BIOL122 water and homeostasis I

What does "Homeostasis" literally mean, and what is its general definition?

Literal meaning: ‘Standing the same’

• Definition: Maintaining a constant internal environment within set limits.

What are the 3 basic components of a homeostatic system?

Receptor: Detects changes. 2. Control centre: Recognises information, processes it, and formulates a response. 3. Effector: Responds. (Note: Negative feedback prevents small changes from becoming big ones.)

How does water content as a percentage of total body weight vary between newborns, adult males, and adult females?

Newborn infant: 80%

• Adult male: 60%

• Adult female: 50%

What are the three major fluid compartments in an adult male (adding up to 40 litres)?

Intracellular fluid (ICF): 25 litres

• Interstitial fluid (IF): 12 litres

• Plasma: 3 litres

Define osmosis as it relates to body fluids.

The movement of water through a selectively permeable membrane (like a plasma membrane) from an area of lower solute concentration to an area of higher solute concentration.

To maintain fluid homeostasis, "Input must = output". What are the specific daily sources of water intake and output based on the lecture?

Intake: Ingested liquids (1600ml) + Water in foods (700ml) + Tissue catabolism (200ml) = 2500ml

• Output: Kidney (1500ml) + Skin (600ml) + Lungs (300ml) + Intestine (100ml) = 2500ml

What are the 4 main components of the urinary system?

1. Kidneys

2. Ureters

3. Urinary bladder

4. Urethra

Trace the path of urine drainage starting from the collecting duct all the way to the bladder.

Collecting duct —> capillary duct in renal pyramid —> Minor calyx —> Major calyx —> Renal pelvis —> Ureter —> Urinary bladder

What are the 6 key structures of a nephron you need to be able to draw and annotate from memory?

1. Glomerulus 2. Bowman’s (glomerular) capsule 3. Proximal convoluted tubule (PCT) 4. Loop of Henle (Descending and Ascending limbs) 5. Distal convoluted tubule (DCT) 6. Collecting duct

According to the nephron diagram, which specific region changes the concentration of urine so that it can be "dilute or concentrated"?

Collecting duct (exiting via the papillary duct)