulin dependent,

Sufferers can still produce insulin,

Constantly high insulin levels due to too much sugar intake,

Beta cells may become ‘exhausted’ and die - thereby producing less insulin in the long term,

Could also happen because inadequate supply of insulin to pancreas (too much insulin is most likely situation),

Usually develops in people over 40,

Positive correlation between diabetes development and obesity with poor diet,

Develops slowly and symptoms are usually less severe than type 1,

Around 90% of people with diabetes have type 2.

30
Q

Treatment For Type 1 Diabetes?

A

Diabetes cannot be cured (although recent evidence involving transplanting insulin-producing cells have shown promise) but diabetes can be treated:

Type 1 - monitored injections of insulin (2-4 times a day),

Insulin can’t be taken orally as it would be digested by enzymes in the alimentary canal because it is a protein,

Dose of insulin must be matched exactly to the glucose intake,

Insulin was originally obtained from non-human sources e.g. pigs,

Care needs to be taken as hypoglycaemia (glucose levels too low) can occur,

As glucose is needed for respiration in brain cells, a lack of glucose (low glucose concentration in blood) can lead to unconsciousness or even death,

Monitored using biosensors or dipsticks,

They must also manage their diet by restricting foods high in sugar or going for long periods without food,

Levels of exercise should also be controlled.

31
Q

Treatment For Type 2 Diabetes?

A

Careful regulation of diet (regulating carbohydrate intake) and matching this to the amount of exercise done,

Choose high fibre, low fat foods,

May move onto using insulin after some time,

In some cases, drugs that stimulate insulin production can also be taken,

Other drugs might slow down the rate at which the body absorbs glucose from the intestine,

Insulin can be fast and slow acting depending on what the patient needs.

32
Q

What Is Osmoregulation?

A

The homeostatic control of the water potential of the blood is called osmoregulation.

The nephron in the kidney controls this.

Most important functions is to maintain the water potential of plamsa (and hence, tissue fluid).

33
Q

Water Gain Statistics?

A

Diet - 2300 (cm3 day-1)
Metabolism - 200 (cm3 day-1)

Total gain - 2500

34
Q

Water Loss Statistics?

A

(All in cm3 day-1)

Urine - 1500
Expired air - 400 
Evaporation from skin - 350
Faeces - 150
Sweat - 100

Total - 2500

35
Q

Sodium Chloride Gain Statistics?

A

(All in g day-1)

Diet - 10.50

Total - 10.50

36
Q

Sodium Chloride Loss Statistics?

A

(All in g day-1)

Urine - 10.00
Faeces - 0.25
Sweat - 0.25

Total - 10.50

37
Q

Structure Of Mammalian Kidney?

A

In mammals, there are two kidneys found at the back of the abdominal cavity,

One on each side of the spinal cord,

Kidney is made up of:

Fibrous capsule,
Cortex,
Medulla,
Renal pelvis,
Ureter,
Renal artery,
Renal vein,

There are around one millions tiny tubular structures in each kidney. These are the nephrons.

38
Q

Fibrous Capsule?

A

Part of the kidney,

Fibrous capsule is an outer membrane that protects the kidney.

39
Q

Cortex?

A

Part of the kidney,

A lighter coloured outer region made up of:

  • renal capsules (also known as Bowman’s capsule),
  • convoluted tubules,
  • and blood vessels.
40
Q

Medulla?

A

Part of the kidney,

A darker coloured, inner region made up of:

  • loops of Henle,
  • collecting ducts,
  • and blood vessels.
41
Q

Renal Pelvis?

A

Part of kidney,

A funnel-shaped cavity that collects urine into the ureter.

42
Q

Ureter?

A

Part of kidney,

A tube that carrier urine to the bladder.

43
Q

Renal Artery?

A

Part of kidney,

Supplies the kidney with blood from the heart via the aorta.

44
Q

Renal Vein?

A

Part of kidney,

Returns blood to the heart via the vena cava.

45
Q

Structure Of The Nephron?

A

The nephron is the functional unit of the kidney,

It is a narrow tube up to 14mm long, closed at one end, with two twisted regions separated by a lip hairpin loop.

