Week 7 Flashcards
What is homeostasis?
Maintaining a constant internal environment (With set limits)
Examples where homeostasis occurs?
Temperature – blood and skin
Salt (electrolytes) concentration- kidneys
Water - kidneys
Proteins, fats (lipids), carbohydrates – the liver
What are the basic components of a homeostatic system?
Receptor - detects changes
Control centre - recognises information, processes it, and formulates a response
Effector – responds
Negative feedback prevents small/acute changes from becoming big ones.
Proportion of body weight represented by water in male, female and neonate
Neonate = 80%
Male = 60%
Female = 50%
What is the distribution of body fluids?
3L plasma
12L Interstitial fluid
25L Intracellular fluid
(40L total)
What is fluid movement influenced by?
Diffusion, osmosis, filtration, reabsorption, secretion
What is osmosis
Movement of water through a selectively permeable membrane (plasma membrane) from an area of lower solute concentration to an area of higher solute concentration.
What is osmolality?
Number of particles that have an osmotic effect
What should the overall water intake and loss per day equal?
0
(2.2L intake + 0.3L metabolic production - (0.9 + 1.5 + 0.1)L output = 0)
What are the basic components of the urinary system?
Kidneys
Ureters
Bladder
Urethra
Why is the renal artery located above the renal vein in the kidney?
To create a pressure gradient
What does the renal corpuscle refer to?
Glomerulus and Bowman’s capsule
Where does blood enter and exit the glomerulus?
Enters via the afferent arteriole and exits the efferent arteriole of glomerulus.
What occurs in the glomerulus?
Filtration.
Water and all solutes (eg glucose, amino acids, ions, waste products, etc) enter Bowman’s capsule (but not proteins >65KD)
How does filtration occur in the glomerulus?
The afferent arteriole has a larger diameter than the efferent, therefore creating high pressure in the glomerulus.
Where unfiltered blood leaves via the efferent vessel, and filtered fluid moves to the proximal convoluted tubule
Components of the filtration membrane in the nephron?
Glomerular endothelial cell
Pore: All plasma passes
Basal lamina of glomerulus: Large proteins held back
Slit membrane between pedicels: Medium-sized proteins held back
What is the role of the proximal convoluted tubule?
Reabsorption back into the blood:
Water 65%, osmosis
Na+ 65% (symporters and others)
Glucose 100% (symporters)
Cl- 50%
HCO3 80-90% (bicarbonate)
Secretion into tubular fluid:
H+ (variable)
NH4+ (variable)
Urea (variable)
What do we start to see glucose within the urine (glycosuria)?
[Glucose] plasma > 10mmol/L
(Usually indicating diabetes)
What transport process does the proximal convoluted tubule use?
Active transport
Therefore lots of mitochondria are present.
And surface area for reabsorption is increased by microvilli
Why does water move out of the descending limb of loop of Henle?
The medulla solute concentration increases. (osmosis occurs in this tubule)
Therefore, tubular fluid is very concentrated at hairpin
What occurs at the ascending limb of the LoH?
NaCl diffuses into medulla interstitial fluid at base of LoH.
Active transport of NaCl in thick section of LoH. Creates salt concentration gradient in the medulla (ascending limb is impermeable to water)
What occurs at the distal convoluted tubule?
Reabsorption back into blood:
- Na+ ions 5% (increased by action
of aldosterone enabling
more water reabsorption by
osmosis)
- Water 10-15% (osmosis)
- Cl- 5%
Secretion into the tubular fluid:
H+ (variable)
K+ (variable)
NH4+ (variable)
Urea (variable)
What occurs in the collecting duct in the nephron? (reabsorption)
Reabsorption back into blood:
- Water variable (ADH causes insertion of aquaporin 2, water channels into into Principal cells of collecting duct so concentrated urine is made)
- Na+ (therefore, if no ADH, dilute urine is made)
- Urea (recycling into base of LoH to increase solute conc in medulla)
What occurs in the collecting duct of nephron? (secretion)
Secretion into tubular fluid:
K+ (variable)
H+ (variable) - adjust blood pH