Exercise

Question 1

What is acute exercise?

Answer 1

Exercising quickly from a standing start

acute dynamic exercise = increase in blood pressure (e.g. sprints)

Question 2

What is blood pressure?

Answer 2

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

Question 3

What is the equation for blood flow?

Answer 3

Flow = change in blood pressure / resistance

Question 4

Why is maintenance of mean arterial pressure important?

Answer 4

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.

Question 5

What is ‘normal’ resting arterial blood pressure?

Answer 5

120 / 80 mmHg (millimetres of mercury)

120 = systolic pressure
80 = diastolic pressure

Question 6

Where is normal resting arterial blood pressure measured?

Answer 6

Measured in brachial artery

Question 7

Why does blood pressure vary during 24 hrs?

Answer 7

There is always a morning surge
Other factors may be due to:
sleeping
activity / exercise
meals
stress
medication

Question 8

Why is there a morning surge in blood pressure?

Answer 8

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

Question 9

Why is blood pressure lower when we are asleep?

Answer 9

It is under the control of the parasympathetic nervous system.

Question 10

On a blood pressure graph, which area is systolic and which is diastolic?

Answer 10

Top area = Systolic bp
Bottom area = Diastolic bp

Question 11

What is the equation for Arterial blood pressure?

Answer 11

Arterial blood pressure = Cardiac output X Total peripheral resistance

Question 12

What is the equation for Cardiac output?

Answer 12

Cardiac output = heart rate x stroke volume

Question 13

What are heart rate and stroke volume and artery diameter all under the control of?

Answer 13

Autonomic nervous system

Question 14

What controls blood pressure?

Answer 14

The baroreflex

Question 15

How does the baroreflex work?

Answer 15

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)

Question 16

Why does blood pressure increase after dynamic exercise?

Answer 16

• Increased O2 needed by active skeletal
  muscle
• Increased consumption of O2

Question 17

How does the body meet the demands of exercising muscle?

Answer 17

= 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

Question 18

During maximal exercise where is the majority of the distribution of blood flow?

Answer 18

= to muscle ( 60% of cardiac output)

in heavy exercise some blood goes to the skin -> a homeostatic response to regulate / reduce temperature

Question 19

Why is a rise in blood pressure important?

Answer 19

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

Question 20

What happens to sympathetic activity during exercise?

Answer 20

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

Question 21

What is the main cause for the increase in blood pressure during exercise?

Answer 21

The exercise pressor reflex

2 divisions:
1. Metaboreflex
2. Mechanoreflex

Question 22

How does the exercise pressor reflex act alongside the central command?

Answer 22

The central command from the brain - cardiovascular control centre (medulla oblongata)
–> increased sympathetic activity

= increased blood pressure

Question 23

What is the muscle mechanoreflex?

Answer 23

Mechanoreceptors in skeletal muscle monitor physical state
The mechanoreflex responds to mechanical pressure / distortion of muscle

Question 24

How does the mechanoreflex work?

Answer 24

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

Question 25

What is the metaboreflex?

Answer 25

Chemoreceptors in the skeletal muscle monitor the muscle’s chemical state

Question 26

What metabolic by-products increase during exercise?

Answer 26

1. ATP
2. pH of muscle (due to increased CO2)

Question 27

What is the function of the metaboreflex?

Answer 27

Increases sympathetic nerve activity to increase blood pressure.v

Question 28

What happens to sympathetic nerve activity and skeletal muscle blood flow during exercise?

Answer 28

Sympathetic nerve activity increases during exercise - vasoconstriction

Vasodilation occurs in skeletal muscle

Question 29

Why does vasodilation occur in skeletal muscle ?

Answer 29

called Sympatholysis

• Produces produced during exercise block the effects of sympathetic nerve activity

e.g nitric oxide = vasodilation

Question 30

Main function of the baroreflex in exercise?

Answer 30

Is the central command - adjusts set point.

central command adjusts normal blood pressure set point depending on activity