Hormones, Homeostasis, and the Kidney

Question 1

What are the three forms of nitrogenous waste?

Answer 1

Urea, ammonia, and uric acid.

Question 2

Differentiate between osmoregulators and osmoconformers.

Answer 2

• Osmoregulators maintain a constant internal solute concentration.
• Osmoconformers tend to have the same internal solute concentration as their environment

Question 3

Define bowman’s capsule.

Answer 3

Highly porous wall which collects the filtrate.

Question 4

Define glomerulus.

Answer 4

Knot-like capillary bed where high pressure filtration takes place (site of ultrafiltration).

Question 5

Define proximal convoluted tubule.

Answer 5

Twisted section of nephron where water, nutrients, and salts are reabsorbed into the blood. Contains many mitochondria and microvilli.

Question 6

Define loop of henle.

Answer 6

Hairpin shaped tube with a descending and ascending limb. Osmoregulation occurs here.

Question 7

Define distal convoluted tubule.

Answer 7

Twisted section of the nephron where water and salts are reabsorbed back into the blood. Contains many mitochondria and microvilli.

Question 8

Define collecting duct.

Answer 8

A slightly wider tube that carries the filtrate to the renal pelvis.

Question 9

How does the bowman’s capsule do ultrafiltration?

Answer 9

• Fenestrated wall of capillary allows fluid to escape but not blood cells.
• Basement membrane covers and supports walls of capillaries. Forms a mesh which prevents plasma proteins from being filtered out.
• Podocytes form inner wall of bowman’s capsule. Have extensions wrapping around capillaries and glomerulus called foot processes. Prevent small molecules from being filtered out.

Question 10

Differentiate between the afferent and efferent arteriole.

Answer 10

Afferent: blood coming into glomerulus.
Efferent: blood leaving glomerulus.

Question 11

Where does selective reabsorption occur? What is reabsorbed?

Answer 11

• Proximal convoluted tube

- Ions, water, glucose

Question 12

Define osmoregulation.

Answer 12

Maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations.

Question 13

Distinguish between the ascending and descending parts of the Loop of Henle.

Answer 13

• Descending limb reabsorbs water, increasing osmolarity

- Ascending absorbs sodium ions, lowering overall osmolarity compared to before entering the loop.

Question 14

What is the role of the collecting duct in osmoregulation.

Answer 14

Determines how much water is reabsorbed after the loop of Henle, as regulated by ADH.

Question 15

Define hormones.

Answer 15

Regulatory substances produced to stimulate specific cells or tissues into action.

Question 16

How is homeostasis based on a system of negative feedback?

Answer 16

Uses hormones to raise or lower conditions, making it negative feedback.

Question 17

What two hormones are secreted by the pancreas?

Answer 17

Insulin and glucagon.

Question 18

Outline the use of insulin.

Answer 18

• Produced by beta-cells in pancreas
• secreted to skeletal muscle and liver
• converts glucose to glycogen to reduce blood sugar

Question 19

Outline the use of glucagon.

Answer 19

• produced by alpha-cells in pancreas
• secreted to hepatocytes
• converts glycogen into glucose to raise blood sugar

Question 20

Thyroxin: What secretes it? What does it act on? What does it regulate? How does it act?

Answer 20

• Thyroid gland
• all cells in body
• body. temperature
• Leads to more mRNA->more proteins->increased metabolism->more heat->increase temp.

Question 21

Leptin: What secretes it? What does it act on? What does it regulate? How does it act?

Answer 21

• Adipose (fat) tissue
• hypothalamus
• appetite
• Acts as suppressant when there are fat reserves and as exponent for eating when there isn’t.

Question 22

melatonin: What secretes it? What does it act on? What does it regulate? How does it act?

Answer 22

• Pineal gland
• Suprachiasmatic nuclei (SCN)
• sleep
• Promotes sleep through lowering body temp. and respiration rate

Question 23

Explain the relationship between the hypothalamus and pituitary gland.

Answer 23

• Hypothalamus controls the release of hormones in the pituitary and links the nervous system to the endocrine system through it
• Hypothalamus secretes releasing factors, which stimulate secretion of anterior pituitary gland’s hormones. Carried to pituitary gland from portal vein.
• Impulses sent to pituitary by neurosecretory cells.