Nervous Tissue

Question 1

Axons

Answer 1

Axons
• cell processes; destinations: other organs/neurons
• need cell body to make proteins; protein distribution via microtubule dependent axoplasmic transport
• terminate in presynaptic membranes

Question 2

Dendrites

Answer 2

Dendrites
• receive incoming impulses, deliver them to the nerve body
• postsynaptic membranes: distal ends of dendrites

Question 3

pseudounipolar

Answer 3

pseudounipolar

• 1 axon stems from the cell, divides into afferent and efferent branches

Question 4

afferent

Answer 4

afferent ex. dendrites
afferent branch
* receives sensory impulses from the periphery

Question 5

efferent

Answer 5

efferent (axons, aka nerve fibers) (mm to m long)

efferent branch
* transmits impulses to second order sensory neurons in brain or spinal cord

Question 6

soma

Answer 6

cell body of neuron; perikaryon

Question 7

epineurium

Answer 7

epineurium
• outermost CT layer enclosing an entire nerve
• dense irregular CT
• made of collagen and elastic fibers

Question 8

perineurium

Answer 8

perineurium

• dense irregular CT, surrounds individual nerve fasicles

Question 9

endoneurium

Answer 9

endoneurium
• loose, delicate CT, surrounds individual axons (nerve fibers)
• external to myelin sheath
• contains capillaries

Question 10

How are nerves arranged? Are they similar to or different from muscles?

Answer 10

nerves are like muscle fibers

* bundles of individual fibers surrounded by CT (endoneurium) within an overarching CT perineurium

Question 11

myenteric plexus

Answer 11

Myenteric plexus (Auerbach's plexus)
enteric ganglia between circular and longitudinal smooth muscle layers of gut wall; can also see neuronal bodies

Question 12

autonomic ganglia

Answer 12

autonomic ganglia

* postganglionic neuron cell bodies (second neuron in 2-neuron chains / SNS, PSNS)

Question 13

axon hillock

Answer 13

axon hillock

* where axon originates/branches from the cell body

Question 14

dendrites

Answer 14

Dendrites

• receive incoming impulses, deliver them to the nerve body
• postsynaptic membranes: distal ends of dendrites

Question 15

enteric ganglia

Answer 15

enteric ganglia

• autonomic ganglia within gut wall (where preganglionic parasympathetic neurons synapse)
• 100 million neurons in this system
• controls peristalsis and glandular secretion w/o other autonomic input
• GI is complex – ex. Crohn’s disease, IBS
• Enteric ganglia is more of a plexus than a discrete ganglion (highly interconnected network)

Question 16

Meissner’s plexus

Answer 16

submucosal plexus or Meissner’s plexus

* within submucosa

Question 17

multipolar neurons

Answer 17

multipolar neurons in the ANS communicate with preganglionic axons through synapses
* more than two processes emanate from the cell body, * the cell body receives synaptic input just like the dendrites

Question 18

Nissl substance

Answer 18

rough ER in neuronal cell body

Question 19

pseudounipolar neurons

Answer 19

pseudounipolar neurons

* single axon exits the cell and bifurcates into afferent and efferent branches

Question 20

satellite cells

Answer 20

• supporting cell

* in a cross-section/H&E, you can see cell bodies surrounded by a complete/partial ring of satellite cells

Question 21

Schwann cells

Answer 21

• supporting cell
  o Derived from the neural crest and surround all peripheral nerve axons (forms Schwann cell sheath)
  o Nerve repair, rapid action potentials – adding myelin
  o Nodes of Ranvier: small gaps between myelin produced by adjacent Schwann cells
  o Saltatory conduction: myelination insulates the axon → AP jump from node to node; increases transmission speed
  o Schmidt-Lanterman incisures: interruptions in the myelin, to permit communication between the axon and Schwann cell in myelinated axons; narrow cytoplasmic channels between axon and Schwann cell
  o Stain: high lipid content of myelin sheath: most of the sheath is lost during tissue prep; residual protein may be stained (ex. eosin) – neurokeratin (misnomer, not keratin): residual matrix

Question 22

sensory ganglia

Answer 22

sensory ganglia
o distinct CT capsule with entering/exiting nerve fibers
o no perineurium, no blood-nerve barrier
o a type of dorsal root ganglia
• contain cell bodies of all sensory neurons (somatic sensory and visceral sensory) except cranial/in head
• no synapses (unlike autonomic ganglia)
o most are pseudounipolar
• 1 axon stems from the cell, divides into afferent and efferent branches
• afferent branch receives sensory impulses from the periphery
• efferent branch: transmits imulses to second order sensory neurons in brain or spinal cord
o x-section: complete ring of satellite cells surrounding the cell body
• usually don’t see axonal processes (1 per cell)
• don’t see dendrites (no synapses, either)
• central nuclei
• surrounded by satellite cells: form a complete ring around the soma

Question 23

synapse

Answer 23

• synapses: sites of nerve cell to cell info transfer – chemical signals
o axodendritic
o axoaxonal
o axosomatic
o neuromuscular junctions (skeletal, cardiac, smooth muscle)
o electrical