8nerve tissue histology

Question 1

what are the two categories of the nervous system? what are their contents?

Answer 1

1. Anatomical
   
   1. CNS
      
      1. brain and spinal cord
   2. PNS
      
      1. ganglia, nerves and nerve endings
2. Functional
   
   1. somatic nervous system
   2. autonomic nervous system

Question 2

What are the two principal typs of cells?

What is the basic unit of structure and funciton, list 3 main categories?

Answer 2

1. Nerve tissue two types
   
   1. neurons
   2. supporting cells, NEUROGLIAL
2. Neurons=basic funciton
   
   1. sensory
   2. motor
   3. interneurons or intercalated neurons

Question 3

What is the classification of neurons based on? what are they?

Answer 3

classification basd on thenumber of processes, extending from the cells body

1. multipolar neurons
   
   1. structure
      
      1. one axon
      2. 2+ dendrites
   2. funciton
      
      1. impulse direction is from dendrite to soma to cell body
      2. cell body and dendrites are impulde generators and axon is for impulse conduction
   3. example
      
      1. motor neurons
      2. interneurons
2. bipolar neurons
   
   1. structure
      
      1. 1 axon + 1 dendrite
   2. function
      
      1. used in specialized receptors
   3. example
      
      1. retina of eye
      2. ganglia for vestibulocochlear nerve in ear
3. pseudo unipolar neurons
   
   1. structure
      
      1. 1 process= axon that divides close to the body into two long axonal branches.
   2. function
      
      1. sensroy neurons located close to the CNS
   3. example
      
      1. dorsal root ganglia
      2. cranial nerve ganglia
         1.

Question 4

What are the functional components of the neruron? what are the functinal components of the neruons’ contents?

Answer 4

functional components of neuron

1. soma
2. axon
3. dendrites

conents

1. soma
   
   1. surface membrane and dendrtitic tree
      
      1. specialized for
         
         1. reception of information
         2. integration of information
   2. nucleus- w/ prominent nucleolous
   3. PERIKARYON- the perinuclear cytoplasm
   4. abundant organells
      
      1. mitochondria
      2. golgi apparatus
      3. lysosomes
      4. rER
         
         1. stains with basophilic dye because of NISSL BODIES
      5. free ribosomes
2. axon
   
   1. originates from the soma at the axon hillock and ends at the TELODENDRON
   2. each terminal branch of telodendron has an enlarged ending, synaptic terminal
   3. specialized for 2 transmisison types of information in the form of
      
      1. action potential - or-
         
         1. ​change in voltage across a cell membrane
      2. nerve impulse
         
         1. ​the message sent via action potential
3. dendrites
   
   1. shorter processes that transmit impulses from the periphery toward cell body

Question 5

Can neurons divide? What is different about the brain?

Answer 5

Neurons do NOT divide

However in some areas of the brain, neural stem cells are present that are able to differentiate and replace damaged nerve cells

Question 6

The designation of groups of neurons and axons. categorize, define and give examples where relevant.

1. nuclei
2. stratum aka lamina
3. columns
4. tracts/fasciculi/lemnisci
5. ganglion
6. motor
7. nerves, rami, roots

Answer 6

1. CNS
   
   1. nuclei
      
      1. functionally an dstructurally reltated neurons form aggregates
         
         1. example
            
            1. cerebral cortex
   2. stratum/lamina
      
      1. clusters of neurons arranged in a layer
   3. columns
      
      1. when neurons form longitudinal groups
   4. tracts/fasciculi/lemnisci
      
      1. bundles of axons in the CNS
         
         1. example
            
            1. optic tract
2. PNS
   
   1. ganglion
      
      1. cluster of neurons
      2. can be
         
         1. sensory
            
            1. ​example
               
               1. ​dorsal root ganglia
               2. trigeminal ganaglion
         2. motor
            
            1. ​example
               
               1. ​viceromotor
               2. autonomic
   2. nerves, rami, roots
      
      1. organization of axons derived from a ganglion

Question 7

Answer 7

synapse on a neuron

1. conduction of impulse is acheived by nerotransmitters such as
   
   1. ACh
   2. carecholamine
   3. serotonin
   4. 5-hydroxytrptamine(5HT)

Question 8

List the CNS neuroglia

1. location
2. structure
3. function

Answer 8

CNS neuroglia

1. astrocytes
   
   1. location
      
      1. closely associated with CNS neurons
      2. largest concentration of neuroglia in CNS
   2. structure
      
