Renal Acid Base and Micturition

What is normal blood pH?

7.4

What is the immediate regulation of acid-base balance?

intra/extracellular buffers

What is the within minutes regulation of acid-base balance?

respiratory system

What is the within days regulation of acid-base balance?

kidney

What is the normal goal of acid-base regulation?

prevention of excess acid-base build up

Out of the three regulation pathways, which ones are simply able to stabilize the acid-base balance? Not actually excrete acid.

intra/cellular buffers and respiratory system

Out of the three regulation pathways, which one is able to excrete acid to regulate the acid-base balance?

kidneys excrete excess acid (H+) and maintain plasma bicarb levels (reabsorb or excrete)

In pathological conditions, how does circulating volume regulate acid base balance?

dehydration decreases volume causing an increase in bicarbonate resorption

In pathological conditions, how does aldosterone regulate acid base balance?

stimulates H+/ATPase in collecting tubule

In pathological conditions, how does plasma potassium regulate acid base balance?

a decrease extracellularly causes an intracellular acidosis

What are the three things the kidneys can do to regulate acid-base balance?

secrete acid (H+), reabsorb filtered bicarbonate, produce new bicarbonate

What are the key locations of acid-base regulation?

proximal tubule and collecting duct

How does carbonic anhydrase help the kidneys reabsorb filtered bicarb and secrete acid efficiently?

makes H+ and HCO3- readily available

How does tubular transporters help the kidneys reabsorb filtered bicarb and secrete acid efficiently?

efficiently moves ions around

How do buffers help the kidneys reabsorb filtered bicarb and secrete acid efficiently?

trap H+ and minimize ion increases in tubular fluid

How is H+ secretion regulated in the proximal tubule, thick loop of henle, and collecting duct? (distal not included)

Na+/H+ exchager, H+ ATPase pump, H+/K+ ATPase pump

What is renal net acid excretion (NAE)?

intracellular formation of new bicarbonate and it’s transport into the interstitium

What is NAE determined by?

amount of urine acid and ammonium concentration (both acids) minus the total urine bicarbonate concentration

Where does most acid secretion occur?

proximal tubule and thick loop of Henle

What generates the largest component of NAE and new bicarbonante?

renal ammonia metabolism

What is ammoniagensis?

glutamate is metabolized to NH3 and H+ and new bicarbonate in the proximal tubule

What are the three ways to buffer?

HCO3-, HPO42-, NH3

Proximal tubule absorbs ___% of HCO3. ____ capacity but _____ low gradient

80%, high but low

Since the collecting duct determines final pH, ____ capacity but ___ gradient

low but high

What is the rule of thumb for compensation for respiratory acid/base disorders?

plasma bicarbonate doesn’t increase (3.5) due to elevation in PCO2 as much as it can decrease (5) due to decline in PCO2

What is the detrusor muscle?

bladder smooth muscle that contracts all at once to facilitate bladder emptying

What is the internal sphincter of the bladder?

smooth muscle that prevents emptying until pressure reaches critical threshold

What is the external sphincter of the bladder?

skeletal muscle that can prevent urination in the face of involuntary control indicating urination

What is the parasympathetic innervation contracting the detrusor muscle to facilitate voiding?

pelvic nerve

What is the sympathetic innervation relaxing the detrusor muscle to facilitate filling?

hypogastric nerve

What does motor innervation to the external sphincter?

pudendal nerve

What is the micturition reflex for bladder filling?

micturition contractions build up as sensory stretch receptors are activated by increased fill causing contraction of bladder outlet and inhibition of detrusor and the contraction of external sphincter to prevent urination

What is the micturition reflex for bladder voiding?

once powerful enough pudendal nerve will inhibit external sphincter and parasympathetic is stimulated to cause sustained detrusor contraction

What is the micturition cycle?

progressive and rapid increase in pressure, period of sustained pressure, and return to baseline

What is the facilitatory and inhibitory center allowing to prevent micturition when needed or facilitate when desired?

brainstem

What is the primary inhibitory center allowing to prevent micturition when needed?

cerebral cortex