Chapter 16, Problem 1TYR

Hot and cold stimuli are detected by

1. a. free nerve endings.
2. b. proprioceptors.
3. c. end bulbs.
4. d. lamellar corpuscles.
5. e. tactile corpuscles.

Summary Introduction

Introduction:

Structures that are specialized for the detection of a stimulus are referred to as a sensory receptor. Such receptors can either be real sense organs or simple nerve endings. Receptors can be classified into three categories based on the stimulus origin, modality, and its location in the body. The encapsulated nerve endings denote nerve fibers that are wrapped in connective tissue or glial cells, whereas the unencapsulated nerve endings denote dendrites without the wrapping of connective tissues.

Answer to Problem 1TYR

Correct answer:

The free nerve endings includes warm and cold receptors that respond to hot and cold stimuli, respectively. Therefore, option a is correct.

Explanation of Solution

Justify reasons for the correct statement:

The unencapsulated nerve endings includes peritrichial endings, free nerve endings, and tactile discs. The free nerve endings respond to the rise and fall in temperature, and pain. The abundance of these bare dendrites is found in the mucous membranes and skin.

Option (a) is given as, “free nerve endings”.

The cold receptors in the skin can be located by the gentle touch of the graphite of the pencil. In the location of such receptors, a cold sensation will be generated by conducting the skin’s heat away.

Hence, option (a)is correct.

Justify reasons for the incorrect statements:

Option (b) is given as, “proprioceptors”.

Proprioceptors occur in tendons, muscles, and joint capsules and sense the movements and position of the body or various parts of it. Hence, it is a wrong answer.

Option (c) is given as, “end bulbs”.

Similar to tactile corpuscles, end bulbs also sense texture and light touch. They are ovoid bodies found in tongue and lips (mucous membrane), large nerves (epineurium), and eye (conjunctiva – anterior surface). Hence, it is a wrong answer.

Option (d) is given as, “lamellar corpuscles”.

Lamellar corpuscles chiefly sense vibration. They are large ovoid bodies (receptors) found in the bones (periosteum), some viscera, and in the pancreas.Hence, it is a wrong answer.

Option (e) is given as, “tactile corpuscles”.

Similar to end bulbs, tactile corpuscles also sense texture and light touch. They are ovoid to pear-shaped and are found in abundance in hairless sensitive areas like palms, fingertips, lips, and eyelids.Hence, it is a wrong answer.

Hence, options (b), (c), (d), and (e) are incorrect.

Conclusion

Free nerve endings detect the cold and hot stimuli.