Cardiovascular system Flashcards
(29 cards)
What is the function of the pulmonary circuit?
It carries deoxygenated blood to the lungs and oxygenated blood back to the heart.
What is the function of the systemic circuit?
It carries oxygenated blood to the body and deoxygenated blood back to the heart.
Which step in the conduction system does the Sino- atrial (SA )node work, and what is its function?
It is the first step.
It generates the electrical impulse and fires it through atrial walls.
Also known as the ‘pacemaker’
Which step in the conduction system does the atrio- ventricular (AV) node work, and what is its function?
It is the second step.
It collects the impulse and delays it for approximately 0.1 seconds to allow the atria to finish contracting.
It then release the impulse to the bundle of his.
What step in the conduction system does the bundle of his work, and what is its function?
It is the third step.
It splits the impulse in two, ready to be distributed through each seperate ventricle.
What step in the conduction system does the perkinje fibres work, and what is its function?
It is the fourth step.
They distribute the impulse through the ventricle walls, causing them to contract.
What is diastole?
The relaxation of the cardiac muscle.
The atria and then ventricles relax, they expand drawing blood into the atria.
The pressure in the atria increases, opening AV valves.
Blood passively enters the ventricles.
Semi- Lunar valves are closed to prevent blood from leaving the heart.
What is Atrial systole?
The atria contract, forcing remaining blood into the ventricles.
What is ventricular systole?
The ventricles contract, increasing the pressure closing the AV valves to prevent back flow into the atria.
Semi lunar valves are forced open as blood is ejected from the ventricles into the aorta and pulmonary artery.
Define heart rate (beats per minute).
The number of beats per minute.
What is the average resting heart rate?
72 beats per minute.
What is bradycardia?
Athletes get a resting heart rate lower than 60 beats per minute, which can result in cardiac hypertrophy.
Define stroke volume (ml)
The volume of blood ejected from the left ventricle per beat.
What is the average resting stroke volume?
Approximately 70ml.
What is cardiac output (litres per minute)?
The volume of blood ejected from the left ventricle per minute.
What is the calculation for cardiac output?
Cardiac output = Heart rate x Stroke volume
What are the three control mechanisms that control the cardiac control centre (CCC)
-Neural control
-Intrinsic control
-Hormonal control
Explain the parts of Neural control.
Chemoreceptors:
detect changes in the blood stream, eg. increased levels of CO2 and lactic acid.
Proprioceptors:
detect motor activity.
Baroreceptors:
Detect changes in blood pressure.
Explain the parts of Intrinsic control.
Temperature changes:
Affect viscosity of the blood and speed of nerve impulse transmission.
Venous return changes:
Affect the stretch in ventricle walls, force of ventricular contraction and therefore stroke volume.
Explain the parts of hormonal control.
Adrenaline and noradrenaline are released from the adrenal glands:
Increasing the force of ventricular contraction, therefore stroke volume.
It also increases the spread of electrical activity through the heart, therefore heart rate.
What is venous return?
The return of blood back to the heart.
List the mechanisms of venous return
-Pocket valves
(prevent the backflow of blood)
-Smooth muscle
(vasoconstrics to aid the movement of blood)
-Gravity
(helps blood from the upper body return to the heart)
-Muscle pump
(skeletal muscle contracts and compresses the veins between them)
-Respiratory pump
(pressure difference between thoracic and abdominal cavity is created to squeeze blood back to the heart)
Describe the heart rate response to exercise.
Initial heart rise due to release of adrenaline.
Rapid increase in heart rate at the start of exercise to increase oxygen transport.
Steady state heart rate as oxygen supply meets demand.
Initial rapid decrease in heart rate as muscle pump reduces.
A more gradual decrease in heart rate to resting levels.
Describe the stroke volume response to exercise.
Increased venous return to increase volume of blood returning to the heart.
Increased heart rate doesnt allow enough time for the ventricles to completely fill with blood in the diastolic phase, limiting starlings law.
