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What does the Filtrate/Filtrand ratio tell us?
Shows whether a substance can cross a filtration membrane.
What hormones regulate Plasma Glucose?
Insulin and Glucagon.
What is tubular reabsorption?
The movement of ions, water, and some solutes along the renal tubule back into the blood.
What is countercurrent flow? Where is it used?
The flow of two fluids in opposite directions in order to increase absorption of solutes. It is found in fish gills (Water vs blood) and in the renal system.
What is special about molecules with renal clearance?
The don't get reabsorbed.
What is a renal threshold?
The concentration up to which a molecule is filtered but completely reabsorbed from the urine. (found with Glucose, for example)
Why might reabsorption of a molecule max out?
Saturation of the molecule's transporters.
What is Acidosis?
- Tubular secretion of H+
- Decreased H+ into filtrate and Increased HCO3- secretion.
What is the difference between Secretion and Excretion?
- Secretion of a molecule goes from (blood) to (Urine)
- Excretion of a molecule is the expulsion of the molecule from the body.
What does the loop of Henle do?
- Descending loop: Increase of H2O
- Decrease in Na and Urea
- Ascending loop: Decrease in H2O
- Increased Na, Decrease Urea.
What causes hyperosmotic blood?
Loop of Henle (By countercurrent multiplication)
What is ADH? What does it do?
- AntiDiuretic Hormone. It comes from the hypothalamus to the kidney, and limits the amount of urine produced (Pushes more water into the blood). It is used when:
- There is low blood volume,
- Low blood pressure,
- or if ECF osmolality increases.
Why does the Kangaroo Rat only need a very tiny amount of water to remove it's metabolic wastes?
Huge loops of Henle.
How do the Magnocellular neurons in the hypothalamus know to release ADH?
The cell body swells, stretch-inactivated channeles close, and ADH release decreases. The opposite happens if there is low fluid levels; the cell gets smaller, stretch-inactivated channels open and ADH is released more.
What is the Juxtaglomerular apparatus?
Changes the reabsorption rate of sodium via Renin secretion which signals the Adrenal cortex which releases Aldosterone; this increases Na+ reabsorption.
What is the Feedback loop for Electrolyte balance in the kidney?
- Decrease plasma Na+
- -> Increase Renin
- -> Increase Aldosterone
- -> Increase Na+ Retention.
Define Osmotic Regulation
The control of tissue osmotic pressure by movement of solutes.
Define ionic regulation.
Control of ionic composition of body fluids.
How do most marine animals deal with ion exchange?
- For the most part, they are osmoregulators.
- Some are osmoconformers.
Define Perturbing Solutes, give 2 examples.
These solutes disrupt macromolecular function at normal concentrations found within the animal. Often inorganic ions, for example potassium and chloride.
Define Compatible Solutes. Give 2 examples.
These solutes have very little effect on the functions of macromolecules, and can accumulate to high concentrations without causing problems. Ex: Glucose, Glycerol.
Define Counteracting Solutes. Give 2 examples.
A classification of solutes that, on their own, are destructive to the body. However, when deployed in combination with other counteracting solutes, they negate each other's effects. Ex: Methylamines and urea.
Succumbs after very modest changes in external osmolarity.
Has a relatively wide range of external osmolarity.
What is a nephron?
The functional unit of a kidney. This is where most ion and molecular balancing happens.
Describe the bowman's capsule and it's function
The mouth of the renal tubule, this unit cups the glomerulus, collecting fluids that leave the blood in the glomerulus.
The process by which a larger molecule (such as a small protein) passes into an epithelial cell from a filtrate (primary urine), and then through the epithelial cell on the other side into to second liquid (blood).
Describe renal threshold.
The facility for reabsorption of solutes (example glucose). If there is too much solute in the primary urine, the transport machinery will be unable to keep up, and not all will be recovered to the blood.
What are the four steps to urine production?
- 1. Glomerular filtration
- 2. Tubular reabsorption
- 3. Tubular secretion
- 4. Excretion
What happens in Glomerular filtration?
- Filters out Water, salts, glucose, urea, etc.
- Non-selective filtration, except for red blood cells and large plasma proteins.
What happens in tubular reabsorption?
Where does this occur?
99% of the water is reabsorbed, as well as most salts, and (usually) all glucose. Mostly occurs in the proximal tubule by active transport and passive diffusion.
What happens in tubular secretion?
The blood (with the help of transporters in the epithilial cells) push solutes back into the tubular fluid.
Describe Renal Clearance.
The relationship between the amount of substance in blood plasma and the amount in urine.
What do the Magnocellular neurons of the hypothalamus do?
Influence ADH Release. If the osmolarity of blood is low, the cell swells and ADH release is decreased. The opposite happens for increased osmolarity.
Describe BAT and WAT.
- WAT is white adipose tissue. It is an energy reserve and a heat sink, helps with non-shivering thermogenesis. Insulative, buoyant, and a nitrogen sink for deep-diving mammals.
- BAT is brown adipose tissue; very vascularised, oxidation and heat production. Specialize in non-shivering heat production. Many mitochondria. Warms blood (Energy produced isn't stored as ATP).
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