Question

Your blood pressure suddenly decreases. What nucleus or nuclei in the central nervous system provides the stimulus to speed the heart rate and restore pressure?

a) cardio-excitatory center

b) basal nuclei

c) pons

d) cerebellum

e) none of the above

Answer 1

Question

Your blood pressure suddenly decreases. What nucleus or nuclei in the central nervous system provides the stimulus to speed the heart rate and restore blood pressure?

Answer: a) cardio-excitatory center.

Explanation: The medulla oblongata of the brain has cardiovascular center which controls the activity of the heart as well as the blood vessels including the blood pressure. The cardiovascular center has three parts namely cardio-excitatory center, cardio-inhibitory center and vasomotor center.

The ascending aorta and carotid artery has sensory receptors within sinuses present inside their walls called as baroreceptors. These baroreceptors detect change the blood pressure and send signals to the cardiovascular center of the medulla for appropriate intervention to regulate the blood pressure.

When the blood pressure suddenly drops, the baroreceptors detect this change and decreases it's signal transmission to the brain. This stimulates the cardio-excitatory center which increases sympathetic activity which in turn increases the heart rate and cardiac output causing increase in the blood pressure.

Also due to fall in the blood pressure, the firing from the vasomotor center increases which increase the tone of the blood vessels. This causes vasoconstriction thereby increasing the blood pressure and bringing it back to the normal level.

Other options :- b) basal nuclei - these are a group of nuclei located in the basal part of the forebrain which are involved in controlling the voluntary motor activities and learning new skills. They are also concerned with emotions and behaviour.

c) Pons - It is a part of brain stem located between midbrain and medulla oblongata. It is concerned with the control of breathing and sleep cycles. It also conveys sensory information to the cerebellum and connects the forebrain with the hindbrain relaying information between them.

d) Cerebellum - It is a part of the brain located beneath the cerebral hemispheres and helps in controlling the posture, balance and equilibrium of the body. It also controls and coordinates the motor activities and eye movements. It also helps in maintaining tone of the muscles.