Chapter 50, Problem 50.1CR

Sensory receptors transduce stimulus energy and transmit signals to the central nervous system (pp. 1106-1 110)

n The detection of a stimulus precedes sensory transduction, the change in the membrane potential of a sensory receptor in response to a stimulus. The resulting receptor potential controls transmission of action potentials to the CNS, where sensory information is integrated to generate perceptions. The frequency of action potentials in an axon and the number of axons activated determine stimulus strength. The identity of the axon carrying the signal encodes the nature or quality of the stimulus.

n Mechanoreceptors respond to stimuli such as pressure, touch, stretch, motion, and sound. Chemoreceptors detect either total solute concentrations or specific molecules. Electromagnetic receptors detect different forms of electromagnetic radiation. Thermoreceptors signal surface and core temperatures of the body. Pain is detected by a group of nociceptors that respond to excess heat, pressure, or specific classes of chemicals.

To simplify sensory receptor classification, why might it make sense to eliminate nociceptors as a distinct class?

Summary Introduction

To determine: The reason why it makes sense to classify nociceptors as a distinct class of sensory receptors.

Introduction:

Nociceptors are the sensory receptors that respond to threat stimuli. They are also called pain receptors because they sense any threat to the body and then alarm the brain and spinal cord. They are free nerve endings of a sensory neuron, and they are found in every tissue. When the electric current generated by the neurons reaches above the threshold value, nociceptors get activated and send signals to the central nervous system.

Explanation of Solution

In response to any kind of threat or pain, sensory neurons transmit the signals to interneurons in the spinal cord for the integration of these signals. Substance P is the neurotransmitter that stimulates the interneurons, which carry the signals to the spinal cord. The spinal cord then sends the signals to the brain and the thalamus and the perception of the pain starts. The nociceptors are similar with the other classes of receptors by the kind of stimulus they recognize but are different from the other classes of receptors in the way they recognize the stimulus. Hence, it creates a sense to “eliminate nociceptors as a distinct class of receptors”.