Osmoregulation and Renal Physiology - 1 and 2 Flashcards
What is osmosis?
The flow of water across a partially permeable membrane .
What determines osmosis?
The osmolarity of the solution
What happens if osmosis is not controlled?
It can lead to problems e.g. oedema or swelling
How does osmosis affect cell volume?
Cells swell or shrink depending on the osmolarity (tonicity) of the bathing solution
What happens in a hypotonic bathing solution?
There is a net water movement in => cell swells
Increased cell volume - cell may burst
What happens in a hypertonic bathing solution?
Net water movement out the cell => cell shrinks
Reduced cell volume
What happens in a isotonic bathing solution?
An equal amount of water moves in and out of the cell
There is no change in cell volume
How is extracellular (ECF) and intracellular fluid (ICF) separated?
Separated by a semi-permeable cell membrane.
How is the osmolarity of the extracellular fluid (ECF) maintained?
By homeostatic mechanisms
What is intracellular fluid (ICF) osmolarity dependent on?
the extracellular fluid (ECF) osmolarity
What is homeostasis?
The maintenance of a constant internal environment.
- a dynamic equilibrium
- variables change but are continually
corrected and kept within very narrow limits - occurs by negative feedback
What is one of the key principles in physiology?
Maintaining the balance of solutes and removal of waste products.
What is a key organ in homeostasis?
= the kidney
How is body fluid osmolarity maintained?
Body fluid osmolarity is a controlled variable. The kidney is a key organ in the regulation of body fluid osmolarity.
Anytime there is a stress correcting mechanisms come into play and it is returned to the optimum environment.
What factors can affect water balance?
Normal body fluid ~ 60% of total body weight
affected by :
- dry vs humid environment
- physiological factors
- dry vs wet food
Water in = water out
What are sources of water intake for the body?
Ingestion of water in drinks and within food
What are sources of water output for the body? (Excretory organs)
- Skin - Sweat (water, salts, urea)
- Lungs - CO2, water
- Gastrointestinal tract - Water, Bile
- Kidneys - Urine (metabolites, (including urea), water, salts, drugs)
Which sources of water secretion are controlled and which are not?
Water loss in urine is tightly controlled by the kidney.
Excretion via skin, lungs, GI tract is not controlled.
What are the 2 main mechanisms in controlling body water osmolarity?
Urine concentration and thirst
What is the main organ in regulating body fluid osmolarity?
Kidney
What are the functions of the kidney? (renal functions)
- Regulation of water balance
- Regulation of salt balance - Na+, K+
-Removal of metabolic waste products -
Urea/uric acid - Removal of foreign substances - drugs or
metabolites - Regulation of pH
- Hormone production
What makes up the urinary tract?
Kidney (cortex, medulla, capsule, renal artery,
renal vein)
Ureter
Urethra
What is the ureter?
The tube that carries urine and waste products out of the kidney to the bladder.
What is the nephron?
The key functional unit of the kidney - filtration
What % of cardiac output does renal blood supply make up?
Approx 20% of cardiac output