Lecture 4 Water Homeostasis & the Urinary System

Question 1

Homeostasis

Answer 1

Maintaining a constant internal environment (within set limits)

E.g.
- temperature- blood & skin
- salt concentration- kidneys
- water - kidneys
- proteins, fats, carbohydrates- liver

Question 2

What are 3 basic components of homeostatic system?

Answer 2

1. Receptor - detects change
2. Control centre- recognises information, processes it & formulates a response
3. Effector- responds
4. **Negative feedback ** - prevents small changes from becoming big ones

Question 3

What proportion of body weight is represented by water in a newborn, male and female?

Answer 3

Neonate(newborn) - 80%
Male - 60%
Female - 50%

Question 4

Distribution of body fluids (3)

Answer 4

• Plasma 3L
• Interstitial fluid 12L
• Intracellular fluid 25L

40L in total

Question 5

What is fluid movement influenced by? (5)

Answer 5

1. Diffusion
2. Osmosis
3. Filtration
4. Reabsorption
5. Secretion

Question 6

Osmosis

Answer 6

Movement of water through a selectively permeable membrane (plasma membrane) from an area of lower solute concentration to an area of higher solute concentration

Question 7

What are the sources of water intake & loss?

Answer 7

Water gain
1. Food & drink 2.2 L
2. Metabolism 0.3 L

Water loss (per day)
1. Skin & Lungs - insensible water loss 0.9L
2. Urine 1.5 L
3. Feces 0.1 L

Question 8

Components of urinary system (4)

Answer 8

1. Kidneys
2. Ureters
3. Bladder
4. Urethra

Question 9

How many nephrons in the kidney?

Answer 9

1 million