Cardiovascular system

Question 1

State and describe the 2 circuits within the cardiovascular system

Answer 1

1. Pulmonary circuit - connects the heart and the lungs
2. Systemic circuit - connects the heart and muscles / body tissues

Question 2

State the 5 structures within the conduction system and describe what they do

Answer 2

1. SA node - generates electrical impulse causing atria walls to contract. Also known as the pacemaker + determines HR
2. AV node - collects impulse and delays it by 0.1 seconds to allow the atria to finish contracting
3. Bundle of his - located in the septum, splits impulse into 2 ready to be distributed into ventricles
4. Bundle branches - carries impulse to the base of the ventricles
5. Purkinje fibres - distribute the impulse through the ventricle walls causing them to contract

Question 3

State the 2 stages of the cardiac cycle

Answer 3

1. Diastole (relaxation) -

• relaxation of the atria and ventricles means lower pressure within the heart
• blood passively flows through atria and ventricles
• AV valves are open allowing blood to move freely from the atria to ventricles
• semilunar valves are closed at this time

2. Systole (contraction)

2.1 - atrial systole

• atria contact forcing blood into the ventricles

2.2 - ventricular systole

• ventricles contract
• AV valves close
• semilunar valves open
• blood is pushed out of the ventricles and into the large arteries leaving the heart

Question 4

Define heart rate + state the typical resting value

Answer 4

The number of times the heart beats per minute (72 bpm)

Question 5

Define stroke volume and state the typical resting value

Answer 5

The amount of blood ejected from the left ventricle per beat (70 ml)

Question 6

Define cardiac output and state the typical resting value

Answer 6

The amount of blood ejected from the left ventricle per minute ( 5 l/min)

Question 7

Define bradycardia and define the typical resting value

Answer 7

A resting heart rate below 60 bmp (<60 bpm)

Question 8

How do you work out resting heart rate?

Answer 8

Calculated by subtracting your age from 220

Question 9

Describe HR response to sub-maximal exercise

Answer 9

1. Anticipatory rise occurs before exercise has began
2. Rapid increase
3. Steady state
4. Rapid decrease post exercise

Question 10

Describe HR response to maximal (anaerobic) exercise

Answer 10

1. Anticipatory rise pre exercise
2. Rapid increase
3. Slower increase
4. Rapid decrease post exercise
5. Follows by slower decrease

Question 11

Describe HR response to fluctuating intensities of exercise

Answer 11

1. Anticipatory rise pre exercise
2. During periods of work HR increases
3. During periods of rest HR decreases

Question 12

Describe stroke volume response to exercise and state the 2 reasons for it being able to increase

Answer 12

SV increases in proportion to exercise intensity until a plateau is reached.

1. Increased venous return
2. The frank-starling mechanism (increased venous return leads to increase SV due to an increased stretch of ventricular walls and therefore force of contraction)

Question 13

Describe cardiac output response to exercise

Answer 13

CO increases in line with exercise intensity and plateaus during maximal exercise

Question 14

Describe HR, SV + CO in recovery

Answer 14

• SV is maintained during the early stages of recovery
• HR rapidly reduces
• this maintains blood flow and the removal of waste products while lowering the stress and work load on the cardiac muscle
• CO sees a rapid decrease followed by a slower decrease to resting levels

Question 15

What centre is responsible for the regulation of heart rate during exercise. State the 2 systems within this centre

Answer 15

1. The cardiac control centre (controlled by the automatic nervous system and determines the firing of the SA node)
2. The sympathetic nervous system = increases HR (via the accelerator nerve)
3. Parasympathetic nervous system = decreases HR (via the vagus nerve)

Question 16

State and define the the 3 types of neural control

Answer 16

1. Proprioceptors - in muscles, tendons and joints and inform the CCC that movement has increase
2. Chemoreceptors - located in arteries and detect a decrease in blood pH due to an increase in lactic acid and CO2
3. Barorecptors = located in blood vessel walls and inform the CCC of increased blood pressure

Question 17

State and Define the 2 types of intrinsic control

Answer 17

1. Temperature - changes in temp will affect blood viscosity and the speed of nerve impulse transmission
2. Venous return - changes will affect the stretch of ventricle walls, force of contraction and therefore SV

Question 18

State and define one type of hormonal control

Answer 18

1. Adrenaline and noradrenaline - these are released from adrenal glands and increase SV + HR

Question 19

State and describe the 3 types of blood vessels

Answer 19

1. Arteries and arterioles -

• carry oxygenated blood from the heart to muscles and organs
• carry blood at high pressure
• large layer of smooth muscle and elastic tissue which can vasoconstrict + vasodilate

2. Capillaries

• walls are one cell thick
• where gaseous exchange takes place

3. Veins

• carry deoxygenated blood back to the heart
• contain blood under low pressure
• one-way pocket valves to prevent the back flow of blood
• small layer of smooth muscle allowing them to vasodilate + venoconstrict

Question 20

State and define the venous return mechanisms

Answer 20

1. Pocket valves = located within veins to prevent the backdrop of blood
2. Smooth muscle = vasoconstricts helping push blood back to the heart
3. Gravity = blood from above the heart is aided back by gravity
4. Muscle pump = veins situated between muscles squeeze helping push blood back to the heart
5. Respiratory pump = helps return blood in the thoracic cavity and abdomen back to the heart (due to an increase in inspiration and expiration at exercise)

Question 21

Describe the vascular shunt mechanism and how blood distributed around the body during rest and exercise

Answer 21

1. The redistribution of cardiac output around the body from rest to exercise which increases the flow of blood to the skeletal muscles
2. Vasoconstriction - decreases blood flow
3. Vasodilation - increases blood flow

At rest -

• more blood to organs less blood to muscles

During exercise -

• more blood to working muscles less blood to organs

Question 22

State what the vasomotor control centre (VCC) controls and where it receives information from

Answer 22

1. Alters the level of stimulation sent to the arterioles and pre capillary sphincters at different sites in the body, thus allowing vascular shunt mechanism

Receives info from -

• chemoreceptors (chemical changes)
  -baroreceptors (pressure changes)