Each nephron (there’s about a million) is made up of:

  • Renal capsules (also knows as Bowman’s capsule),
  • Proximal convoluted tubule,
  • Loop of Henle,
  • Distal convoluted tubule,
  • Collecting duct.
46
Q

Blood Vessels Associated With Nephron?

A

With each nephron are a number of blood vessels:

  • Afferent arteriole,
  • Glomerulus,
  • Efferent arteriole,
  • Blood capillaries.
47
Q

Bowman’s Capsule?

A

Part of the nephron.

Also known as Renal capsule,

The closed end at the start of the nephron,

It is a cup-shaped structure,

It surrounds a mass of blood capillaries known as the glomerulus,

The inner layer of the Bowman’s capsule is made up of specialised cells called podocytes.

48
Q

Proximal Convoluted Tubule?

A

Part of the nephron.

A series of loops surrounded by blood capillaries,

It’s walls are made of epithelial cells which have microvilli.

49
Q

Loop Of Henle?

A

Part of the nephron,

A long, hairpin loop that extends from the cortex into the medulla of the kidney and back again.

It is surrounded by blood capillaries.

50
Q

Distal Convoluted Tubule?

A

Part of nephron,

A series of loops surrounded by blood capillaries.

It’s walls are made of epithelial cells, but it’s is surrounded by fewer capillaries than the proximal tubule.

51
Q

Collecting Duct?

A

Part of nephron.

A tube into which a number of distal convoluted tubules from a number of nephrons empty.

It is lined by the epithelial cells and becomes increasingly wide as it empties into the pelvis of the kidney.

52
Q

Afferent Arteriole?

A

A blood vessel associated in the nephron,

This blood vessel is tiny and arises from the renal artery and supplies the nephron with blood.

The afferent arteriole enters the Bowman’s capsule of the nephron where it forms the glomerulus.

53
Q

Glomerulus?

A

One of the blood vessels associated with the nephron.

Made up of the Afferent arteriole.

The glomerular capillaries are made of endothelial cells with pores between them.

Glomerulus is a many branched knot of capillaries from which fluid is forced out of the blood.

The glomerular capillaries recombine to form the efferent arteriole.

It is inside the Bowman’s capsule.

54
Q

Efferent Arteriole?

A

One of the blood vessels associated with the nephron,

Efferent arteriole is a tiny vessel that leaves the renal capsule.

It has a smaller diameter than the Afferent arteriole and so causes an increase in blood pressure within the glomerulus.

The efferent arteriole carries blood away from the Rena capsule and later branches to form the blood capillaries.

55
Q

Blood Capillaries?

A

One of the blood vessels that is associated with the nephron.

Blood capillaries are a network of capillaries that surround the:

  • proximal convoluted tubule,
  • the loop of Henle,
  • and the distal convoluted tubule,

They re-absorb mineral salts, glucose and water from these places in the nephron.

These capillaries merge together into venules (tiny veins) that in turn merge together to form the renal vein.

56
Q

Series Of Osmoregulation?

A

Nephron carries out its role of Osmoregulation in series of stages:

  • Ultrafiltration,
  • Reabsorption,
  • Loop of Henle,
  • Distal convoluted tubule.
57
Q

Ultrafiltration?

A

Step 1 of Osmoregulation.

Blood enters the kidney through the renal artery which branches to give the Afferent arteriole.

The Afferent arteriole enters Bowman’s capsulise to form glomerular capillaries.

The glomerular capillaries leave the Bowman’s capsule to efferent arteriole.

Diameter of the afferent arteriole is larger than the efferent arteriole so when the blood leaves the glomerular capillaries:

  • Hydrostatic pressure is built up.
  • Water, glucose and mineral ions are squeezed out of the capillary to form glomerular filtrate.
  • Blood cells and proteins are too large to pass through.

The movement of the filtrate out of the glomerulus is resisted by:

  • Capillary endothelial cells.
  • Low water potential of the blood.
  • Epithelial cells of renal capsule.
  • Hydrostatic pressure of fluid in interstitial space.

