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C3.1.14—Heart rate feedback control

Heart rate feedback control links named stimuli, coordinating structures and effectors so body systems or plant tissues produce an integrated biological response.

Syllabus
First assessment 2025
Objective
C3.1.14
Level
HL

Exam analysis

Chance of appearing9%of analysed past papers
Latest appearanceNovember 2024
Most common paperPaper3
Typical marks1–3

Common command terms

  • Outline
  • Identify
  • State
  • Compare
  • Describe
  • Explain

Scoring notes

Common mistake
Treating low oxygen as the only trigger and omitting carbon-dioxide-driven pH change.

Recent exam appearances

November 2024Paper3 ["HL"] · TZ021(b)[ 1 ]C3.1.14—Heart rate feedback control
May 2024Paper1 ["HL"] · TZ125[ 1 ]C3.1.14—Heart rate feedback control
May 2024Paper3 ["HL"] · TZ123(c)[ 3 ]C3.1.14—Heart rate feedback control
May 2022Paper1 ["HL"] · TZ121[ 1 ]C3.1.14—Heart rate feedback control
November 2020Paper3 ["HL"] · TZ022(c)[ 2 ]C3.1.14—Heart rate feedback control
Practice this objective

Coverage 2014–2024 · Updated 16 Jul 2026

Heart rate is adjusted by feedback from the body

Heart rate is adjusted by negative feedback after baroreceptors and chemoreceptors send sensory information to the medulla.

Baroreceptors in the carotid sinus and aortic arch monitor arterial pressure. Chemoreceptors in carotid and aortic bodies and the brainstem monitor blood pH and oxygen/carbon-dioxide concentrations.

The medulla integrates this input and changes autonomic nerve impulses to the heart. This alters heart rate and the strength of contraction, changing stroke volume so circulation opposes the detected disturbance.

If arterial pressure falls, reduced baroreceptor firing causes medullary output that increases heart rate and contraction strength, helping restore cardiac output and pressure.

Heart rate is only one component of cardiac output: cardiac output = heart rate × stroke volume. Receptors detect changes; the medulla coordinates the response.

Heart rate feedback control

Assessment in practice

1–4 marks
How it is assessed

This objective is assessed through structured response, commonly using Outline / Identify / State.

Command terms

Outline / Identify / State / Compare / Describe / Explain

What earns marks

Mark schemes reward named structures, correct direction of information flow and explanations that keep the sequence causal.

Watch for

Treating low oxygen as the only trigger and omitting carbon-dioxide-driven pH change.

Representative question

Question 1

[Maximum number: 7]

Explain the control mechanism of the heart rate.

Body-System Integration

  • Nervous signals, hormones and blood transport integrate organs into coordinated systems; emergent functions arise from their interactions.
  • Sensory neurons carry receptor input to the CNS; motor neurons carry output to effectors. Mixed nerves contain both fibre types.
  • Reflex arcs provide rapid involuntary responses through sensory, relay and motor neurons. The spinal cord also links the brain and peripheral nerves.
  • Cerebral hemispheres support conscious processing; the cerebellum coordinates movement and balance; the medulla adjusts ventilation and heart activity.
  • The hypothalamus links nervous and endocrine control through the pituitary. Pineal melatonin helps time sleep; adrenal epinephrine supports acute stress responses.
  • Baroreceptors and chemoreceptors provide feedback about pressure, CO2, pH and O2.
  • The CNS controls voluntary swallowing and egestion, while the enteric nervous system coordinates gut peristalsis.

Concept essentials

  • Heart rate feedback control depends on linking the stimulus to the coordinating structure or signal.
  • The pathway for heart rate feedback control must keep information flow and response direction clear.
  • Named tissues, hormones, neurons or effectors give heart rate feedback control its biological specificity.
  • Evidence about heart rate feedback control is strongest when structure, mechanism and outcome are connected.