PBL 2

Question 1

define systole

Answer 1

this is contraction of the heart muscle, the ventricles and atria both undergo systole and contract

Question 2

define diastole

Answer 2

relaxation of the heart muscle both the ventricles and atria relax

Question 3

define stroke volume

Answer 3

this is the volume of blood pumped from the left ventricle per beat

Question 4

define pulse pressure

Answer 4

pulse pressure is the difference between systolic and diastlolic blood pressure, it is measured in mmHG
- it represents the force the heart generates with each conditions

Question 5

define mean arterial pressure

Answer 5

the mean arterial pressure is an average blood pressure in the arteries an individual during a single cardiac cycle

Question 6

define total peripheral resistance

Answer 6

this is the mean arterial pressure – mean venous pressure divided by the cardiac output – this is the resistance of the arteries to flow, resistance increases as they constrict and resistance decreases as they dilate

Question 7

define cardiac output

Answer 7

the volume of blood pumped out the heart from the ventricles to the body per minute
- measured using an echocardiogram or a doppler ultrasound

Question 8

how does systole change during exercise

Answer 8

Systolic
Systole = contraction of the heart
Systolic blood pressure = maximum pressure in the arteries
Limits
>140 mm Hg systolic marginal hypertension.
>160 mm Hg definite intervention threshold.
Exercise
- decreased end systolic residual volume as the stroke volume is maintained due to the contraction of the atria which help transfer blood into the ventricles during diastole
- there is a progressive increase in systolic blood pressure it rises to between 160 – 220mmHg during exercise

Question 9

how does diastole changes during exercise

Answer 9

• Shortens allows increase in heart rate – once you get above 200 beats per minute no time to fill the ventricles and heart during diastole less tiem for the blood to go into the heart
• Diastolic blood pressure remains the same

Question 10

how does cardiac output change during exercise

Answer 10

• Increases nearly 4 times to cope with increased demand for oxygen
• Increases by either increasing heart rate up to 2.5 times resting or increasing stroke volume up to 1.5 times
• Most of the increased volume goes to exercising muscles that need the extra oxygen supply
• Measured by heart beat x stroke volume

Question 11

How does pulse pressure change in exercise

Answer 11

Pulse pressure increases with exercise due to increased stroke volume

• this is because the systolic pressure increases whereas the diastolic pressure remains about the same this causes an increase in stroke volume and cardiac output
• pulse pressure is systolic – diastolic pressure

Question 12

how does mean arterial pressure change in exercise

Answer 12

• during exercise the cardiac output increases more than the total resistance decreases so the mean arterial pressure increases by a small amount
• mean arterial pressure is calculated as diastolic plus 1/3 of pulse pressure
• diastolic pressure does not increase but pulse pressure does therefore it has a slight increase in pressure during exercise but not as much as pulse pressure

Question 13

describe the structure of the sympathetic nervous system

Answer 13

• prevertebral and paravertebral ganglia
• chain extends from T1 to L2
• prevertebral is T1-T4
• paravertebral is T5-L2
• prevertebral has three cervical ganglia these are the superior middle and inferior cervical ganglia
• paravertebral have 3 ganglia – these are the coelic, superior and inferior mesenteric ganglia
• 25 pairs of ganglia that are joined by nerve trunks
• Sympathetic – supply vascoconstrictor nerves

Question 14

what happens to the sympathetic system during exercise

Answer 14

• When exercise begins local chemical vasodilators are released from the exercising muscles
• Increase muscle blood flow to supply the extra oxygen needed by the muscles
• Vasodilation reduces total peripheral resistance this could cause a total drop in blood flow but sympathetic outflow causes a global vasoconstriction which increases vascular resistance in nonactive muscles resulting in the total peripheral resistance being maintained
• Sympathetic activity also increases heart rate which increases cardiac output
• Cardiac output supplies more blood and oxygen to the exercising muscles
• Noreadnrealine – globally constricts blood vessels enabling there to be an adequate supply of blood to the vasodilated active muscle and redistributes the cardiac output to the exercising muscle – released from the medulla of the adrenal glands
• Adrenaline – releases glucose into the blood from the liver and muscle cells for extra energy this increases cardiac output and respiration and dilates airways which increases oxygen intake – released from the medulla of the adrenal glands

Question 15

name the alpha receptors and what they do

Answer 15

Alpha 1 is the main receptor on vascular smooth muscle
Acts to increase contraction.
Alpha 2 receptors are found on presynaptic sympathetic nerve terminals
Act to reduce noradrenaline release by negative feedback

Question 16

name the beta receptors and what they do

Answer 16

Beta 1 receptors found mainly in heart (and kidneys)
Act to increase force & rate of contraction of myocardium
Beta 2 found mainly in bronchial smooth muscle (but also in smooth muscle of gastrointestinal tract, liver, uterus)
Act to relax the muscle
Beta 3 receptors increase lipolysis and gluconeogenesis in adipose tissue, thus providing energy-rich substrates for the actively metabolizing muscles.