BUT…
• Podocytes – specialised cells which line
the inner layer of the renal capsule. They have spaces in-between them. This allows filtrate to pass between and beneath their branches. Filtrate passes BETWEEN theses cells rather than through them.

• Endothelium of the glomerular capillaries also have spaces between them (up to 100nm wide) which allows filtrate to pass through.

As a result of this, the hydrostatic pressure of the blood in the glomerulus is sufficient to overcome the resistance and so the filtrate passes from the blood into the renal capsule.

The filtrate contains urea but does not contain other cells or plasma proteins which are too large to pass across the connective tissue. Many of the substances in the 125cm3 of filtrate passing out of blood each minute ate extremely useful to the body and are reabsorbed.

58
Q

Osmoreceptors?

A

Osmoreceptors in the hypothalamus monitor the water potential of the blood.

This varies the amount of antidiuretic hormone (ADH) released into the bloodstream.

The kidneys respond to a change in ADH concentration by adjusting the volume and concentration of the urine.

59
Q

Reabsorption?

A

Step 2 of Osmoregulation.

In the proximal convoluted tubule, nearly 85% of the filtrate is reabsorbed back into blood.

Most useful molecules are reabsorbed but waste molecules are removed (urea).

  • Na ions are actively transported out of the PCT cells into the blood which carries them away – so lowers Na ion concentration.
  • Na ions now diffuse down the conc graditent from the lumen of the PCT into the epithelial cells (using carrier proteins by facilitated diffusion).
  • These carrier proteins carry another molecule along with the NA ions – co-transport.
  • These molecules then diffuse into the blood and are reabsorbed.

About 180dm3 of water enters the nephron each day. Of this volume, only about 1dm3 leaves the body as urine. 85% of the reabsorption of water occurs in the PCT. The remainder is reabsorbed from collecting duct as a result of the loop of Henle.

60
Q

Adaptations Of Proximal Convoluted Tubule?

A

Proximal convoluted tubule (PCT) is adapted by:
- Microvilli (large surface area)
- Infoldings at their base to give large surface area to
reabsorb substances into blood capillary.
- Lots of mitochondria to provide ATP for active transport.

61
Q

What Is Loop Of Henle?

A

The loop of Henle is a counter current multiplier.

The loop of Henle extends into the medulla.

It is responsible for:
- the reabsorption of water in
the collecting duct so that urine has a lower water potential than blood.

The concentration of the urine is related to the
length of the loop of Henle.

Loop Of Henle has 2 regions:

  1. Descending limb – narrow, thin permeable walls.
  2. Ascending limb – wider, thick impermeable walls
62
Q

Loop Of Henle - Steps?

A
  1. Na ions are actively transported out of the ascending limb using ATP provided by mitochondria.
  2. Low water potential (high ion concentration) is created between limbs (called the interstitial region). In normal circumstances, water would pass out via osmosis but the walls of ascending limb are thick and impermeable to water. Nearly no water leaves but a tiny, tiny bit does.
  3. Water, however, does move out of the descending limb from the filtrate into the interstitial space and then into the blood capillaries by osmosis.
  4. Water is lost as the filtrate moves down the descending limb, meaning that the lowest water potential is at the bottom of loop of Henle.
  5. Na ions diffuse out at the base of the ascending limb and then are actively pumped out.
  6. This means that the water potential in the filtrate gets progressively higher.
  7. In the interstitial space, there is a gradient of water potential, with the highest water potential at the cortex and lowest water potential at the bottom of the medulla.
  8. Water is lost from the collecting duct (because it is permeable to water) by osmosis into the blood vessels that occupy this space. Water is taken away.
  9. Any water that moves out of the collecting duct is moved by channel proteins. Water moves out of the collecting duct by osmosis the whole way down the collecting duct and also out of the interstitial space. This means the gradient is maintained.

This counter-current multiplayer system makes sure there is always water being drawn out of the collecting duct.

63
Q

Channel Proteins In Collecting Duct?

A

Any water that passes out of the collecting duct by osmosis does so through channel proteins that are specific to water (aquaporins).

