Myelin sheath is formed by concentric layers of proteins layed with Lipids. Segment of nerve fibre between two nodes is called internode. The area where myelin sheath is absent is called Nodes of Ranvier. It is not continuous and absent at regular intervals. It is a thick lipoprotein sheath, which insulates the myelinated nerve fibre. Myelin sheath is responsible for the white color of the nerve fibre. Nerve fibers insulated by Myelin sheath are Myelinated Nerve Fibre. These Nerve fibres are not covered by Myelin sheath. It is the continuation of the cell membrane of the cell body.Īxoplasms along with axolemma are called the Axis cylinder of the nerve fibre.Īxis cylinder of the nerve fibre is covered by a membrane called neurilemma. Internal structure of Axon- Axis Cylinder:Īxon has a long central core of cytoplasm called axoplasm.Īxoplasm is covered with axolemma. The whole nerve is covered by Epineurium. Myelin acts as an insulator for some axons.Įach nerve is formed by many bundles of nerve fibres and each bundle of nerve fibres is called a Fasciculus.Įach nerve Fibre is covered with Endoneurium.Myelin covering may or may not be present.Information is transmitted away from the cell body.They are long, thin projections from the cell body of neuron. Synapses act as a relay station transmitting signals from one neuron to another. At the end of the terminal button is a gap, known as synapse. The terminal buttons are located at the end of the neuron and are responsible for sending the signal on to other neurons. Transmits information to the cell body.However,some neurons may have only one dendrite.They are tree-like projections,which receive information from other neurons.They make connections with other neurons through synapses. This is involved in packaging and processing of proteins into granules.ĭendrite is a branched process of neurons and it is branched repeatedly. These powerhouse of the cell are present in soma and axon. They consist of microfilaments and microtubules. Neurofibrils are thread-like features characteristic of neuron. Granules appear after the recovery of fatigue or regeneration of nerve fibres. During fatigue or injury to the neuron, these bodies fragment and disappear by a process called chromatolysis. Number of Nissl bodies in a nerve varies according to the condition of the nerve. They also have ribosomes for protein synthesis. Nissl granules are called tigroid substances because of the spotted appearance of soma ( Tigroid means spotted or striped appearance ), after suitable staining. Nissl bodies or Nissl granules are found in cytoplasm of Neuron and are present in soma and dendrite, but not in axon or axon hillock. The nerve cell cannot multiply like other cells because it doesn't have a centrosome.Ĭentrosome is the structure involved in cell division. Nissl bodies and neurofibrils are found only in nerve cells and not in any other cell of the body.Įach neuron has one centrally placed Nucleus, with one or more prominent nucleoli. The cytoplasm has large nucleus, Nissl Bodies, neurofibrils, mitochondria and Golgi apparatus. It’s irregular in shape and has a cytoplasm called neuroplasm, covered with a cell membrane. Synonyms of Nerve Cell Body are Soma or Perikaryon Dendrites are short processes while axons are long processes.ĭendrites and Axons are commonly called Nerve Fibres. STRUCTURE OF NEURONĭendrites and Axons are processes of neuron. They are present in Brain ( cerebral cortex ) and spinal cord. While the cell body is in different parts of the central nervous system, while their axons reach the remote peripheral organs. Generally each sensory neuron has a short axon and long dendrites. Sensory neurons, receive signals from all sensory organs and transmit them to central nervous system through the short axons Generally, each motor neuron has a long axon and short dendrite. Motor neurons send motor commands from the cortex to the spinal cord or from the spinal cord to the muscles or in other words from the central nervous system to the peripheral effector organs like the muscles, glands, blood vessels etc. On the basis of function they are divided into two types While one of the pole gives rise to Axon, and all other poles give rise to dendrites. Axons arise from one pole, while the dendrites arise from other pole. THese type of neurons are present only in the embryonic stage in humans.īi means two. Axon and Dendrites arise from a single pole. On the basis of number of poles they possess,they are divided into three types Neurons are classified by three different methods, Neuron, also called the nerve cell, is the functional unit of nervous system.Ībundant during birth and shortly thereafter, they tend to remain constant throughout life and once they die they don’t regenerate nor divide unlike other cells of the body.
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