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Physiology

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Cardiovascular System

Question
1 out of 7
 

Which of the following statements about vasomotor centre (VMC) is true (AIIMS 2011 MAY)



A Independent of corticohypothalamic inputs

B Influenced by baroceptor signals but not by chemoreceptors

C Acts along with the cardiovagalcentre (CVC) to maintain blood pressure

D Essentially silent in sleep

Ans. C Acts along with the cardiovagalcentre (CVC) to maintain blood pressure
  1. The main control of blood pressure is exerted by groups of neurons in the medulla oblongata that are sometimes called collectively the vasomotor area or vasomotor center.
  2. As we can see from the table listed below (from Ganong) the VMC can be excited by Cortical signals (example increased HR & BP during sexual excitement and anger) or inhibited.
  3. Also the Baroreceptors are inhibitory to VMC but chemoreceptors are stimulatory.
  4. In sleep these centre are working to maintain BP just like respiratory centres are maintaining respiration.
  5. The Cardio Vagal Centre (CVC) inhibits the VMC pressor area. And there is a functional interaction between the CVC and VMC. The pattern of discharge from CVC is not tonic but together they both maintain a normal BP.

Factors Affecting the Activity of the Vasomotor Area in the Medulla.

Direct stimulation

CO2

Hypoxia

Excitatory inputs

From cortex via hypothalamus

From pain pathways and muscles

From carotid and aortic chemoreceptors

Inhibitory inputs

From cortex via hypothalamus

From lungs

From carotid, aortic, and cardiopulmonary baroreceptors