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C3.1.12—Epinephrine (adrenaline)

Epinephrine (adrenaline) links named stimuli, coordinating structures and effectors so body systems or plant tissues produce an integrated biological response.

Syllabus
First assessment 2025
Objective
C3.1.12
Level
SL

Exam analysis

Chance of appearing2%of analysed past papers
Latest appearanceNovember 2021
Most common paperPaper2
Typical marks1

Common command terms

  • State
  • Explain
  • Identify
  • Describe

Scoring notes

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

Recent exam appearances

November 2021Paper2 ["SL"] · TZ04(c)[ 1 ]C3.1.12—Epinephrine (adrenaline)
May 2012Paper1 ["SL"] · TZ229[ 1 ]C3.1.12—Epinephrine (adrenaline)
May 2011Paper2 ["SL"] · TZ21(h)[ 1 ]C3.1.12—Epinephrine (adrenaline)
Practice this objective

Coverage 2011–2021 · Updated 16 Jul 2026

Epinephrine prepares several organs for immediate demand

Epinephrine prepares several organs for immediate demand.

Epinephrine from the adrenal medulla binds receptors in target tissues during acute stress. It raises cardiac output, widens airways and mobilises glucose so muscles can respond quickly.

hormone source; receptor-bearing target; response in heart, airways and liver; adaptive purpose.

A sudden threat increases epinephrine, accelerating heart rate and glycogen breakdown while reducing investment in digestion.

The hormone does not affect every cell equally: receptor type and tissue context determine the response.

Epinephrine (adrenaline)

Assessment in practice

1 marks
How it is assessed

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

Command terms

State / Explain / Identify / Describe

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: 2]

Describe two ways in which epinephrine in the body facilitates intense muscle contraction. [2]
1.
2.

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

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