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BIOL 260 HUMAN PHYSIOLOGY (Part IV) – Important Terms/Concepts 5/15/2008 (list NOT exhaustive)
23. ENDOCRINE CONTROL of GROWTH & METABOLISM (& Ch. 7):
Hypothalamus-Pituitary Axis: HT=CNS, Anterior pituitary (endocrine;
trophic hormones) Æ Prolactin, TSH (thyrotropin), ACTH, GH, FSH, LH.
Posterior Pituitary (neuroendocrine from HT) Æ Vasopressin (ADH),
Oxytocin. Long-Loop and Short-Loop Negative feedback. Secretion
Disorders
Æ
Primary, Secondary, diagnosis. Adrenal Gland : Adrenal
Medulla – catecholamines (EPI). Adrenal Cortex – cortisol, aldosterone,
sex hormones. HT: CRH Æ (ant pit) ACTH Æ (adr cort) CORTISOL
(Diurnal rhythms, stress, cytoplasmic receptors) – peaks late AM, low early
AM. Carrier protein in plasma = Corticosteroid Binding Globulin / CBG.
STRESS hormone: essential, protective against hypoglycemia, permissive
on glucagons and catecholamines. Anti-HypOglycemia: ↑gluconeogenesis
in liver, ↑ catab of musc prot, ↑ lipolysis,, ↓ immune, ↓Ca++ in body, brain –
mood/memory. Hypercortisolism (Cushing’s syndrome): primary (adr cort
tumor), secondary (pit tumor/ ACTH), Iatrogenic (medicinal)—muscle & fat
tissue breakdown, fat trunk and face, hyperglycemia, mood swing.
Hypocortisolism (Addison’s) = autoimmune destr’n, excess
androgen/masculinization.
THYROID: C cells Æ Calcitonin, Follicle cells Æ TH’s
[Thyroglobulin into colloid (storage) Æ iodinated = T4 Æ secreted (plasma
with TBG) Æ deiodinase in target cells to T3 (active thyroxine/TH); nuclear
receptor]. Heat, cold tolerance, mood. Thermogenic, ↑↑ metabolism (O2
consum’n; mitoch transport), permissive on GH. Myelination,
synaptogenesis. HyperTH = warm, sweaty, prot loss/weakness, exciteable
reflexes, ↑HR & SV (CO; β1 AdrR upreg’n). HypoTH = slow metab’m, cold-
intol, ↓ prot synth, accum’n polysacc/glycoprot Æ mexedima, slow child
growth, slow reflexes/fatigue, bradycardia. TSH ↑↑ Æ Goiter (or by
autoimmune TSI’s / Graves, or ↓Iodine).
Growth Hormone/GH: (Ant Pit pept; nec for child growth; TH,
insulin, sex H = permissive), adequate diet, low stress, genetics. GH/
Somatotropin = anabolic, esp in Children (GHRH↑, GHIH / somatostatin↓).
TH’s & insulin = permissive. HypoGH = dwarfism, HyperGH = gigantism,
acromegaly. GH Æ ↑bone/tissue, ↑plasma gluc, ↑ILGFs. Hypertrophy =
↑cell size; Hyperplasia = ↑ cell number. Bone growth: calcium phosphate/
hydroxyapatite (HA)Æ embeds in collagen matrix. Osteoblasts – growth;
Osteoclasts – resorption. Epiphysial plates Æ chondrocytes secrete Æ
osteoblasts/osteocytes deposit HA. GH, sex hormones.
CALCIUM BALANCE: (Ca++ Æ intracellular messenger, muscle
contraction, NT exocytosis, tight junctions, coagulation cofactor). ECF =
high/2.5mM, ICF = low/ 1µM, bone = major reservoir. Osteoclasts Æ
resorption, proteases + acid. HypoCalcemia Æ ↑ neur Na perm, depol’n,
NS hyperexc, tetany!. HyperCalcemia Æ depressed NS. Parathyroid:
PTH Æ respond/prevent hypocalcemia: ↑resorption by osteoclasts, ↑renal
reabsorption (distal nephron),
↑
renal EXCRETION of PHOSPHATE. PTH
Æ Calcitriol (Vit D3) Æ ↑↑ intestinal absorption of Ca++. Calcit made
from sun/vitD Æ made in liver + kidneys. Enhances Ca uptake in SI, renal
reabs’n, mobil’z from bone to ECF. ↑calcit Å by Prolactin, breast-feeding
women. C Cells in Thyroid Æ Calcitonin (peptide): release and action to
prevent ↑Ca++ ECF/plasma. ↓bone resorp, ↑renal excretion! Stabilize
bone loss medically. Child growth, lactating mothers. Hydroxyapatite:
Phosphate homeostasis parallels Ca++. VitD enhances SI abs’n of PO4.
PTH: PO4 excretion. Resorption > bone deposition ..Æ Osteoporosis.
