Nervous System

Question 1

Synapse

Answer 1

• Termination of nerve process at surface of another cell
  
  • Nerve to nerve: responsible for signaling between nerves
  • Nerve to effector cell: responsible for stimulation or inhibition of post synaptic cell

Question 2

Functional Classification of Neurons

Answer 2

• Afferent/Sensory Neurons
  
  • Have axons that carry signals toward CNS
• Efferent/Motor Neurons
  
  • Have axons that carry signals away from CNS
    
    • Somatic motor neurons innervate skeletal MM
    • Autonomic motor neurons innervate visceral MM and glands
• Interneurons
  
  • CNS neurons that transmit signals between other CNS neurons

Question 3

Schwann Cells

Answer 3

• Supporting cells (Neuroglia) of PNS derived from neural crest cells
• Insulate nerve fibers:
  
  • Unmyelinated fibers lie in fold of Schwann cell plasma membrane
  • Myelinated fibers surrounded by multiple layers of lipid bilayer, derived from Schwann cell plasma membrane
• Distinguished as oval, pale-staining nuclei in peripheral NN

Question 4

Satellite Cells

Answer 4

• Supporting cells of PNS derived from neural crest cells
• Cover perikarya of neurons
• Distinguished by round/oval, pale-staining nuclei in close association with neuronal perikarya in ganglia

Question 5

Ependymal Cells

Answer 5

• Supporting cells of CNS
• Simple columnar epithelia derived from embryonic neuroectoderm
  
  • Line ventricles of brain and central canal of spinal cord
  • Contribute to production of cerebrospinal final (CSF)

Question 6

Fibrous Astrocytes

Answer 6

• Supporting cells of CNS
• Distinguished as small cell bodies with multiple, elongated, smooth cell processes, found exclusively in white matter
• Only visible with silver stain
• Contributes to blood-brain barrier
  
  • Elongated processes (Periavascular feet) cover capillaries and produce extracellular matrix

Question 7

Protoplasmic Astrocytes

Answer 7

• Supporting cells of CNS
• Distinguished as small cell bodies with multiple, elongated, “lumpy” cell processes, found exclusively in gray matter
• Only visible with silver stain
• Contributes to blood-brain barrier
  
  • Elongated processes (Periavascular feet) cover capillaries and produce extracellular matrix

Question 8

Oligodendrocyte

Answer 8

• Supporting cells of CNS that form myelin
• Found in both gray and white matter:
  
  • Distinguished as lightly-stained nuclei in close apposition to neuronal perikarya in gray matter and nerve fibers in white matter
• Visible only with silver stain

Question 9

Microglia

Answer 9

• Phagocytic cells in CNS derived from monocytes
• Distinguished as small cells with multiple short processes
• Visible only with silver stain

Question 10

Dura Mater

Answer 10

• Thick, outermost layer of collagenous CT
• Cranial:
  
  • Continuous with periosteum of skull
  • Extends into interior of brain and forms venous sinuses
    
    • Collects blood from brain and drains into internal jugular VV
• Spinal Cord:
  
  • Forms separate tubular layer covering spinal cord

Question 11

Arachnoid Mater

Answer 11

• Thinner CT layer on inner surface of dura mater covered by simple squamous epithelium
• Forms thin, tubular trabeculae that extend across subarachnoid space to pia mater
• Subarachnoid space filled with CSF

Question 12

Pia Mater

Answer 12

• Thin, delicate layer lying directly on surface of brain and spinal cord, covered by simple squamous epithelium
• Continuous with CT of underlying blood vessels
• Tubular extensions cover blood vessels that penetrate brain and help to form blood-brain barrier

Question 13

Gray Matter

Answer 13

• Region contain neuronal perikarya, unmylinated nerve fibers, and glial cells
• Appears gray in fresh preparations due to absence of myelin

Question 14

White Matter

Answer 14

• Region contain nerve fibers and glial cells
• No neurons!
  
  • Cell nuclei belong to glial cells and blood vessels
• Appears white in fresh preparations due to presence of myelin

Question 15

Blood-Brain Barrier

Answer 15

• Prevents free passage of fluids, solutes, and pathogens from blood vessels into brain
• Components:
  
  • Non-leaky, continuous capillaries
    
    • Zonula occludens junctions form tight intercellular seal
  • Endothelial basement membrane
  • Pia mater
  • Perivascular feet of astrocytes

Question 16

Dorsal Root Nerve

Answer 16

• Passes through dorsal root ganglion, carrying axons of afferent sensory neurons into spinal cord
• Continuous with dorsal horn

Question 17

Ventral Root Nerve

Answer 17

• Carries axons of motor and autonomic neurons away from spinal cord
  
  • Axons exit via ventral horn and cross white matter to enter ventral root nerve

Question 18

Spinal Nerves

Answer 18

• Formed by union of dorsal and ventral root nerves distal to dorsal root ganglion
• 31 spinal nerves total
  
  • 8 cervical
  • 12 thoracic
  • 5 lumbar
  • 5 sacral
  • 1 coccygeal

Question 19

Endoneurium

Answer 19

• Thin layer of fine collagen fibers external to Schwann cell covering that cover individual nerve fibers

Question 20

Perineurium

Question 21

Epineurium

Answer 21

• Thick, vascularized layer of CT surrounding entire nerve
• May contain adipose cells

Question 22

Dorsal Root Ganglion

Answer 22

• Consists of clustered perikarya of pseudounipolar sensory neurons covered by satellite cells
• Situated on spinal nerves
• Enclosed by CT capsule (continuous with dura mater of spinal cord and epineurium of spinal nerves) that divide into trabeculae to support perikarya

Question 23

Paravertebral Ganglia

Answer 23

• Autonomic ganglion - sympathetic division
• Consists of aggregations of autonomic multipolar perikarya partially covered by satellite cells, CT capsule, capillaries, and nerve fibers with associated Schwann cells
• Located in chain on either side of vertebral column

Question 24

Prevertebral Ganglia

Answer 24

• Autonomic ganglion - sympathetic division
• Consists of aggregations of autonomic multipolar perikarya partially covered by satellite cells, CT capsule, capillaries, and nerve fibers with associated Schwann cells
• Located in plexuses within CT of abdominal cavity

Question 25

Cranial Ganglia

Answer 25

• Autonomic ganglia - parasympathetic division
• Consists of one to several perikarya of multipolar neurons and satellite cells
• Situated on cranial nerves

Question 26

Enteric Ganglia

Answer 26

• Classification of autonomic ganglia situated within the gastrointestinal tract
  
  • Auerbach’s plexus (between layers of muscularis)
  • Meissner’s plexus (within submucosa)
• Consists of perikarya of multipolar neurons and satellite cells