Arterial Pressure Regulation - Nordgren Flashcards
What components make up the arterial baroreceptor reflex?
- Afferent Pathways:
- Arterial Barorecptors
- Sensory receptors
- Aortic Baroreceptor
- Carotid Sinus Barorecptor
- Mechanoreceptors (sense stretch)
- Sensory receptors
- Solitary Tract
- Arterial Barorecptors
- Central Integration:
- Medullary Cardiovascular Centers
- Efferent Pathways:
- Spinal cord
- SNS and PNS postganglionic fibers terminate on the heart & vessels
What is the location of the arterial baroreceptors? What is their operation?
- Location:
- Aortic arch
- Carotid sinus
- Operation:
- active at normal pressures (supply a tonic signal)
- sense stretch and rate of change
- increased stretch = increased AP generation
How do changes in the afferent input from arterial baroreceptors influence the activity of the sympathetic and parasympathetic preganglionic fibers?
- If afferent input says mean arterial pressure is too low:
- increase sympathetic activity → vasoconstriction
- decrease parasympathetic activity → increase HR & CO
- If afferent input says mean arterial pressure is too high:
- decreased sympathetic activity → vasodilate
- increased parasympathetic activity → decrease HR & CO
What are the chain of events that are initiated by the arterial baroreceptor reflex to compensate for a change in arterial pressure?
- Decreased MAP (1°)
- Decreased baroreceptor discharge
- Medullary CV center
- Increased Sympathetic activity
- increased arterial tone
- vasoconstriction
- increased TPR (2°)
- decreased capillary pressure
- Transcapillary fluid reabsorption
- increased blood volume
- increased peripheral venous pressure
- increased central venous pressure
- increased SV
- vasoconstriction
- increased venous tone
- increased cardiac contractility
- increased HR
- increased arterial tone
- Decreased Parasympathetic activity
- increased HR
- increased cardiac output (2°)
What are the mechanisms involved in the Bezold-Jarisch reflex?
- Cardiopulmonary baroreceptors in atria, ventricles, coronary vessels & lungs
- elicit Bezold-Jarisch decompressor reflex by application of strong stimuli to coronary vessel chemoreceptors in the left ventricle
- activation causes certain MI patients to present with bradycardia and hypotension instead
What are the mechanisms involved in the Cushing reflex?
- Rise in intracranial pressure will result in a rise in arterial pressure
- prevents the collapse of cranial vessels and preserves adequate blood flow to the brain
- reaction to reduced cerebral circulation, ischemia
What are the mechanisms involved in the alerting reaction?
- Excitement/Sense danger → fight-or-flight
- increase in blood pressure caused by a general increase in cardiovascular sympathetic nervous activity and decreased parasympathetic activity
What are the mechanisms involved in blushing?
- Loss of sympathetic vasoconstrictor activity
- only to particular cutaneous vessels
- engorgement (filling) of cutaneous venous sinuses
What are the mechanisms involved in vasovagal syncope?
- Fainting caused by:
- decreased cerebral blood flow produced by a sudden dramatic loss of arterial blood pressure
- occurs as a result of sudden loss of sympathetic tone and simultaneous large increase in parasympathetic activity
What are the mechanisms involved in the dive reflex?
- Response to submersion in water
- Bradycardia → enhanced PNS
- Vasoconstriction → enhanced SNS
- Prolongs submersion by limiting rate of oxygen use and directing flow to essential organs
- brain
- heart
What are the mechanisms involved in the cardiovascular responses to pain?
- Can have either positive or negative effect on arterial pressure
- Superficial/cuctaneous pain causes a rise in blood pressure (like alerting response)
-
Deep pain from receptors in viscera/joints cause decreased sympathetic tone, increased parasympathetic tone, & severe decrease in blood pressure (like vasovagal)
- contributes to shock
What is baroreceptor adaptation?
- Baroreceptor firing rate adapts to prolonged changes in arterial pressure
- continually elevated pressure over several days leads to gradual decrease in firing rate
- baroreceptor reflex is only good for short-term pressure regulation!
What influence do changes in body fluid volume have on arterial pressure?
- ↓ Blood volume → ↓ Peripheral venous pressure
- Left shift of venous function curve
- ↓ Central venous pressure → ↓ Cardiac output
- ↓ Arterial pressure
What is the mechanism whereby altered pressure alters glomerular filtration rate and renal tubular function to influence urinary output?
- Fluid Volume Mechanism
- ↑ Arterial pressure (disturbance) →
- ↑ Urinary output rate →
- Urinary output rate = Glomerular filtration rate − Renal fluid reabsorption rate
- RAAS
- ↓ Fluid volume →
- ↓ Blood volume →
- ↓ Cardiac output →
- ↓ Arterial pressure (compensation)
How is mean arterial pressure adjusted in the long term to that which causes fluid output rate to equal fluid intake rate?
- Regulation of electrolyte composition in plasma
- Na+
- Glomerular Filtration
- dependent on hydrostatic/oncotic pressures
- RAAS:
- Renin converts angiotensinogen → angiotensin I (inactive)
- ACE converts inactive Angiotensin I → Angiotensin II
- Angiotensin II controls release of Aldosterone
- causes Na+ reabsorption
