Control of Heart Rate Flashcards
The heart is myogenic….. What does this mean?
Myogenic means that the heart can contract and relax without the need for external nervous stimulation
Modifying the Heartbeat
In the brain the area that controls the rate of the heartbeat is called the ___________________centre and is situated in the __________(aka _________ ____________)
In the brain the area that controls the rate of the heartbeat is called the cardioregulatory centre and is situated in the medulla (aka medulla oblongata)
The cardioregulatory centre consists of 2 discrete parts
what are they?
The cardioacceleratory centre responsible for speeding up the heartbeat
The cardioinhibitory centre responsible for slowing down the heartbeat
autonomic nervous system (ANS).
The ANS is divided into 2 :
the _______________nervous system . At the nerve endings, a chemical called __________________ is secreted and this generally speeds up activities
the ________________________nervous system . At the nerve endings, ___________________is secreted which generally slows down any activity
The ANS is divided into 2 :
the sympathetic nervous system (SNS) . At the nerve endings, a chemical called noradrenaline is secreted and this generally speeds up activities
the parasympathetic nervous system (PNS). At the nerve endings, acetycholine is secreted which generally slows down any activity
One effect of exercise is to increase the __________ __________ & lactic acid concentration in the blood which lower pH and could ____________proteins.
This can be detected by _____________in the ______close to the heart and in the ___________ arteries that pass through the neck to the brain
One effect of exercise is to increase the carbon dioxide & lactic acid concentration in the blood which lower pH and could denature proteins.
This can be detected by chemoreceptors in the aorta close to the heart and in the carotid arteries that pass through the neck to the brain
If high blood CO2 levels ( ___ pH)
__________________ in ______and ________artery (the artery that supplies the brain) detect the fall in pH.
They send impulses along _________neurones to the ____________.
The ______________________centre increases the frequency of impulses sent along __________________neurones to the SAN.
These impulses cause the release of ____________________at the end of the neurones in the SAN
Noradrenaline causes the SAN to ____________the rate at which it produces w______of e__________ a__________.
These impulses cause an __________in the rate of the heartbeat which results in blood delivered to the lungs ______to ____________the blood CO2 level.
If high blood CO2 levels ( low pH)
Chemoreceptors in aorta and carotid artery (the artery that supplies the brain) detect the fall in pH.
They send impulses along sensory neurones to the medulla.
The cardioacceleratory centre increases the frequency of impulses sent along sympathetic neurones to the SAN.
These impulses cause the release of noradrenaline at the end of the neurones in the SAN
Noradrenaline causes the SAN to increase the rate at which it produces waves of electrical activity.
These impulses cause an increase in the rate of the heartbeat which results in blood delivered to the lungs faster to decrease the blood CO2 level.
If low blood CO2 levels ( high __)
________________in _____and ________ detect this
They send impulses along sensory neurones to the __________
The _____________________centre increases the frequency of impulses sent along the ________________________nervous system to the SAN
__________________is secreted at nerve endings which binds to _____________on the SAN
______________inhibits the production of impulses by the SAN and the _____________of impulses by the AV node
The inhibition of these impulses slows down the heart rate of the heartbeat and the ___________of each contraction.
If low blood CO2 levels ( high pH)
Chemoreceptors in aorta and carotid detect this
They send impulses along sensory neurones to the medulla
The cardioinhibitory centre increases the frequency of impulses sent along the parasympathetic nervous system to the SAN
Acetylcholine is secreted at nerve endings which binds to receptors on the SAN
Acetylcholine inhibits the production of impulses by the SAN and the transmission of impulses by the AV node
The inhibition of these impulses slows down the heart rate of the heartbeat and the strength of each contraction.
In practice, the situation seems to be less straightforward.
If the oxygen concentration of the blood is low or if the carbon dioxide concentration is high, the ventilation rate ____________. This somehow also causes the rate of heartbeat to _____________
In practice, the situation seems to be less straightforward.
If the oxygen concentration of the blood is low or if the carbon dioxide concentration is high, the ventilation rate increases. This somehow also causes the rate of heartbeat to increase
Heart rate is also affected by changes in blood pressure.
Pressure receptors (___________________) occur within the walls of the __________arteries and the ______.
They are stretch receptors
Heart rate is also affected by changes in blood pressure.
Pressure receptors (baroreceptors) occur within the walls of the carotid arteries and the aorta.
They are stretch receptors
If blood pressure is low, the baroreceptors detect this and send impulses along sensory neurones to the __________, which sends more impulses along the _________________neurones. These secrete _______________, which binds to ____________on the SAN . This causes the heart rate to _______ __ in order to increase blood pressure back to ___________
If blood pressure is low, the baroreceptors detect this and send impulses along sensory neurones to the medulla, which sends more impulses along the sympathetic neurones. These secrete noradrenaline , which binds to receptors on the SAN . This causes the heart rate to speed up in order to increase blood pressure back to normal
If blood pressure is high, the baroreceptors detect this and send impulses along sensory neurones to the ___________which sends more impulses along ______________neurones to the SAN. These secrete _________________which binds to ___________on the SAN. This causes the heart rate to ______ _____in order to reduce the blood pressure back to ___________.
If blood pressure is high, the baroreceptors detect this and send impulses along sensory neurones to the medulla which sends more impulses along parasympathetic neurones to the SAN. These secrete acetylcholine which binds to receptors on the SAN. This causes the heart rate to slow down in order to reduce the blood pressure back to normal.
1.What is the difference between the sympathetic and parasympathetic nervous system?
Sympathetic in general stimulates effectors and so speeds up any activity. Parasympathetic in general inhibits effectors and so slows down any activity
2.What could act as a stimulus to change the heart rate?
Blood pressure, blood carbon dioxide concentration, blood pH, blood oxygen concentration
3.Anaemia is a condition in which the oxygen carrying capacity of the blood is reduced. Use your knowledge of the control of the heart to explain why a person with anaemia is likely to have a more rapid heart rate that someone without anaemia
The chemoreceptors in a person with anaemia will detect low oxygen levels in the blood. The chemoreceptors will send impulses along sensory neurones to the medulla which will send impulses along sympathetic neurones. These neurones will secrete noradrenaline which will bind to receptors on the SAN and cause the heart rate to increase in an attempt to increase oxygen levels in the blood.
5 What are the advantages to an athlete of a rise in heart rate during exercise?
A greater rate of delivery of oxygen and glucose to the muscles and a greater rate of removal of carbon dioxide/lactate from the muscles
