Proprioceptors detect body position and movement, baroreceptors detect changes in blood-vessel stretch associated with blood pressure, and chemoreceptors detect changes in the chemical composition of blood or other body fluids. Together, they send sensory information to the central nervous system so that coordinated responses maintain movement and homeostasis.
The Mechanism
These receptors are specialized sensory structures. A stimulus causes them to generate nerve impulses that travel through sensory neurons to the central nervous system, which processes the information and sends signals to appropriate effectors.
| Receptor | What it detects and where | Function during exercise |
|---|---|---|
| Proprioceptors | Muscle length, muscle tension, joint position, and movement; located in muscles, tendons, and joints | Provide feedback about limb position and force, helping coordinate movement, posture, balance, and muscle contraction. Examples include muscle spindles and Golgi tendon organs. |
| Baroreceptors | Stretch in arterial walls; mainly located in the carotid sinus and aortic arch | A rise in blood pressure increases arterial stretch and baroreceptor firing. Cardiovascular control centers adjust autonomic output to alter heart rate, contractility, and blood-vessel diameter. |
| Chemoreceptors | Blood or fluid concentrations of oxygen, carbon dioxide, and hydrogen ions | Peripheral chemoreceptors in the carotid and aortic bodies respond especially to reduced oxygen, increased carbon dioxide, and decreased pH. Central chemoreceptors respond mainly to pH changes in cerebrospinal fluid caused by carbon dioxide. These signals help regulate ventilation. |
This demonstrates inter-system communication: receptor information links the nervous system with the muscular, cardiovascular, and respiratory systems. For example, increased carbon dioxide production during exercise stimulates chemoreceptor-mediated adjustments that increase ventilation.
A common misconception is that baroreceptors directly measure blood pressure. They actually detect arterial-wall stretch, which changes as blood pressure changes.
Exam Technique
For an IB SEHS response, identify the receptor, state its specific stimulus, and explain the resulting physiological adjustment. If the command term is explain, connect the full sequence: stimulus, receptor, sensory signal, central processing, effector, and response.
