Question

select all the correct answers.
jon likes hiking. he observes that whenever he hikes up a hill, he breathes heavier than when he is on flat ground. which two statements explain why this happens?
sensors in the brain detect a lack of oxygen.
the muscles in his body need more energy and therefore more oxygen.
the body has too little carbon dioxide to maintain function.
the body is using carbon dioxide instead of oxygen to make energy.
blood pressure has decreased, so less blood is being pumped to the muscles.

Explanation:

1. Analyzing "Sensors in the brain detect a lack of oxygen": When hiking uphill, the body's oxygen demand increases. If oxygen levels drop, brain sensors detect this, triggering heavier breathing to get more oxygen. This is a valid explanation.
2. Analyzing "The muscles in his body need more energy and therefore more oxygen": Hiking uphill is more strenuous, so muscles work harder, needing more energy (produced via cellular respiration which requires oxygen), so more oxygen is needed, leading to heavier breathing. This is correct.
3. Analyzing "The body has too little carbon dioxide to maintain function": The body produces more CO₂ during strenuous activity, and CO₂ levels don't become too low; in fact, excess CO₂ is a trigger for breathing, so this is incorrect.
4. Analyzing "The body is using carbon dioxide instead of oxygen to make energy": The body uses oxygen (not CO₂) in cellular respiration to make energy, so this is incorrect.
5. Analyzing "Blood pressure has decreased, so less blood is being pumped to the muscles": During exercise like hiking uphill, blood pressure typically increases to supply more blood to muscles, so this is incorrect.

Answer:

• Sensors in the brain detect a lack of oxygen.
• The muscles in his body need more energy and therefore more oxygen.