CNS Embryogenesis

Question 1

Somatic ns

Answer 1

• Innervates skin and most skeletal muscle

Question 2

Visceral (autonomic) ns

Answer 2

• Innervates viscera smooth muscle and glands
• Sympa and parasympa divisions
• Both have pre and post ganglionic fibers

Question 3

Neural tube closure

Answer 3

• Neural plate thickens and elongates
• Lateral folding occurs
  
  • Neural groove
  • Median hinge point
  • Lateral hinge point
• Fusion of opposing neural folds and seperation from overlying ectoderm
  
  • Neural crest cells

Question 4

What initiates brain development and what establishes sensory and motor regions

Answer 4

• Molecular signals at neural plate initiate
• BMP for sensory
• SHH for motor

Question 5

Primary CNS segmentation

Answer 5

• Brain segments/vesicles
  
  • Prosencephalic (forebrain)
  • Mesencephalic (midbrain)
  • Rhombencephalic(hindbrain)
• Spinal cord
• Flexures
  
  • Cephalic
  • Cervical

Question 6

Regulation of rhombomeres

Answer 6

Differentiation of rhombomeres is regulated by HOX genes

Question 7

Secondary CNS segmentation

Answer 7

• Prosencephalon
  
  • Telencephalon
  • Diencephalon
• Mesencephalon
• Rhombencephalon
  
  • Metencephalon
  • Myelencephalon
• Neural canal in each segments forms a primitive ventricle
• Spinal cord
• Flexures
  
  • Mesencephalic (cranial)
  • Cervical
  • Pontine

Question 8

Proliferation in neural tube

Answer 8

• Consists of Pseudostratified epithelium
  
  • External limiting membrane (BM)
    
    • DNA synthesis
  • Lumen
    
    • Mitotic division

Question 9

Neurite Outgrowth

Answer 9

• Axons and dendrites
• Growth cones
  
  • Numerous filopodia (small spindle like feet)
  • Filopodia regularly extend and retract to test enviroment

Question 10

Later changes of brain vesicles

Answer 10

• Telencephalon–> cerebrum
• Diencephalon–> Thalamus, hypothalamus, oineal gland, pituitary, eyes
• Mesencephalon–> Auditory colliculi
• Metencephalon–> Pons and cerebellum
• Myelencephalon–> Medulla oblongata

Question 11

Peripheral nevers development

Answer 11

• Outgrowth of axons from motor neuroblasts in basal plate
• Neural crest cells form spinal ganglion
  
  • Dendrites grow towards periphery
  • Axons grow towards dorsal horn
• Interneurons form btw sensory neuron termination and motor neurons
• Reflex arc is formed
  
  • Sensory information–>motor response

Question 12

What forms the sympathetic and parasympathetic ganglion

Answer 12

ALL are formed from neural crest cells

Question 13

Stabilization

Answer 13

• Interaction between neuron and target structure influence connection type and number
• Spoptosis
  
  • Eliminates axons that fail to reach normal target
  • Reduces size of neuronal pool to match target or presynaptic input
  • Elinates connection errors

Question 14

Neural crest cells differntiation

Answer 14

• Hypothesis
  
  • Equal developmental potential
    
    • Differntiation exclusvly determined by enviroment
  • Preprogrammed before migration
    
    • Diff exclusively determined by internal factors
• Both are true
  
  • Factors
    
    • Origin
    • time of migration
    • proximity to inducing tissue

Question 15

Cranial NCC

Answer 15

• Leave before neural tube closure
• Origin specifies destination (unlike trunk ncc)
• Responsible for facial tissues

Question 16

Circumpharyngeal NCC

Answer 16

• Marks the pathway for 2 groups
• Vagal crest cells
  
  • Migrate to developing gut
  • Precursors to parasympathetic innervation
• Cardiac crest cells
  
  • Outflow tract of the heart and great vessels
  • Associate with thymus, parathyroid, thyroid

Question 17

Trunk NCC

Answer 17

• Leave after NT closes
  
  • Sixth somite–>caudal
• 3 main paths
  
  • Dorsolateral
    
    • Melanocytes
  • Ventrolateral
    
    • Sensory ganglia
  • Ventral
    
    • Sympathoadrenal
      
      • Adrenal chromaffin cells
      • Sympathetic ganglia
      • Sympathetic neurons

Question 18

What do Neuroglial cells do and how many types

Answer 18

• Provide neuronal support and nutrition
• Maintain homeostasis
• Forms myelin
• Participates in transmission
• Out number neurons 10:1
• 6 diff types
  
  • 4 in CNS
  • 2 PNS

Question 19

Neuron characteristics

Answer 19

• Conducting potential
• Longevity
• Amitotic
• High metabolic rate

Question 20

Soma

Answer 20

• Cell body or perikaryon
  
  • Nucleus and most organelles
• Nissl bodies
  
  • Neuronal rough ER
  • Described as gray matter
  • Intermediate filaments (neurofibrils) maintain integrity
• Form clusters
  
  • CNS Nuclei
  • PNS ganglia

Question 21

Resting potential

Answer 21

• Neurons are highly polarized
  
  • Differential permeability to potassium and sodium and K/Na pump
  • Presence of intracellular impermeable anions

Question 22

6 types of glial cells

Answer 22

• Astrocytes (CNS)
• Oligodendrocytes (CNS)
• Microglia (CNS)
• Ependymal cells (CNS)
• Scwann cells (PNS
• Satellite cells (PNS)

Question 23

Astrocytes

Answer 23

• Largest and most numerous
• Controls ionic enviroment
• Assists in migration of developing neurns
• Maintains blood brain barrier

Question 24

Oligodendrocytes

Answer 24

• Produce and maintain insulating myelin sheaths on local neurons

Question 25

Microglia

Answer 25

* Specialized immune cells * Derived from WBC * Act as macrophages of CNS * Clear unwanted decris caused from CNS lesions

Question 26

Ependymal cells

Answer 26

* Form lining of fluid filled ventricles of CNS * Cuboidal/columnar cells. Source of cerebrospinal fluid * Circulates CSF, by ciliary movement

Question 27

Satellite cells

Answer 27

* Surround neuronal cells in ganglia * Provide structural and metabolic support * Insulation * Efficient metabolic exchange

Question 28

Schwann cells

Answer 28

* Myelinate a portion of a single axon