Cardiovascular Flashcards
Define and give resting, sub max and max values for HR
Number of times heart beats per min
Rest: Untrained - 60-75bpm, Trained - 50
Sub maximal: Up to 100-130bpm
Maximal: 220 minus age
Define and give resting, sub max and max values for SV
Volume of blood leaving left ventricle per beat
Rest: Untrained - 70ml, Trained - 100ml
Sub maximal: Untrained - 80-100, Trained - 160-200
Maximal: Untrained - 100-120, Trained - 160-200
Define and give resting, sub max and max values for Q
Volume of blood leaving left ventricle per minute
Rest: 5L/min
Sub maximal: Up to 10L/min
Maximal: Untrained: 20-30, Trained - 30-40
Factors affecting HR
Gender
Genetics
Fitness
Factors affecting SV
Venous return
Ventricular elasticity and contractibility
SV/EDV=Ejection Fraction - % of blood ejected from ventricle during ventricular systole
What is the Cardiac cycle
Represents one heart beat and is controlled by the conduction system
3 phases of the cardiac cycle
Diastole - relaxation phase where the atria fill
Atrial systole - Contraction of atria to force blood to ventricles through valves
Ventricular systole - both ventricles contract to eject blood into aorta and pulmonary artery
5 steps of conduction system and link to cardiac cycle
- No electrical impulse - Diastole
- SA node initiates an impulse - Atrial systole
- This is received by AV node and delays impulse
- Impulse passed down bundle of HIS and splits into left and right bundle branches
- Impulse passes through purkunje fibres - Ventricular systole
Heart rate response to sub maximal exercise
- Anticipatory rise: (prior to the start of exercise) due to the release of the hormone adrenaline prior to the start of exercise
- A rapid increase: (start of exercise) to increase blood and oxygen delivery, in line with exercise intensity
- A ‘steady state HR’: (throughout sustained exercise) oxygen supply meets the demand of exercise
- Initial rapid decrease: (recovery entered) action of the muscle pump reduces
- Gradual decrease of HR: HR returns to resting levels.
Heart rate response to maximal exercise
- Anticipatory rise: (prior to the start of exercise) due to the release of the hormone adrenaline prior to the start of exercise
- Rapid increase: this increases at a faster rate as a greater amount of oxygen is required to be supplied
- Slower increase: the heart rate does not plateau as exercise intensity continues to increase. There is a growing demand for oxygen and waste removal which HR must continually strive to meet.
- Rapid decrease: the muscle pump action reduces
- Slower gradual decrease: this takes longer as the heart must continue to remove waste products at a higher rate as well as taking a longer time to return the HR back to resting values.
Heart rate response to fluctuating levels of exercise
We still have an anticipatory rise as there is always the hormone
adrenaline presence
However, the HR will fluctuate due to varying intensities of exercise and in line with the demands placed upon the heart.
e.g. team sports – netball, rugby and football.
Stroke volume in response to exercise
Stroke Volume will increase in proportion to exercise intensity until a
plateau is reached at approximately 40-60% of working capacity.
For example: when running, SV will increases linearly as the running
speed/intensity increases
However, once running speed reaches 40-60% of maximal intensity SV plateaus.
This suggests that SV values are reached during sub-maximal exercise and cannot further increase beyond this.
Stroke volume is increased due to…
Increased Venous Return – volume of blood which returns from the
body to the heart
During exercise venous return increases meaning there is a greater
volume of blood returning to the heart and filling the ventricles
This is due to the muscles surrounding the veins which ‘contract’ to
pump the blood back to the heart
Starlings law
Increased venous return leads to an increased stroke volume, due to an increased stretch of the ventricle walls and therefore, increased force of contraction
Increased volume of blood returning to the RA
Increased EDV in the ventricles (greater volume of blood)
Thus, stretching the ventricle walls further
Increase in force of ventricular contraction
Larger volume of blood ejected
The lower the HR the more time available to maximise this effect hence why we see greater exercising SV’s in trained athletes.
Why does SV plateau during sub max exercise
An increased HR to maximal intensities does not allow enough time for the ventricles to completely fill with blood in the diastolic phase
This limits the Frank-Starling Mechanism
SV during recovery phase
SV is maintained during the early stages of recovery as HR rapidly
reduces.
This will maintain the blood flow and removal of waste products while lowering the stress and workload of the cardiac muscle.
Cardiac control
Although the heart is myogenic, when the heart rate needs to
increase or decrease, the brain becomes involved. This is known as cardiac control.
The Cardiac Control Centre (CCC) is located in the Medulla Oblongata of the brain. This is primarily responsible for Regulating the heart
The CCC is controlled by the Automatic nervous system (ANS)
This means that it is under involuntary control and consists of sensory and motor nerves from either the sympathetic or parasympathetic nervous system.
