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103 theme 2 > Blood Pressure > Flashcards

Blood Pressure Flashcards

1
Q

where is blood pressure measured

A

at the brachial artery

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2
Q

units of blood pressure

A

`mmHg (or KPa – metric pressure)

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3
Q

what is a series path

A

two paths in a row (flow in both parts is the same), pressure is higher in the first path than the second one as energy is lost as blood experiences friction/resistance

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4
Q

what is a parallel path

A

branching paths so flow is split between two, pressure is the same at the start of both paths (identical resistance so have same pressure)

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5
Q

what is a portal system

A

a capillary bed reassembles to a blood vessel that splits into another capillary bed

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6
Q

what does a portal system enable

A

Allows transport of chemicals from one tissue to another without dilution by mixing with blood at the heart.

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7
Q

what is an example of a portal system

A

Hepatic Portal system – food us absorbed in gut capillaries, assemble into the portal veins, goes to liver and breaks into capillaries. liver- nutrients in blood (and dietary toxins eg alcohol) at high conc before distribution to the body

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8
Q

what are arterial pressures

A

low in diastole and high in systole, vary over time

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9
Q

what is pulse pressure

A

difference between diastolic and systolic pressure

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10
Q

how is mean pressure calculated

A

Mean = diastolic + (systolic-diastolic/3)

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11
Q

what is stroke volume

A

volume of blood pumped out of the ventricle during a single heartbeat

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12
Q

what is heart rate

A

BPM

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13
Q

What is the reciprocal of heart rate

A

RR interval which is 60/HR

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14
Q

what is cardiac output

A

Cardiac Output is the volume of blood pumped from a ventricle per minute
CO= HR X SV

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15
Q

what does atrial systole do

A

adds final 20-25% of blood to fill ventricles

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16
Q

what is end diastolic volume

A

volume of blood in a ventricle at the end of filling (diastole). Associated with preload (how stretched the muscle is)

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17
Q

what is end systolic volume

A

vol of blood remaining in a ventricle at the end of contraction (systole)

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18
Q

how is stroke volume calculated

A

SV=EDV-ESV

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19
Q

what is ejection fraction

A

percentage of filled ventricular volume pumped out during a heartbeat
SV/EDV

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20
Q

how does radius effect blood flow

A

Vasoconstriction = smaller radios so higher resistance and lower flow rate

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21
Q

how is conductance calculated

A

Conductance (g) = 1/Resistance (R)

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22
Q

what happens to flow and resistance when radius increases

A 
Flow increases (to power of 4 assuming pressure stays the same)
resistance decreases (power of 4 too)
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23
Q

what causes dilation and constriction of individual blood vessels

A

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

24
Q

how does exercise effect blood flow

A

Peripheral dilation (muscle/skin)
Vasoconstriction (splanchnic circulation)
BP systolic increases, diastolic decreases
HR increases vastly

25
Q

what happens to blood pressure when standing

A 
Initial drop in BP (compensatory recovery)
Peripheral vasoconstriction (Arterial and Venous and increased HR)
BP no change in systolic but diastolic increases as does HR
26
Q

how is systemic blood pressure controlled

A

Local decisions related to endothelial cells, make NO to relax blood vessels
Neurological control via ANS (sympathetic – noradrenaline)
Humoral (HORMONAL) – renal/pituitary/adrenal (kidney central to BP)

27
Q

what is local vasomotor control

A

Endothelial cells release vasodilator compounds eg NO

28
Q

what happens in local vasomotor control

A

Controlled by local blood flow conditions (hydrostatic pressure, shear force)

29
Q

how is BP controlled autonomically

A

Higher centres (eg eyes), hypothalamus, medullary centres, Vagal (parasympathetic) and Sympathetic balance out for appropriate effect on BP.

30
Q

How does the sympathetic nervous system effect blood vessels

A

Sympathetic constricts blood vessels (increase PR, pressure, HR, cardiac output)

31
Q

what do baroreceptors do

A

detect pressure and feed back to the brain

Activity decreases BP (maintain homeostasis)

32
Q

where are baroreceptors located

A

Located in transverse aortic arch and carotid sinuses of L and R internal carotid arteries

33
Q

what do chemoreceptors do

A

Detect when O2 levels are low and feedback to brain

34
Q

where are chemoreceptors located

A

Located in carotid bodies and aortic bodies

35
Q

what does the frank-starling mechanism explain

A

How the heart always pumps the right amount of blood (same enters as leaves)

36
Q

what is the frank starling mechanism

A

Left ventricle end diastolic pressure is higher, the more blood is pumped out as more is pushed in so cant overfill.

37
Q

what is venous return

A

the rate of blood flowing back to heart by the veins

38
Q

what is preload

A

is the initial stretching of cardiac myocytes during diastoles

39
Q

what is the pathological state when preload is too large

A

Volume overload is a pathological state (too large for the heart to pump out)

40
Q

what factors effect preload

A

Atrial contractility (increases it)
Ventricular Compliance (more ventricle stretches, increases)
HR (decreases)
Aortic Pressure (leads to back pressure so ventricle cant evacuate itself, increases)
Central venous pressures (increases)

41
Q

what is after load

A

resistance the chambers must overcome to eject blood (resistance during systole)

42
Q

what increases after load

A

Increased by back pressure (aorta or PA)
Increases if exit valve fails to open completely
Pressure overload (elevated afterload)

43
Q

how does the thoracic pump lead to venous return

A

Pulls blood towards right atrium during inspiration

44
Q

why does the thoracic pump work

A

Intrathoracic pressure is negative (abdominal pressure, compression of organs by diaphragm) is positive) so pressure gradient to drive blood to the heart

45
Q

how does the muscle pump lead to venous returns

A

Rhythmical contraction of limb muscles as occurs during normal locomotor activities
Squeezes blood from nearby veins and valves ensure one way flow to heart

46
Q

what is pulmonary circulation

A

High capillary density so low vascular resistance to act as a blood reservoir
Acts a filter

47
Q

what controls pulmonary circulation

A

Endocrine control of BP (ACE, an enzyme)

48
Q

why is pulmonary circulation special

A

O2, CO2 and pH effects opposite compared to systemic system
Low O2 in lungs causes arterioles to constrict (CO2 and H+ high = vasoconstriction)
Poor ventilation = reduced perfusion
Minimises amount of blood poorly oxygenated

49
Q

why is coronary circulation special

A

Cardiac muscle has a high demand
More flow happens in diastole (squeezed shut in systole)
Obtains blood almost before aorta

50
Q

what is hypertension

A

High blood pressure (eg high diastolic pressure)
Often asymptomatic
May result in coronary artery disease and MI

51
Q

what causes hypertension

A

Caused by mismatch between blood volume and circulatory capacity
Most cases are idiopathic (partly due to hormones (ANG II) and brain medulla (NTS))
Secondary to kidney disease

52
Q

what can chronic hypertension lead to

A

Aneurysm or stroke
MI
Kidney/ heart failure
Cardiac hypertrophy

53
Q

why is orthostatic hypotension

A

Low BP on standing (decrease in venous return)

Dizziness or syncope

54
Q

what causes orthostatic hypovalaemia

A

drugs, hypovalaemia and age

55
Q

what is cardiogenic shock

A

Tachycardia or Tachypnoea (compensatory mechanisms)

Low er urine output, hypotension, confusion, syncope, acidosis (failure to compensate)

103 theme 2 (7 decks)

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