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Physiology 3120 Lecture Notes - Splanchnic Nerves, Baroreflex, Nitric Oxide

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Tom Stavraky

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Human Physiology
Monday, January 25, 2010
“CV X”
Cardiovascular Regulatory Mechanisms
Local (autoregulation)
Myogenic theory
Resistance cells in arterioles are sensitive to pressure; can adjust resistance based
on resistance changes
Metabolic theory
Adjusts vascular resistance as well
Angiotensin II see Renal notes to review formation of AII
oHas direct & indirect effects
Vasopressin (ADH)
oHigh concentration in blood following hemorrhage
Bradykinin: formed from alpha-2 globulin in plasma
Histamine: derived from eosinophils & mast cells
Adenosine: product of ATP metabolism
Nitric oxide
Neural (mainly within the ANS) mostly control of blood pressure; function is to maintain a
normal arterial pressure
Cholinergic control
Stimulates parasympathetic fibres to heart; causes decrease in heart and decrease
in blood pressure
Adrenergic control
Stimulates sympathetic fibres to heart; release NE, which increase CO and BP
Stimulates splanchnic nerve to adrenal medulla; release ACh, which increases CO
and BP
Stimulates sympathetic vasoconstrictor fibres to peripheral vessels; releases NE,
which increases peripheral resistance and BP
ANS control of arterial pressure
Mechanoreceptor (baroreceptor reflex pathway); respond to mechanical stretch; pathway
conveys info to CV centres in brainstem, which then feeds into efferent pathway to effector
organs (i.e. vascular muscle, heart, and sometimes glands)
Anatomic organization; see study guide
Sensors; can’t tell you absolute pressure – detect deviations
Baroreceptors located in aorta and carotid artery
CV centres in medulla (bilateral structures)
Vagal nucleus – parasympathetic output
Vasomotor centre – sympathetic output; solitary tract nucleus regulates this area
Medullary structures relatively autonomous (involuntary)
Any info received in solitary tract nucleus is also sent to higher centres of brain; weigh-in
more in more urgent situations
Areas connected to each other by interneurons
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