Afferent nerve fiber
Afferent nerve fiber | |
---|---|
Details | |
System | Nervous system |
Identifiers | |
Latin | neurofibrae afferentes |
TA98 | A14.2.00.017 |
TH | H2.00.06.1.00015 |
FMA | 76570 |
Anatomical terms of neuroanatomy |
Afferent nerve fibers are
In the peripheral nervous system, afferent nerve fibers are part of the sensory nervous system and arise from outside of the central nervous system. Sensory and mixed nerves contain afferent fibers.
Structure
Afferent neurons are
All of the axons in the dorsal root, which contains afferent nerve fibers, are used in the transduction of somatosensory information. Somatosensory receptors include senses such as pain, touch, temperature, itch, and stretch. For example, a specific muscle fiber called an
All of these sensations travel along the same general pathways towards the brain. One pathway—
Types
Types of afferent fibers include the
Alternatively, in the
Myelination
|
μm )
|
m/s )
|
From muscles
|
From skin | Receptors |
---|---|---|---|---|---|
Thick | 12-20 | 72-120 | I | Aα | Proprioceptors (muscle spindle, Golgi tendon organ )
|
Medium | 6-12 | 35-75 | II | Aβ | lamellar corpuscle, Bulbous corpuscle
|
Thin | 1-6 | 4-36 | III | Aδ | Free nerve ending |
None | 0.2-1.5 | 0.4-2.0 | IV | C | Free nerve ending |
Function
In the nervous system, there is a "closed loop" system of sensation, decision, and reactions. This process is carried out through the activity of sensory neurons, interneurons, and motor neurons. A touch or painful stimulus, for example, creates a sensation in the brain only after information about the stimulus travels there via afferent nerve pathways.
Etymology and mnemonics
Afferent is derived from Latin participle afferentem (af- = ad- : to + ferre : bear, carry), meaning carrying into, whereas efferent is derived from ex ferens, meaning carrying away (e- = ex- means 'from'). Ad and ex give an
Another mnemonic device used for remembering afferent and efferent (in terms of the spinal cord, with its dorsal/ventral organization) is SAME DAVE. Sensory Afferent Motor Efferent, Dorsal Afferent Ventral Efferent.
Afferent and efferent are connected to affect and effect through their common Latin roots: afferent nerves affect the subject, whereas efferent nerves allow the subject to effect change.
See also
References
- ^ PMID 30969668. Retrieved June 24, 2020.
- ^ ISBN 9780205239399.
- ^ Gardner & Johnson (2013), pp. 488–495
- ^ Gardner & Johnson (2013), p. 477
- ^
Pearson, Keir G; Gordon, James E (2013). "35 - Spinal Reflexes". In Kandel, Eric R; Schwartz, James H; Jessell, Thomas M; Siegelbaum, Steven A; Hudspeth, AJ (eds.). Principles of Neural Science (5th ed.). United States: McGraw-Hill. Table 35-1 Classification of Sensory Fibers from Muscle, p. 796. ISBN 978-0-07-139011-8.
- ^ MedicalMnemonics.com: 3502 3463 367 115
Other References
- Gardner, Esther P; Johnson, Kenneth O (2013). "22 - The Somatosensory System: Receptors and Central Pathway". In Kandel, Eric R; Schwartz, James H; Jessell, Thomas M; Siegelbaum, Steven A; Hudspeth, AJ (eds.). Principles of Neural Science (5th ed.). United States: McGraw-Hill. ISBN 978-0-07-139011-8.