Derivatives of neural crest
Written by D C MorganDuring the 4th week of embryonic life, as the neural folds close to form the neural tube, a longitudinal strip of cells arise one on each side from the apices of neural folds i.e., from the neuro-ectodermal junction. These strips are the neural crests (Fig.20), which extend from the mesencephalon caudally to the rest of […]
Tags: metencephalo, neural crest, neurons
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Internuncial neurons or interneurons
Written by D C MorganInternuncial neurons or interneurons (II) are confined within the CNS: they behave in a number of ways :
1. Some of these internuncial neurons synapse directly or indirectly by way of other internuncial neurons (depending on the complexity of the pathway) with the cell bodies or dendrites of efferent neurons situated in the ventral horn […]
Tags: neurons
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Sensory or afferent neuron
Written by D C MorganSensory or afferent neuron (I) : The cell body is located in the sensory ganglion (dorsal root ganglia or one of the ganglia of cra¬nial nerves). On entering the central nervous sytem, say spinal cord, the central process of the sensory neuron bifurcates into ascending and descending limbs which extend for variable distances and give […]
Tags: hindbrain, neurons
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Neuromuscular transmission
Written by Dr.ChrisNeuromuscular transmission : Acetyl-choline is the transmitter substance at the mo¬tor endplate. When a nerve impulse arrives at the motor endplate acetylcholine is liberated from the synaptic vesicles. This stimulates the muscle fibre to contract, and is later broken down by the enzyme acetyl-cholinesterase.
Each muscle fibre receives one motor end¬plate, but each axon by virtue […]
Tags: Mitochondria, neurons
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Peripheral nerves
Written by Dr.ChrisPeripheral nerves consist of collection of axons, and dendrites that resemble axon in structure. They contain two types of fibres : (a) sensory (afferent) fibres are peripheral processes of sensory neurons; (b) motor (efferent) fibres are axons of motor neurons situated in the spinal cord, brainstem or autonomic ganglia.
The constituent fibres in most of the […]
Tags: Endoneurium, Epineurium, neurons, Perineurium, sheath of Henle
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Ganglia
Written by Dr.ChrisGanglia
A ganglion is a collection of nerve cells located outside the CNS. There are two types of ganglia.
· Sensory ganglia (ganglia of conduction)
All sensory ganglia contain unipolar neurons except vestibular and cochlear ganglia, which are bipolar cells. Each ganglion has a thin connective tissue capsule within which the nerve cells are peripherally placed. Each ganglion […]
Tags: CNS, ganglia of conduction, ganglia of synapse, neurons
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Motor (efferent) neurons
Written by Dr.Chris Motor (efferent) neurons are also multipolar cells. They are found in the grey matter of CNS. Their dendrites lie within CNS, but the axons leave the CNS to run in peripheral nerves to supply skeletal muscles.
Within the skeletal muscle each axon breaks up into a […]
Tags: ANS, CNS, neurons
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Internuncial (association) neurons
Written by Dr.Chris Internuncial (association) neurons are multipolar cells. They are also termed interneurons.
They are confined within CNS and transmit nerve impulses from sensory to motor neurons and also connect different groups of nerve cells within CNS.
Tags: CNS, neurons
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Sensory (afferent) neurons
Written by Dr.ChrisSensory (afferent) neurons are mostly unipolar neurons except vestibular and cochlear ganglia, which are bipolar neurons. They bring information from sense organs to the CNS. The cell bodies of afferent neurons lie outside the CNS in sensory ganglia of cranial nerves and dorsal root ganglia […]
Tags: Bipolar neurons, CNS, neurons
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Dendrites, Dendritic field
Written by Dr.ChrisThe dendrites, one or many, are afferent processes of the neuron and carry nerve impulses towards the cell body. They are short, thick and branch profusely like a bush and they terminate near the cell body. The area occupied by the dendrites of a neuron is called its dendritic field.
The internal structure of a dendrite […]
Tags: neurons
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Axon (axis cylinder)
Written by Dr.ChrisThe axons are efferent processes of the neuron and usually carry nerve impulses away from the cell body to other neurons, or effector organs. Each neuron has only one axon and arises from the cell body from a small conical elevation called axon hillock. The axon is long, slender and uniform in diameter; the longest […]
Tags: axon hillock, Mitochondria, neurons
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Cytoplasm (Neuroplasm)
Written by Dr.Chris1. Neurofibrils (stained by silver salts) are thread like cytoplasmic fibrils in the cell body where they form a closely meshed branching network, and extend into all processes. They provide mechanical support and stability to the cell.
2. Nissl’s bodies are small granular bodies containing RNA. They are stained by basic aniline dyes e.g., toluidine blue. […]
Tags: Chromatolysis, Mitochondria, Neurofibrils, neurons, RNA
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ANATOMY OF NEURON
Written by Dr.ChrisA neuron is the structural and functional unit of nervous system composed of a cell body and one or more processes. The neurons are specialized for the receipt, processing and transmission of information. The processes are the axon and the dentrite. Each neuron has only one axon, while the dendrite may be one or many(Figs. […]
Tags: CNS, nervous system, neurons, Perikaryon
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Classification of nervous system
Written by D C Morgan• Central nervous system (CNS) comprising of spinal cord and brain, lying within vertebral canal and cranial cavity respectively.
• Peripheral nervous system (PNS) comprises of cranial nerves, spinal nerves, and ganglia, which link, the central nervous system with sensory receptors and with effector organs, namely muscle and glands throughout the body. The peripheral nervous system […]
Tags: CNS, neurons, PNS
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What is Neuroanatomy
Written by D C MorganNeuroanatomy deals with the study of structure and function of the nervous system. The nervous system detects changes in the external and internal environment, and brings about appropriate responses in muscles and glands. It may be defined as the stimuli response reaction system. The receptors receive sensory stimuli, physical or chemical, and convert them into […]
Tags: CNS, nervous system, neurons
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