      1. glial fibrillary acid proteins (GFAP)
         
         1. ​seen with antibody stain
   3. function
      
      1. provide support modulate the activity of neurons
         
         1. movment of substances and waste to and from the neuron.
         2. help maintain tight junctions of the BBB
2. oligodendrocytes
   
   1. location
      
      1. CNS, axon processes
   2. function
      
      1. produce and maintain the myelin sheath
3. microglia
   
   1. location
      
      1. 5% of all glial cells of CNS, BUT proliferate and become actively phagocytic in regions of injury and disease
   2. function
      
      1. reactive microglial cells, phgocytic cells
4. ependymal cells
   
   1. location
      
      1. epithelial like lining the ventricles of the brain and spinal cord
   2. function
      
      1. create cerebral spinal fluid (CSF), line the ventricles of the brain and central canal of the spinal cord. These cells are cuboidal to columnar and have cilia and microvilli on their surfaces to circulate and absorb CSF.
      2. cuboidal to low columnar cells that are tightly bound by junctional complexes

Question 9

compare teh CNS to the PNS supportive cells. breif categorization.

Answer 9

1. CNS
   
   1. central neuroglia
      
      1. types
         
         1. astrocytes
         2. oligodendroctyes
         3. microglia
         4. ependymal cells
2. PNS
   
   1. peripheral neuroglia
      
      1. types and details
         
         1. Schwann cells
            
            1. produce
               
               1. Myelin sheath
                  
                  1. surrounds the axons and ensures rapid conduction of nerve impulses
                  2. is segmented due to several schwann cells along the axon.
                     
                     1. between segments is the node of ranvier
         2. satellite cells
            
            1. ​surround the neuronal cell bodies of the ganglia
         3. motor end plate retina
         4. ganglia located in the alimentary canal(mouth to anus)

Question 10

Abnormalities in oligodendrocytes can apear in what disorders? why?

Answer 10

Several autoimmunce disorders

problem is the oligodendrocytes demyleinate and lead to the decreases in signal transduction efficacy.

Question 11

describe the structures and organization of a peripheral nerve

Answer 11

peripheral nerves

1. nerve fibers collected into fascicles
   
   1. thes fascicles are enclosed by epineureum
      
      1. thick connective tissue sheath
2. bunch of fascicles com together and are surround by CT (flattened epitheloid cells) and then perineureum
3. the very smallest structure of the nerve
   
   1. each nerve fiber is associated with scwann cells and a slender endonereum
      
      1. composed of collagenous and reticular fibers with fibroblasts and macrophages

Question 12

after receiving an injury to the peripheral nerve axon, what are the events? can the pathway be recovered?

compare PNS vs CNS

Answer 12

neuronal injuries induce a complex sequence of events

1. PNS
   
   1. have the capability of regeneration
   2. sequence of events for neuronal injuries
      
      1. axonal degredation
         
         1. macrophages and glial cells quickly errode the axon downstream of the axon hillock
      2. neuronal regeneration
         
         1. stem cells slowly regenerate the axonal connection
      3. until the axon is repaired, the muscle is paralyzed in that region, muscles ungero atrophy
         
         1. ​intesnse physio therapy is necessary for paralyzed/atrophic muscles
2. CNS
   
   1. impaired ability to regenerate
      
      1. cause
         
         1. glial and macrophages quickly phagocitize the debris
      2. reactive gliosis
         
         1. when a region of the CNS is injured, astrocytse near the lesion are activated
            
            1. they divide and hypertrophy and result in a permanent scar formation-reactive gliosis plaque
         2. common featuer in
            
            1. strokes
            2. neurotcic damage
            3. genetic diseases
            4. inflammatory demyelination
            5. neurodegeneratieve diseases
               
               1. multiple sclerosis