Metabolism Flashcards
Nutrient Metabolism in Mammals
Both growth hormone and GCs act synergistically w epinephrine to enhance epinephrine effect on lipid breakdown
Several hormones such as growth hormone, thyroid hormone and androgens are important in growth of young b/c they promote formation of proteins
Vasopressin
Salt & Water Balance
peptide neurohormone that stim the conservation of water
Aldosterone
Salt & Water Balance
steroid hormone that stim the excretion of K+ and conservation of Na+
The renin–angiotensin–aldosterone system
maintain blood volume and blood pressure
Corrects low extracellular fluid volume and low blood pressure
Renin initiates the steps that lead to the production of angiotensin II from angiotensin I, which:
- increase blood volume and pressure
- stim aldosterone secretion from adrenal cortex
- constrict arterioles, promote thirst, vasopressin secretion
Juxtaglomerular cells secrete renin in response to reduced stretch of afferent arteriole wall (which results from low blood pressure) and to sympathetic stimulation.
Atrial natriuretic peptide (ANP)
maintain blood volume and blood pressure
Corrects high extracellular fluid volume and high blood pressure
Specialized muscle cells in atria of the heart secrete ANP when they are stretched
ANP:
- inhibits reabsorption of Na+ at the nephron
- inhibits secretion of vasopressin and renin to reduce extracellular fluid volume and blood pressure
Arginine vasopressin (AVP) (conserve water)
AVP stim incorporation of AQP-2 channels into apical membranes of epithelial cells in collecting duct of nephron, resulting in return of water to extracellular fluid
1) AVP bind to receptors in collecting duct
2) Stim 2nd messenger (cAMP) which activates PKA—shuttle storage vesicles
3) Storage vesicles fuse w apical membrane to incorp AQP-2 channels
4) Facilitate movement of water from urine thru AQP-2 channels into collecting duct and extracellular fluid thru AQP-3
PTH (peptide)
Calcium Metabolism
Secreted by chief cells of the parathyroid glands when extracellular Ca2+ is low
PTH stimulates cells in the nephron of the kidney to:
- reabsorb Ca2+ and secrete phosphate
- increase the conversation of inactive vitamin D to active vitamin D
PTH stimulate bone reabsorption
All functions contribute to increase Ca2+ in the extracellular fluid (blood)
Active vitamin D
Calcium Metabolism
Formed when extracellular Ca2+ is low
Is a steroid, binds to intracellular receptors to influence genes transcription in target tissues
An active vitamin D:
- promotes absorption of dietary Ca2+ across the intestinal epithelium
- resorption of the bone
- reabsorption of both Ca2+ and phosphate in the nephron
Increase Ca2+ and phosphate in the extracellular fluid
Calcitonin (peptide)
Calcium Metabolism
Targets osteoclasis in bone to inhibit bone reabsorption
At the kidney nephron, calcitonin increases the excretion of calcium and phosphate ions
These actions decrease Ca2+ and phosphate in the extracellular fluid
Hemimetabolous
Insect Metamorphosis
gradual or partial metamorphosis
- cockroaches
Holometabolas
Insect Metamorphosis
complete metamorphosis
- butterflies, moths
PTTH
Neuroendocrine cells secrete PTTH =stimulate secretion of ecdysone from prothoracic glands
Ecdysone is converted to 20-hydroxyecdysone (20E) by peripheral activation → stimulates the epidermis to secrete enzymes required for molting → new cuticle
Cuticle Shedding
- PETH/ETH
- JH
- ecdysone
- bursicon
Under control of PETH and ETH, insect performs stereotyped muscle contractions in order to shed old cuticle
Nonneural endocrine cells in the corpora allata secrete JH which prevents metamorphosis into the adult form (maintain immature characteristics—promotes formation of larval and nymphal structures)
During last larva/nymph instar, corpora allata inactive and stop releasing JH
At end of pupation, ecdysone secreted again, converted to 20E, triggers metamorphosis into adult form
Relative amounts of JH and 20E in hemolymph determine whether the epidermis will produce juvenile, pupal, or adult structures
After ecdysis, new cuticle expands and bursicon promotes hardening and darkening
In adults, JH functions as a gonadotropin:
Insects
Stim production of sex attractant pheromones
Stim secretion of ecdysone, which promote incorporate of yolk into eggs
