Homeostasis and Excretion

Question 1

Homeostasis:

Answer 1

Maintaining constant conditions in the body/ internal environment

Question 2

What is osmoregulation?

Answer 2

This is the regulation of water and salt content in the body

Question 3

What is the internal environment of your body?

Answer 3

This is the surroundings of the cells, includes blood and tissue fluid

Question 4

What nitrogenous waste is excreted by humans?

Answer 4

Urea

Question 5

Explain the deamination process

Answer 5

Amino acid + oxygen ➡ carbohydrates + ammonia

Ammonia + carbondioxide ➡ urea + water

Question 6

The pathway of urine in the kidney:

Answer 6

Renal artery
⬇
Blood capillaries
⬇ 
Nephrons (cortex)
⬇
Medulla (bulges called pyramids)
⬇ 
Pelvis
⬇ 
Ureters
⬇
Bladder
⬇
Urethra

Question 7

Process of ultrafiltration in the nephron

Answer 7

Capillaries (glomerulus)
⬇
Bowman's capsule (a hollow cup of cells)
⬇
Capillary networks surrounding  the nephron
*Resistance to flow caused by the glomerulus
⬇
High blood pressure: the fluid is forced out
⬇ 
Capillary wall (permeable)
⬇ 
Basement membrane (not made up of cells-fine molecular filter)
⬇
Capsule wall (coarse filter)
⬇ 
Capsule (glomerular filtrate)

Question 8

Name the two coiled tubules:

Answer 8

• Proximal convoluted tubule

- Distal convoluted tubule

Question 9

Role of the Loop of Henle:

Answer 9

Involved in concentrating the fluid by causing more water to be reabsorbed into the blood

Question 10

Meaning of diuresis and anti-diuresis

Answer 10

Diuresis: the flow of urine

Anti-diuresis: producing less urine

Question 11

Describe the negative feedback loop for osmoregulation

Answer 11

Low water levels in the blood
⬇ 
Receptors in the hypothalamus
⬇ 
The pituitary gland releases ADH
⬇ 
It acts on kidney tubules to become more permeable
⬇ 
More water is reabsorbed into the blood
⬇ 
Urine becomes more concentrated
⬇  
Normal: switch off the release of ADH

*Stimulates the thirst centre ➡ blood becomes more dilute

Question 12

Mammals are warm-blooded or ____________

Answer 12

Homeotherms (they maintain a constant body temperature despite changes in the surrounding temperature)

OR

Endotherms

Question 13

Functions of the skin:

Answer 13

• Provides protection against microorganisms
• Prevents water loss (impermeable)
• Controls heat loss
• Sense organ
• A tough outer layer that prevents mechanical damage

Question 14

What is the outer epidermis layer made of?

Answer 14

Dead cells

Question 15

Describe hypodermis and dermis layers of the skin

Answer 15

Hypodermis: contains fatty tissue which provides insulation and acts as an energy store

Dermis: sensory receptors, hair follicles, sweat glands, tiny blood vessels (capillary loops)

Question 16

How does sweat help regulate body temperature?

Answer 16

Sweat secreted onto the skin surface has a cooling effect when it evaporates.
When this liquid evaporates into a gas, it makes use of the body’s heat as the latent heat of vaporization.

Question 17

How do capillary loops help regulate temperature?

Answer 17

When your body is too hot, arterioles leading to capillary loops dilate (due to the sphincter muscles in the walls of the arterioles), allowing more blood to flow to the skin’s surface, and more heat is lost: VASODILATION

Question 18

Other methods to regulate body temperature:

Answer 18

• Shivering

- Changes in the metabolism (due to adrenaline, the liver can also produce metabolic heat)

Question 19

Steps for dialysis:

Answer 19

• An operation is conducted to join a vein to an artery to raise BP. A tube s permanently joined to a vein.
• In the dialysis machine, the patient’s blood is separated from the dialysis solution (of salts and glucose in exact concentrations) by a Visking membrane (large SA: many long narrow tubes/ stack of flat sheets)
• Diffusion of waste products and excess water and salts
  .
• Dialysis fluid is replaced with a fresh solution all the time. After several hours, the patient is going to have a balance of salts and glucose in their blood, and the waste products removed.
• The purified blood is going to be returned via a second tube attached to the vein.

Question 20

Features of a dialysis machine (apart from Visking tube):

Answer 20

• Pumps to keep the blood and dialysis fluid flowing
• Traps to prevent air bubbles from getting into the blood
• Oxygenation and the temperature of the blood are controlled