The beat starts inside the heart muscle itself with and electrical signal from the SAN
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Where does the bundle of His go?
It branches down the septum into the Purkinje fibres
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Neural control mechanism
This involves the sympathetic nervous system and the parasympathetic coordinated in the medulla oblongata
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Sympathetic nervous system does what to heart rate?
Stimulates the heart to beat faster
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Parasympathetic nervous system does what to heart rate?
Stimulates the heart to return to its resting level
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What is the cardiac control centre stimulated by?
Baroreceptors, Chemoreceptors and Proprioceptors
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Chemoreceptors detect what?
An increase in blood carbon dioxide levels. Higher levels will cause increase in heart rate, lower levels will cause decrase in heart rate
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Baroreceptors detect what?
An increase in blood pressure. Higher blood pressure will cause the heart rate to decrease, lower blood pressure will cause an increase in heart rate
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Proprioceptors detect what?
An increase in muscle movement. Higher movement levels will cause an increase in heart rate, lower levels of movement will cause a decrease in heart rate
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Stroke Volume
The amount of blood pumped out of the heart ventricles in each contraction. Stroke volume increases with intensity of exercise
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What does stroke volume depend on?
Venous return, the elasticity of cardiac fibres and the contractility of the myocardium (cardiac tissue).
When your coronary arteries, which supply the heart muscle with oxygenated blood, become blocked or start to narrow by a gradual build up fatty deposits. The fatty deposits are called atheroma
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Cholesterol
LDL (Low Density Lipoproteins) = bad cholesterol. HDL (High Density Lipoproteins) = transport excess cholesterol to the liver to be broken down
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