Practice Flashcards
Flip to reveal answersWhat is the normal set point for blood pH?
Track your progress — Sign up free to save your progress and get smart review reminders based on spaced repetition.
All 8 Flashcards — Blood pH & ventilation control
Sign up free to track progress and get spaced-repetition review schedules.
Question
What is the normal set point for blood pH?
Answer
About **pH 7.4** (slightly alkaline).
Question
Why does a rise in blood CO2 lower the blood pH?
Answer
CO2 dissolves to form **carbonic acid**, which releases **H+**, making the blood **more acidic** (lower pH).
Question
What detects a change in blood pH / CO2?
Answer
**Chemoreceptors** — in the **medulla** of the brain and in the walls of the **aorta** and **carotid arteries**.
Question
Which part of the brain controls breathing rate?
Answer
The **medulla** (in the brainstem).
Question
What does the body do when blood pH falls below 7.4?
Answer
It **increases ventilation rate and depth** (breathes faster and deeper) to **remove more CO2** and raise pH back to the set point.
Question
What does the body do when blood pH rises above 7.4?
Answer
It **decreases ventilation** so **CO2 is retained**, which lowers pH back to the set point.
Question
Why is blood-pH control an example of negative feedback?
Answer
Because the response **reverses the change** (pH down → breathe faster → CO2 removed → pH up) and then switches off at the set point.
Question
Which gas, not oxygen, mainly drives the urge to breathe?
Answer
**CO2** — rising CO2 (and falling pH) is what the chemoreceptors mainly sense.
Read the notes
Full study notes for Blood pH & ventilation control
Topic 4.9 hub
Homeostasis
More from Topic 4.9
All flashcards in this topic
Biology exam skills
Paper structures & tips
Track your progress with spaced repetition
Sign up free — Aimnova tells you exactly which cards to review and when, so you remember everything before your IB exam.
Start Free