Controlling the heartbeat
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Flip to reveal answersWhat does it mean that the heart is 'myogenic'?
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All 12 Flashcards — Controlling the heartbeat
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Question
What does it mean that the heart is 'myogenic'?
Answer
The heartbeat **starts within the heart muscle itself** (at the SA node), not from a signal sent by the brain.
Question
What is the SA node and where is it?
Answer
The **sinoatrial (SA) node** — a patch of special muscle in the **wall of the right atrium**. It is the heart's natural **pacemaker** and starts every beat.
Question
What is a pacemaker (in the heart)?
Answer
The structure that **sets the rhythm** of the heartbeat. In a healthy heart this is the **SA node**.
Question
What is the role of the AV node?
Answer
The **atrioventricular (AV) node** **delays** the impulse between the atria and ventricles, so the **atria empty before the ventricles contract**.
Question
In what order does a heartbeat happen?
Answer
**SA node fires → atria contract → AV node delays → ventricles contract.**
Question
Why does the AV node delay the impulse?
Answer
So the **atria can finish emptying** their blood into the ventricles **before** the ventricles contract — keeping the beat coordinated.
Question
Which cardiac-muscle feature aids conduction of the impulse?
Answer
**Intercalated discs** containing **gap junctions**, which let the impulse pass **directly from cell to cell**.
Question
How does the nervous system change heart rate?
Answer
Nerves from the brain's **medulla** reach the SA node — one **speeds it up**, one **slows it down**.
Question
Which hormone raises heart rate, and how?
Answer
**Adrenaline** — it reaches the SA node and **speeds it up**. It always raises heart rate.
Question
What 'always raises heart rate'?
Answer
**Adrenaline** — it speeds up the SA node and never slows it down.
Question
What is an artificial pacemaker for?
Answer
An implanted device that sends **regular electrical impulses** to keep a normal rhythm when the **SA node is faulty**.
Question
On an ECG-style trace, what is the heart doing during the T wave?
Answer
The **ventricles are relaxing / recovering** (repolarising) after contracting.
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Topic 3.6 hub
Integration of body systems
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