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Review: The Cardiac Cycle

Review: The Cardiac Cycle. Label the diagram of the heart in as much detail as you can. Annotate the next three diagrams to show the different stages of the cardiac cycle. What structure?. The cardiac cycle. Myogenic stimulation of the heart. Today we are covering from the specification:.

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Review: The Cardiac Cycle

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  1. Review: The Cardiac Cycle • Label the diagram of the heart in as much detail as you can. • Annotate the next three diagrams to show the different stages of the cardiac cycle.

  2. What structure?

  3. The cardiac cycle

  4. Myogenic stimulation of the heart

  5. Today we are covering from the specification:

  6. How is the nervous system organized?

  7. Control of Heart Rate Autonomic Parasympathetic Sympathetic Positive stimulation (speed up activity) Inhibitory (slows down activity) Uses the neurotransmitter noradrenaline. Uses the neurotransmitter acetylcholine.

  8. Control of heart rate Heart rate is controlled by the part of the brain called cardioregulatory centre in the medulla oblongata Has two centres: • Acceleratory centre- Increases heart rate (linked to the sinoatrial node by the sympathetic nervous system) • Inhibitory centre - Decreases heart rate (linked to the sinoatrial node by the parasympathetic nervous system) The centre that is stimulated depends on: • Chemical changes in the blood • Pressure changes in the blood

  9. Control by chemoreceptors Found in the walls of the carotid artery and aorta (in the carotid and aortic bodies). Sensitive to changes in the pH of the blood that result from changes in carbon dioxide concentration (in solution CO2 forms carbonic acid.)

  10. Control by pressure receptors Pressure receptors (baroreceptors) occur within the walls of the carotid arteries and the aorta. When a blood pressure is higher than normal: 1) Nervous impulses are transmitted to the cardioinhibitory centre. 2) Impulses are sent via the parasympathetic nervous system to the SAN, decreasing heart rate. http://www.youtube.com/watch?v=G2nLL_O_U7w

  11. Control by pressure receptors When a blood pressure is lower than normal: 1) Nervous impulses are transmitted to the cardioacceleratory centre. 2) Impulses are sent via the sympathetic nervous system to the SAN, increasing heart rate. N.B. This system relies on the different neurotransmitters released at the SAN by the two systems.

  12. Brain Cardioaccelerator centre Cardioinhibitory centre Medulla oblongata Spinal cord Carotid body Sympathetic nerve Carotid arteries Aortic body Parasympathetic nerve Aorta SAN Left atrium AVN Bundle of His Right atrium Left ventricle Right ventricle

  13. Try the questions on p142-143.

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