central chemoreceptors

Examples of central chemoreceptors in the following topics:

• Chemoreceptor Regulation of Breathing

  • Chemoreceptor regulation of breathing is a form of negative feedback.
  • Central chemoreceptors: These are located on the ventrolateral surface of medulla oblongata and detect changes in the pH of spinal fluid.
  • They do not desensitize, and have less of an impact on the respiratory rate compared to the central chemoreceptors.
  • There are several other examples in which chemoreceptor feedback applies.
  • Chemoreceptor feedback also adjusts for oxygen levels to prevent hypoxia, though only the peripheral chemoreceptors sense oxygen levels.

• Hypoxia

  • In humans, hypoxia is detected by chemoreceptors in the carotid body.
  • This response does not control ventilation rate at normal pO2, but below normal the activity of neurons innervating these receptors increases dramatically, so much so to override the signals from central chemoreceptors in the hypothalamus, increasing pO2 despite a falling pCO2.

• Circumventricular Organs

  • The CVOs allow for the linkage between the central nervous system and peripheral blood flow and are an integral part of neuroendocrine function.
  • Area postrema: Site of the chemoreceptor trigger zone for vomiting, sends major and minor efferents to sections of the brain involved in the autonomic control of cardiovascular and respiratory activities.

• Classification of Receptors by Stimulus

  • Sensory receptors are primarily classified as chemoreceptors, thermoreceptors, mechanoreceptors, or photoreceptors.

• Overview of Sensation

  • The peripheral nervous system (PNS) consists of sensory receptors that extend from the central nervous system (CNS) to communicate with other parts of the body.
  • Our nervous system has sensory systems and organs that mediate each sense and these systems rely on chemoreceptors, photoreceptors, mechanoreceptors, or thermoreceptors to detect the state of the internal or external environment.

• Cutaneous Sensation

  • It consists of both sensory receptors and sensory neurons in the periphery (skin, muscle, and organs for example), to deeper neurons within the central nervous system.
  • The system reacts to diverse stimuli using different receptors: thermoreceptors, nociceptors, mechanoreceptors, and chemoreceptors.

• Adjustments at High Altitude

  • At high altitude, in the short term, the lack of oxygen is sensed by the peripheral chemoreceptors, which causes an increase in breathing rate (hyperventilation).
  • Additionally, the peripheral chemoreceptors cause sympathetic nervous system stimulation, which causes the heart rate to increase while stroke volume decreases, and digestion is impaired.

• Neural Mechanisms (Respiratory Center)

  • The respiratory centers contain chemoreceptors that detect pH levels in the blood and send signals to the respiratory centers of the brain to adjust the ventilation rate to change acidity by increasing or decreasing the removal of carbon dioxide (since carbon dioxide is linked to higher levels of hydrogen ions in blood).
  • There are also peripheral chemoreceptors in other blood vessels that perform this function as well, which include the aortic and carotid bodies.

• Role of the Cardiovascular Center

  • Hormones such as epinephrine and norepinephrine or changes in pH such as an acidification due to carbon dioxide accumulation in a tissue during exercise are detected by chemoreceptors.

• Adjustments During Exercise

  • Additionally, the respiratory rate increases as a result of higher carbon dioxide levels (through chemoreceptor regulation), which allows the body to release more carbon dioxide while increasing oxygen intake.
  • In the long run, exercise results in increased levels of arterial oxygen levels at rest, due to chemoreceptor desensitization to carbon dioxide levels and a lack of oxygen supply relative to oxygen demands during exercise.