![]() Axons can emerge from dendrites known as axon-carrying dendrites in some animals. Some neurons lack an axon and instead send messages through their dendrites. Axons differ from dendrites in several ways, including shape (dendrites often taper, whereas axons usually maintain a constant radius), length (dendrites are restricted to a small region around the cell body, whereas axons can be much longer), and function (dendrites are restricted to a small region around the cell body, whereas axons can be much longer) (dendrites receive signals whereas axons transmit them). Nerve fibres are one of two forms of cytoplasmic protrusions from a neuron’s cell body dendrites are the other. Many hereditary and acquired neurological illnesses have been linked to axon malfunction, which can impact both functions. The axons of certain sensory neurons (pseudounipolar neurons), such as those for touch and temperature, are called afferent nerve fibres, and the electrical impulse travels down them from the periphery to the cell body, and then along another branch of the same axon to the spinal cord. The axon’s job is to communicate information between neurons, muscles, and glands. In vertebrates, an axon (from Greek v áxn, axis), also known as a nerve fibre (or nerve fibre), is a long, slender projection of a nerve cell, or neuron, that normally carries electrical impulses known as action potentials away from the nerve cell body. ![]() Now we will take a deeper look at nerve fibres,how nerve fibres differ from muscle fibres in having dendrites and lastly will take a look at properties of nerve fibres notes. Type I,II,III and IV are four different types of sensory fibres. Both sensory and motor fibres are included in these groupings. Myelinated groups A and B are myelinated, but unmyelinated group C is unmyelinated. Group A nerve fibres, group B nerve fibres, and group C nerve fibres are the three kinds of nerve fibres. See spinal cord blood supply.In vertebrates, an axon (from Greek v áxn, axis), also known as a nerve fibre (or nerve fibre), is a long, slender projection of a nerve cell, or neuron, that normally carries electrical impulses known as action potentials away from the nerve cell body. Blood supplyīlood supply is discussed separately. In general, fibers found posteriorly process and relay sensory information, fibers found laterally are preganglionic visceral motor neurons and somatic motor fibers are found anteriorly 4. Lateral columns primarily contain the corticospinal tracts which are the principal motor pathway connecting the cerebral cortex to spinal motor neuronsĪnterior spinal commissure is located between the posterior-most extent of the anterior median fissure anteriorly and the ventral grey matter commissure posteriorly 5. The white matter contains nerve fibers or tracts and is divided into anterior, dorsal and lateral columns (also known as funiculi) as well as the anterior spinal commissure 3,5.Īnterior columns primarily contain the spinothalamic tract s which are responsible for pain, temperature, coarse (non-discriminative) touch and pressure sensationsĭorsal columns contain ascending fibers which are responsible for vibration, conscious proprioception, and fine (discriminative) touch sensations Receive primary afferents from the dorsal roots of the spinal nervesĭivided into ventral and dorsal grey matter commissures Send efferent fibers via the ventral nerve rootsĬontain autonomic neurons for pelvic and visceral organs It is divided into anterior, dorsal and lateral horns and periependymal grey matter 3,5:Ĭontain motor neurons for skeletal muscle The grey matter contains the cell bodies of neurons and glia and is enlarged in the cervical and lumbosacral regions to provide fibers to the large nerve plexuses. There are 31 nerve roots in total:Ī transverse section of the spinal cord shows a peripheral mass of white matter surrounding an ‘H’ or butterfly-shaped central mass of grey matter with a small ependyma-lined central canal filled with CSF 2. The cord is incompletely divided into left and right halves by the posterior median sulcus (shallow) and the anterior median fissure (deep) 6. The spinal cord is segmented by the nerve roots that emerge from it. ![]() The spinal cord is divided into cervical, thoracic and lumbar parts and terminates at the conus medullaris at approximately the L1 vertebral body level in adults. Throughout its length paired dorsal and ventral nerve roots enter its dorsolateral and ventrolateral surface respectively. ![]() Like the brain, it is composed of grey and white matter, however, opposite to the brain, the grey matter is on the internal aspect of the cord and the white matter tracts are external. The spinal cord measures approximately 42-45 cm in length, ~1 cm in diameter and 35 g in weight.
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