BIO 365S Lecture Notes - Lecture 31: Ph, Alkalosis, Urinary System
3. Acid-Base Balance
Body needs to maintain a small wiggle room for normal range of pH.
Most of the time body is dealing with acidosis situations because have much more input of H+
than base.
If buffer system not working, have ventilation (lungs, quick on/off system), but if this one is still
not working you have your kidneys (directly filters your blood, can dump directly H+ out).
1. Why is acid-base regulation critical?
• Acidosis or alkalosis causes denaturation of proteins
• Net effect:
• Acidosis (pH < 7.4)—hypoexcitability
• Alkalosis (pH > 7.4) –hyperexcitability =>Muscle tetanus
• Goal = ICF pH ~ 7.2 therefore plasma pH ~ 7.4
pH needs to be maintained because body is made up of protein, which can be denatured if pH
is wrong. Maintenance of pH is critical.
How is H+ regulated?
Primary acid input = CO2
1. Buffers
– CO2 + H2O = H2CO3 = H + HCO3
2. Respiratory Mechanisms
– Respiratory mechanisms directly deal with CO2.
3. Renal Mechanisms
– Real ehais = he first to sstes do’t ork.
4. CO2 dissolves in plasma, release H+. If try to get CO2 out too much = hyperventilation,
respiratory alkalosis (panic attacks).
CO2 can dissolve in blood, become carbonic acid, which dissociates to become bicarbonic acid
and H+.
CO2 + H20 H2CO3 H+ + HCO3-
NORMAL RATIO OF CO2 TO HCO3- IS 1:20
When CO2 increases, the formula is driven to the right, increasing the H+ and lowering the pH.
When H+ increases, the formula is driven to the left, decreasing the H+ and increasing the pH.
Chemoreceptors send signals to RCC in medulla, which can control breathing rates by
controlling breathing muscles, which eventually increase rate/depth of breathing. Directly deal
with CO2. Once deal with CO2, H+ is maintained. Buffer first deal with H+ and turn into CO2,
and then breathing system quickly increase ventilation to get rid of that CO2.
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Document Summary
Body needs to maintain a small wiggle room for normal range of ph. Most of the time body is dealing with acidosis situations because have much more input of h+ than base. Co2 + h2o = h2co3 = h + hco3: respiratory mechanisms. Respiratory mechanisms directly deal with co2: renal mechanisms. Re(cid:374)al (cid:373)e(cid:272)ha(cid:374)is(cid:373) = (cid:449)he(cid:374) first t(cid:449)o s(cid:455)ste(cid:373)s do(cid:374)"t (cid:449)ork: co2 dissolves in plasma, release h+. If try to get co2 out too much = hyperventilation, respiratory alkalosis (panic attacks). Co2 can dissolve in blood, become carbonic acid, which dissociates to become bicarbonic acid and h+. When co2 increases, the formula is driven to the right, increasing the h+ and lowering the ph. When h+ increases, the formula is driven to the left, decreasing the h+ and increasing the ph. Chemoreceptors send signals to rcc in medulla, which can control breathing rates by controlling breathing muscles, which eventually increase rate/depth of breathing.
