Cardiovascular system

Question 1

What is the function of the pulmonary circuit?

Answer 1

It carries deoxygenated blood to the lungs and oxygenated blood back to the heart.

Question 2

What is the function of the systemic circuit?

Answer 2

It carries oxygenated blood to the body and deoxygenated blood back to the heart.

Question 3

Which step in the conduction system does the Sino- atrial (SA )node work, and what is its function?

Answer 3

It is the first step.

It generates the electrical impulse and fires it through atrial walls.

Also known as the ‘pacemaker’

Question 4

Which step in the conduction system does the atrio- ventricular (AV) node work, and what is its function?

Answer 4

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.

Question 5

What step in the conduction system does the bundle of his work, and what is its function?

Answer 5

It is the third step.

It splits the impulse in two, ready to be distributed through each seperate ventricle.

Question 6

What step in the conduction system does the perkinje fibres work, and what is its function?

Answer 6

It is the fourth step.

They distribute the impulse through the ventricle walls, causing them to contract.

Question 7

What is diastole?

Answer 7

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.

Question 8

What is Atrial systole?

Answer 8

The atria contract, forcing remaining blood into the ventricles.

Question 9

What is ventricular systole?

Answer 9

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.

Question 10

Define heart rate (beats per minute).

Answer 10

The number of beats per minute.

Question 11

What is the average resting heart rate?

Answer 11

72 beats per minute.

Question 12

What is bradycardia?

Answer 12

Athletes get a resting heart rate lower than 60 beats per minute, which can result in cardiac hypertrophy.

Question 13

Define stroke volume (ml)

Answer 13

The volume of blood ejected from the left ventricle per beat.

Question 14

What is the average resting stroke volume?

Answer 14

Approximately 70ml.

Question 15

What is cardiac output (litres per minute)?

Answer 15

The volume of blood ejected from the left ventricle per minute.

Question 16

What is the calculation for cardiac output?

Answer 16

Cardiac output = Heart rate x Stroke volume

Question 17

What are the three control mechanisms that control the cardiac control centre (CCC)

Answer 17

-Neural control
-Intrinsic control
-Hormonal control

Question 18

Explain the parts of Neural control.

Answer 18

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.

Question 19

Explain the parts of Intrinsic control.

Answer 19

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.

Question 20

Explain the parts of hormonal control.

Answer 20

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.

Question 21

What is venous return?

Answer 21

The return of blood back to the heart.

Question 22

List the mechanisms of venous return

Answer 22

-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)

Question 23

Describe the heart rate response to exercise.

Answer 23

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.

Question 24

Describe the stroke volume response to exercise.

Answer 24

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.

Question 25

What is starlings law?

Answer 25

Increased venous return leads to an increased stroke volume, due to an increased stretch of the ventricle walls and therefore force of contraction.

Question 26

What is the function of the vascular shunt mechanism?

Answer 26

The redistribution of blood flow from one area of the body to another.

Question 27

Describe the vascular shunt mechanism at rest.

Answer 27

Arterioles to the organs vasodilate, increasing blood flow.
While arterioles to the muscles vasoconstrict to limit blood flow.

The pre- capillary sphincters dilate, opening up the capillary beds to allow more blood flow to the organ cells, while constricting, closing the capillary beds to the muscle cells.

Question 28

What is the purpose of vasomotor control.

Answer 28

To control the vascular shunt mechanism.

Question 29

Where does the vasomotor control centre receive information from?

Answer 29

Chemoceptors detect chemical changes

Baroreceptors detect pressure changes on the arteriole walls