Homeostasis Flashcards
Hypothalamus
Controls all homeostatic processors
Negative feedback example of metabolism
- HypoT produces a release factor substance
- causes stimulation of anterior pituitary gland to produce TSH
- TSH reaches thyroid via blood
- thyroid gland stimulation = thyroxine secretion
- thyroxine increases respiration in tissues, increasing body temp
- once higher thyroxine level detected, hypoT’s release factor is inhibited so TSH release by pituitary is prevented
Blood sugar cycle negative feedback example
- ↑blood glucose
- detected by islets of Langerhans cells
- β cells secrete insulin
- more blood glucose diffuse into cells including liver an muscle
- ↓blood glucose
- detected by islets of Langerhans cells
- α cells secrete glucagon
- glycogen changed to glucose in liver
- glucose released from liver to blood
- story starts again
Ornithine cycle
Ammonia, NH3 is taken up by ornithine to help make urea
Deamination
Lowers excess AAs
AA+O2 →Keto acid+2NH3
Transamination
Keto acid’s R group is transferred to an AA
Kidney process
1) Blood from renal artery →glomerulus
2) glomerular filtrate →nephron vi ultrafiltration method
3) selective reabsorbtion in proximal tube allows all glucose and 80% water back into blood
4) urea continues through tubule →ureter
5) further reabsorbtion can occur at distal tubule
Loop of Henle
1) Na+ & Cl- from loop of Henle’s ascending limb →medulla
2) Only ions can leave ascending limb (no water). They diffuse to descending limb
3) high Na & Cl levels in medulla cause water to leave collecting duct and descending limb
4) water passes to capillary network and is reabsorbed
Distal tubule role
Maintains blood pH of ~7.4
If plasma ↓7.4:
OH- from plasma →filtrate
HCO3- from plasma →filtrate
ADH (antidiuretic drug) role in water balance (warm climate)
•HypoT IDs ↑solute concentration in plasma
•Secretes ADH to post pituitary gland
•Passes via blood to kidneys
-↑collecting ducts and distal tubules permeability so water can be reabsorbed
•Resulting urine has low water, high solutes, to balance out sweat water loss
ADH (antidiuretic drug) role in water balance (cold climate)
- HypoT IDs ↓solute concentration of plasma
- Produces less ADH
- Less ADH leaves post lobe of pituitary gland, and less reaches kidneys
- Collecting ducts and distal tubules less permeable
- Less water reabsorbtion
- Urine is of greater volume due to water content
Menstrual cycle stages
1a) FSH, follicle stimulating hormone secreted to bloodstream by pituitary gland
b) simultaneously, pit gland secretes LH (leutinising hormone) which reinforces FSH effect
2) as follicle develops, it secretes oestrogen whih stimulates endometrium development
3) oestrogen temporarily inhibits FSH
4) oestrogen’s peak occurs and results in a surge of LH with some FSH (uninhibited now)
5) LH peak →ovulation
6) follicle →corpus luteum and starts progesterone secretion
7a) progesterone keeps endometrium in place in case of fertilisation
b) progesterone inhibits FSH & LH secretion, preventing ovulation
8) no sperm →corpus luteum degenerating and progesterone ↓. Low progesterone doesn’t inhibit FSH and LH so they are secreted again
The cycle continues >.<
Kidney purpose
Filter urea from blood
Filter excess Na and H2O
Bowman’s capsule features
Contains glomeruli - capillaries with high bp
Ultrafiltration site: NaCl, urea, H2O, AAs glucose forced into nephron
Proximal convoluted tubule
Selective reabsorption site
Substances diffuse into surrounding cells and adapted for reabsorption.
Via active transport into intercellular spaces, then nearby capillaries
Result: 80-90% H2O reabsorbed back into blood
