Afferenttien

Afferenttien are the nerves and nerve fibers that carry sensory information from peripheral receptors toward the central nervous system. They form the afferent arm of the nervous system, contrasted with efferent pathways that carry motor commands away from the CNS.

They convey diverse sensory modalities including somatic senses such as touch, pressure, vibration, temperature, and proprioception, as well as visceral sensations such as fullness or pain from internal organs. The signals originate in specialized receptors—mechanoreceptors, thermoreceptors, nociceptors, and proprioceptors—that transduce stimuli into electrical impulses.

Afferent fibers are classified by conduction speed and myelination into groups such as A fibers (Aα, Aβ, Aδ), B fibers, and C fibers. Aβ fibers convey fine touch and proprioception; Aδ fibers convey fast pain and temperature; C fibers convey slow, dull pain and other sensations. Sensory information enters the CNS through dorsal roots of the spinal cord or via cranial sensory nerves; the cell bodies are located in dorsal root or cranial sensory ganglia.

Within the CNS, afferent signals reach distinct pathways: the dorsal column-medial lemniscus for fine touch and proprioception, and the spinothalamic tract for pain and temperature, among others. Visceral afferents project to autonomic centers and higher cortical areas via various thalamic and brainstem relays.

Clinical relevance includes sensory loss from peripheral neuropathies, nerve injuries, or diseases affecting dorsal root or cranial sensory pathways. The term afferenttien is commonly used in contrast to efferent pathways, which carry motor commands away from the CNS.