The countercurrent multiplier and thus reducing the

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