VPB 121: Veterinary Physiology - II (2+1)

THERMOCEPTORS

• The hypothalamus of the animals has central thermoceptors to monitor their internal temperature.
• Two different receptors to mediate warmth and cold.
  • The warmth receptors are situated near deep blood vessels.
    • They are Ruffini end organ which can also serve to detect tactile sensation (Poly modal receptor).
    • Ruffini’s corpuscles are located in the connective tissue of the skin in association with collagen fibers. Hence detect skin stretch and are involved in proprioception.
    • Warmth receptors detect change in temperature of 20° C to 47° C.
    • The frequency of action potential increases with increase in the temperature. Cold sensation is mediated by the end organ of Krause.
  • The Cold receptors detect and are stimulated at the temperature between 10° C to 35° C.
    • These are extremely sensitive and can detect change in even 0.5° C.
    • There are also another thermoceptor which detect painful hot stimuli. The temperature ranges above 45° C.
    • The frequency of action potential generated is in accordance with the amount of pain sensation.

Mechanism of Action

• Free nerve ending of the thermoreceptor neurons have specific thermoreceptor proteins. They are known as Thermo TRPs. The thermo TRPs are many, variable to different temperature range, and some are to detect distinct temperature. They get stimulated and act through ion channels and gating mechanism by modifying the protein configuration.