Control Of Heart Rate Flashcards
Cardiac muscle is myogenic
What does myogenic mean?
> Contracts on its own accord
> Rate of contraction is controlled by the nervous system
Sinoatrial Node (SAN)
> Located where?
> Role?
> Located in right atrium
> Also known as pacemaker, so sets the pace that the heart beats
Atrioventricular node (AVN)
> Located where?
> Border of left ventricle & right atrium
Bundle of His?
> Bundle of tissues that run through the septum
Purkyne fibres?
> Branch through ventricle walls
What does the SAN release across the atria?
> A wave of depolarisation across the atria, causing it to contract
After the SAN releases a wave of depolarisation across the atria, causing it to contract, what does the AVN release?
> AVN releases another wave of depolarisation when the first wave reaches it
> A non-conductive later between the atria and ventricles prevents the wave travelling down the ventricles
Due to the non-conductive later between the atria and ventricles preventing the wave from travelling down the ventricles, where does the wave of depolarisation go?
> The bundle of His conducts the wave of depolarisation down the septum and Purkyne fibres
Why is it an advantage that the bundle of His conducts the wave of depolarisation down the septum and Purkyne fibres?
> This results in a short delay before the ventricles contract
> This allows enough time for the atria to pump all the blood into the ventricles
What happens after the atria pump all the blood into the ventricles?
> The cells depolarise and the cardiac muscle relaxes
What controls the heart rate via the autonomic nervous system?
> The medulla oblongata in the brain
What are the two parts of the autonomic nervous system?
> A centre linked to the SAN to increase heart rate via the sympathetic nervous system
> Another that decreases heart rate via the parasympathetic nervous system
Heart rate changes in response to pH and blood pressure, these stimuli are detected by..?
> Chemoreceptors and pressure receptors in the aorta and carotid artery
Response to pH
> pH of the blood decreases during high respiratory rate ( CO2 / lactic acid production )
> This must be removed from the blood to prevent enzymes denaturing
> Done by increasing heart rate ( more impulses sent via sympathetic nervous system to SAN )
Response to pressure
> To reduce blood pressure, more impulses are sent via parasympathetic nervous system to decrease heart rate
> If blood pressure is too low, more impulses are sent via sympathetic nervous system to increase the heart rate
