5 - Heart function Flashcards
How does the heart contract?
The heartbeat is myogenic, it generates its own impulses to start at the SA node, the impulse then travels to the AV node where it pauses for the atria to contract, then it goes down the Bundle of His to the purkinje fibres for the ventricles to contract.
What is stroke volume?
The volume of blood leaving the heart per beat.
What is ejection fraction?
Proportion of blood left in the ventricle after each beat.
What is cardiac-output
Volume of blood leaving the left ventricle per minute
How do you calculate cardiac-output?
stroke volume x heart rate
What is Starling’s Law?
The greater the venous return the greater the contraction strength. The larger the ejection fraction
What detect changes in the blood?
chemoreceptors
How is the heartbeat regulated?
The change in blood acidity is detected by the chemoreceptors, they send a message to the medulla oblongata. A message is sent down a nerve back to the SA node (etc) to readjust the heart rate
What is hypertrophy / athletes heart?
The increase in the size of the heart muscle due to training
What is Bradycardia?
the reduction in resting heart rate due to training
When an athletes resting heart rate is below 60 bpm
Explain Cardiovascular drift
An increase in heart rate that occurs during prolonged exercise that compensates for a decrease in stroke volume in an attempt to maintain cardiac output.
It occurs 10 minutes into training.
How does a lower resting heart rate affect oxygen delivery to muscles?
Less oxygen needed for contractions of heart
More oxygen available for muscle contractions
Increased heart rate range
