Question

Central chemoreceptors are sensitive to the
A. the pH of their environment
B. Level of oxygen
C. High blood pressure
D. Level of sugar in the blood.

Answer 1

Central chemoreceptors are composed of neural chemoreceptors ( bunch of neurons). It is responsible for detecting the changes of $C{O_2}/{H^ + }$within the brain. The ventrolateral medullary surface comprises central chemoreceptors of the central nervous system or CNS near the exit of ${9^{th}}$ and ${10^{th}}$ cranial nerves.

Complete answer:
Central chemoreceptors are sensitive to the pH of their environment. It balances the pH level of surrounding CSF. When the concentration of carbon dioxide increases within the blood it causes the blood to become acidic. An increased level of carbon dioxide causes the diffusion of carbon dioxide from the blood to CSF through the blood-brain barrier. After entering into the CSF carbon dioxide reacts with water which leads to the formation of carbonic acid. Formed carbonic acid results in a decrease in $\;pH$.
Central chemoreceptors use a negative feedback system to control the pH of CSF. When a $\;pH$ level decreases in CSF it stimulates the chemoreceptors. Central chemoreceptors then provide stimulation to the effects to prevent further imbalance of the system.

Hence, the correct answer is option (A).

Additional information:
A sensitive barrier of endothelial cells is responsible for preventing the entry of solute from the bloodstream to the Central nervous system is called the blood-brain barrier. Some molecules like ions, nutrients, water, glucose, etc can be transported by the blood-brain barrier via passive diffusion and selective transport.

Note: The bunch of neurons that are responsible for reacting according to the environmental chemical changes within the body is called chemoreceptors.there are two types of chemoreceptors are found, named peripheral chemoreceptors and central chemoreceptors. Peripheral chemoreceptors are found in the peripheral nervous system extensions.