1. What happened to HR when the subject held their breath (near the end of breat
ID: 213763 • Letter: 1
Question
1. What happened to HR when the subject held their breath (near the end of breath hold)?
2. Assuming this is a sympathetic nervous system effect on the heart, explain how this response was triggered and why.
3. The rate of color change in the beakers is proportional to which physiological variable in the subject?
4. People who hyperventilate my get dizzy due to cerebral vasoconstriction, causing anxiety and further hyperventilation. Such people are sometimes urged to breathe into a paper bag. What good would this do? Explain the physiological mechanisms involved.
5. Explain the difference between a respiratory and a metabolic acidosis.
Explanation / Answer
Answer 1)
When one tries to breathe out hard against a closed airway, the pressure inside the chest rises. This prevents venous blood returning to the heart normally, so the heart receives less blood than normal. As a result, to maintain the output of blood, the heart beats faster.
Then, as the pressure is released, there is a rush of pent-up blood back to the heart which causes a reflex slowing of the heart rate for a few seconds until the pressures all normalise.
But in general holding your breath for short time will not affect the heart rate more.
Answer 2)
When a person’s face enters water, they usually enter a state in which the body attempts to conserve oxygen. This is known as the mammalian diving reflex. This conservation of oxygen is done via the activation of the parasympathetic nervous system from nerves on your face and causes bradycardia.The diving reflex stimulates peripheral constriction of the blood vessels in the outer extremities of your body. This will prevent blood circulation to non-vital areas while maximizing the supply of oxygen to vital organs, such as the brain. The diving reflex is sometimes activated to treat ventricular tachycardia, a type of increased rhythm of your heart.
Answer 3)
The rate of color change in the beakers is proportional to light. Some reagents are light sensitive, when they come in contact with light or dark, color of the sample changes.
Answer 4)
Breathing into a paper bag would force expired CO2 back into the hyperventilated person. During hyperventilation the person has a high pH value (respiratory alkalosis) that is ultimately causing the dizziness. Rebreathing exhaled CO2 would drive the equation to the right, resulting in a rise in hydrogen ion concentration and a fall in pH. In this way the normal pH level is restored, removing the dizziness and hopefully, the anxiety.
Answer 5)
Respiratory acidosis:
a- Associated with respiration.
b-Occurs when the lungs fail to remove excess carbon dioxide from our bloodstream during the process of respiration.
c- Impairment of diffusion of CO2 across alveolar membrane, obstruction to escape of CO2 from alveoli, insufficient pulmonary blood flow.
Metabolic acidosis:
a-Associated with metabolism.
b- Metabolic acidosis occurs as the results of disruptions to the bicarbonate and carbonic acid components of the chemical buffers.
c-Abnormal increase in anions due to endogenous production of acid ions, ingestion of acidifying salts, and renal insufficiency.
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