Summary of Au coeur des organes : Le rythme cardiaque

The video explains the autonomic regulation of the heart rate, highlighting the interplay between the nervous system and cardiovascular function:

The heart, though capable of automatic beating, is influenced by the autonomic nervous system, which regulates heart rate involuntarily.
Two complementary branches of the autonomic nervous system control heart rate:
- Sympathetic nervous system: cardioaccelerator, increases heart rate.
- Parasympathetic nervous system: cardiomoderator, decreases heart rate.
Both systems are always active to some degree, maintaining heart rate around 70 to 75 beats per minute and regulating blood pressure.
Heart rate regulation occurs through a feedback loop involving:
- Baroreceptors located in the carotid sinus and aortic arch, sensitive to blood pressure changes.
- Nerve signals transmitted by the Nerves of Hering and Sion to a nerve center in the medulla oblongata.
When blood pressure rises:
- Baroreceptors increase signaling.
- The medulla increases parasympathetic activity and decreases sympathetic activity.
- Parasympathetic nerves release Acetylcholine, slowing the heart rate and reducing blood pressure.
When blood pressure falls:
- Baroreceptor signaling decreases.
- The medulla decreases parasympathetic activity and increases sympathetic activity.
- Sympathetic nerves release Noradrenaline, accelerating heart rate and increasing blood pressure.
This feedback mechanism forms a regulatory loop that maintains blood pressure within a narrow, stable range.

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