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103: Theme 3 > Blood pressure > Flashcards

Blood pressure Flashcards

1
Q

Measurements and units of pressure

A

Units: mmHg or kiloPascals

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2
Q

Series circuit

A

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

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3
Q

Parallel circuit

A

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

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4
Q

Hepatic portal system

A
  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
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5
Q

Causes of increased blood pressure (3)

A

Increased:

  • peripheral resistance
  • cardiac output
  • blood volume
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6
Q

Pmean=

A

Pdiastolic + (Psystolic - Pdiastolic)/3

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7
Q

Stroke volume

A

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

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8
Q

Heart rate

A

Measured in beats per minute

Its reciprocal is the RR interval

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9
Q

Cardiac output

A

Volume of blood pumped out of a ventricle per minute

=HRxSV

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10
Q

End diastolic volume

A

Volume of blood in a ventricle at the end of diastole

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

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11
Q

End systolic volume

A

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

SV=EDV-ESV

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12
Q

Ejection fraction

A

Percentage of ventricular volume pumped out during a heart beat

=SV/EDV

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13
Q

Conductance

A

=1/ resistance

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14
Q

Poiseuille’s law

A

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

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15
Q

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

A

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

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16
Q

Effect of exercise on blood distribution

A 
Peripheral vasodilation
Vasoconstriction of splanchnic circulation
Increase in systolic pressure
Decrease in diastolic pressure
Increase in heart rate
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17
Q

Standing

A 
BP initially drops then compensatory recovery
Peripheral vasoconstriction
Increased heart rate
No change in systolic pressure
Increase in diastolic pressure
Increase in heart rate
18
Q

Control of systemic blood pressure

A

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

19
Q

Local vasomotor control

A

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

20
Q

Shear force

A

The force on the endothelium in the direction of blood flow

21
Q

Laminar flow

A

Flow without turbulence or eddies

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

22
Q

Baroreceptors

A

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

23
Q

Chemoreceptors

A

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

Located in the carotid bodies and aortic arch

24
Q

The Frank-Starling mechanism

A

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

25
Q

Venous return

A

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

26
Q

Preload

A

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

27
Q

Volume overload

A

Results when preload becomes too large

Chronic pathological stress on myocardial tissue

28
Q

Contractility

A

The force of contraction with which muscle contracts

If heart contractility increases it will pump more blood per minute with greater force

29
Q

Factors increasing ventricular preload

A
  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
30
Q

Afterload

A

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

31
Q

Pressure overload

A

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

32
Q

Thoracic pump

A

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

33
Q

Muscle pump

A

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

34
Q

Pulmonary circulation

A

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

35
Q

Coronary circulation

A

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

36
Q

Hypertension

A

High blood pressure
Often asymptomatic
May result in CAD or MI

37
Q

Causes of hypertension

A

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

Secondary to kidney disease

38
Q

Consequences of chronic hypertension (5)

A 
Aneurysm of stroke
Myocardial infarction
Kidney failure
Heart failure
Cardiac hypertrophy
39
Q

Orthostatic hypotension

A

Low BP on standing
- decreased venous return

Dizziness or syncope

Causes: drugs, hypovolaemia, age

40
Q

Cardiogenic shock: signs and symptoms

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

103: Theme 3 (17 decks)

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