méasurements y wn\' pressure measurements did not confirm. Mio\'s dizziness pers
ID: 238968 • Letter: M
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méasurements y wn' pressure measurements did not confirm. Mio's dizziness persists. High-salt diet, fludrocortisone administration Mio's blood pressure and heart rate are relatively constant, but her dizziness persists. Orthostatic (postural) intolerance "It appears that none of the potential causes (listed above) explain Mio's symptoms! In fact, her blood pressure seems to be somewhat elevated," exclaims Dr. Dorf in exasperation: It appears that way, but you are making assumptions which should not be made," replies Dr. Rodríguez. Think carefully, What would happen to Mio's ability to maintain appropriate blood flow to her brain if fewer adrenergic receptors were found in her blood vessels, specifically those delivering blood to the head?" If you were a doctor participating in this conversation, what would be your answer to the question, "What would happen to Mio's ability to maintain appropriate blood flow to her brain if fewer adrenergic receptors were found in her blood vessels, specifically those delivering blood to the head?" View Available Hint(s) o unnrelase df ore l reing n proutn s be brain. A lack of constriction would occur in the presence of norepinephrine and epinephrine, resulting in increased peripheral resistance, resulting in decreased blood pressure to the brain A lack of constriction would occur in the presence of norepinephrine and epinephrine, resulting in decreased peripheral resistance and decreased blood pressure to the brain. Upon release of norepinephrine and epinephrine, blood vessels constrict, increasing peripheral resistance, resulting in normal blood pressure to the brain causing dizziness SubmitExplanation / Answer
The cerebral autoregulation is multifactorial phenomenon of the cerebral circulation including myogenic, autonomic and metabolic mechanisms.
In case the autonomic regulation fails to do its work other two regulatory mechanisms will function to sustain blood flow to the brain.
The myogenic response is the intrinsic property of vascular smooth muscle to respond to changes in intravascular pressure. It arises from arteries and arterioles denuded of endothelium and autonomic nerve control. Nonetheless, endothelium produces several vasoactive mediators including nitric oxide, prostocycline, and endothelium derived hyperpolarizing factor that play critical roles in vascular tone and cerebral autoregulation.
Nonetheless the action of autonomic regulation may be dominated by myogenic and metabolic action under normal physiological condition.
As the brain have limited energy storage, local brain activity has to be complied with the coincidental increase of cerebral blood flow through the action of numerous vasoactive agents (E.g., Nitric oxide), referred as neurovascular coupling.
Under normal physiological condition, adult human brain exclusively relies on aerobic respiration for energy metabolism, encompassing glycolysis, citric acid cycle and oxidative phosphorylation, consuming oxygen and producing ATP and carbon dioxide. On the other hand brain perfusion is highly sensitive to changes in partial blood pressure of arterial carbon dioxide. Carbon dioxide has a profound dilatory action in cerebral arteries and arterioles resulting in increase of cerebral blood flow. In case of decreased partial blood pressure of arterial carbon dioxide there will be a vasoconstriction.
So decreased peripheral vascular resistance due to vasodilatation will leads to activation of myogenic response and metabolic response resulting in increased blood pressure in brain through vasoconstriction.
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