Control of blood water potential

Question 1

What is osmoregulation?

Answer 1

The maintenance of the water potential of the blood

Question 2

What is the role of the hypothalamus in osmoregulation

Answer 2

Osmoreceptors in the hypothalamus detect the water potential in the blood. They send electrical impulses accordingly.

Question 3

What is the role of the posterior pituitary gland in osmoregulation?

Answer 3

They receive electrical impulses from osmoreceptors, if there is low blood water potential, they will release ADH.

Question 4

Is osmoregulation part of the sympathetic or parasympathetic nervous system?

Answer 4

Parasympathetic

Question 5

What is the role of ADH in osmoregulation?

Answer 5

It is secreted by the posterior pituitary gland in order to increase the permeability of the collecting duct in the nephrons of the kidneys.

Question 6

How is glomerular filtrate formed?

Answer 6

Ultrafiltration occurs in the glomerulus at the nephron. The glomerulus is a network of capillaries that will allow the filtration of smaller molecules (such as glucose, water, urea and salts) into the proximal convoluted tubule. Large molecules (like proteins) will not be filtered through.

Question 7

Describe the selective re-absorption of glucose in the proximal convoluted tubule.

Answer 7

• Reabsorbed by active transport
• Glucose molecules enter the lumen via facilitated diffusion and co-transport with sodium ions
• They diffuse into the capillary via facilitated diffusion
• Sodium ions are actively transported outside the lumen through a sodium/potassium pump.

Question 8

Explain the role of the loop of Henle in the absorption of water from the filtrate.

Answer 8

• Sodium ions actively removed in ascending limb
• Ascending limb is impermeable to water
• Sodium ions diffuse into descending limb (permeable to water)
• Water in descending limb moves out by osmosis
• Deeper into medulla = lower water potential
• Water leaves collecting duct by osmosis

Question 9

What increases the diffusion rate of glucose at the proximal convoluted tubule?

Answer 9

• Microvilli increase surface area
• Channel proteins allow the movement of glucose through the membrane
• Capillary walls are one cell thick, short diffusion pathway

Question 10

What is the medulla and the cortex?

Answer 10

Medulla- inner layer of kidney

Cortex- layer outside medulla