Ch 13/14 Cardiovascular Physiology (Day 6) Flashcards

1
Q

Blood Pressure

A

Affected by blood volume, stroke volume, total peripheral resistance, and HR

  • Increase in any of these will increase blood pressure.
  • Vasoconstriction of arterioles raises blood pressure upstream in the arteries.
BP(arterial) = CO  X TPR
CO = SV x HR
TPR = vasoconstriction

The blood pressure of blood vessels is related to the total cross- sectional area

  • Capillary blood pressure is low because of large total cross-sectional area.
  • Artery blood pressure is high because of small total cross-sectional area
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2
Q

Blood Pressure Regulation

A
  • Kidneys can control blood volume and thus stroke volume.

- Sympathoadrenal system stimulates vasoconstriction of arterioles (raising TPR) and increased CO.

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3
Q

Baroreceptor Reflex

A
  • Activated by changes in blood pressure detected by baroreceptors (stretch receptors) in the aortic arch and carotid sinuses
  • Increased blood pressure stretches these receptors, increasing action potentials to the vasomotor and cardiac control centers in the medulla.
  • Most sensitive to drops in blood pressure
  • The vasomotor center controls vasodilation and constriction.
  • The cardiac center controls heart rate.
  • Fall in blood pressure = Increased sympathetic and decreased parasympathetic activity, resulting in increased heart rate and total peripheral resistance
  • Rise in BP has the opposite effects.
  • Good for quick beat-by-beat regulation— (e.g. going from lying down to standing)
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4
Q

Structures of the Baroreceptor Reflex

A
  1. Baroreceptors (sensors)
  2. Vasomotor & cardiac control centers in medulla (integrating centers)
  3. Symp/parasymp axons to heart & blood vessels (effectors)
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5
Q

Atrial Stretch Reflexes

A

Activated by increased venous return to:

  • Stimulate reflex tachycardia (sympathetic)—physiologic significance unknown
  • Inhibit ADH release; results in excretion of more urine
  • Stimulate secretion of atrial natriuretic peptide; results in excretion of more salts and water in urine
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6
Q

BP Measurement

A
  • Measured in mmHg using sphygmomanometer.
  • Blood pressure cuff produces turbulent flow of blood in the brachial artery—detected as Korotkoff sounds via stethoscope.
    1) Cuff inflated to beyond systolic blood pressure to occlude artery;
    2) Pressure gradually released, the first (tapping) sound is heard at systole; 3) second “sound” is the last “tap” before sounds disappear—when pressure in cuff = diastolic pressure.
  • Average BP is 120/80 (systolic/diastolic).
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7
Q

Pulse Pressure

A

“Taking the pulse” is a measure of heart rate.

Each “pulse” = increased blood pressure in that artery at systole.

  • -> P(systolic) – P(diastolic) = pulse pressure.
  • -> e.g. if BP = 120/80, pulse pressure = 120 – 80 = 40 mmHg.

Pulse pressure is a reflection of stroke volume

How is pulse pressure a reflection of stroke volume?

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8
Q

Mean Arterial Pressure

A

MAP = average pressure in the arteries in one cardiac cycle.

Significance: MAP – venous pressure = driving force for blood flow into capillaries.

Not a simple arithmetic average, since diastole is longer than systole.

Approximated as: diastolic pressure + 1/3 pulse pressure
–> e.g. for BP = 120/80, pulse pressure = 40, and MAP = 80 + 1/3* 40 = 93 mm Hg.

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9
Q

Hypertension

A

High Blood Pressure

  • Incidence increases with age
  • Increases risk of cardiac diseases, kidney diseases, and stroke.
  • Classified as “essential” or “secondary.”
  • Essential or primary hypertension—Most people fall in this category. Causes not clearly defined in all cases; may include:
    a) ↑salt intake coupled with decreased kidney filtering ability
    b) ↑ sympathetic nerve activity  ↑’s HR
    c) altered responses to paracrine regulators from the endothelium
    d) ↑ TPR

Secondary hypertension is a symptom of another disease, such as kidney disease.

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10
Q

Dangers of Hypertension

A
  • Vascular damage within organs, especially dangerous in the cerebral vessels and leading to stroke
  • Ventricular overload to eject blood due to abnormal hypertrophy, leading to arrhythmias and cardiac arrest
  • Contributes to the development of atherosclerosis
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11
Q

Treatments for Hypertension

A
  • Lifestyle modification: ↓ salt intake; ↓ smoking and drinking; ↓ weight; ↑ exercise
  • K+ (and possibly calcium) supplements
  • Diuretics to increase urine formation
  • Beta blockers to decrease cardiac rate
  • ACE inhibitors to block angiotensin II production
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12
Q

What is circulatory shock?

A

Inadequate blood flow to match oxygen usage in tissues

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13
Q

What is hypovolemic shock?

A
  • Due to low blood volume from an injury, dehydration, or burns
  • ↓ CO and BP
  • Blood is diverted to the heart and brain at the expense of other organs.
  • Compensation includes baroreceptor reflex, which in response to lower pressure, raises heart rate, raises peripheral resistance, and produces cold, clammy skin and low urine output.
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14
Q

What is septic shock?

A
  • Dangerously low blood pressure (hypotension) due to an infection (sepsis)
  • Bacterial toxins (endotoxins) induce NO production, causing widespread vasodilation.
  • Mortality rate is high (50−70%).
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15
Q

What are other causes of circulatory shock?

A
  1. Severe allergic reactions –> anaphylactic shock due to production of histamine and resulting vasodilation.
  2. Spinal cord injury or anesthesia –> neurogenic shock due to loss of sympathetic stimulation.
  3. Cardiac failure –> cardiogenic shock due to significant loss of myocardial function.
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16
Q

congestive heart failure

A

CO insufficient to maintain blood flow required by the body

a. Caused by myocardial infarction, congenital defects, hypertension, aortic valve stenosis, or disturbances in electrolyte levels (K+ and Ca2+)
b. Similar to hypovolemic shock in symptoms and response

17
Q

What are the types of CHF?

A

a. Left-side failure – raises left atrial pressure and produces pulmonary congestion and edema causing shortness of breath
b. Right-side failure – raises right atrial pressure and produces systemic congestion and edema