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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
Equation to get MAP with important relationships?
Mean arterial pressure= cardiac output x systemic vascular resistance MAP= CO x SVR
26
What is cardiac outpu?
Volume of blood pumped by each ventricle of the heart per minute
27
Equation to find cardiac output?
Cardiac output= Heart rate x stroke volume | C0= HR x SV
28
Define stroke volume?
Volume of blood pumped by each ventricle of the heart per heart beat
29
Another equation to find MAP relationships?
MAP= Stroke vol x heart rate x systemic vascular resistance
30
Define systemic vascular resistance?
sum of resistance of all vasculature in the systemic circulation
31
Another term for systemic vasculature resistance?
Total peripheral resistance
32
What are the major resistance vessels?
Arterioles
33
Summary equation of MAP?
MAP= CO x SVR= HR x SV x SVR
34
What does negative feedback do?
Acts to minimize any disturbance to a controlled variable
35
Where are baroreceptors?
Aortic and carotid
36
why is the baroreceptor reflex important?
Moment to moment regulation of arterial BP including prevention of postural changes
37
When a normal person stands up from a lying down position?
- 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
How does postural hypotension occur?
Results from failure of Baroreceptor responses to gravitational shifts in blood, when moving from horizontal to vertical position
39
Risk factors for orthostatic hypotension?
- Age related - Medications - Certain diseases - Reduced intravascular volume - Prolonged bed-rest
40
Symptoms of postural hypotension?
Cerebral hypoperfusion- ``` Light headedness Dizziness Blurred vision Faintness Falls ```
41
What do baroreceptors only respond to?
Acute changes in BP
42
When does baroreceptor firing decrease?
Sustained high blood pressure
43
Control of MAP in the long term is done by?
Plasma volume by hormones
44
Baroreceptor response due to decreased BP?
- 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
Baroreceptor response due to increased BP?
- 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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