Control of heart rate

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  • control of heartrate
    • heart rate
      • 1: heart is myogenic
      • 2: heart contains pace-maker the sino- atrial node
      • 3: this initiates waves of excitation over the atria walls through the atriventricular node, down the purkyne fibres to ventircles, causing them to contract
      • 4: the heart is supplied with nerves from the medulla oblongata in the brain
      • 5: these nerves connect with the SAN and they affect the frequency of the contractions
    • response of the heart
      • action potential sent down accelerator nerve increases heart rate
      • action potenital sent down the vegus nerve decreases the heart rate
      • the frequency of excitation waves are controlled by the cardiovascular center in the medulla oblongata
      • the heart also responds to Adrenalin in the blood
    • factors affecting heart rate
      • stretch receptors in limbs send impulses to cardiovascular centre
        • causes cardiovascular centre to increase frequency of action potential down accelerator nerve
      • CO2 from increases respiration reduces blood pH level and is detected by chemo receptors
        • chemo receptors send impulses to cardiovascular centre and they increase frequency of action potential down the accelerator nerve
      • blood pressure is monitored by stretch receptors in the walls of carotid sinus
        • they send signals to cardiovascular centre and increase frequency of impulse along accelerator nerve
      • stress and shock are detected by the hypothalamus and adrenaline is secreted from adrenyl medulla
        • binds to cell surface membrane and activates adenyl cyclase t convert ATP to cAMP
          • fight or flight response-
            • hypothalamus also releases CRF into blood which stimulates release of ACTH into blood to stimulate secretion of other hormones from adrenyl cortex
          • adrenaline binds to receptors in mucles


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