How the renal compensatory mechanism works to return the body to homeostasis

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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, a measure of acidity or alkalinity. Here’s how the respiratory and renal systems work to achieve homeostasis in different scenarios:

8. Renal Compensation in Metabolic Acidosis:

  • Problem: Metabolic processes can produce excess acid, lowering blood pH.
  • Solution: The kidneys kick in!
  • Excreted: The kidneys excrete hydrogen ions (H+) in the form of ammonium (NH4+).
  • Reabsorbed: The kidneys reabsorb bicarbonate (HCO3-), preventing its loss in the urine. This helps retain alkaline reserves in the blood.
  • Net Effect: By eliminating excess acid and conserving bicarbonate, the kidneys help raise blood pH towards normal levels.

9. Respiratory Acidosis:

  • Cause: Occurs when the respiratory system fails to eliminate enough carbon dioxide (CO2) – a major acid byproduct.
  • Example: In Chronic Obstructive Pulmonary Disease (COPD), narrowed airways hinder CO2 exhalation.
  • Breathing Rate: The body attempts to compensate by increasing the breathing rate (tachypnea) to expel more CO2.
  • pCO2: pCO2 (partial pressure of CO2) increases due to CO2 buildup in the blood.
  • H+ concentration: Increased CO2 reacts with water to form carbonic acid (H2CO3), which dissociates into bicarbonate (HCO3-) and hydrogen ions (H+), leading to a rise in H+ concentration and lowered blood pH.

10. Sally’s Breath-Holding Tantrum:

  • Feedback Mechanism: The chemoreceptor reflex is the key player here.
  • Anatomical Structures: Chemoreceptors are specialized cells located in the carotid bodies (near the neck) and aortic bodies (near the chest).
  • CO2’s Influence: When pCO2 increases due to Sally holding her breath, chemoreceptors sense the rise in acidity.
  • Triggering Respiration: This triggers signals to the brainstem, the control center for breathing. These signals override the voluntary control of breathing and stimulate involuntary diaphragm contractions, forcing Sally to inhale despite her tantrum.

Summary Table:

Condition Problem Compensatory Mechanism Excreted Reabsorbed Net Effect pCO2 H+ pH
Metabolic Acidosis Excess Acid Renal H+ HCO3- Increased pH Normal Increased Decreased
Respiratory Acidosis CO2 Retention Respiratory (Increased Breathing) None None Improved CO2 Elimination (goal not fully achieved) Increased Increased Decreased

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