Urinary System: Part 3 PDF

Urinary System: Part 3 Important Endocrine and Nervous Mechanisms Anatomy & Physiology II BIOL2220 Version 1 1 The Urinary System Key Biochemical Players Physiology AD...

Urinary System: Part 3 Important Endocrine and Nervous Mechanisms Anatomy & Physiology II BIOL2220 Version 1 1 The Urinary System Key Biochemical Players Physiology ADH/AVP Vasoconstrictor which increases systemic BP, and decreases GFR Retention of Water (Only Water!) is controlled by ADH Released in response to Hypothalamic Stimulation (Dehydration) or increased AgII levels. ADH Increases the number of Aquaporins incorporated into the membrane of the Tubule Cells. –More Aquaporins=More Water Reabsorbed 2 The Urinary System Key Biochemical Players Physiology ANP It is released by atrium in response to atrial stretching due to increased blood volume ANP enhances Na+ and water losses by increasing glomerular flow (Aff. Art. VD) It also inhibits ADH secretion Thus, it promotes increased sodium excretion (natriuresis) and water excretion (diuresis) in urine 3  The Urinary System Key Biochemical Players Physiology Aldosterone Sodium Balance is largely controlled by Aldosterone: –Released in response to increased AgII levels –The net effect of Aldosterone is to make the kidneys Reabsorb Na+ (Water Follows!) and Secrete K+ into the Tubule Fluid. –Works by stimulating the Na+- K+ ATPase pump on the basolateral (backdoor pump) side of the tubule cell membranes. –Aldosterone also increases the Na+ permeability of the luminal side of the membrane. 4 The Urinary System Key Biochemical Players Physiology Angiotensin II Stimulation of aldosterone release from adrenal cortex. Stimulation of ADH/AVP release from Post Pit. Vasoconstriction of many systemic arterioles. –Increased BP Vasoconstriction of the afferent arterioles. --Decreased GFR 5 The Urinary System Key Biochemical Players Physiology Renin: Pronounced “Ree-nin” It is an enzyme that catalyzes the conversion of Angiotensinogen to AgI. Regulation of Renin Secretion: Renal Mechanism: Macula densa (content of the Na+ ion in the distal convoluted tubule) Nervous Mechanism: Sympathetic nerve stimulation of JG cells Hormonal Mechanism: 6 Epi, Prostaglandin stimulation of JG cells The Urinary System Key Players: Nervous Physiology Innervation Nerves from the renal plexus (sympathetic nerves) of the autonomic nervous system enter kidney at the hilumàinnervate smooth muscle of afferent arteriolesàregulates blood pressure & flow throughout kidney Effect: (1) Reduce the GFR and through contracting (VC) the afferent arteriole (α receptor) (2) Increase the Na+ reabsorption in the proximal tubules (β receptor) (3) Increase the release of renin (β receptor) 7 The Urinary System Operation of the Nephron Physiology-Nephron Overview EFF ART ▲ BP ▲ RAS ADH Aldo TGF PTH CT Capsule & JGA Glomerulus PCT DCT (GFR) Na+ Concentration in K+ & H+ U DCT Fluid, SNS, R Prostaglandins I H2O NaCl N AFF ART E VC: Ag II, NE, UREA ADH/AVP, Adenosine VD: ANP, NO TO RESORB: LOOP C Na+ Na+ A K+ Ca++ Glu L H2 O H2O Y The AA Countercurrent C Multiplier E S 1 PERITUBULAR CAPILLARIES & 8 VASA RECTA The Urinary System Urination/Micturition: Overview Neurological Players in Urination/Micturition Flow in the formation and releasing of urine: 1. Glomerulus (Blood) 1 2 3 2. Glomerular capsule (Filtrate) PSNS SNS Somatic (Vol) Motor 3. PCT (Filtrate) 4. DL (Filtrate) 5. Loop of Henle (Filtrate) 6. AL (Filtrate) 7. DCT (Filtrate) 8. Collecting duct (Filtrate/Urine) Two things: SNS Voluntary #1. PSNS Normally 9. Minor calyx (Urine) Normally Inhibits Motor System 10. Major calyx (Urine) Maintains Bladder Normally 11. Renal pelvis (Urine) Internal Contraction, Maintains 12. Ureter (Urine) Sphincter tone, so it must to External so it must be “quiet” during Sphincter 13. Urinary bladder (Urine) “quiet” during urination Tone, so it 14. Internal sphincter (Sm. Muscle) urination must be 15. Urethra (Urine) #2. PSNS “quiet” causes the 16. External sphincter (Sk. Muscle) bladder to during urination contract during urination. 