Do axons have Nissl substance?
Nissl bodies occur in the somata and dendrites of neurons, though not in the axon or axon hillock.
What is the axonal reaction?
Axonal reaction This term indicates various reactive changes that occur as a result of axonal damage. It most commonly indicates retrograde damage toward the neuronal cell body (soma), particularly following axonal damage, and the resultant neuronal swelling is referred to as central chromatolysis.
What happens during Chromatolysis?
Chromatolysis is the dissolution of the Nissl bodies in the cell body of a neuron. It is an induced response of the cell usually triggered by axotomy, ischemia, toxicity to the cell, cell exhaustion, virus infections, and hibernation in lower vertebrates.
Do axons have microtubules?
In vertebrate neurons, axons have a uniform arrangement of microtubules with plus ends distal to the cell body (plus-end-out), and dendrites have equal numbers of plus- and minus-end-out microtubules.
Why Nissl granules are absent in axon?
– Axon cannot synthesize its protein hence it depends on soma. – The Soma also called a cell body of a neuron contains the nucleus and other structures common to living cells. – Small nerve cells of the central nervous system sometimes contain no Nissl bodies. – So, Nissl granules are absent in the axon.
What is a nissl substance?
Nissl substance is a reticulum of channels within neurons. Its external membranes are studded with rows, loops, and spirals of ribosomes, although some regions are smooth. Ribosomes also lie free in the cytoplasm as polysomal rosettes between cisternae.
What is nissl substance?
Is Wallerian degeneration anterograde or retrograde?
Wallerian (orthograde) degeneration is axonal degeneration occurring distal to the site of injury. It is frequently accompanied by retrograde degeneration, in which axonal degeneration occurs proximal to the site of injury.
Is Chromatolysis is seen in demyelination?
Chromatolytic motor neurons have been found in autopsies of patients with a wide range of acquired and inherited diseases, such as chronic inflammatory demyelinating polyneuropathy,316 acute motor axonal neuropathy/acute motor and sensory axonal neuropathy,161 Werdnig-Hoffmann disease,61 poliovirus,30 amyotrophic …
Is nissl granules absent in axon?
– The Soma also called a cell body of a neuron contains the nucleus and other structures common to living cells. – Small nerve cells of the central nervous system sometimes contain no Nissl bodies. – So, Nissl granules are absent in the axon. Hence, the correct answer is option (A).
What is a nissl body?
Medical Definition of Nissl bodies : discrete granular bodies of variable size that occur in the cell body and dendrites but not the axon of neurons, are composed of RNA and polyribosomes, are stained with basic dyes (as methylene blue), and give a striped appearance to the cell.
What is the dissolution of Nissl bodies in a neuron?
Chromatolysis is the dissolution of the Nissl bodies in the cell body of a neuron.
What kind of neurons are sensitive to Nissl?
Purkinje cells are large neurons, with large, eosinophilic cell bodies that contain some Nissl substance, and like large neurons elsewhere in the CNS, appear particularly sensitive to toxicological insult: trimethyl tin is a classic example. Long axons run through the granular cell layer to the deep nuclei of the cerebellum.
How did the Nissl substance get its name?
Nissl substance, named after Franz Nissl, a neurologist in Heidelberg in the late nineteenth and early twentieth centuries, this organelle is also termed chromophilic substance, as in other cells. It takes the form of clumps of cytoplasmic material more or less large and conspicuous, which stain deeply with basic aniline dyes ( Fig. 21H ).
Where are Nissl bodies found in the body?
Nissl bodies appear as large chunks of basophilic material in pyramidal cells and motor neurons, cells with long axons and distant terminals to maintain. By contrast, they are dispersed in powdered form in sensory ganglion cells, which also have long axons.