Veterinary Histology: Nerve Tissue

Front 1

CNS

Back 1

-geographic division
-neurons
-supportive cells: glial cells->astrocytes, oligodendrogliocytes, microglia
-meninges
-choroid plexus
-ependymal cells

Front 2

PNS

Back 2

-geographic division
-neurons
-supportive cells:satellite cells, Schwann cells
-neuronal bodies are located in ganglia

Front 3

Somatic Nervous System

Back 3

-functional division
-provides sensory and voluntary motor innervation for most of the obdy

Front 4

Autonomic Nervous System

Back 4

-functional division
-provides involuntary control over smooth and cardiac muscle and glands
-conducts sensory information from the viscera
-further divided into the sympathetic and parasympathetic systems

Front 5

CNS development

Back 5

-develops from the neuroectoderm of the neural tube

Front 6

PNS development

Back 6

-develops from neural crest

Front 7

Neurons (General)

Back 7

-3 anatomic and functional divisions: cell body (soma), dendrites (sensory), axon (output)
-contain neurofilaments (intermediate filaments)

Front 8

Neuronal cell body/Soma

Back 8

-contains large nucleus with huge nucleolus and euchromatin
-lots of rER (Nissl substance) and golgi
-older neurons have lipofuscin (wear and tear pigment consisting of the end-products of lipid metabolism)

Front 9

Axons

Back 9

-single, large processes
-branch terminally
-can be very long
-arises from the soma at the axon hillock
-may be myelinated
-

Front 10

Dendrites

Back 10

-neuronal processes
-shorter and thicker than axons
-unmyelinated
-great variation in dendrite numbers

Front 11

Chomatolysis

Back 11

-visible loss of Nissl substances as a result of neuronal injury

Front 12

Sensory neurons

Back 12

-transmit impulses from periphery to CNS
-there are somatic afferent and visceral afferent fibers

Front 13

Motor neurons

Back 13

-transmit impulses from the CNS to peripheral effector organs
-there are somatic efferent and visceral efferent fibers

Front 14

Interneurons

Back 14

-largest group of neurons (>99%)
-facilitate and modulate info exchange between sensory and motor neurons

Front 15

Multipolar neurons

Back 15

-many dendritic processes
-one axon
-polygonal cell body
-most numerous in the body

Front 16

Bipolar neurons

Back 16

-two axonal processes
-found in special sense organs of sight, hearing and balance

Front 17

Pseudounipolar neurons

Back 17

-have one axonal process that leaves the cell body
-arises from the fusion of two axons during development
-found in sensory ganglia of cranial and spinal nerves

Front 18

Synapse

Back 18

-contact point between 2 neurons or between a neuron and an effector cell
-involve chemical transmission of signals
-may be excitatory or inhibitory

Front 19

Axodendritic synapse

Back 19

-synapse between a proximal axon and a distal dentrite

Front 20

Axosomatic synapse

Back 20

-synapse between an axon and a soma

Front 21

Axoaxonic synapse

Back 21

-synapse between two axons

Front 22

Excitatory synapse

Back 22

-neurotransmitters are acetylcholine, glutamine, serotonin
-cause influx of Na+ ions, depolarization of post-synaptic membrane and subsequent action potential generation

Front 23

Inhibatory synapse

Back 23

-neurotransmitters are GABA and glycine
-cause an influx of Cl- ions and hyperpolarization of the post-synaptic membrane, suppressing action potential generation

Front 24

Acetylcholine

Back 24

-excitatory neurotransmitter
-present at neuromuscular junctions and autonomic nervous system
-inhibited by botulinum toxin

Front 25

Catecholamines

Back 25

-present in peripheral ANS

Front 26

Serotonin

Back 26

-excitatory neurotransmitter
-tryptophan derived
-present in CNS and enteric nervous system

Front 27

Amino acid neurotransmitters

Back 27

-GABA
-glutamate
-aspartate
-glycine

Front 28

Axonal transport

Back 28

-needed to transport various vesicles and molecules made in the ER down the axon to the synapse
-network of microtubules and neurofilaments

Front 29

Anterograde

Back 29

-movement distally away from the soma
-powered by kinesin a motor protein that crawls along microtubules, carrying other molecules with it

Front 30

Retrograde

Back 30

-movement from the synapse to the soma
-powered by dynein (functions similar to kinesin)
-important in recycling of synapse vesicles

Front 31

Axonal transport speed

Back 31

-can vary from 4mm/day to 4cm/day
-fast retrograde transport systems can be hijacked by the rabies virus, tentanus toxin or Listeria bacilli

Front 32

Schwann cells

Back 32

-function the same as oligodendroglioycytes in the brain
-envelop axons in myelin sheaths
-Schwann cell myelinates a single axon (oligodendrogiocyte many myelinate multiple axons)

Front 33

Myelination process

Back 33

-driven by teh axon and not the Schwann cell
-initiated by axonal expression of neuregulin
-amount of neuregulin determines myelin sheath thickness
-the myelin wrapping is gradually tightening around the axon resulting in a lipid heavy sheath

Front 34

Node of Ranvier

Back 34

-exists where two Schwann cell myelin sheaths meet along an axon

Front 35

Schmidt-Lanterman clefts

Back 35

-areas along a myelinated nerve where not all of the cytoplasm/organelles have been extruded from the myelin

Front 36

Axonal dysfunction

Back 36

-transmission can be disrupted if
1. there is demyelination
2. there is a degenerative disease that involve axons or neuronal bodies

Front 37

Axonal injury

Back 37

-wallerian degeneration occurs when an axon is severed or injured
-axon distal to the injury fragments and swells

Front 38

Axonal regeneration

Back 38

-in the PNS, schwann cells and basement membranes remain to provide a scaffold for axonal regrowth
-may or may not regenerate properly...

Front 39

Satellite cells

Back 39

-small, inconspicuous cells
-surround neurons within ganglia of the PNS
-insulate the adjacent neurons

Front 40

Glial cells

Back 40

-refers to a group of cells: astrocytes, oligodendrogliocytes, microgial cells, ependymal cells
-supportive cells of the CNS
-special stains are needed to see anything besides the nuclei
-in pathologic conditions in the CNS, glial cells can proliferate and hypertrophy--> gliosis

Front 41

Astrocytes

Back 41

-largest glia
-two types: fibrous and protoplasmic
-provide the structural framework for neuropil
-important in maintaining the microenvironment
-processes end in club-like "end feet" that form the blood-brain barrier

Front 42

Fibrous astrocytes

Back 42

-found in white matter
-contain long, wispy projections

Front 43

Protoplasmic astrocytes

Back 43

-found in the grey matter
-have shorter, branching processes

Front 44

Oligodendrogliocytes

Back 44

-enevelop axons in myelin sheaths
-sheaths meet at nodes of ranvier and the nodes are covered by astrocyte foot processes in the CNS

Front 45

Microgliocytes

Back 45

-part of monocyte-macrophage system
-function in phagocytosis and CNS immune responses
-multiply in pathologic conditions

Front 46

Ependymal Cells

Back 46

-simple, cuboidal epithelial cells
-line most of the ventricular system and spinal canal
-exhibit apical microvilli and cilia
-dorsal margins linked by desmosomes
-basal borders abutted by astrocyte foot processes
-contributes to the blood-CSF barrier

Front 47

Choroid Plexus

Back 47

-loose, spongy organ
-associated with the ventricular system of the brain-loose vascular network line by modified ependymal cells
-joint by tight junctions
-produce cerebrospinal fluid