9 The Urinary System Urination/Micturition: Neurologic Reflex Step in Urination/Micturition 1.Bladder filled to about 200 ml 2.Afferent NS (sensory) stimulated Rest Urination 3.Parasympathetic response is Bladder Relaxed Contracted both + and -, but Sympathetic SNS+ PSNS + is just – to bladder (Detrusor-smooth muscle) 4.Signal to bladder to Contract SNS- Detrusor (smooth) muscle Internal Sphincter Contracted Relaxed (PSNS) (smooth muscle) PSNS + PSNS – 5.Relax internal sphincter 6.Voluntary control over external sphincter is all that External Sphincter Contracted Relaxed holds back urine flow at this (skeletal muscle) Somatic Motor + Somatic Motor - point 7.Pons gets signal that bladder is stretched 8.“Is urination OK” now? 9.inappropriate—then steady train of nerves from brainstem to external sphincter—keep tight, urine is held 10.Appropriate—then impulses Note: inhibited, sphincter relaxed Sympathetic promotes urinary retention 11.Detrusor muscle contracts, Bladder is compressed Parasympathetic promotes urinary elimination 12.Urine released 10  The Urinary System Urinalysis-Brief Overview FYI Urinanalysis: Definitions Oligouria – excrete < 300 ml/day. Might be “physiological” as in hypotension or hypovolemia where we compensate, but more often due to renal disease or obstructive nephropathy. Polyuria – persistent, large increase in urine output usually associated with nocturia. Must distinguish from higher frequency of small volumes of urine. Usually due to hysterical intake of water, increased excretion of solute (e.g. hyperglycemia/glycosuria), defect in concentrating ability or ADH failure. Osmolality – useful for determining the concentration of urine. Urinary pH – mainly for acidosis/alkalosis determination Urinalysis: Appearance Blood (hematuria) Check with Dipstix (blood, sugar, protein). Simple, cheap, routine, easy to re-check and unlikely to make mistakes. But not quantifiable, just checks for presence. Concentrated – can have a dark/smoky color. Dilute-can be almost clear. Discoloration may also be due to: Jaundice, hemoglobinuria. Drugs (e.g. antibiotics). Food (e.g. beets). Disease (e.g. porphyria – “Madness of King George” where his urine was purple) Urinalysis: Microscopy Clean, mid-stream sample needed. Things to Look for: White cells 10 or more WBC’s per cm3 indicates inflammation (e.g. suspect urinary tract infection (UTI)) Red cells – often accompanied by pain. Casts Cylindrical bodies made from precipitated proteins, often seen normally after exercise. Red cell casts (even one) -->suspect disease or injury. Bacteria – allows you to decide if antibiotic therapy is appropriate. 11 The Urinary System Renal Analysis: Blood Testing FYI If there is poor renal function, you might expect any one of: Hyperkalemia Decreased bicarbonate – poor filtration or acid/base disorders Elevated urea (BUN) Elevated creatinine Elevated uric acid Hypocalcemia Hyperphosphatemia pH changes– acid/base disorders pCO2 away from 40mmHg – acid/base disorders Hypernatremia These are the most common plasma constituents we would measure if we were analyzing renal function in the lab. Cheap, easy, routinely done, and provide a large amount of information quickly. 12