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Control of the Heartbeat

Control of the Heartbeat. Page 304. Can you. Hold your breath for over 20 seconds? Stop your heart on purpose? Messages that control our breathing rate come from the brain . Messages that control our heartbeat comes from... the heart !!!. Heartbeat control. Sinoatrial node (S-A node):

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Control of the Heartbeat

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  1. Control of the Heartbeat Page 304

  2. Can you... Hold your breath for over 20 seconds? Stop your heart on purpose? Messages that control our breathing rate come from the brain. Messages that control our heartbeat comes from... the heart!!!

  3. Heartbeat control • Sinoatrial node (S-A node): • Bundle of tissue located in the wall of the right atrium. • Stimulates muscle fibres to contract and relax rhythmically. • Also known as the PACEMAKER.

  4. The S-A node produces an electrical impulse that spreads over the two atria and makes them contract at the same time. • As atria contract, impulse reaches another node called the atrioventricular (A-V) node. (where have you seen this word before?!) • Electrical impulse is sent from this A-V node to the ventricles. • Ventricles contract.

  5. So... S-A node: pacemaker. Generates electrical impulse to make atria contract. Electrical impulse reaches A-V node. This transmits impulse to the ventricles. Ventricles contract.

  6. Electrocardiograph (ECG) Tracings

  7. Seatwork/Homework Read the remainder of “recording heart rate”, page 305, and make sure you understand it. Read the section “Chemical Regulators” on pages 305-306 and make brief notes. Read the sections “Cardiac Output and Fitness” and “Heart Defects” starting on page 306. Make detailed notes. Section Review: page 311 #1, 3, 4, 7.

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