pH and Buffers

at
Categories
Tags

 

During respiratory alkalosis, explain how the renal compensatory mechanism works to return the body to homeostasis. Be sure to indicate which substances are excreted AND reabsorbed from the body. For example, does H+ concentration increase or decrease? Does HCO3 reabsorption increase or decrease? Does the pH increase or decrease? 8. During metabolic acidosis, explain how the respiratory compensatory mechanism works to return the body to homeostasis. Be sure to indicate which substance is removed from the body. For example, does H+ concentration increase or decrease? Does CO2 loss increase or decrease? Does the pH increase or decrease? 9. Explain how respiratory acidosis occurs. For example, how is the respiratory system affected by a patient with COPD? What happens to the breathing rate? Does pCO2 increase or decrease? Does H+ concentration increase or decrease? Does the pH increase or decrease? 10. 3-year-old Sally decided to throw a temper tantrum, holding her breath, and stomping her feet. However, it is known that she can only hold her breath for a limited time before she will involuntarily begin to breathe again. Describe the feedback mechanism and anatomical structure that initiates involuntary breathing. Include how an increased level of CO2 affects this mechanism. For example, does pCO2 increase or decrease? Does pO2 increase or decrease? Does H+ concentration increase or decrease? What triggers Sallys respiration?(No references needed)

Sample Solution

The body tightly regulates blood pH through a complex interplay between the respiratory and renal systems. Let’s break down how these systems work in different scenarios:

8. Renal Compensation in Metabolic Acidosis:

  • Problem: Increased H+ concentration due to metabolic processes (e.g., diabetic ketoacidosis).
  • Goal: Excrete excess H+ and restore blood pH.
  • Mechanism: Kidneys:
    • Increase H+ excretion: Kidneys secrete more H+ ions along with bicarbonate (HCO3-).
    • Reabsorb HCO3-: Kidneys reabsorb filtered HCO3- back into the bloodstream, preventing its loss and preserving its buffering capacity.
  • Net effect: Excreted H+ lowers blood H+ concentration, and retained HCO3- helps buffer remaining H+, raising blood pH towards normal.

9. Respiratory Acidosis:

  • Cause: Impaired gas exchange in the lungs, leading to CO2 retention.
  • Problem: Increased CO2 (pCO2) leads to formation of more carbonic acid (H2CO3), lowering blood pH (respiratory acidosis).
  • Mechanism: Respiratory system:
    • Increase ventilation rate and depth: This blows off more CO2, lowering pCO2 and carbonic acid formation.
  • Net effect: Decreased pCO2 reduces carbonic acid, raising blood pH towards normal.

Example: COPD (Chronic Obstructive Pulmonary Disease):

  • In COPD, damaged airways and lung tissue hinder CO2 removal.
  • Breathing rate increases: This attempts to compensate for the inefficiency of gas exchange.
  • pCO2 increases: Due to impaired CO2 removal, pCO2 rises.
  • H+ concentration increases: As pCO2 rises, more carbonic acid forms, releasing H+ ions and lowering blood pH (respiratory acidosis).

10. Sally’s Breath-Holding Tantrum:

  • Feedback mechanism: Chemoreceptors.
    • These are specialized cells located in the brainstem and the carotid bodies near the aorta.
    • They sense changes in blood pH, pCO2, and oxygen (pO2) levels.
  • Trigger for involuntary breathing:
    • Increased pCO2: As Sally holds her breath, pCO2 rises in the blood.
    • Chemoreceptors detect the rising pCO2 as the primary trigger for involuntary breathing to resume.
    • Decreased pO2: This plays a secondary role. It dips slightly during breath-holding but is not the main driver for immediate breathing resumption.
    • H+ concentration: This might rise slightly due to CO2 buildup, but the effect is minor compared to pCO2’s direct impact.

In conclusion:

  • The kidneys and respiratory system work together to maintain blood pH balance.
  • Renal compensation focuses on excreting excess acid and conserving buffers.
  • Respiratory compensation adjusts breathing rate and depth to regulate CO2 levels.
  • Chemoreceptors primarily sense pCO2 changes to trigger involuntary breathing and maintain homeostasis.

This question has been answered.

Get Answer