Hormones, Homeostasis, and the Kidney Flashcards
What are the three forms of nitrogenous waste?
Urea, ammonia, and uric acid.
Differentiate between osmoregulators and osmoconformers.
- Osmoregulators maintain a constant internal solute concentration.
- Osmoconformers tend to have the same internal solute concentration as their environment
Define bowman’s capsule.
Highly porous wall which collects the filtrate.
Define glomerulus.
Knot-like capillary bed where high pressure filtration takes place (site of ultrafiltration).
Define proximal convoluted tubule.
Twisted section of nephron where water, nutrients, and salts are reabsorbed into the blood. Contains many mitochondria and microvilli.
Define loop of henle.
Hairpin shaped tube with a descending and ascending limb. Osmoregulation occurs here.
Define distal convoluted tubule.
Twisted section of the nephron where water and salts are reabsorbed back into the blood. Contains many mitochondria and microvilli.
Define collecting duct.
A slightly wider tube that carries the filtrate to the renal pelvis.
How does the bowman’s capsule do ultrafiltration?
- 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.
Differentiate between the afferent and efferent arteriole.
Afferent: blood coming into glomerulus.
Efferent: blood leaving glomerulus.
Where does selective reabsorption occur? What is reabsorbed?
- Proximal convoluted tube
- Ions, water, glucose
Define osmoregulation.
Maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations.
Distinguish between the ascending and descending parts of the Loop of Henle.
- Descending limb reabsorbs water, increasing osmolarity
- Ascending absorbs sodium ions, lowering overall osmolarity compared to before entering the loop.
What is the role of the collecting duct in osmoregulation.
Determines how much water is reabsorbed after the loop of Henle, as regulated by ADH.
Define hormones.
Regulatory substances produced to stimulate specific cells or tissues into action.
How is homeostasis based on a system of negative feedback?
Uses hormones to raise or lower conditions, making it negative feedback.
What two hormones are secreted by the pancreas?
Insulin and glucagon.
Outline the use of insulin.
- Produced by beta-cells in pancreas
- secreted to skeletal muscle and liver
- converts glucose to glycogen to reduce blood sugar
Outline the use of glucagon.
- produced by alpha-cells in pancreas
- secreted to hepatocytes
- converts glycogen into glucose to raise blood sugar
Thyroxin: What secretes it? What does it act on? What does it regulate? How does it act?
- Thyroid gland
- all cells in body
- body. temperature
- Leads to more mRNA->more proteins->increased metabolism->more heat->increase temp.
Leptin: What secretes it? What does it act on? What does it regulate? How does it act?
- Adipose (fat) tissue
- hypothalamus
- appetite
- Acts as suppressant when there are fat reserves and as exponent for eating when there isn’t.
melatonin: What secretes it? What does it act on? What does it regulate? How does it act?
- Pineal gland
- Suprachiasmatic nuclei (SCN)
- sleep
- Promotes sleep through lowering body temp. and respiration rate
Explain the relationship between the hypothalamus and pituitary gland.
- 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.
