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Cardio Week 2 > Lecture 13: CV Control through Regulation of Arterial Pressure > Flashcards

Lecture 13: CV Control through Regulation of Arterial Pressure Flashcards

1
Q

What is systemic arterial pressure?

A

Time varying pressure within the systemic arterial system

Experienced putting a thumb on your carotids

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2
Q

What is the role of the systemic arterial pressure?

A

Provides the POTENTIAL ENERGY that drives systemic blood flow to all systemic tissues
-analogous to the electric company’s line voltage
Effective operation of the systemic circulation requires that systemic arterial pressure be regulated within a relatively narrow range

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3
Q

What is the most important parameter to adjust for patients in CV distress?

A

Cardiac output and tissue perfusion
If you only focus on systemic arterial pressure, you may decrease CO and tissue perfusion at great detriment
CO = your flow ninjaaa

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4
Q

What are the key equations to understand about maintaining adequate systemic arterial pressure?

A

Fluid Resistance = Pressure gradient/flow through vascular bed
R = voltage/current
Change in pressure = Flow x resistance

SVR (systemic vascular resistance) = MAP (mean arterial pressure)/CO (cardiac output
SVR = MAP/CO

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5
Q

What regulates the systemic arterial pressure over the short term?

A
  1. posture
  2. post-prandial state
  3. physical exercise
    DISEASE STATES
  4. Shock
  5. heart failure
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6
Q

What regulates the systemic arterial pressure over the long term?

A

Hypertension and antihypertensive/vasodilator drugs

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7
Q

What are the requirements for systemic arterial pressure regulatory mechanisms?

A

A series of negative feedback loops

  1. Pressure sensor(s)
  2. afferent neural pathways
  3. central neural coordinating center
  4. efferent neural pathways
  5. effectors that modulate parameters that affect systemic arterial pressure
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8
Q

What are the challenges in the regulation of the systemic arterial pressure?

A
  1. many parameters and influences can alter systemic arterial pressure
    • multiple sensors interact to determine systemic arterial pressure (short and long term)
    • multiple effector mechanisms interact to respond to pressure altering influences
    • integrating control system is needed to analyze the inputs and orchestrate the outputs
  2. Many of the mechanisms evolved as responses to stress and can be detrimental
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9
Q

What is systemic arterial pressure analogous to?

A

The line voltage
It is the potential of delivery
Not the most important parameter (because flow is the most important parameter)

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10
Q

What equation defines systemic arterial pressure?

A 
SVR = MAP/CO or MAP = CO x SVR
MAP = mean arterial pressure
SVR = systemic vascular resistance
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11
Q

What determines SVR?

A

Aggregate regulated diameter of the systemic arterioles in all of the components of the systemic vascular bed

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12
Q

What is a Wood unit?

A

Resistance measurement (kinda like Ohms)
Change in Pressure/CO
MAP/CO

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13
Q

Where is the neural control center of the circulatory center?

A 
Medulla
Receives input from
	i. Pressure
	ii. volume
	iii. oxygen/CO2 content 
Orchestrates integrated CV response
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14
Q

What are the short term systemic arterial pressure sensors?

A
  1. arterial baroreceptors
  2. ventricular baroreceptors (not known)
  3. atrial baroreceptors
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15
Q

What are the long term systemic arterial pressure sensors?

A

Renal baroreceptors

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16
Q

What are the key characteristics of the arterial baroreceptors?

A

Stretch receptors located at the carotid SINUS and the aortic arch
Cationic channels open in response to stretch
Afferents = CN IX and X
-the more pressure = greater rate of CN IX and X firing
Efferents = sympathetic and parasympathetic systems
Most responsive to pulsatile changes rather than static

17
Q

What is resetting?

A

When the new pressure (be it higher or lower) is maintained consistently, the firing rate will decay back to baseline
Resets when static pressure applied

18
Q

When are the arterial baroreceptors most reactive?

A

In response to extreme CHANGE in pressure (ie fast pressure drop may induce lightheadedness and syncope)
Cationic channels increase permeability when stretched and this is what depolarizes the receptor and increases rate of firing

19
Q

What is the carotid sinus?

A

Dilated area in the bifurcation of the common carotid

Right where the common carotid branches into the EXTERNAL and INTERNAL carotid artery

20
Q

What are the key characteristics of atrial baroreceptors?

A

Sense atrial distension
Hormonal response
Stimulate the release of atrial natriuretic peptide (ANP) in response to atrial distension
Induces diuretic action to decrease intravascular volume
Does not operate through the CNS

21
Q

What are the key characteristics of renal baroreceptors?

