the countercurrent multiplier and thus reducing the osmotic gradient in medulla and making the collecting duct unable to reabsorb as much water as usual o Ex: furosemide (Lasix) ° ° Renal cleanance: Renal clearance- the volume of blood plasma from which a particular waste is completely removed in 1 minute o Glomerular filtration rate + amount added by tubular secretion – amount removed by tubular reabsorption = renal clearance U (urea concentration in urine)= 6.0 mg/mL V (rate of urine output)= 2 mL/min P (urea concentration in the plasma)= 0.2 mg/mL Renal clearance (C)= UV/P °
° Glomerular filtration rate: Requires a substance that the renal tubule does not reabsorb or secrete, such as inulin or creatinine o Some of the urea in the urine is secreted by renal tubule, not filtered by the glomerulus o Much of the urea filtered by the glomerulus is reabsorbed by the tubules o GFR is equal to the renal clearance GFR=UV/P Solute is reabsorbed by the renal tubules will have a renal clearance less than GFR Solute is secreted by the renal tubules will have a renal clearance greater than the GFR ° ° Urination: Detrusor muscle- the muscle of the bladder Rugae- conspicuous wrinkles in the relaxed bladder Trigone- triangular area marked by two ureters and the urethra Micturation- the act of urinating Micturation reflex- controls micturation Involuntary micturation reflex: o 1. Stretch receptors detect filling of bladder, transmit afferent signal to spinal cord o 2. Signals return to bladder from spinal cord segments via parasympathetic fibers in the pelvic nerve o 3. Efferent signals excite detrusor muscle o 4. Efferent signals relax internal urethral sphincter. Urine is involuntarily voided if not inhibited by the brain Voluntary control: o 5. For voluntary control, micturition center in pons receives signals from stretch receptors o 6. If it is timely to urinate, pons return signals to spinal interneurons that excite detrusor muscle and relax internal urethral sphincter. Urine is voided o 7. If it is untimely to urinate, signals from pons excite spinal interneurons that keep external urethral sphincter contracted. Urine is retained in the bladder
o 8. If it is timely to urinate, signals from the poins cease and external urethral spinchter relaxes. Urine is voided. Valsalva maneuver- used to compress the bladder and excite the stretch receptors early, thereby getting the reflex started. ° °
Anat. & Phys. Study Guide: Exam #2 Chapter 24- Water, Electrolyte, and Acid-Base Balance ° Fluid compartments: Fluid compartments- areas separated by selectively permeable membranes and differing from each other in chemical composition o 65% intracellular fluid o 35% extracellular fluid 25% tissue (interstitial) fluid 8% blood plasma and lymph 2% transcellular fluid (cerebrospinal synovial, peritoneal, pleural, and pericardial fluids: vitreous and aqueous humors of the eye; bile; and fluid in the digestive, urinary, and respiratory tracts o exchanged between compartments by means of capillary walls and plasma membranes o
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- Nephron, Glomerulus