diving response 2

Question 1

what is the main purpose of the diving response

Answer 1

preserving life

Question 2

Apnea time depends on:

Answer 2

1. Physiological response to hypercapnia and hypoxia
2. Intensity of metabolism (larger activity of the anaerobic and
   reduced aerobic metabolism)
3. Capacities for O2 and CO2 (TLC, training, hyperventilation)
4. Psychological tolerability to hypercapnia and hypoxia

Question 3

What major physiological challenges occur during breath-hold or deep diving?

Answer 3

Hypoxia & hypercapnia response:
 – PaO₂ drops to 20–30 mmHg
 – SaO₂ falls to ~50%
 – PaCO₂ rises to 55+ mmHg

• Extreme hydrostatic pressure:
   – Risk of barotrauma (descent & ascent)
   – Pulmonary edema and alveolar hemorrhage
• Increased gas uptake / nitrogen effects:
   – Nitrogen narcosis
   – Decompression sickness (requires deco stops)

Question 4

What are the metabolic challenges and compensatory responses during a breath-hold?

Answer 4

• Peripheral vasoconstriction mainly in skin and skeletal muscle to reduce metabolic oxygen demand
• Liver blood flow is maintained
• Blood is preferentially redirected to the brain to preserve oxygen supp

Question 5

What psychological factors affect breath-hold performance?

Answer 5

• Physical and psychological responses are closely linked
• Staying calm reduces sympathetic activation and conserves oxygen
• Self-awareness of limits helps safely suppress the urge to breathe as CO₂ rises

Question 6

5 mechanissms

Answer 6

1. Changes of cardiac rhythm (bradycardia)
2. Peripheral vasoconstriction and redistribution of blood
   to the central blood reservoir
3. Arterial pressure alterations
4. Reduction of cardiac output
5. Contraction of the spleen

Question 7

What cardiac rhythm changes occur during the diving response?

Answer 7

• Bradycardia is the primary mechanism
• Begins with anticipatory tachycardia from stress, lung stretch receptors, or hyperventilation
• Parasympathetic activation slows the SA node
   – Triggered by cold water on the face (trigeminal nerve)
   – Increased venous return → distention of heart chambers
• Can lead to arrhythmias such as bradyarrhythmias and occasional extra beats

Question 8

What happens during peripheral vasoconstriction in the diving response?

Answer 8

Sympathetic activation causes strong vasoconstriction in skin and peripheral tissues
* Peripheral blood flow decreases, forcing those tissues into anaerobic metabolism → lactate rises
* Blood is centralized to vital organs, especially the brain and heart
* Cerebral blood flow can increase by up to 100% through the MCA

Question 9

How does the diving response affect arterial blood pressure?

Answer 9

• Peripheral vasoconstriction ↑ total peripheral resistance → raises arterial blood pressure
• Involuntary breathing contractions during long breath-holds cause large swings in BP (pressure spikes and drops)

Question 10

: Why does cardiac output decrease during a maximal breath-hold?

Answer 10

• The hemodynamics resemble phase II of the Valsalva maneuver
• High lung volumes compress the heart and great vessels
• This reduces venous return → ventricular filling ↓ → cardiac output

Question 11

Q: What is the role of spleen contraction during the diving response?

Answer 11

The spleen acts as a blood reservoir (RBCs, WBCs, platelets) in many mammals
* Exercise and diving trigger spleen contraction
* Adrenergic stimulation (α1) causes the spleen to contract
* Result: extra red blood cells are released into circulation, boosting oxygen-carrying capacity