BRAINCAKEHormonal Control of Heart Rate
Heart rate is also controlled by hormones, especially during the fight or flight response. When a threat is detected, the hypothalamus activates the sympathetic nervous system, which stimulates the adrenal medulla to release adrenaline into the blood.
Adrenaline travels in the blood to the heart and binds to receptors on the cells of the sinoatrial node (SAN). This increases the frequency of excitation of the SAN, so heart rate increases. Adrenaline also increases the force of contraction of the ventricles, so stroke volume increases.
Noradrenaline released by the accelerator nerve endings has a similar effect directly at the SAN.
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Key terms in this lesson
- sinoatrial node
- The patch of specialised tissue in the wall of the right atrium that generates the heartbeat and sets its rate.
More in Hormonal Communication
- Diabetes Mellitus
- The Fight or Flight Response
- Coordinating Nervous and Hormonal Responses
- Adrenaline and the Second Messenger Model
- The Cardiovascular Centre in the Medulla
- Control of Heart Rate
- Baroreceptors
- Chemoreceptors
All 19 lessons in Hormonal Communication · All OCR A-level Biology topics