Concept explainers
_____ 1. Unencapsulated, terminal endings of dendrites of sensory neurons are called
- a. lamellated corpuscles.
- b. free nerve endings.
- c. bulbous corpuscles.
- d. end bulbs.
Introduction:
The un encapsulated tactile receptors are the tips or apex of sensory neurons which are uncovered. There are three types of unencapsulated nerve receptors: free nerve endings, root hair plexuses, and tactile discs.
Answer to Problem 1DYKB
Correct answer:
Free nerve endings are the tactile receptors which are unencapsulated on the apex.
Therefore, option (b) is correct.
Explanation of Solution
Reason for the correct statement:
Option (b) is given as “free nerve endings”. The free nerve endings are the apex of any tactile sensory receptor which is not covered by any protective layer on its end. These receptors are found very close to superficial layer of skin. The free nerve endings are sensitive to pain and temperature stimuli. These may be phasic receptor or tonic receptor.
Hence, option (b) is correct.
Reasons for incorrect statements:
Option (a), is given as “lamellated corpuscles”.
These receptors are found on the skin of fingers which is sensitive to touch and pressure. These are oval in shape and the apex of receptor is covered with a protective layer. Hence, it is incorrect
Option (c), is given as “bulbous corpuscles”.
These nerve endings are also called as ruffini endings. These receptors are found in cutaneous tissues. These are spindle shaped neurons and have a covering layer. Hence, it is incorrect.
Option (d), is given as “end bulbs”.
These are rounded or oval structures found at the nerves fiber endings. These receptors are sensitive to touch, pain and cold. These receptors are covered with a protective layer. Hence, it is incorrect.
Hence, options (a), (c), and (d) are incorrect.
Free nerve endings are the receptors which are unencapsulated. Lamellated corpuscles, bulbous corpuscles, and end bulbs are the nerve ends which contain a protective covering on their tips.
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