BIOS 162-a Review: Cardiovascular II
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Transcript of BIOS 162-a Review: Cardiovascular II
BIOS 162-a Review: Cardiovascular II
September 26, 2011
Important Regulated Variable: Mean Arterial Pressure (MAP)
• MAP = Diastolic Pressure + 1/3 (Systolic Pressure – Diastolic Pressure)
Systolic pressure
Diastolic pressure
Feedback mechanism for mean arterial pressure
Stimulus:decrease in MAP
Sensor:Stretch receptors in
arteries
Feedback mechanism for mean arterial pressure
Stimulus:decrease in MAP
Sensor:Stretch receptors in
arteries
Afferent pathway:Afferent neurons
Integrating center:Brainstem
Set point: 100 mmHg
How much can the set point vary?
Feedback mechanism for mean arterial pressure
Stimulus:decrease in MAP
Sensor:Stretch receptors in
arteries
Afferent pathway:Afferent neurons
Integrating center:Brainstem
Set point: 100 mmHg Efferent pathways
Neurons Endocrine
Effectors
How to change MAP?
• MAP = Cardiac Output x Total Peripheral Resistance
Heart Rate Stroke Volume
Arteriolar Resistance
Feedback mechanism for mean arterial pressure
Stimulus:decrease in MAP
Sensor:Stretch receptors in
arteries
Afferent pathway:Afferent neurons
Integrating center:Brainstem
Set point: 100 mmHg Efferent pathways
Neurons Endocrine
Effectors
Heart Arteries
Increased Stroke Volume
Increased Heart Rate
IncreasedResistance
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More Detailed: Control of Heart Rate
• Neural– Sympathetic/parasympathetic activity at SA and
AV node
• Endocrine– Epinepherine from the adrenal gland
More Detailed: Control of Stroke Volume
• Neural– Sympathetic activity increases contractility
More Detailed: Control of Arteriolar Resistance
• Note: resistance is directly proportional to diameter of blood vessel!
• Neural– Increase in sympathetic activity
(epinepherine/norepinepherine)• Endocrine– Local (vasodilation): metabolites, decreased oxygen,
NO, prostaglandins, EDHF– Systemic (vasoconstriction): vasopressin, angiotensin
II
Hypertension
• Increased blood volume– Blood glucose and change in osmotic pressure– Renal dysfunction
• Increased total peripheral resistance– Atherosclerosis
Quiz!
Why might women have lower hematocrit than men?
• Low hematocrit = anemia• Blood loss can lead to low hematocrit when
blood cell production can’t keep up: menstrual cycle
• Nutritional deficiencies?
What is the problem with “blood doping”?
• Increases risk of abnormal blood clotting• Enlargement of spleen• Can damage bone marrow, may lead to
leukemia
Explain why my ankle would swell after a sprain? How does the swelling
go down after it heals?• Swell: normally, proteins can’t get through blood
vessels. This provides osmotic pressure to keep fluid in blood vessels. When damage occurs (ankle sprain), immune cells release cytokines that increase permeability of blood vessels (to allow in macrophages). But, proteins can move in too, changing osmotic gradient.
• Decrease swelling: ice (causes vasoconstriction), lymphatic vessels (return interstitial fluid to circulatory system)
Swelling of the feet may be an indication of what?
• Right heart failure leads to build up of fluid in the systemic organs, especially the feet
Why might a soldier standing at attention eventually faint?
• Skeletal muscle pump, which requires contraction of skeletal muscles, moves blood back to heart. Without contraction (as in during standing at attention), blood cannot get back to heart and therefore to brain.
Someone with AV block would have a heart rate that is the same
as/higher/lower than someone without AV block
• Lower:
Partial AV block
Complete AV block
Indicate which is atrial/ventricular defibrillation, and the concerns
associated with each?Atrial: less concerning, because only ~15% of cardiac output comes from atrial contraction. However, concern for blood clotting
Ventricular: more concerning, most cardiac output provided here. Describe how a heart would look during ventricular defibrillation?
Describe the abnormal heart sounds, and what causes each?
• Normal heart sounds: lub=AV valve closing, dub=semilunar valves closing
• S3: tensing of chordae tendineae (indicates excessive volume in ventricles in adults, normal in children)
• S4: Atrium contracting against a stiffening ventricle
• Murmur: insufficient valve closing