Control Of The Heart Rate Flashcards
(10 cards)
What is the somatic nervous system?
It controls conscious actions.
What is the automatic nervous system?
It control unconscious actions.
What is the sympathetic part of the automatic nervous system?
It speeds the body up and gets it ready for action.
What is the parasympathetic part of the automatic nervous system?
It slows the body down.
What are chemoreceptors and where are they found?
- They are receptors that detect a change in oxygen and carbon dioxide in the blood.
- They are found in the medulla, aorta and carotid arteries.
What are baroreceptors and where are they found?
- They are receptors that detect a change in blood pressure.
- They are found in the aorta and carotid arteries.
How do the baroreceptors and chemoreceptors react in response to high pressure, high oxygen concentration and low carbon dioxide concentration in the blood ( high pH)?
- The baroreceptors detect an increase in blood pressure. The chemoreceptors detect an increase in pH.
- They send impulses to the medulla.
- The medulla sends more frequent impulses along the parasympathetic neurones to the SAN.
- This means the SAN send less frequent impulses to the AVN.
- This means the cardiac muscles contract less frequently and the heart rate decreases.
How do the baroreceptors and chemoreceptors react in response to low blood pressure, low oxygen concentration and high carbon dioxide concentration in the blood ( low pH)?
- The baroreceptors detect a decrease in blood pressure and a decrease in the blood pH.
- This is because there is more time for oxygen to diffuse into cells, so the oxygen concentration in the blood is low. This means there is more respiration and more carbon dioxide is released into the blood, so the carbon dioxide concentration in the blood is high.
- They send impulses to the medulla.
- The medulla sends more frequent impulses down the sympathetic neurones to the SAN.
Why is the cardiac muscle described as myogenic?
It contracts and relaxes without external stimulation from the nervous or endocrine system.
What is the role of the SAN, AVN, the bundle of his and the outline fibres in controlling the myogenic stimulation of the heart?
- The SAN sends out a wave of depolarisation across the atria, causing them to contract.
- Non-conductive tissue between the atria and the ventricles prevents the waves of depolarisation from passing directly into the ventricles. This prevents immediate contraction of the ventricles.
- The waves of electrical activity hit the AVN. This delays the impulse and allows the atria enough time to contract and empty completely.
- The AVN sends waves o down the bundle of His, which takes the waves of depolarisation into the Purkinje fibres. This causes the ventricles to contract from the base up.