Exercise Flashcards
What is acute exercise?
Exercising quickly from a standing start
acute dynamic exercise = increase in blood pressure (e.g. sprints)
What is blood pressure?
a measure of the force exerted by the heart to pump blood around the body
blood pressure = a critical variable in the body
Controlled variable = mean arterial pressure
What is the equation for blood flow?
Flow = change in blood pressure / resistance
Why is maintenance of mean arterial pressure important?
For perfusion of the organs with blood. It ensures the tissues e.g. brain, heart, etc have adequate O2 and get rid of enough CO2.
If blood pressure is too low, organs won’t be perfused adequately
Muscles also need a resting rate of perfusion to keep them alive.
What is ‘normal’ resting arterial blood pressure?
120 / 80 mmHg (millimetres of mercury)
120 = systolic pressure
80 = diastolic pressure
Where is normal resting arterial blood pressure measured?
Measured in brachial artery
Why does blood pressure vary during 24 hrs?
There is always a morning surge
Other factors may be due to:
sleeping
activity / exercise
meals
stress
medication
Why is there a morning surge in blood pressure?
Sympathetic drive of nervous system - increasing heart rate + restricting blood supply to areas we don’t need to action - opens up blood to surrounding muscles
Why is blood pressure lower when we are asleep?
It is under the control of the parasympathetic nervous system.
On a blood pressure graph, which area is systolic and which is diastolic?
Top area = Systolic bp
Bottom area = Diastolic bp
What is the equation for Arterial blood pressure?
Arterial blood pressure = Cardiac output X Total peripheral resistance
What is the equation for Cardiac output?
Cardiac output = heart rate x stroke volume
What are heart rate and stroke volume and artery diameter all under the control of?
Autonomic nervous system
What controls blood pressure?
The baroreflex
How does the baroreflex work?
Increased arterial blood pressure –> Stretches arterial baroreceptors = Increases firing
To the heart: Parasympathetic nervous system increases
-> sympathetic nervous system decreases
= heart rate and contractility decreases
To blood vessels: Sympathetic nervous system decreases
= Vasodilation decreases
(and the other way round for increased vasodilation)
Why does blood pressure increase after dynamic exercise?
- Increased O2 needed by active skeletal
muscle - Increased consumption of O2
How does the body meet the demands of exercising muscle?
= increased blood flow
- Increased blood pressure (via cardiac output)
- Dilation of vessels supplying active skeletal
muscle
Blood pressure goes up, resistance goes down (in skeletal muscle) therefore a BIG difference in flow
During maximal exercise where is the majority of the distribution of blood flow?
= to muscle ( 60% of cardiac output)
in heavy exercise some blood goes to the skin -> a homeostatic response to regulate / reduce temperature
Why is a rise in blood pressure important?
It predicts cardiovascular events:
- heart attack
- stroke
- overall mortality
The larger the increase of systolic blood pressure at maximum exercise - indicates greater chance of mortality
What happens to sympathetic activity during exercise?
Sympathetic activity is increased during anticipation and initial stages of exercise.
An increase in heart rate and contractility = generalised vasoconstriction via alpha receptors
Blood vessels dilate to fulfil requirements for metabolism. Via beta mediated vasodilation due to adrenaline - a small effect
In exercise there is an override of sympathetic activity in some tissues - the action of the baroreflex is not useful in exercise
What is the main cause for the increase in blood pressure during exercise?
The exercise pressor reflex
2 divisions:
1. Metaboreflex
2. Mechanoreflex
How does the exercise pressor reflex act alongside the central command?
The central command from the brain - cardiovascular control centre (medulla oblongata)
–> increased sympathetic activity
= increased blood pressure
What is the muscle mechanoreflex?
Mechanoreceptors in skeletal muscle monitor physical state
The mechanoreflex responds to mechanical pressure / distortion of muscle
How does the mechanoreflex work?
CNS –> Increased sympathetic nerve activity =
Noradrenaline –> Beta - adrenergic receptors = 1. Increased heart rate
2. Increased contractility
3. Increased stroke volume
Noradrenaline –> Alpha adrenergic receptors = 1. Vasoconstriction
What is the metaboreflex?
Chemoreceptors in the skeletal muscle monitor the muscle’s chemical state
What metabolic by-products increase during exercise?
- ATP
- pH of muscle (due to increased CO2)
What is the function of the metaboreflex?
Increases sympathetic nerve activity to increase blood pressure.v
What happens to sympathetic nerve activity and skeletal muscle blood flow during exercise?
Sympathetic nerve activity increases during exercise - vasoconstriction
Vasodilation occurs in skeletal muscle
Why does vasodilation occur in skeletal muscle ?
called Sympatholysis
- Produces produced during exercise block the effects of sympathetic nerve activity
e.g nitric oxide = vasodilation
Main function of the baroreflex in exercise?
Is the central command - adjusts set point.
central command adjusts normal blood pressure set point depending on activity
