Histology (Nervous Tissue) (1st year)

Bismillahirahmanirrahim

Asalamua'laikum wbt :) hey you there ;) Are you okay? hee. Please3x.. I beg you, put one 'smile' on your face :D

Ok, today, Najwa will share with all you about "Nervous Tissue"

In our body, we have nervous tissue that function to send impulses in order to give signal. If you put your hand on hot kettle or Malaysian called it 'cerek', you'll immediately take up your hand right? Impossible if you just let it stay like nothing is happening :P If you do.. then prove it to me :P hehe.

Okay!

Nervous tissue actually consist of two types of cell :

1. Neuron (nerve cell)

2. Neuroglia (host of supportive cell)

For neuron, the typical structure is like shown in the picture below;

It got :

1. Body cell / soma that have nucleus inside it that surrounded by cytoplasm called perikaryon.

2. It also have lots of processes there called dendrites

3. And long slender process called axon.

Ok.. neuron was divided into 3 types :

1. Unipolar

2. Bipolar

3. Multipolar

For "neuroglia", there is variety of supportive cells can be seen. E.g. 

1.Purkinje cell in the cerebellar cortex

2.Oligodendrocytes of the brain

                                      (it's quite simple in structure compare to fibrous astrocyte)

3. Fibrous astrocyte of the brain

                                                              (more complex in structure)

4. Microglia of the brain

(This one more slender and don't have much processes)

5. Schwann cell

                              (This picture just show 'nuclei' of neurolemmocyte which is schwann cell)

6. Ependymal cell

                                                     (*I don't have the picture for this, sorry*)

Okay... we've been through the neuron and glial cell. Now, we move to myelinated nerve fibres.

How doest it form?

Before that, I'll explain to the different between 'myelinated and unmyelinated' nerve fibres.

Myelinated: Surrounded by multiple layer of Schwann cell. Divided into segment by 'nodes of Raniver' or internodal segment.

Unmyelinated : surrounded by 'only single layer' of schwann cell.

Erm..how does the myelin sheath form?

ok..

First, there is axon, and there is schwann cell. Then, axon will invaginate into Schwann cell.

Second, the invagination of axon into Schwann cell will form 'mesoaxon'. 

Last one, after it form mesoaxon, the mesoaxon will round the axon several times, then it form adjacent layer.The adjacent layer between mesoaxon was fill with lipid. Thus, Lipid + mesoaxon will form 'myelin sheath'.

Outside of the myelin sheath, there is thin layer of cytoplasm = neurolemma. Neurolemmal sheath also call Schwann sheath.

What is the function of myelinated axon?

1. Increase velocity of conduction of impulse

2. Decrease the energy expanded conduction

Where is this axon terminate?

*Telodendria*

(End in the small swelling)

Usually it terminate when come into contact with another neuron called 'synapse'.

Our 'large peripheral nerve' enclosed by 3 different layers:

(From outside - inwards)

1. Epineurium

2.Perineurium

3. Endoneurioum

#Epineurium#

*Held together fasciculi

*consist of : Fat which cushion the nerve fibre. Loss of fat in certain patient, give pressure to nerve when compress, and it leads to paralysis.

#Perineurium#

*Held 'each' fascicle

* consist of: flattened cell separated by collagen fibre

*Function: control in and out substance of axon

#Endoneurium#

*Held each fibre

* Consist : Delicate loose connective tissue consisting of small fibrils of collagen, fibroblast, fixed macrophages, capillaries, perivascular mast cell & extracellular fluid.

Okay my dear friend :) now we have to enter into important topic.

" Autonomic ganglia (Sympathetic ganglia) & Sensory ganglia (Dorsal root ganglia"

What's the difference?

Ok..

Autonomic :

1. Multipolar neuron

2. Nissl substance are not well define

3. Myelinated fibre

Sensory :

1. Unipolar neuron

2. Nissl substance are well define

3. Unmyelinated & thin myelinated

Ok.. thats all for now :) see u later :D

Share site : http://www.proprofs.com/quiz-school/story.php?title=unit-iii-muscular-system.