Estrogen/progesterone Æ HRT (hormone replacement therapy), many side-
effects. Bisphosphonate drugs ↓osteoclast activity.
19. KIDNEY/RENAL Physiology:
salt/water or fluid/electrolyte balance. Regulate: ECF volume, Osm
(290mOsm, blood), Ion Balance (Na+, K+, Ca++), pH (H+, -HCO3, NH4+),
metabolic wastes excretion (urea, creatinin, uric acid, urobilinogen); foreign
compounds: (saccharin, benzoate), hormone producion (erythropoietin,
rennin, vitD3 conversion). Function @ 25% (huge reserve capacity!).
Kidney: nephrons in (Cortex, Medulla, Renal pelvis, ureter, bladder,
urethra). NEPHRON: glomerus/ Bowmans Capsule (renal corpuscle)
Æ proximal tubule Æ Descending loop of Henle Æ Ascending loop of
henle Æ Distal tubule -Æcollecting tubules & common collecting ducts.
Peritubular capillaries, vasa recta. Afferent/efferent arterioles bound
glomerulus on each side (Portal System!!). Distal tubule twists back
between afferent & efferent arterioles = Juxtaglomerular Apparatus.
180L/day filtered, but only 1.5L/day = excreted. Filtration (capsule; 300
mOsm plasma & filtrate), Reabsorption (bulk in prox tub; solute in Henle
loop = 100 mOSm; distal & collecting), Secretion (selective via membr
prots; distal & collecting). Urine Excretion: 1.5L/day, 50-1200 mOsm.
FILTRATION: glomerular capillaries = fenestrated – fluids/ ions
pass, cells/proteins held in. Filtr. Reg’n: Podocytes and Mesanglial
cells (cytokines/immune ) regulate capillary filtration area. Basal
lamina barrier, Bowmen’s capsul epithelium. Hydrostatic pressure >
colloid osmotic pressure Æ Filtration!! GFR = 125ml/min = 180L/day
(plasma volume = only ~3L). ↑BP Æ ↑PH Æ ↑GFR. Afferent
vasoconstr’n Æ ↑GFR; Efferent VC’n Æ↓GFR. Autoregulation: ↑BP
Æ myogenic vasoc’n (strech-sens. Channels open);
Tubuloglomerular Feedback Æ MD cells in distal tubule secrete
paracrines re: high fluid flow Æ paracrine VC’n of afferent arteriole
(JuxtaGlomerular Apparatus). Low flow: JG cells secrete Renin Æ
Aldosterone, Angiotensin (see Ch. 20). Hormones: ANG-II VC’n,
Prostaglandin VD’n; also act on podocytes & mesanglial cells.
Autonomic NS: Sympathetic NE Æ αR Æ afferent & efferent VC’n!
↓↓BP Æ symp adaptive conserv’n of BV.
REABSORPTION: >99% of the filtered 180L/day. Rapid clearing
of toxins/wastes, regulation of ions and water. Reabsorption = active
transport (water follows ion gradents, if permeable). Na+ actively
reabsorbed Na/K ATPase; glucose, AAs, Ions cotransported (2° active)
with Na+. Urea is passively concentrated in the ECF of the kidney; urea
gradient created when water and salts exit proximal tubule and urea left
behind -Æ moves down gradient out of lumen into renal ECF. Small
proteins and hormones may be filtered, by reabsorbed by transcytosis.
Saturation of transport in renal reabsorption = all protein carriers loaded,
so all excess cannot be reabsorbed, remains in lumen, and is excreted in
uring. Concentration of transported substrate at saturation = Tm =
transport maximum Plasma concentration at which Tm is reached, and
a substance (eg: glucose in diabetis mellitus) firstr appears in the urine –
Renal Threshold.
SECRETION: selectively enhances excretion of compounds (eg:
H+, K+). Eg: Probenecid competes with transporter Æ ↓ Penicillin
secr’n. EXCRETION: Glucose, amino acids, useful metabolites
reabsorbed, not excreted. Organic wastes concentrated, ions and water
variable. Clearance = (~inulin, creatinine) = of solute is # ml urine free of
solute/time. For substance freely filtered, but neither secreted nor
reabsorbed, Clearance = GFR. Clearance = Urine excretion rate
(mg/min)/plasma concentration (mg/ml plasma). Determines renal
handling of a solute.
MICTURITION: Bladder-urethra sphincter, internal sphincter =
smooth muscle of bladder, external sphincter = skeletal muscle
(somatic control; CNS tonic contraction). Micturition/urinary reflex: =
Spinal reflex: bladder fills, smooth muscle stretches Æ parasympathetic
Æ ↑ sm musc contr’n (pushes open internal sphincter); ↓motor neurons
to external sphincter Æ urination! Inhibit reflex by learned input from
brain stem & cerebral cortex to override micturition reflex.
