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Cardio > Control of Arterial Blood pressure > Flashcards

Control of Arterial Blood pressure Flashcards

1
Q

What is Blood pressure?

A

The (outwards) hydrostatic pressure exerted by the blood on the blood vessel walls

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2
Q

Define systolic blood pressure?

A

The pressure exerted by blood on the walls of the aorta and systemic arteries when the heart contracts (Shouldn’t reach/exceed 140mmHg when resting

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3
Q

Define diastolic blood pressure?

A

The pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes (should not normally reach/exceed 90mm Hg under resting conditions)

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4
Q

Define Hypertension?

A

Clinical blood pressure of 140/90mmHg or higher and a daytime average of 135/85mmHg or higher

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5
Q

Define pulse pressure?

A

The difference between systolic and diastolic blood pressures (normally between 30-50mmHg)

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6
Q

How does blood flow in arteries normally?

A

In a laminar fashion - not audible through a stethoscope

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7
Q

What can you use to estimate arterial blood pressure?

A

Stethoscope or sphygmomanometer

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8
Q

What happens if external pressure exceeding the systolic is applied to an artery?

A

The flow of that artery would be blocked and no sound heard through a stethoscope

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9
Q

What happens if external pressure is applied to an artery and kept between systolic and diastolic pressure?

A

The flow becomes turbulent when blood pressure exceeds external pressure - this flow is audible through a stethoscope

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10
Q

When estimating BP- to hear Korotkoff sounds- when is the first sound heard ?

A

The first sound is heard at peak systolic pressure- this is the followed by intermittent sounds due to turbulent spurts

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11
Q

What happens when a cuff is applied and its pressure is less than 80 mmHg and is below blood pressure in the cardiac cycle?

A

Blood flows in an smooth laminar fashion

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12
Q

When is the last Korotkoff sound heard>

A

Minimum diastolic pressure (Muffled/muted)- no sounds are heard after cause there is continuous smooth laminar blood flow

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13
Q

When is diastolic pressure heard in BP?

A

The 5th Korotkoff sound

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14
Q

What is the main force for blood flow and why?

A

The main driving force for blood flow is MAP because the RA pressure is close to 0

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15
Q

What drives the blood around the systemic circulation ?

A

Pressure gradient between the RA (right atrium) and the Aorta (AO)

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16
Q

Pressure gradient equation?

A

Mean arterial pressure - central venous (Right atrial) pressure
PG=MAP-CVP

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17
Q

What is mean arterial blood pressure?

A

The average arterial blood pressure during a single cycle which involves contraction and relaxation of the heart

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18
Q

Which portion of the cardiac cycle is longer?

A

Diastolic- twice as long as systolic

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19
Q

Formula for MAP? equation 1

20
Q

Formula for MAP? equation 2

A

diastolic blood pressure + 1/3 pulse pressure

21
Q

Normal range of MAP?

A

70-105mmHg

22
Q

Minimum MAP to perfuse coronary arteries, kidneys and brain?

23
Q

Normal arterial BP?

24
Q

Why must MAP be regulated to within a narrow range?

A
  • Pressure is high enough to perfuse internal organs (kidney, brain and heart)
  • Pressure is not to high to damage blood vessels or place extra strain on heart
25
Q

Equation to get MAP with important relationships?

A

Mean arterial pressure= cardiac output x systemic vascular resistance
MAP= CO x SVR

26
Q

What is cardiac outpu?

A

Volume of blood pumped by each ventricle of the heart per minute

27
Q

Equation to find cardiac output?

A

Cardiac output= Heart rate x stroke volume

C0= HR x SV

28
Q

Define stroke volume?

A

Volume of blood pumped by each ventricle of the heart per heart beat

29
Q

Another equation to find MAP relationships?

A

MAP= Stroke vol x heart rate x systemic vascular resistance

30
Q

Define systemic vascular resistance?

A

sum of resistance of all vasculature in the systemic circulation

31
Q

Another term for systemic vasculature resistance?

A

Total peripheral resistance

32
Q

What are the major resistance vessels?

A

Arterioles

33
Q

Summary equation of MAP?

A

MAP= CO x SVR= HR x SV x SVR

34
Q

What does negative feedback do?

A

Acts to minimize any disturbance to a controlled variable

35
Q

Where are baroreceptors?

A

Aortic and carotid

36
Q

why is the baroreceptor reflex important?

A

Moment to moment regulation of arterial BP including prevention of postural changes

37
Q

When a normal person stands up from a lying down position?

A
  • The venous return to the heart decreases- Gravity
  • MAP transiently decreases
  • Reduces the rate of firing of baroreceptors
  • Vagal tone to heart decreases- sympathetic tone to heart increases- increases the HR and SV
  • Sympathetic constrictor tone increases - this increases the SVR
  • Sympathetic constrictor tone to the veins increases the venous return to heart and stroke volume

-Result= rapid correction of transient fall in MAP - HR, SV & SVR increase

38
Q

How does postural hypotension occur?

A

Results from failure of Baroreceptor responses to gravitational shifts in blood, when moving from horizontal to vertical position

39
Q

Risk factors for orthostatic hypotension?

A
  • Age related
  • Medications
  • Certain diseases
  • Reduced intravascular volume
  • Prolonged bed-rest
40
Q

Symptoms of postural hypotension?

A

Cerebral hypoperfusion-

Light headedness 
Dizziness
Blurred vision
Faintness 
Falls
41
Q

What do baroreceptors only respond to?

A

Acute changes in BP

42
Q

When does baroreceptor firing decrease?

A

Sustained high blood pressure

43
Q

Control of MAP in the long term is done by?

A

Plasma volume by hormones

44
Q

Baroreceptor response due to decreased BP?

A
  • Decreased arterial BP
  • Decreased baroreceptor discharge
  • CV integrating center (medulla)
  • (1)Decreased vagal activity, (2)increased cardiac sympathetic activity, (3) Increased sympathetic constrictor tone
  • (1) + (2)= increased HR and increased SV
  • (3) = veno and vasoconstriction
  • Venoconstriction= increased SV
  • Vasoconstriction= Increased SVR
  • Increased HR & SV= Increased CO
  • Increased CO & SVR = Increased arterial BP
45
Q

Baroreceptor response due to increased BP?

A
  • Increased arterial BP
  • Increased baroreceptor discharge
  • CV integrating centre (medulla)
  • (1)Increased vagal activity, (2)decreased cariac sympathetic activity and (3)decreased sympathetic constrictor tone
  • (1) + (2)= decreased HR and SV
  • (3)= Veno and vasodilation
  • Venodilation- decreased SV
  • Vasodilation- decreased SVR
  • Decreased HR & SV= decreased CO
  • Decreased CO & SVR = decreased arterial BP

Cardio (36 decks)

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