Blood pressure

Question 1

Series

Answer 1

2 paths in a row
Flow in both paths is the same
Pressure is higher in the first path than the 2nd path
b/c energy is lost as blood experiences friction/resistance

Question 2

Parallel

Answer 2

Branching paths
Flow is split between 2 paths
Pressure is same at start of both paths.
If paths have identical resistance same pressure

Question 3

Pmean

Answer 3

Pdiastolic + (Psystolic - Pdiastolic)/3

Question 4

Stroke volume

Answer 4

Volume of blood pumped out of a ventricle during one beat of the heart
70ml

Question 5

Cardiac output

Answer 5

Volume of blood pumped out of a ventricle per minute

4.9L/min

Question 6

End Diastolic Volume

Answer 6

Volume of blood in a ventricle at the end of filling (diastole). EDV is associated with “pre-load”, how stretched the muscle is.
120ml

Question 7

End Systolic Volume

Answer 7

Volume of blood remaining in a ventricle at the end of contraction (systole). So: SV = EDV – ESV
50ml

Question 8

Ejection Fraction

Answer 8

Percentage of ventricular volume pumped out during a heart beat: SV / EDV
55-70%

Question 9

vasoconstriction

Answer 9

Smaller radius

• > higher resistance
• > lower flow rate

Question 10

Dilation and constriction of BV causes

Answer 10

Central regulation: CNS, Autonomic, Endocrine
Exercise

Local regulation of pressure

Immune

Haemostasis

Question 11

Excercise

Answer 11

peripheral vasodilatation
muscle/skin

vasoconstriction
splanchnic circulation

Increase HR and systolic BP
Decrease diastolic BP

Question 12

Standing

Answer 12

Initially a drop in BP
- then compensatory recovery (ie increase back to normal):

peripheral vasoconstriction

• Arterial + venous
• & Increased HR

Question 13

Systemic BP control

Answer 13

Local 
- Endothelial
- Nitric Oxide (NO)
Neurological – the autonomic system
- Sympathetic: noradrenaline
Humoral – renal / pituitary / adrenal
- The kidney is central to Blood Pressure

Question 14

Local Vasomotor control

Answer 14

Endothelial cells release vasodilator compounds

• Nitric Oxide
• Causes smooth muscle relaxation
• Vasodilatation

Controlled by local blood flow conditions
Hydrostatic pressure
Shear force
- Made greater by laminar flow
- Shear force is atheroprotective

Question 15

Baroreceptors

Answer 15

Detect pressure and feed back to the brain
Located in the transverse aortic arch and the carotid sinuses of the left and right internal carotid arteries
Activity —> decreased BP

Question 16

Chemoreceptors

Answer 16

Detect when O2 levels are low & feed back to the brain

Located in the carotid bodies and aortic bodies

Question 17

Frank-Starling

Answer 17

The stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (the end diastolic volume)

Question 18

Venous return

Answer 18

The volume of blood flowing back to the heart through the veins

Question 19

Preload

Answer 19

The initial stretching of the cardiac myocytes during diastole (prior to contraction). Depends on venous return

Question 20

Volume Overload

Answer 20

Results when preload becomes too large

Question 21

Afterload

Answer 21

The resistance that the chambers of the heart must overcome in order to eject blood out of the heart
Resistance during systole

Increased by back pressure
from Aorta or pulmonary arteries

Increases if the exit valve fails to open completely

Pressure Overload
Results from elevated afterload

Question 22

Thoracic Pump

Answer 22

“Pulls” the blood (from below) towards the right atrium.
during inspiration
intrathoracic pressure is negative
abdominal pressure is positive (compression of abdominal organs by diaphragm).
Creates a pressure gradient

Question 23

Muscle Pump

Answer 23

Rhythmical contraction of limb muscles
as occurs during normal locomotor activity
Squeezes blood out of nearby veins
Venous valves assure one-way flow toward heart

Question 24

Pulmonary Circulation

Answer 24

High Capillary Density

Low Vascular Resistance

Acts as Blood Reservoir

Endocrine control of BP (ACE)

Acts as Filter

Question 25

Pulmonary Circulation - O2, CO2 and pH

Answer 25

O2, CO2, pH effects opposite those in systemic circulation If O2 is low in a region of the lung, the arterioles constrict (likewise if CO2 or H+ are high, vasoconstriction) Poor ventilation reduced perfusion This minimises the amount of blood that is poorly oxygenated

Question 26

Coronary Circulation

Answer 26

Cardiac Muscle has High Demand Most Flow occurs during Diastole Obtains blood almost before aorta

Question 27

Hypertension

Answer 27

High blood pressure esp. high diastolic pressure Often Asymptomatic May result in coronary artery disease and MI

Question 28

Hypertension caused by

Answer 28

Mismatch between blood volume and circulatory capacity ``` Most cases are idiopathic Hormones (Ang II) Brain Medulla (NTS) ``` 2ndary to Kidney disease

Question 29

Cardiogenic shock - failure to compensate

Answer 29

``` Low urine output Hypotension Syncope Confusion Acidosis ```

Question 30

Cardiogenic shock - compensatory mechanisms

Answer 30

Tachycardia | Tachypnoea