14.6 Controlling Heart Rate Flashcards
What nervous system is the heart rate controlled by?
autonomic nervous system
What part of the brain is responsible for heart rate regulation?
medulla oblongata
What is the medulla oblongata linked to, to increase heart rate?
it is linked to the sino-atrial node in the heart by motor neurones
what are the two centres of the medulla oblongata and how do they control heart rate?
-One centre increases heart rate, by sending impulses through the sympathetic nervous system, these impulses are transmitted by the accelerator nerve
-One centre decreases heart rate, by sending impulses through the parasympathetic nervous system, these impulses are transmitted by the vagus nerve
What nervous system works to decrease heart rate?
parasympathetic
What nervous system works to increase heart rate?
sympathetic
What nerve works to increase heart rate?
accelerator nerve
What nerve works to decrease heart rate?
vagus nerve
How does the medulla oblongata know to control heart rate?
depend on information received from receptors, baroreceptors and chemoreceptors
What do chemoreceptors detect?
chemical changes in the blood stream, including changes in pH, carbon dioxide level etc.
Where are chemoreceptors located?
aorta, carotid arteries, medulla
What do baroreceptors detect?
changes in blood pressure
Where are baroreceptors located?
aorta, vena cava, carotid arteries
What happens when chemoreceptors detect a decrease in blood pH?
a response is triggered to increase heart rate
Why do pH levels of the blood decrease?
If carbon dioxide levels in the blood increase, pH will decrease because carbonic acid is formed when carbon dioxide interacts with water
Why do pH levels of the blood increase?
When the carbon dioxide levels in the blood decreases, the pH will rise
When pH is high what happens?
There will be a reduction in the frequency of nerve impulses being sent from the medulla oblongata. In turn, this reduces the frequency of impulses being sent to the SAN via the sympathetic nervous system. Parasympathetic nervous system is stimulated to decrease heart rate through the vagus nerve
What happens if blood pressure is too high?
Impulses are sent to the medulla oblongata to decrease heart rate. Medulla oblongata will send impulses along the parasympathetic nervous system via the vagus nerve to the SAN which decrease there firing rate therefore heart rate will decrease, reducing blood pressure back to normal
What happens if blood pressure is too low?
Impulses are sent to the medulla oblongata to increase heart rate. Medulla oblongata will send impulses along the sympathetic nervous system via the accelerator nerve to the SAN which increases its firing rate therefore heart rate will increase, increasing blood pressure back to normal
How is heart rate also controlled by hormones?
-In times of stress adrenaline and noradrenaline are released, which affect the SA node directly to speed up heart rate by increasing the frequency of impulses
