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Facial nerve—a clinical and anatomical review
Published in J. Belinha, R.M. Natal Jorge, J.C. Reis Campos, Mário A.P. Vaz, João Manuel, R.S. Tavares, Biodental Engineering V, 2019
Fernand Gentil, J.C. Reis Campos, Marco Parente, C.F. Santos, Bruno Areias, R.M. Natal Jorge
The facial nerve is a mixed nerve, being 80% of it motor fibers to the face (Toulgoat et al. 2013). The facial nerve and the VIII pair (auditory nerve) enter the inner ear canal, the middle ear and mastoid and emerge from the base of the skull, splitting into two branches which are distributed on the face and neck. This nerve performs basically four functions: Motor – controls the muscles of the face and neck.Sensitive – responsible for the external ear sensitivity.Secretory – the secretory fibers control the lacrimal gland, the mucous membranes of the nose and mouth, and the submandibular and sublingual salivary glandsSensory – tasting fibers of the anterior 2/3 of the tongue.
Mechanism of peripheral nerve modulation and recent applications
Published in International Journal of Optomechatronics, 2021
Heejae Shin, Minseok Kang, Sanghoon Lee
The main structure of the PNS is a nerve that has an enclosed structure like a cable bundle in which neurons are gathered, playing the role of the passage for the electrochemical signals. As shown in Figure 1(a), a neuron consists of a cell body with the nucleus, a dendrite that receives nerve signals, generating an action potential when the signals exceed the threshold, and an axon that transmits the generated signals to an axon terminal to transfer the signal to another neuron. In some cases, this axon is covered with a myelin sheath, making the speed transmission is significantly faster compared to the unmyelinated neurons, which are covered with connective tissue called the endoneurium. In addition, the axon terminal forms a synapse with adjacent neurons, in which the electrical signal transmitted through the axon is converted into a chemical signal by releasing a molecule called a neurotransmitter that is a chemical messenger inhibiting or activating the neuron by influencing the receptor on the targeted neuron or organ. The aggregate of these nerve fibers is called a fascicle, and this fascicle is surrounded by connective tissue called the perineurium. Inside the fascicle, afferent fibers that send afferent (sensory) signals to the CNS and efferent fibers that send efferent (motor) signals from the CNS could be both located in a fascicle or a nerve which is called a mixed nerve fiber. The group of fascicles is called a nerve. A nerve is surrounded by epineurium, and it also consists of blood vessels that provide nutrients for the whole structure. (Figure 1(b)).[10]