Question 17

what is the normal pulse pressure

Answer 17

30-50 mmHg

- it is raised during exercise and can reach 100mmHg

Question 18

what is a low pulse pressure

Answer 18

• a low pulse pressure less than 25% of systolic pressure
• decrease in stroke volume usually - for example in aortic stenosis, heart failure blood loss, shock, and cardiac tamponade

Question 19

what is a high pulse pressure

Answer 19

• greater than 100mmHg is high
• increase in stroke volume or reduction of arterial compliance- for example aortic regurgitation, volume overload and ageing

Question 20

what are the calculations for mean arterial pressure

Answer 20

MAP (estimation) = DP + 1/3(PP)

MAP (calculation) = (CO x TPR) + CVP

Normal: 65-110 mmHg

Question 21

how do you measure stroke volume

Answer 21

EDV-ESV

- measured using an echocardiogram

Question 22

what is the stroke volume of a typical man

Answer 22

Typically 70ml/min at rest in a 70kg man

Question 23

what is the definition of preload

Answer 23

end-diastolic ventricular volume

Question 24

what is the definition of afterload

Answer 24

the systemic resistance the ventricles must
overcome to eject blood into vasculature aka total
peripheral resistance

Question 25

where is High cardiac output seen in

Answer 25

Exercise, sepsis, anaemia, pregnancy, hyperthyroidism

Question 26

where is low cardiac output seen in

Answer 26

Heart failure, drugs (beta-blocker, negative inotropes), aortic
stenosis

Question 27

why is the stroke volume able to stay high even though there is shorter filling time

Answer 27

Able to stay high even though there is shorter filling time as a result of high
heart rate

Due to sympathetic activity increasing ventricular contractility and decreasing
end systolic volume

This leads to increased passive filling of ventricle at start of diastole

Atria also contracts during diastole to push blood into ventricles

Vasoconstriction via sympathetic activity mobilises blood from the great veins,
increasing preload and SV

Question 28

why is there an increase in pulse pressure

Answer 28

• systolic pressure is increased due to the increase in stroke volume
• diastolic pressure stays the same or decreases due to decrease in total peripheral resistance

Question 29

describe what cause the increase in cardiac output in different types of exercise

Answer 29

Mild exercise:
Increase in CO due to
increase in both
stroke volume and
heart rate

Moderate exercise:
Stroke levels start to
reach maximum
levels. Heart rate
continue to increase

Intense exercise:
Increase in CO mostly
due to changes in
heart rate

Question 30

describe how blood distribution changes with exercise

Answer 30

At rest 20-25% of resting CO is
delivered to muscles, but in
exercise this can rise to 80-90% of
CO.

Blood flow to brain doesn’t change
much

Increased blood flow to skin is
important in thermoregulation

In intense exercise,
vasoconstriction takes over and
blood redirected to skeletal
muscles at the expense of the
cooling action (i.e. temperature
will rise).

Question 31

what are the 2 main mechanisms that regulate blood flow

Answer 31

Systemic regulation

Local factors

Question 32

what are local factors

Answer 32

Regulatory factors from blood vessels

or from surrounding tissues

Question 33

what do endothelial factors do

Answer 33

Nitric oxide relaxes smooth muscle cells and causes

dilatation of blood vessels.

Question 34

what do tissues factors do

Answer 34

Adenosine and inorganic phosphates, carbon dioxide,
hydrogen ions (H+) and potassium ions (K+) released
from contracting muscles.

Vasodilatory metabolites causing dilatation of blood
vessels.

Question 35

how does blood pressure change during exercise

Answer 35

• MAP stays constant during exercise
• Increase in systolic pressure due to increased force of ventricular contraction and increased SV
• Stable diastolic pressure or even decreased due to reduced TPR.