1.2a - The CV system Flashcards
Define Heart rate
- number of ventricle contractions per minute
Define stroke volume
- volume of blood ejected from the heart in one ventricular contraction
Define cardiac output
- volume of blood ejected from the ventricles in one minute
- Q= SV x HR
What are the typical resting values for heart rate (trained and untrained)
- 70 bpm (untrained)
- 50 bpm (trained)
What are the typical resting values for stroke volume (trained and untrained)
- 70ml (untrained)
- 100ml (trained)
What are the typical resting values for cardiac output (trained and untrained)
- 5000ml for both
Sub maximal values for HR, SV and Q
HR - 100/130bpm
SV - 100ml (untrained), 160/200ml (trained)
Q - 10 L/min, 36 L/min
Maximal values for HR, SV and Q
HR: 220 - age
SV: 100ml (untrained), 160/200ml (trained)
Q - 20-40 L/MIN
Explain hormonal regulation of the heart during exercise
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
Explain changes to stroke volume during sub maximal exercise
- 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
Describe how the conduction system of the heart controls the systolic phase of the cardiac cycle
- 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
Define systole and diastole
systole- contraction
diastole - relaxation
What term is used to describe the redistribution of blood during physical activity (1)
- Vascular shunt mechanism
Explain how the redistribution of blood during physical activity is achieved (4)
- 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
Describe intrinsic control of the heart during exercise (4)
- 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
Explain why more oxygen dissociates from the blood into the muscle cell during exercise (5)
- 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
Three mechanisms of venous return (3)
- pocket valves
- Respiratory/ muscle pump
- smooth muscle
Explain how an increase in venous return during exercise affects the quality of an athletes performance
- 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
Describe Neural factors which regulate the cardiac system and respiratory system during exercise
- Controlled by ANS (SNS part of it)
- Receptors detect change
- send it to the ccc in the medulla
- sends an impulse to the SA node to increase rate of firing
- heart rate increases and therefore cardiac output increases
- Receptors also send info to the RCC
- sends an impulse to increase the force of contraction of external intercostals and recruit additional muscles during inspiration
^compare to rest - expiration (recruitment of additional muscles)
- compare to rest
- overall affect (minute ventillation)
- effect on endurance performer
State the steps of the cardiac cycle
- 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)
What is the function of the chemo recpetors
- detect chemical changes
- increase of CO2 during
What is the function of the baro receptors
- Detect blood pressure changes
What is the function of the proprioceptors
Detect muscle movements
