*Just for an overview, remember that a solute is what is dissolved, while a solvent the solute is dissolved in. The "universal solvent" is water.

*Also remember the emperical formulas for different molecules in digestion.

Carb - CH2O

Fat - CHO

Protein - CHNO

Nucleic Acid - CHNOP

As you know, homeostasis refers to an animal's ability to regulate its internal environment. Thermoregulation refers to how animals maintain their internal temperature, and osmeoregulation refers to how they regulate solute balance and water content.

The digestion and utilization of proteins creates the greatest need for osmeoregulation in the kidneys.

Thermoregulation takes place through the following processes:

1. Adjustment of rate of heat exchange between the animal and its environment - through insulating hair, feathers and fat - is accomplished through vasodilation (in increase in the diameter of blood vessels at the skin, which cools the blood) or vasoconstriction (the opposite of vasodilation).

2. Evaporation across the skin (through panting or sweating)

3. Behavioral responses (changes in location or posture) Eg. Shivering, or lizards moving off of a hot rock.

4. Alteration of the rate of metabolic heat production (only in endotherms)

Most metabolic wastes must be exreted from the body. One of the most important waste products is nitrogen-containing breakdown products proteins/nucleic acids.

Mammals have two kidneys, and each is supplied with blood by a renal artery and a renal vein. Urine leaves the kidneys through the uterers, which drain into the urinary bladder. Urine is expelled from the body through the urethra.

*Know your U's!

The kidney has two regions: the outer renal cortex and the inner renal medulla. These 2 regions are packed with nephrons, which are the functional units of the kidney.

Nephrons are made up of a single long tubule and the glomerulus, a ball of capillaries. At the end of the tubule is the Bowman's Capsule, a c-shaped capsule that surrounds the glomerulus.

The filtrate flows through the proximal tube, the descending loop of Henle, the loop of Henle, the ascending loop of Henle, and the distal tubule. The distal tubule empties into a collecting duct, which receives wastes from many nephrons.

In the human kidney, most of the nephrons are cortical nephrons that are in the renal cortex. The rest are juxtamedullary nephrons with long loops of Henle that extend into the renal medulla.

Capillaries called afferent arterioles are associated with nephrons, and as they leave the glomerulus, the capillaries converge into an efferent arteriole. This vessel subdivides again to form peritubular capillaries, which surround the proximal and distal tubules.

Questions:

1. What is the first stage inside the nephron and what is occuring?

a. Filtration - materials from the blood are moving from the glomerulus into the Bowman's capsule

b. Filtration - materials from the proximal tube are diffusing back into the blood stream and interstitial fluid

c. Reabsorption - materials from the blood are moving from the glomerulus into the Bowman's capsule

d. Reabsorption - materials from the proximal tube are diffusing back into the blood stream and intersitial fluid

2. Which of the following is NOT true?

a. During vasodilation, the blood vessels farest away from your skin are expanding and cooling your blood.

b. The liquid inside the Bowman's capsule is filtered blood

c. Juxtamedullary nephrons extend into the medullary, not just inside the renal cortex

d. The renal artery takes blood to the kidney

3. During vasoconstriction, what is happening?

a. The superficial blood vessels dilate, which cools the blood

b. The superficial blood vessels constrict, which cools the blood

c. The superficial blood vessels dilate, which heats the blood

d. The superficial blood vessels constrict, which heats the blood

Answers: a, a, c