Nerve Tissue

Question 1

What dose the nerve tissue control ?

Answer 1

It controls and integrates the functional activities of the organs and organ systems

Question 2

What are the three basic functions of the nerve tissue ?

Answer 2

1.sensing changes with sensory receptors
2.interpreting and remembering those changes
3.reacting to those changes with effectors

Question 3

What dose the central nervous system (CNS) contain ?

Answer 3

• Brain (cerebrum)
• Cerebellum
• Spinal cord (Medulla Spinalis)

Question 4

What dose the peripheral nervous system (PSS) contain ?

Answer 4

• Ganglions :
➢ Autonomic (sympathetic and
parasympathetic) ganglia
➢ Dorsal root (spinal or sensory) ganglia
• Nerves
➢ Cranial nerves (those emerge from
brain)
➢ Spinal nerves (those emerge from
spinal cord)
• Nerve endings

Question 5

How is the nervous system formed ?

Answer 5

Formed by a network of many billion nerve cells(neurons) and many more supporting cells called glial cells.

Question 6

How is the nervous tissue distributed ?

Answer 6

Nerve tissue is distributed throughout the body as an integrated communications network.

Question 7

What are the two types of cells that is found in both central and peripheral nerve tissue ?

Answer 7

1- Neurons
2- Glial cells

Question 8

What are the features of the nerve tissue ?

Answer 8

• Nervous tissue contains nerve cells
  (neurons), neuroglia cells and very
  few connective tissues.
• Nerve cells are separated from
  connective tissue by a wall called
  blood brain barrier.
• Nerve cells do not exhibit
  mitosis(non-divided). Neuroglia
  cells exhibit mitotic activity.

Question 9

What is the origin of the nerve tissue cells ?

Answer 9

CNS neurons and central glia, except microglial cells, are derived from
neuroectodermal cells of the neural tube.
• microglia cells are derived from mesodermal macrophage precursors, specifically
from Granulocyte/monocyte progenitor (GMP) cells in bone marrow.
• PNS ganglion cells and peripheral glia are derived from the neural crest.

Question 10

What dose the cell body ( perikaryon, soma ) of the neuron contain ?

Answer 10

Nucleus and cytoplasm

Question 11

What dose the projections of the neuron contain ?

Answer 11

a. Dendrites : Multiple, receives stimuli
b. Axon : Single, conducts impulses away

➢ Synaptic boutons are small swellings that are found at the terminal ends of axons.

Question 12

What is the cell body ( perykarion ) of the neuron ?

Answer 12

It is the dilated region of the neuron that contains a large, euchromatic nucleus with a prominent nucleolus and surrounding perinuclear cytoplasm.

Question 13

What dose the perinuclear cytoplasm contain ?

Answer 13

abundant rough-surfaced endoplasmic reticulum and free ribosomes. On light microscopy, the rough endoplasmic reticulum with rosettes of free ribosomes appears as small bodies, called Nissl bodies.

Question 14

Where are Nissl bodies rarely in?

Answer 14

Dendrites

Question 15

Where is nissl bodies is not found in ?

Answer 15

The axon

Question 16

What is the axon hillock ?

Answer 16

The area where the axon exits the trunk, the area where the action potential begins.

Question 17

How dose dendrites work ?

Answer 17

receive information from other neurons at specialized areas of contact called synapses.

Question 18

What are dendrites ?

Answer 18

They are projections that branch many times, forming small, tree-shaped structures protruding from the cell body that provide locations for other neurons to communicate with the cell body.

Question 19

What are dendrites ?

Answer 19

They are projections that branch many times, forming small, tree-shaped structures protruding from the cell body that provide locations for other neurons to communicate with the cell body.

Question 20

How dose information flow through a neuron ?

Answer 20

from the dendrites, across the cell body, and
down the axon.

Question 21

Where is the axon in the cell body ?

Answer 21

a single thin process, much longer than the
dendrites, Its thickness is directly related to conduction velocity, which increases with axonal
diameter.
The portion of the axon between the cell body and the beginning of the myelin sheath is the initial segment., The axonal cytoplasm is called axoplasm

Question 22

What are the three sheets of the axon ?

Answer 22

• Axolemma; continuation of neuron cell
m e m b r a n e
• Myeline sheet; covers the axon (In the CNS)
* Neurolemma (Neurilemma); at the outside
of myelin sheet when the nerve enters PNS.
• Near the distal end of axon
1. Myeline sheet disappears
2. Neurolemma disappears
3. Axon ends surrounded only with axolemma

Question 23

How are neurons classified according to the number of their processes ?

Answer 23

• Multipolar neurons ( majority )
• Bipolar neurons ( special sensory organs like cohlear, vestibular, ganglions, retina and olfactory mucosa )
• Pseudounipolar neurons
• Unipolar and apolar neurons
• Anaxonic neurons

Question 24

What are the three types of neurons according to the number of extensions radiating from their bodies ?

