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General - Histology πŸ”¬ > L7: Nervous tissue > Flashcards

L7: Nervous tissue Flashcards

1
Q

What is the nervous system classified into?

A

The nervous system is classified into:

  • Central nervous system (C.N.S): include brain and spinal cord.
  • Peripheral nervous system (P.N.S):
    Peripheral nerves: may be cranial or spinal nerves

Ganglia: may be spinal or autonomic ganglia.

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2
Q

What is the definition of neurons?

A

❖ Neurons are the structural& functional unit of the nervous system.

❖ It is a specialized cell that transmit impulses within the nervous system.

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3
Q

What is the structure of the neuron?

A

❖ The neuron or the nerve cell consists of:

Cell Body: It contains the nucleus and surrounding cytoplasm contain many organelles (Nissl granules, Golgi apparatus, Mitochondria)

Processes: axon and dendrites.

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4
Q

What is the shape of nissl granules under LM?

A

Basophilic granules scattered in the cytoplasm.

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5
Q

What is the distribution of Nissl granules?

A

All over the neuron except in:

 Around the nucleus.
 Axon

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6
Q

What is the stain of Nissl granules?

A

Stained basophilic by Hx

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7
Q

What is the function of Nissl granules?

A

Synthesis of protein

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8
Q

Compare between the processes of the nerve cell

A
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9
Q

What is the classification of New Orleans according to the number of processes (polarity)?

A

Unipolar nerve cells

Pseudounipolar nerve cells

Bipolar neurons

Multipolar neurons

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10
Q

Unipolar nerve cells

A
  • Nerve cells are rounded with only one process.
  • e.g. mesencephalic nucleus of trigeminal nerve.
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11
Q

Pseudounipolar nerve cells

A
  • Nerve cells are rounded.
  • single process which divides in inverted T-shaped manner into 2 branches, a dendrite and an axon.
  • e.g. sensory ganglia or spinal ganglia
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12
Q

Bipolar neurons

A
  • The cells are fusiform, with 2 processes, a dendrite and an axon.
  • e.g. bipolar neurons of retina and olfactory epithelium
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13
Q

Multipolar neurons

A
  • Have many dendrites and one axon.
  • Have star-shaped body.
  • e.g. neurons in sympathetic ganglia
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14
Q

What is the definition of nerve fibers?

A

It is the axon of the nerve cell with its surrounding membranes.

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15
Q

What is the structure of nerve fibers?

A
  • The axon membrane named (axolemma) and its cytoplasm named β€œaxoplasm”.
  • Have no Nissl granules.
  • It may be:
     Naked or ensheathed (with myelin sheath, neurolemma or both).
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16
Q

What is a histological appearance of myelin sheath?

A
  • White tubular covering of the axon
  • Interrupted at intervals called (nodes of Ranvier)
  • Segment between two successive nodes is called (internodal segment)
  • Appears in the form of concentric layers derived mainly from the cell membrane of Schwann cell
17
Q

What is the function of myelin sheath?

A

Insulation of the nerve impulses.

18
Q

What is the histological appearance of Neurolemmal Sheath (Schwann Cells)?

A

οƒœ Chain of cells forming a tube around myelin sheath

οƒœ Each cell has a flat oval nucleus

οƒœ Corresponds to an internodal segment

19
Q

What are the functions of Neurolemmal Sheath (Schwann Cells)?

A

οƒœ Insulation in nonmyelinated nerve fibers.

οƒœ Regeneration of peripheral nerve after injury.

οƒœ Myelin formation

20
Q

What are the types of nerve fibers according to its covering?

A

1) Naked Fibers:

 (Non-myelinated without neurolemma) e.g. gray matter.

2) Ensheathed fibers:

 Myelinated with neurolemma: e.g. peripheral nerves.

 Myelinated without neurolemma: e.g. nerve fibers in the white matter.

 Non-myelinated with neurolemma: e.g. sympathetic nerve fibers.

21
Q

What is the structure of nerve trunk?

A

1) Nervous component:
 Groups of nerve fibers (myelinated axons with neurolemma) arranged in
bundles.

2) C. T. component:
 Epineurium: It is a dense C. T. surrounds the whole nerve trunk.

 Perineurium: It is a dense C. T. surrounds the bundles of nerve fibers.

 Endoneurium: It is a delicate loose C. T. lie between the individual nerve fibers.

22
Q

What is neuroglia?

A

❖ It is the interstitial supporting tissue of the nervous system

❖ Non-neuronal cells present in the CNS& PNS.

23
Q

What is the Neuroglia Of CNS?

A

οƒœ Astrocytes
οƒœ Oligodendroglia
οƒœ Microglia
οƒœ Ependymal cells

24
Q

What is the neuroglia of PNS?

A

οƒœ Satellite cells
οƒœ Schwann cells

25
Q

What is the shape and function of astrocytes?

A

Shape: It is star-shaped branching cells

Function: Nutrition by connecting neurons to blood vessels

26
Q

What is the shape of Microglia?

A

It is small cells having spiny processes

27
Q

What is the function of microglia?

A
  • can transform into a macrophage that migrate to the site of infection or injury to phagocytose foreign bodies or bacteria.
  • Hence, microglia are described as (police man of the brain).
28
Q

What is the shape of oligodendroglia?

A

It is cells have few processes

29
Q

What is the function of oligodendroglia?

A

Formation of myelin sheath of nerve fiber in the CNS.

30
Q

What is the shape of ependymal cells?

A

It is cells Line the spinal cord and the ventricular system of the brain

31
Q

What is the function of ependymal cells?

A

Secretion of cerebrospinal fluid (CSF).

32
Q

What is the shape of satellite cells?

A

It is small cells that surround neurons in sensory, sympathetic, and parasympathetic ganglia

33
Q

What is the function of satellite cells?

A

They are highly sensitive to injury and inflammation

34
Q

What is the shape of Schwann cells?

A

It is Flat cells forming a tube around myelin sheath of nerve fiber

35
Q

What is the function of Schwann cells?

A

Formation of myelin sheath of nerve fiber in the PNS.

36
Q

Notes about neuroglia

A

❖ In CNS: Oligodendrocyte have processes that wrap around the axons. One oligodendrocyte forms myelin sheath for several neurons (3- 50 neurons).

❖ In PNS: only one Schwann cell provides myelination for one axon (only a segment of one axon).

37
Q

What is the definition of nerve ganglia?

A

❖ Collection of nerve cells and nerve fibers, covered by a C. T. capsule, outside the C. N. S.

38
Q

What are the types of nerve ganglia?

A

1) Spinal.

2) Autonomic: Sympathetic or Parasympathetic.

39
Q

Compare between spinal (dorsal root) ganglion and sympathetic ganglion

A

Photo

General - Histology πŸ”¬ (8 decks)

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