Nervous Tissue

Question 1

Goals

Answer 1

• Define various basic terms
  
  • Central Nervous Sysetm
  • Peripheral Nervous System
  • Autonomic Nervous System
  • Nervous tissue
  • Nerve and Tract
  • Ganglion and Nucleaus
  • Gray and White matter
• Describe structure of neuron
• Classify tyes of neurons
• Describe myelin sheath
• Describe glial cells

Question 2

Central Nervous System

Answer 2

Brain and spinal cord

Question 3

Peripheral Nervous system

Answer 3

Comprised of nerves and ganglia

Question 4

Autonomc Nervous Syste

Answer 4

• Functional nervous system
  
  • Sympathetic: Fight or flight
  • Parasympathetic: Rest and Digest

Question 5

Nervous Tissue

Answer 5

• Neurons
• Supporting elements
  
  • Glial cells (CNS)
  • Schwann cells (PNS)
  • Satallite cells (PNS)

Question 6

Neuron

Answer 6

• Structural and functional unit of nervous system
• 3 parts:
  
  • Cell body
  • Dendrites
  • Axon

Question 7

Cell Body

Answer 7

• “Soma” or “perikaryon”
• Processes information/signals
• Contains:
  
  • Nucleus:
    
    • Centrally located, generally spherical with prominent nucleolus
    • Euchromatic - intense activity
  • Cytoplasm:
    
    • Contrains RER that appear as clumps of basophilic material called Nissl substance
      
      • ​Nissl substance is abundant in large nerve cells
        
        • Motor neurons
  • Neurotubules:
    
    • Microtubules
  • Neurofilaments:
    
    • Intermediate fibers with a diameter of 10 nm

Question 8

Nucleus

Answer 8

Collection of neuronal cell bodies in the Central Nervous System

Question 9

Ganglion

Answer 9

Collection of neuronal cell bodies in the Peripheral Nervous System

Question 10

Dendrites

Answer 10

• Cell processes, branch extensively like tree
• Conduct information toward soma
• Become thinner as they branch
• Covered with spines (gemmules; dendritic spines)
• Contain Nissl substance
• One to many dendrites per nerve cell
  
  • Ex: Single Purkinje cell of the cerebellum has approx. 200,000 dendrites

Question 11

Axons

Answer 11

• Cell processes that conduct information away from the soma
• Most neuron have single axon
• Vary in length and diameter
• Axoplasm contains SER but NO Nissl Substance
• Originate from a pyramid saped region of soma called axon hillock

Question 12

Neuron Types

Answer 12

• Classified based on:
  
  1. Morphology
     
     • Bipolar, pseudounipolar, multipolar
     • Myelinated or unmyelinated
     • Fiber diameter
  2. Function:
     
     • Sensory or motor
     • Visceral or somatic
     • General or special
     • Bodian
  3. Anatomical location
  4. Conductive velocity - fast vs slow

Question 13

Multipolar Neurons

Answer 13

• One axon and two or more dentrites
• Include most motor neurons

Question 14

Bipolar Neurons

Answer 14

• One axon and one dendrite
• Include sensory neurons of retina, olfactory mucosa, and inner ear

Question 15

Unipolar/Pseudounipolar Neurons

Answer 15

• Single process that bifurcates close to the some, with longer branchesextending to peripheral ending and the other toward the CNS
• All other sensory neurons

Question 16

Anaxonic Neurons

Answer 16

• Many dendrites but no true axon
• Do not produce action potentials
• Regulate electrical changes of adjacet neurons
• Fund in the retina

Question 17

Myelin Sheath

Answer 17

• A soft white material of lipid and protein secreted by Schwann cells in the PNS and oligodendrocytes in the CNS
• Allows neurons to conduct action potentials at greater velocities
• The sheath consist of a series of myelinated segments, each extending about 1 mm along the outer surface of axon
  
  • Segments are separated by small gaps called Nodes of Ranvier
  • Sheath prevents the movement of ions/current and hence ion channels are mostly concentrated in the Nodes of Ranvier

Question 18

Myelin Sheath Path

Answer 18

Question 19

Tract

Answer 19

Collection of axonal processes in the central nervous system

(ascending tract)

Question 20

Nerve

Answer 20

Collection of axonal processes in the peripheral nervous system

(phrenic nerve)

Question 21

Glial Cells

Answer 21

• Central Nervous System
  
  • Astrocytes
  • oligodendroglia
  • Microglia
  • Ependymal cells
• Peripheral Nervous System
  
  • Ganglionic gliocytes (Satallite cells)
  • Neurolemmocytes (Schwann cells)

Question 22

Grey Matter

Answer 22

• Composed of neuronal cell bodies,dendrites, and axonal terminals
• Integration of information received from the periphery for neural processing
• Output for appropriate regulation in response to received signals

Question 23

White Matter

Answer 23

• Composed of bundles of axons
• Relay between brain and spinal cord

Question 24

Functions of Glial cells

Answer 24

• Provide support
  
  • CNS is poor in connective tissue
  • After injury “scars” are formed by proliferating astrocytes
• Nutrition
• Communication

Question 25

Eppendymal Cells

Answer 25

* Line cavities of the brain and spinal cord * Cilia are present on some cells * Typically cuboidal or columnar * Contribute to formation of cerebrospinal fluid (CSF)

Question 26

Schwann and Satellite Cells