Osmoregulation and the Kidney

Question 1

What is homeostasis?

What are examples of homeostatic conditions in the body (blood sugar and body temp)?

Answer 1

The process by which a constant internal environment is maintained despite changes in the external environment
Blood sugar: 0.1%
Body temperature: 37°C
-also includes blood pH, oxygen and carbon dioxide concentrations, and watery/solute balance

Question 2

What is negative feedback?

Answer 2

The process by which a mechanism is activated to restore conditions to their original state
Ex: an increase in blood sugar activates a mechanism to decrease blood sugar levels to their normal resting state

Question 3

Uterine contractions that occur as a result of a decrease in progesterone, which in turn triggers the release of oxytocin to strengthen these contractions, is an example of what?

Answer 3

Positive feedback

Question 4

Describe the body’s response to heat stress.

Answer 4

• Increase in body temperature detected by temperature receptors in the skin (during exercise or high environmental temperature)
• Nerve message is relayed to the hypothalamus
• hypothalamus send signal to affect her’s
• sweat glands initiate sweating and evaporative cooling occurs
• skin blood vessels dilate to allow for increased blood flow to the skin to exude heat from skin surface

Question 5

Describe the body’s response to cold stress.

Answer 5

• Decrease in body temperature as external temperature drops
• thermo receptors in skin send messages to hypothalamus
• hypothalamus sends signals to effectors
• Reduced blood flow to the skin, hair follicles contracts, hair becomes erect, muscle contractions generate heat through shivering
• Long exposure to cold results in the oxidation of brown fat to generate heat from stored chemical energy

Question 6

What is ADH?

Answer 6

• antidiuretic hormone
• produced in the hypothalamus and stored in the posterior pituitary gland
• causes the membranes of the collecting tubules to become more permeable to water (via aquaporins) -more water is reabsorbed and less urine excreted
• diuretics such as alcohol or green tea decrease the release of ADH, with collecting tubules less permeable to water less water reabsorbed, which leads to large amount of water being excreted and possible dehydration

Question 7

Describe the body’s response to water loss.

Answer 7

• Osmoreceptors in hypothalamus detect increase in osmotic pressure (increased solute conc.)
• Signal sent to posterior pituitary-ADH released
• as kidney tubules reabsorb more water, osmotic pressure drops as cells are hydrated

Question 8

What is aldosterone and what is its purpose?

Answer 8

• A hormone produced in the cortex of the adrenal glands

- Increases sodium ion reabsorption in the distal tubules and in the collecting ducts. Water reabsorption also increases

Question 9

Where does pH and nutrient level regulation occur in the nephron?

Answer 9

Occurs in proximal and distal tubules

• H+ is secreted and HCO3 is reabsorbed
• selective reabsorption of glucose, amino acids and vitamins by active transport. Distal tubule also regulates Na+ and K+ by active transport.

Question 10

Cause, problems, and treatment of diabetes mellitus + types

Answer 10

Cause: lack of insulin from pancreas
Problems: excess sugar remains in tubule; large urine volumes, decreased osmosis of water
Treatment: insulin injections
Type 1 (juvenile onset): pancreas unable to produce insulin; early degeneration of beta cells
Type 2 (adult onset):decreased insulin production or an effective use of the insolent the pancreas produces controlled with diet exercise and oral medication that stimulate the beta cells
Gestational: results from high glucose levels that result from pregnancy

Question 11

Cause, problems, and treatment of diabetes insipidus

Answer 11

Cause: destruction of neurosecretory cells in hypothalamus or in nerve tracts from hypothalamus to pituitary (lack of ADH)
Problems: less water reabsorbed, increased urine output
Treatment: ADH injections

Question 12

Cause, problems, and treatment of Bright’s disease or nephritis

Answer 12

Cause: bacterial toxins destroyed blood vessels in glomerulus
Problems: inflammation of nephrons, proteins pass into Bowman’s capsule, increased urine production
Treatment: treat with antibiotics

Question 13

Cause, problems, and treatment of kidney stones

Answer 13

Cause: mineral solutes from blood precipitate and launch in the renal pelvis, ureter, urethra
Problems: extreme pain; calcium oxalate or calcium phosphate salt damage soft tissue
Treatment: surgery or high energy shockwaves pass through soft tissues and shatter stones

Question 14

What is the kiss?

Answer 14

Juxtaglomerular apparatus

-Where the ascending arm of the loop of Henle has become the distal convoluted tubule and brushes against the glomerulus

Question 15

What is the nitrogenous waste produced in amphibians and mammals?

Answer 15

Urea

Question 16

Nitrogenous waste produced and reptiles, birds and insects?

Answer 16

Uric acid

Question 17

Nitrogenous waste produced in fish?

Answer 17

Ammonia

Question 18

Describe the process of ultrafiltration in the glomerulus?

Answer 18

The glomerulus allows 20% of blood plasma to escape because: the blood pressure is very high because the vessel taking blood away from the glomerulus is narrower than the vessel bringing it, and the capillaries in the glomerulus have many pores

• these pores allow molecules with a small mass to pass through the basement membrane
• The filtrate is collected by the Bowman’s capsule and flows on into the proximal tubule

Question 19

What substance should you not find in the filtrate produced by the glomerulus?

Answer 19

Protein

Question 20

Describe the process of selective reabsorption in the proximal convoluted tubule?

Answer 20

• The proximal tubule contain cells that have microvilli projecting into the lumen, giving a large surface area for absorption
• Pumps in the membrane reabsorb useful substances by active transport. All of the glucose in the filtrate is reabsorbed and most of the sodium and other mineral ions
• The total solute concentration is higher in the membrane than in the filtrate; water therefore moves from the filtrate into the cells by osmosis (not all)

Question 21

Ascending vs descending limbs in the loop of Henle

Answer 21

• descending limbs are permeable to water but not too sodium ions
• ascending limbs are permeable to sodium ions but not to water; they pump sodium ions from the filtrate into the medulla by active transport, creating a high solute concentration in the medulla
• allows for osmosis water into tissue fluid of the medulla to be reabsorbed

Question 22

Where does the highest concentration of solute occur on the loop of Henle?

Answer 22

The bottom

Question 23

Describe the juxtaglomerular-renin-angiotensinogen-angiotensin-aldosterone pathway.

Answer 23

• juxtaglomerular apparatus detects low blood pressure (dehydration)
• specialized cells within apparatus release renin
• renin converts angiotensinogen (plasma protein) into angiotensin
• angiotensin stimulates the release of aldosterone from adrenal gland and causes construction of blood vessels to increase bp
• aldosterone carried to kidneys; acts on nephrons to increase Na+ and H2O reabsorption

Question 24

What is a flame cell?

Answer 24

specialized excretory cell found in the simplest freshwater invertebrates

• connected to a duct system of pores to expel waste
• ciliated tubules filter fluids

Question 25

What is nephridia?

Answer 25

Found in some invertebrates;

Question 26

What is a malpighian tube?

Answer 26

• found in the posterior of insects
• Malpighian tubules are found in the posterior regions of insects, where they work with glands in the rectum to excrete waste and maintain osmotic balance.
• Ions are transported through active pumps found in the malpighian tubules; as the ions are secreted, water and waste are drawn to the tubules due to the change in osmotic pressure.