The nervous system determines the firing rate of the SA node
What happens when exercise begins in terms of cardiac control
The ANS is actioned
Information is sent to the CCC (cardiac control centre)
Located in the medulla oblongata
Impulses are sent via the cardiac accelerator nerve
This increases the firing rate of the SA node
Increasing heart rate
What are the control mechanisms of the CCC
There are three main factors that determine the action of the CCC. These are known as control mechanisms
Neural Control – primary control factor
Hormonal control
Intrinsic control
3 Types of neural control
Chemoreceptors: located in the muscles, aorta and the carotid arteries inform the CCC of any chemical changes in the blood stream such as, Increased levels of CO2 and lactic acid as well as an decrease in pH levels
Proprioceptors: Located in the muscles, tendons and joints. Inform the CCC of motor activity. Detects movement/ changes in joint angles
Baroreceptors: Located in the blood vessel walls inform the CCC of increased blood pressure
2 types of intrinsic control
Temperature changes will affect the viscosity (thickness) of the blood and speed of nerve impulse transmission. (higher the temperature of blood the faster the speed)
Venous return changes will affect the stretch in the ventricle walls, force of ventricular contraction and therefore, stroke volume (Starlings Law)
2 types of hormonal control
Adrenaline and noradrenaline are released from the adrenal glands
increasing the force of ventricular contraction and therefore, SV. This
will increase the HR.
Noradrenaline also acts as a neurotransmitter: a chemical substance
which is released at the end of a nerve fibre, which transmits nerve
impulses across a synapse
Parasympathetic nervous system
Vagus Nerve
Decreases HR
Reduces force of ventricular contraction
Sympathetic nervous system
Accelerator nerve
Increase HR
Increases force of ventricular contraction
If an increase in HR is required
- Sympathetic nervous system is actioned, releasing adrenaline and noradrenaline
- Sends stimulation to the SA node to increase
- Via the accelerator nerve
- Increases HR and increases force of contraction
If a decrease in HR is required
- The parasympathetic nervous system will be actioned
- Sends stimulation to the SA node via the vagus nerve
- This lowers the HR , reduces the force of ventricular contraction
- This reduces SV slowly
How does venous return impact quality of performance (4)
A reduction in SV/Q decreases blood/oxygen flow to the working
muscles, reducing their ability to contract/ work aerobically.
The net effect on performance = exercise intensity must be reduced or muscles will have to work anaerobically. Muscle fatigue will therefore, occur.
Although this is more significant in prolonged aerobic activities e.g.
marathon runner, it can also affect performance in anaerobic activities.
This would mean that a good VR will speed up recovery, and therefore, allow performers to work anaerobically for longer.
5 venous return mechanisms
POCKET VALVES – One way valve located in the veins which prevent the backflow of blood.
MUSCULAR PUMP – The contraction of skeletal muscle during exercise which compresses the veins forcing blood back towards the heart.
RESPIRATORY PUMP – During inspiration and expiration a pressure difference between the thoracic and abdominal cavities is created which squeezes blood back towards the heart.
SMOOTH MUSCLE – The layer of smooth muscle in the walls of the veins venoconstricts to create.
GRAVITY – Blood from above the heart returns towards the heart with the help of gravity.
What is blood pooling
Venous return requires a force to push the blood back towards the heart. If there is insufficient pressure, the blood will sit in the pocket valves of the veins. This is known as blood pooling.
Blood pooling is described as feeling of ‘heavy legs’
Increased Cardiac Output sent to the muscles will pool in the veins if there is an insufficient pressure.
Venous return mechanisms at rest and during exercise
During rest – pocket valves, gravity and smooth muscle are sufficient to maintain venous return however, not during or immediately after exercise.
The additional mechanisms of the skeletal pump and muscular pump are needed to ensure VR is maintained.
An active cool-down helps to maintain these important mechanisms.
Vascular shunt mechanism
The redistribution of blood flow (cardiac output) from one area of the
body to another.
Controlled by the Vasomotor Control Centre (VCC)
This occurs from a period of rest to exercise and allows for a greater
percentage of blood flow to skeletal muscles.
Vascular shunt at rest
At rest a high percentage of Q is distributed to the organs whereas a low percentage is distributed to the working muscles.
This is because Arterioles vasodilate, increasing blood flow to the organs whilst, arterioles vasoconstrict, decreasing blood flow to the muscles. Pre-capillary sphincters dilate, allowing more blood flow to the organ cells, while constricting to the muscle cells
Vascular shunt during exercise
During exercise a low percentage of Q is distributed to the organs whereas a high percentage is distributed to the working muscles.
This is because Arterioles vasodilate, increasing blood flow to the working muscles whilst, arterioles vasoconstrict, decreasing blood flow to the organs. Pre-capillary sphincters dilate, allowing more blood flow to the muscle cells, while constricting to the organ cells
