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Biology > Homeostasis- Controlling Blood Water Potential > Flashcards

Homeostasis- Controlling Blood Water Potential Flashcards

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1
Q

Why does the amount of water in the blood need to be kept constant?

A

As water is essential to keep the body functioning

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2
Q

How is water lost in mammals?

A

Through excretion and through sweat

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3
Q

What is osmoregulation?

A

The kidneys regulate the water potential of the blood so the body has the right amount of water

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4
Q

What happens when the water potential of the blood is too low (the body is dehydrated)?

A

More water is reabsorbed by osmosis into the blood from the tubules of the nephrons- urine is more concentrated so less water is lost during excretion

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5
Q

What happens when the water potential of the blood is too high (the body is too hydrated)?

A

Less water is reabsorbed by osmosis into the blood from the tubules of the nephrons- urine is more dilute so more water is lost during excretion

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6
Q

Where is water reabsorbed into the blood?

A

Along almost all of the nephron

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7
Q

Where does regulation of water potential take place?

A

Loop of Henle, DCT and collecting duct

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8
Q

What controls the volume of water reabsorbed by the DCT and the collecting duct?

A

Hormones

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9
Q

Where is the loop of Henle located?

A

In the medulla of the kidneys

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10
Q

What is the loop of Henle made up of?

A

The descending limb and the ascending limb

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11
Q

What do the limbs in the loop of Henle control?

A

The movement of sodium ions so that water can be reabsorbed by the blood

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12
Q

What happens near the top of the ascending limb?

A

Sodium ions are pumped out into the medulla using active transport

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13
Q

Why does water stay inside the tubule of the ascending limb?

A

It is impermeable to water

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14
Q

What does water staying inside the ascending limb create?

A

A low water potential in the medulla because there’s a high concentration of ions

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15
Q

Why does water move out of the descending limb into the medulla by osmosis?

A

Because there’s a lower water potential in the medulla than the descending limb

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16
Q

What happens near the bottom of the ascending limb?

A

Sodium ions diffuse out into the medulla which further lowers the water potential

17
Q

What happens after sodium ions diffuse out?

A

Water moves out of the distal convoluted tubule by osmosis and is reabsorbed into the blood

18
Q

How is water potential of the medulla lowered?

A

The ion concentration in the medulla is massively increased

19
Q

What does lowered water potential of the medulla cause?

A

Water to move out of the collecting duct by osmosis

20
Q

How is the water in the medulla reabsorbed into the blood?

A

Through the capillary network

21
Q

What is water potential of the blood monitored by?

A

Cells called osmoreceptors in the hypothalamus (in the brain)

22
Q

What happens when the water potential of the blood decreases?

A

Water will move out of the osmoreceptor cells by osmosis which causes the cells to decrease in volume

23
Q

What is caused when osmoreceptors decrease in volume?

A

A signal is sent to the hypothalamus which sends a signal to the posterior pituitary gland which causes the posterior pituitary to release antidiuretic hormone (ADH) into the blood

24
Q

What does ADH do?

A

Makes the walls of the DCT and collecting duct more permeable to water

25
Q

What does the DCT and collecting duct walls becoming more permeable do?

A

More water is reabsorbed from these tubules into medulla and into blood by osmosis- small amount of concentrated urine is produced so less water is lost from the body

26
Q

When do blood ADH levels rise?

A

When you’re dehydrated

27
Q

What happens when you’re dehydrated?

A
  1. Water content of blood drops so water potential drops
  2. Detected by osmoreceptors in hypothalamus
  3. Posterior pituitary gland stimulated to release more ADH into blood
  4. More ADH means collecting duct and DCT become more permeable so more water is reabsorbed into blood by osmosis
  5. Small amount of highly concentrated urine produced and less water is lost
28
Q

When do blood ADH levels fall?

A

When you’re hydrated

29
Q

What happens when you’re hydrated?

A
  1. Water content of blood rises so water potential rises
  2. Detected by osmoreceptors in hypothalamus
  3. Posterior pituitary gland releases less ADH into blood
  4. Less ADH means collecting duct and DCT become less permeable so less water is reabsorbed into blood by osmosis
  5. Large amount of dilute urine produced and more water is lost

Biology (79 decks)

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