control of heart rate Flashcards
Role of the SAN
SAN causes waves of electrical activity/releases wave of depolarisation
Why is there a short delay in AVN before a new wave leaves the AVN?
allows atria to empty before ventricles contract
What two different nerves are responsible for increase or decrease of heart rate?
parasympathetic nerve
sympathetic nerve
How does the heart respond to a low ph of blood?
PH of blood decrease during excercise due to production of co2 and lactic acid.
Increase in heart rate so that co2 can diffuse out into the alveoli more rapidly.
does the parasympathetic nervous e system decrease or increase heart rate?
Decrease
Does the sympathetic system increase or decrease heart rate?
Increase
Which nerve is relevant to the parasympathetic nervous system?
Vagus nerve
What nerve is relevant to the sympathetic nervous system?
sympathetic cardiac nerves
Describe how a heart beat is initiated and coordinated? 5 marks
1.SAN causes waves of electrical activity
2.Non-conducting tissue prevents immediate 3.contraction of ventricles
4.AVN delays whilst blood leaves atria
5.AVN sends waves of electrical activity
6.so ventricles contract from the base up
what is the role of the purkyne tissue?
they carry the wave upwards to the ventricles
role of a chemoreceptor?
Detect chemical changes such as oxygen conc.
carbon dioxide levels and PH of blood
where are chemoreceptors located?
medulla oblongata
where are pressure receptors located?
Carotoid artery and wall of aorta
An increase in muscle activity can cause an increase in heart rate. Explain how. 2marks
Increase in Co2 detected by chemoreceptors.
Send more impulses to medulla
Explain what causes heart rate to increase during excercise
After chemoreceptors and pressure receptors detect a change, what happens next?
More electrical impulses are sent to medulla oblongata
What causes an increase in heart rate during exercise? 6 marks
-Rate of respiration increases
-co2 concentration increases
-detected by chemoreceptors
-more impulses sent to medulla
-increases frequency of impulses
-along sympathetic pathway to SAN
describe route taken when electrical impulses are transmitted from SAN to muscles of ventricles in healthy heart
through cardiac muscle
to AVN
along bundle of His
