Blood pressure

Question 1

Measurements and units of pressure

Answer 1

Units: mmHg or kiloPascals

Question 2

Series circuit

Answer 2

2 paths in a row
Flow in both parts is the same
Pressure is higher in the first than the second because energy is lost as blood experiences friction/ resistance

Question 3

Parallel circuit

Answer 3

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

Question 4

Hepatic portal system

Answer 4

1. Food is absorbed in capillaries of the gut
2. Capillaries assemble into portal vein
3. Portal vein goes to the liver and breaks inter capillaries
4. Liver ‘sees’ nutrients in blood at high concentration before it’s distributed throughout the body

Question 5

Causes of increased blood pressure (3)

Answer 5

Increased:

• peripheral resistance
• cardiac output
• blood volume

Question 6

Pmean=

Answer 6

Pdiastolic + (Psystolic - Pdiastolic)/3

Question 7

Stroke volume

Answer 7

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

Question 8

Heart rate

Answer 8

Measured in beats per minute

Its reciprocal is the RR interval

Question 9

Cardiac output

Answer 9

Volume of blood pumped out of a ventricle per minute

=HRxSV

Question 10

End diastolic volume

Answer 10

Volume of blood in a ventricle at the end of diastole

Associated with pre-load (how stretched the muscle is)

Question 11

End systolic volume

Answer 11

Volume of blood remaining in a ventricle at the end of systole

SV=EDV-ESV

Question 12

Ejection fraction

Answer 12

Percentage of ventricular volume pumped out during a heart beat

=SV/EDV

Question 13

Conductance

Answer 13

=1/ resistance

Question 14

Poiseuille’s law

Answer 14

The fall in pressure along the length of a cylindrical blood vessel is proportional to flow x resistance

Question 15

Causes of dilation and constriction in individual blood vessels (4)

Answer 15

Central regulation: CNS, autonomic, endocrine
Local regulation of pressure
Immune
Haemostasis

Question 16

Effect of exercise on blood distribution

Answer 16

Peripheral vasodilation
Vasoconstriction of splanchnic circulation
Increase in systolic pressure
Decrease in diastolic pressure
Increase in heart rate

Question 17

Standing

Answer 17

BP initially drops then compensatory recovery
Peripheral vasoconstriction
Increased heart rate
No change in systolic pressure
Increase in diastolic pressure
Increase in heart rate

Question 18

Control of systemic blood pressure

Answer 18

Local: endothelial, nitric oxide
Neurological: ANS
Humoral: renal, pituitary, adrenal

Question 19

Local vasomotor control

Answer 19

Endothelial cells release vasodilator compounds
- nitric oxide causes smooth muscle relaxation
- vasodilation
Controlled by local blood flow conditions
- hydrostatic pressure
- shear force

Question 20

Shear force

Answer 20

The force on the endothelium in the direction of blood flow

Question 21

Laminar flow

Answer 21

Flow without turbulence or eddies

Flow of all molecule is directly in the direction of the overall flow of all fluid

Question 22

Baroreceptors

Answer 22

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

Question 23

Chemoreceptors

Answer 23

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

Located in the carotid bodies and aortic arch

Question 24

The Frank-Starling mechanism

Answer 24

The stroke volume of the heart increases in response to an increase in the volume of blood filling the heart

Question 25

Venous return

Answer 25

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

Question 26

Preload

Answer 26

The initial stretching of the cardiac myocytes prior to contraction Depends on venous return

Question 27

Volume overload

Answer 27

Results when preload becomes too large | Chronic pathological stress on myocardial tissue

Question 28

Contractility

Answer 28

The force of contraction with which muscle contracts | If heart contractility increases it will pump more blood per minute with greater force

Question 29

Factors increasing ventricular preload

Answer 29

1. Increase atrial compliance 2. Increase ventricular compliance 3. Increase aortic pressure 4. Increase thoracic venous blood volume 5. Decrease venous compliance 6. Decrease heart rate

Question 30

Afterload

Answer 30

The resistance that the chambers of the heart must overcome in order to eject blood out of the heart Increased by back pressure from aorta or pulmonary arteries Increases if the exit valve fails to open completely

Question 31

Pressure overload

Answer 31

Pathological stress on the myocardial tissue that occurs during systole when myocardium generates force to contract but cannot contract

Question 32

Thoracic pump

Answer 32

During inspiration, intrathoracic pressure is negative, abdominal pressure is positive Pressure gradient pulls blood towards the right atrium

Question 33

Muscle pump

Answer 33

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

Question 34

Pulmonary circulation

Answer 34

High capillary density Low vascular resistance Acts as blood reservoir Endocrine control of BP (conversion of Ang1 to Ang2 by ACE in endothelial cells) Acts as filter O2, CO2, pH effects are opposite to those in systemic circulation

Question 35

Coronary circulation

Answer 35

Cardiac muscle has high demand Most flow occurs during diastole Obtains blood before aorta

Question 36

Hypertension

Answer 36

High blood pressure Often asymptomatic May result in CAD or MI

Question 37

Causes of hypertension

Answer 37

Mismatch between blood volume and circulatory capacity Most cases idiopathic: - hormones (Ang 2) - brain medulla (NTS) Secondary to kidney disease

Question 38

Consequences of chronic hypertension (5)

Answer 38

``` Aneurysm of stroke Myocardial infarction Kidney failure Heart failure Cardiac hypertrophy ```

Question 39

Orthostatic hypotension

Answer 39

Low BP on standing - decreased venous return Dizziness or syncope Causes: drugs, hypovolaemia, age

Question 40

Cardiogenic shock: signs and symptoms

Answer 40

``` Compensatory - Tachycardia - Tachypnoea Failure to compensate - Low urine output - Hypotension - Confusion - Syncope ```