Answer 24

• 1-Multipolar neurons: 1 axon
-2 or more dendrites
• 2-Bipolar neuron: 1 axon,
-1 dendrite: located in taste, smell, hearing and vision organs
• 3-Unipolar (pseudounipolar neuron):
-1 axon divided into 2: found in sensory neurons

Question 25

What are synapses ?

Answer 25

They are specialized junctions between neurons that facilitate the transmission of impulses from one (presynaptic) neuron to another (postsynaptic) neuron.

Question 26

How are Synapses between neurons may be classified morphologically ?

Answer 26

• axodendritic, occurring between axons and dendrites; • axosomatic, occurring between axons and the cell body; or • axoaxonic, occurring between axons and axons

Question 27

How are synapses are classified ?

Answer 27

• Chemical synapses: Conduction of impulses is achieved by the release of chemical substances (neurotransmitters) from the presynaptic neuron. • Electrical synapses: Common in invertebrates, these synapses contain gap junctions that permit movement of ions between cells and consequently permit the direct spread of electrical current from one cell to another

Question 28

How are synapses are classified ?

Answer 28

• Chemical synapses: Conduction of impulses is achieved by the release of chemical substances (neurotransmitters) from the presynaptic neuron. • Electrical synapses: Common in invertebrates, these synapses contain gap junctions that permit movement of ions between cells and consequently permit the direct spread of electrical current from one cell to another

Question 29

What are glial cells ?

Answer 29

They Support neuronal survival and activities and are 10 times more abundant than neurons in the mammalian brain.

Question 30

How many kinds of gilal cells are there ?

Answer 30

There are six major kinds of glial cells, four in the CNS and two in the PNS.

Question 31

What are the 5 functions of neuroglia cells ?

Answer 31

• Provides support and protection to neurons • Myelination • Repairing neuron damage • Regulating the CSF (cerebrospinal fluid) content of the CNS • To ensure metabolic transmission and exchange between vessels and neurons

Question 32

Where are schwann cells ?

Answer 32

They Envelop nerve fibers in the peripheral nervous system.

Question 33

What dose schwann cells produce ?

Answer 33

They produce a myelin sheath.

Question 34

What dose schwann cells assist in ?

Answer 34

The regeneration of damaged fibers

Question 35

What dose the schwann cells allow ?

Answer 35

for faster action potential propagation along an axon in the PNS.

Question 36

What is the type of satellite cell in the neurons and what are there functions ?

Answer 36

Cuboidal or squamous glial cells of ganglia arranged around the cell bodies of neurons, their Function is metabolic and mechanical support to ganglia cells.

Question 37

What are the main components of the PNS ?

Answer 37

Nerves, ganglia and nerve endings.

Question 38

What are peripheral nerves ?

Answer 38

They are bundles of nerve fibers (axons) individually surrounded by Schwann cells and connective tissue.

Question 39

What are nerve fibers ?

Answer 39

A nerve fiber is the basic structural and functional unit of peripheral nerves, As axons course through body tissues, they are associated with Schwann cells, The axon with its associated Schwann cells forms a nerve fiber.

Question 40

What is the myelin sheath ?

Answer 40

The myelin sheath is a spiral layer of insulation around a nerve fiber, Myelin is a large lipoprotein complex, its composition is like that of plasma membranes in general, 20% protein and 80% lipid (phospholipids, glycolipids, and cholesterol)

Question 41

Where is the myelination in the PNS ?

Answer 41

• Myelinated axons: Schwann cells wrapping repeatedly around an axon to form the multilayered myelin sheath. • Unmyelinated axons: Several unmyelinated axons wrapping by one cytoplasm of schwann cell.

Question 42

What happens when one Schwann cell can myelinate only one axon ?

Answer 42

several unmyelinated axons can be enveloped by a one Schwann cell.

Question 43

How are PNS axons myelinated ?

Answer 43

Schwann cell engulfs one portion along the length of a large diameter axon, Schwann cell membrane fuses around the axon and one thin extension of schwann cell elongates greatly and wraps itself repeatedly around the axon to form multiple compacted layers (myelin sheat).

Question 44

How is the nerve fibers and myelin sheath examined ?

Answer 44

• With vital staining (e.g. Methylene blue) axon appears blue and in silver impregnation blackish. •These are the main methods to demonstrate myelinated fibers besides special immunohistochemical techniques. • Weigert's method and osmium stains myelin coat black • Klüver-Barrera and Luxol-fast blue techniques stain myelin blue-green

Question 45

What is the schmidt - lanterman ( myelin cleft ) ?

Answer 45

The axon enveloped by the myelin sheat,which, in addition to membrane, contains some Schwann cell cytoplasm in spaces called Schmidt - Lanterman (myelin cleft) between the major dense lines of membranes.