Controlling the heart beat

• Myogenic- intiate contractions
• SAN acts as a pacemaker
• Medulla Oblongata- nerves between heart and SAN

- accelerator nerve increases heart rate

- vagus nerve decreses heart rate

• Adrenaline- directly effects heart by increasing its heart rate

• Muscles need energy/ ATP to contract- increased respiration (need for more oxygen and glucose/fatty acids)
• Heart increases cardiac output and stroke volume
• More blood pumped to lungs and muscle
• Increased carbon dioxide makes blood more acidic- detected by chemoreceptors in carotid artery and brain
• Chemoreceptors send impulses to cardiovascular centre in the brain, leading to increased heart rate
• Adrenaline acts directly on heart muscle by increasing heart rate
• High blood pressure is detected by stretch receptors in carotid sinus