Antidiuretic hormone (ADH) can alter the number of these channels and so control water loss.

By the time the filtrate, now called urine, leaves the collecting duct on its way to the bladder, it has lost most of its water and so it has a lower water potential (and is more ion concentrated) than the blood.

64
Q

Distal Convoluted Tubule?

A

Have lots of microvilli and mitochondria.

The distal convoluted tubule can absorb material from the filtrate by active transport.

It controls the pH of the blood by reabsorbing selected ions. To do this, the permeability of its walls becomes altered under the influence of various hormones.

65
Q

Counter-Current Multiplier?

A

When two liquids flow in opposite directions past one another, the exchange of substances between them is greater than if they flowed in the same direction next to each other.

The loop of Henle is a counter-current multiplier.

This means that the filtrate in the collecting duct with a lower water potential meets the interstitial fluid that has an even lower water potential.

This means that, although the water potential gradient between the collecting duct and the interstitial fluid is small, it exists for the whole length of the collecting duct and so there is a gradual flow of more water out of the collecting duct and into the fluid.

Around 80% of the water enters the interstitial fluid and hence, the blood. If the two flows were in the same direction, less of the water would enter the blood.

66
Q

How Is The Water Potential Of Blood Chnaged By Humans?

A
  • Not enough water being consumed,
  • Too much sweating,
  • Large amounts of ions, such as sodium chloride, being consumed.
67
Q

ADH Effect On Osmoregulation?

A

ADH- Antidiuretic Hormone (vasopressin).

Synthesised in the Hypothalamus.

Transported via nerve axons and released into the blood by the Pituitary.

Steps Of Release:
1. Osmoreceptors in the hypothalamus detect falls in water potential (osmoreceptors know when water levels fall because water moves out of the osmoreceptors themselves via osmosis and they shirk).

  1. Hypothalamus releases antidiuretic hormone (ADH).
  2. ADH passes to the posterior pituitary gland and then it is secreted into the capillaries.
  3. ADH travels to the kidney via the blood where it increases the permeability of the distal convoluted tubule walls and the collecting duct walls by binding to specific protein receptors on the cell surface.
  4. This binding activates an enzyme called phosphorylase which causes vesicles to fuse with the cell membrane (vesicles contain aquaporins).
  5. The aquaporins have more channel portions on them so when they bind to the wall, this causes the water channels to increase, making the walls more permeable to water.
  6. Collecting duct is now more permeable to urea, which lowers the water potential of the surrounding fluid, so water moves out by osmosis.
  7. Result: more water leaves the collecting duct by osmosis, down a water potential gradient, and re-enters the blood.
  8. Because the reabsorbed water came from the blood in the first place, this will not, increase the water potential of the blood, but prevent it from getting lower.
  9. The osmoreceptors will also send nerve impulses to the thirst centre of the brain, to encourage the individual to seek out and drink more water.
  10. The osmoeceptors in the hypothalamus detect the rise in water potential and send fewer impulses to the pituitary gland when water is drunk. The pituitary gland reduces the release of ADH. This is negative feedback.
68
Q

Result Of ADH Released?

A
  • Small volume of concentrated urine.

- Increase in blood pressure.

69
Q

Result Of ADH Not Being Released?

A
  • Blood pressure decreases,

- More dilute urine and water potential of blood falls.

70
Q

A Fall In Solute Concentration Of Blood?

A

This means less ions are in the blood.

This raises the water potential.

This is caused by:

  • Large volume of water being consumed.
  • Salts used in metabolism or excreted not being replaced in the diet.

The body responds to this by:

  • Nerve impulses sent from hypothalamus (osmoreceptors) to the pituitary gland to reduce the release of ADH,
  • Less water is reabsorbed into the blood from the collecting duct.
  • More die loot urine is produced and the water potential of the blood falls.

When the water potential of the blood has returned to normal, the osmoreceptor is in the hypothalamus caused to raise its ADH release back to normal levels (negative feedback).

71
Q

What Is Tissue Fluid?

A

What surrounds cells, supplies nutrients and removes waste.

A Level || Biology (21 decks)

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