Question

A 29-year-old female develops sepsis and, as a consequence, she experiences profound vasodilation.

a) What effect does vasodilation have on the afterload? Explain why.

b) What effect does vasodilation have on blood pressure? Explain why. How will her body try to bring her blood pressure back to homeostasis?

Answer 1

*Afterload is the resistance against which blood is expelled from Ventricle .Systolic aortic pressure or Systolic Ventricular pressure .

*Afterload = Mean arterial pressure ( MAP) for left Ventricle and Pulmonary artery pressure for right Ventricle

*One of the determinant of Mean arterial pressure is Total Peripheral resistance .

*Cardiac output = Heart x stroke volume

*Blood pressure = Cardiac output x Total Peripheral resistance

*Cardiac outputb decide Systolic Blood pressure and Total peripheral resistance Diastolic blood pressure .

*During sepsis because of release of inflammatory mediators there is Vasodilation of blood vessels and result in fall in Blood pressure

a) Effect of Vasodilation on afterload -- Vasodilation decrease the systemic arterial pressure and resistance of blood vessels so After load also decreases as afterload is the resistance against which blood is expelled from Ventricle .So afterload decreases and blood flow from Ventricle increases and more amount of blood will go to tissues to meet the Metabolic demands In septic shock occuring because of sepsis.

b)Blood pressure is dependent on total peripheral resistance .especially Diastolic blood pressure .Vasodilation decreases total peripheral resistance and hence decreases Diastolic blood pressure .

***Response for low Bp by Baroreceptor mechanism ( Neural) and is most sensitive mechanism for regulating Bp.

*Whenever there is low bP baroreceptors which are stretch receptors are activated and impulses travel via carotid sinus nerve brach of glossopharyngeal nerve and Depressor nerve branch of vagus nerve and they are integrated in Nucleus tractus solitarius in Medulla and response is increased sympathetic vasoconstrictor tone to vessels and increasing sympathetic discharge to heart and increase the cardiac output and increasing the Blood pressure.

Also due to Decrease in Blood flow there is accmulation of Carbon dioxide ,Low oxygen and Increased PH leads to activation of Chemoreceptors Integration is in Vasomotor center in Medulla .Response is Vasoconstrictor And Increases Cardiac output which increase Systolic Blood pressure ,Also it increase heart and help in regulating blood pressure .