1.2a - The CV system

Question 1

Define Heart rate

Answer 1

• number of ventricle contractions per minute

Question 2

Define stroke volume

Answer 2

• volume of blood ejected from the heart in one ventricular contraction

Question 3

Define cardiac output

Answer 3

• volume of blood ejected from the ventricles in one minute
• Q= SV x HR

Question 4

What are the typical resting values for heart rate (trained and untrained)

Answer 4

• 70 bpm (untrained)
• 50 bpm (trained)

Question 5

What are the typical resting values for stroke volume (trained and untrained)

Answer 5

• 70ml (untrained)
• 100ml (trained)

Question 6

What are the typical resting values for cardiac output (trained and untrained)

Answer 6

• 5000ml for both

Question 7

Sub maximal values for HR, SV and Q

Answer 7

HR - 100/130bpm

SV - 100ml (untrained), 160/200ml (trained)

Q - 10 L/min, 36 L/min

Question 8

Maximal values for HR, SV and Q

Answer 8

HR: 220 - age

SV: 100ml (untrained), 160/200ml (trained)

Q - 20-40 L/MIN

Question 9

Explain hormonal regulation of the heart during exercise

Answer 9

1- controlled by the ANS
(Anticipatory rise)
2- sympathetic nervous system is stimulated
3- Adrenalin secreted from adrenal glands
4- stimulates and increase in the rate of firing of the SA node
(increase heart rate)
5- Increases force of contraction
(increases stroke volume)
6- Increased cardiac output

Question 10

Explain changes to stroke volume during sub maximal exercise

Answer 10

• stroke volume plateaus at 200ml and sometimes drops
• increase in venous return = increase in SV
• (at higher heart rate) there is a reduced filling time
• (at higher heart rate) smaller end diastolic volume
• heart is only partially filled with blood

Question 11

Describe how the conduction system of the heart controls the systolic phase of the cardiac cycle

Answer 11

• SA node initiates and sends an impulse
• causes atrial systole (contraction of atria)
• blood forced from atria to the ventricles through the AV valves (tricuspid valves)
• Impulse travels to the AV node
• the impulse then continues down the bundle of his to the purkinje fibres
• causing ventricular systole
• blood is ejected from the ventricles

Question 12

Define systole and diastole

Answer 12

systole- contraction
diastole - relaxation

Question 13

What term is used to describe the redistribution of blood during physical activity (1)

Answer 13

• Vascular shunt mechanism

Question 14

Explain how the redistribution of blood during physical activity is achieved (4)

Answer 14

• more blood to the working muscles, less blood to the non-essential organs
• Chemoreceptors/ proprioceptors and baroreceptors pass info to the vasomotor centre
• vasomotor centre directs messages as to where the blood is needed
• vasodilation of arterioles to working muscles (expansion)
• opening of pre-capillary sphincters to working muscles

vasoconstriction of arterioles leading to some organs
closing of pre capillary sphincters

Question 15

Describe intrinsic control of the heart during exercise (4)

Answer 15

• increase in venous return = increase in stroke volume
• more blood entering right atrium
• right atrium stretches
• excites the SA node to increase rate of firing
• Increasing end diastolic volume
• more blood enters the left ventricle which will cause it to stretch and recoil with more force
• increases stroke volume
• temperature increases which increases heart rate
  ^increases the speed of nerve impulses

Question 16

Explain why more oxygen dissociates from the blood into the muscle cell during exercise (5)

Answer 16

• Oxygen moves from a high partial pressure to a low partial pressure
• (During exercise) the muscles use more oxygen
• Increased oxygen dissociation from haemoglobin
• Low partial pressure of O2 in the muscle cell
• high partial pressure of O2 in the blood
• greater pressure gradient between blood and muscle cell
• increase Co2 in the body
• increase in body temp
• increase in blood acidity

Question 17

Three mechanisms of venous return (3)

Answer 17

• pocket valves
• Respiratory/ muscle pump
• smooth muscle

Question 18

Explain how an increase in venous return during exercise affects the quality of an athletes performance

Answer 18

• an increased venous return= increased stroke volume
• more blood entering the right atrium
• excites SA node to increase rate of firing
• increased end diastolic volume
• ventricle walls stretch (recoil affect)
• increase in cardiac output
• increased blood to working muscles
• increased endurance and delays fatigue

Question 19

Describe Neural factors which regulate the cardiac system and respiratory system during exercise

Answer 19

1. Controlled by ANS (SNS part of it)
2. Receptors detect change
3. send it to the ccc in the medulla
4. sends an impulse to the SA node to increase rate of firing
5. heart rate increases and therefore cardiac output increases
6. Receptors also send info to the RCC
7. sends an impulse to increase the force of contraction of external intercostals and recruit additional muscles during inspiration
   ^compare to rest
8. expiration (recruitment of additional muscles)
9. compare to rest
10. overall affect (minute ventillation)
11. effect on endurance performer

Question 20

State the steps of the cardiac cycle

Answer 20

• Atrial diastole (atrium relaxes and fills with blood)
• SA node (sends cardiac impulse to walls of atria which forces it to contract)
• Atrial systole (atrium contracts meaning that blood leaves
• AV node (AV node sends cardiac impulse to the valves to delay filling so the ventricle can experience diastole
• Bundle of his and purkinje fibres (receives impulse and causes the ventricles to contract)
• Ventricular systole (ventricle contracts and blood leaves the heart)

Question 21

What is the function of the chemo recpetors

Answer 21

• detect chemical changes
• increase of CO2 during

Question 22

What is the function of the baro receptors

Answer 22

• Detect blood pressure changes

Question 23

What is the function of the proprioceptors

Answer 23

Detect muscle movements