A

Juxtaglomerular apparatus
Releases renin, which leads to production of angiotensin II
Arteriolar constrictor and augments retention of Na and H2O

22
Q

What are the key characteristics of ventricular baroreceptors?

A

Limited understanding, limited role
Can trigger fainting because the ventricular baroreceptors are fooled by low intravascular volume states into thinking arterial pressure is elevated

23
Q

What is the most powerful vasoconstrictor molecule?

A

Angiotensin II

24
Q

What chemoreceptors are located in carotid and aortic body? Significance?

A

Sensors for
i. pCO2
ii. pH
iii. O2
Primarily responsible for regulation of respiration
Sends signals to medulla
Can have vasopressor effect on medullary control center, causing increased adrenergic output/systemic arterial pressure

25
Q

What are the effector mechanisms for regulating systemic arterial pressure?

A
  1. Short term responses
    • cardiac
    • systemic arterioles
    • systemic veins
  2. Longer term responses
    • renal
26
Q

What are the cardiac response mechanisms?

A
  1. autonomic regulation
    Direct neural output via adrenergic/muscarinic
    Circulating humoral input (circulating catecholamines)
  2. Heart rate
    -beta adrenergic = increases HR, increased SA depol rate, decreased refractoriness, increased conduction velocity
    -muscarinic = decrease HR, decreased SA depol rate, increased refractoriness, decreased conduction velocity
  3. Ventricular myocardial inotropic state
    Beta adrenergic = increased inotropy
27
Q

What is the systemic arteriole response mechanism?

A

Can regulate vascular resistance via diameter of systemic arterioles
Regulated by series of vasodilators and vasoconstrictors

28
Q

What is the principal determinant of local vascular resistance?

A

Local metabolic rate

29
Q

What are the vasodilators?

A
  1. Adenosine (in response to increase in local metabolic activity)
    • capillaries
  2. Nitric oxide (released in response to shear stress)
    • medium sized arteries
  3. Prostacyclin (produced by endothelial cells, inhibits platelet aggregation and vascular smooth muscle proliferation)
    • when you are inactive, you make less prostacyclin and are more likely to clot
30
Q

What are the pertinent vasoconstrictors?

A
  1. Angiotensin II
  2. Endothelin (produced by endothelial cells, peptide hormone, stimulus for release unknown)
  3. thromboxane (released by activated platelets to promote vasoconstriction/platelet aggregation)
31
Q

How is total intravascular volume regulated?

A

Regulated by the KIDNEY
Regulated by renal regulation of Na and H20 excretion through
i. pressure natriuresis (by arterial inflow pressure)
ii. Renin, angiotensin, aldosterone system
iii. Natriuretic peptides

32
Q

What are the types of natriuretic peptides?

A
  1. ANP
  2. BNP
  3. CNP
33
Q

What are the key characteristics of the atrial natriuretic peptide (ANP)?

A
  1. produced in the atria
  2. released in response to atrial stretch (hypervolemia and exercise)
  3. acts on the kidney to decreasing intravascular volume
    -increased glomerular filtration and decreased Na reabsorption and decreased renin secretion
    4 Acts on vasculature by relaxing smooth muscle
34
Q

What are the key characteristics of the Brain-type Natriuretic Peptide (BNP)?

A
  1. produced in the VENTRICLES
  2. Released in response to ventricular stretch
  3. actions similar to ANP (decrease volume of blood by increasing diuresis)
35
Q

What are the key characteristics of the C-type natriuretic peptide (CNP)?

A

Just discovered
We don’t know but it is out there
Produced in vascular endothelium
No diuretic activity

36
Q

Where is 40% of the blood volume contained?

A

In the large systemic veins

37
Q

Why is vasomotor tone in veins so important?

A

Because it is under autonomic control
Adrenergic stimulation = venous contraction = augmentation of cardiac preload
Muscarinic stimulation = venous dilation = reduces cardiac preload

38
Q

What happens when you go from supine to erect?

A

Gravitation causes
i. higher portions of the body to experience lower perfusion pressure
ii. lower portions of the body to experience higher perfusion pressure
iii. impaired venous return
Need to increase BP (sensed by baroreceptors and carried out by autonomic efferents)

39
Q

What happens when you hemorrhage?

A

Loss of intravascular causes loss of cardiac preload (decreased CO)
Need to the increase BP (sensed by baroreceptors and carried out by autonomic efferents)

Cardio Week 2 (11 decks)

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