Veterinary Histology: Central Nervous System

Front 1

Nerve

Back 1

-bundle of (usually) myelinated axonal processes
-the respective neuronal bodes may reside in the CNS or in peripheral ganglia

Front 2

Where are cell bodies located?

Back 2

-cell bodies of somatic efferent motor neurons are in the CNS
-cell bodies of sensory and motor neurons are located in the spinal dorsal nerve roots

Front 3

Peripheral Nerves

Back 3

-supported, protected and bundled by collagenous CT (unlike CNS)
-3 layers: endoneurium , perineurium, epineurium

Front 4

Endoneurium

Back 4

-thinnest CT layer
-surrounds individual axons and respective Schwann cells

Front 5

Perineurium

Back 5

-divides a single nerve into fascicles (bundles) of axons
-blood-nerve barrier

Front 6

Epineurium

Back 6

-thick type I collagen layer than envelops an entire nerve

Front 7

Ganglia

Back 7

-groups of neuronal bodies located outside of the CNS
-sensory or autonomic

Front 8

Sensory ganglia

Back 8

-dorsal spinal nerve roots, some trunks of cranial nervews
-neurons are pseudounipolar with 2 unmyelinated branches
-one branch goes to sensory terminus, one to CNS

Front 9

Autonomic ganglia

Back 9

-neurons are multipolar
-axons are unmyelinated

Front 10

Spinal Cord

Back 10

-central butterfly of grey matter
-peripheral regions of white matter

Front 11

Grey matter

Back 11

-site of synapses and impulse transmission
-contains nuclei (groups of neuronal bodies) that are analogous to ganglia

Front 12

White matter

Back 12

-only impulse transmission because there are neuronal projections and NO synapses
-axons are bundled in functional related tracts

Front 13

Multipolar motor neuron nuclei

Back 13

-located in the ventral horns
-axons travel through the ventral spinal nerve root to become part of the spinal nerve

Front 14

Sensory neuron nuclei

Back 14

-located in the dorsal spinal root ganglia
-pseudounipolar neurons with one branch carrying info from the periphery and the other extending into the dorsal spinal grey matter

Front 15

Afferent (sensory) Receptors

Back 15

-ends of sensory neurons can be adapted to specialize in receiving particular information from outside sources
-nonencapsulate vs. encapsulated

Front 16

Nonencapsulated ending

Back 16

-bare
-found in epithelia, CT, hair follicles

Front 17

Encapsulated endings

Back 17

-usually sense pressure or stretch
-skin and joint mechanoreceptors such as end bulbs, Meissner's or Pacinian corpuscles
-muscle spindles
-golgi tendon organs

Front 18

Autonomic nervous system

Back 18

-2 or 3 division: sympathetic, parasympathetic +/- enteric
-afferent and efferent components
-arrangment is similar to the somatic nervous system but with a 2-neuron system

Front 19

Sympathetic Division

Back 19

-cell bodies of pre-ganglion neurons are in the thoracic and lumbar spinal grey matter
-cell bodies of post-ganglion neurons are in the sympathetic trunk

Front 20

Parasympathetic Division

Back 20

-cell bodies of pre-gangionic neurons are in the brainstem and sacral spinal grey matter
-cell bodies of post-ganglionic neurons are in or close to target tissue

Front 21

Enteric division

Back 21

-network of neuronal bodies and processes associated with the wall of the GI tract
-functions independently of CNS control
-ganglia are in the submucosa or muscularis externa

Front 22

Cerebrum Grey Matter

Back 22

-consists of axonal, dendritic and glial cell processes called neuropil
-underlying stratified arrangement of neuronal bodies

Front 23

Cerebellum Grey Matter

Back 23

-cortex is folded into folia
-series of well defined layers
1. external germinal layer-present in fetus and neonates and cells eventually migrate down into cerebellar cortex
2. molecular layer- neuropil-like layer with cell processes of underlying Purkinje cells but no nuceli
3. purkinje layer- composed of a single layer of purkinje cell neurons that supply the info output
(inhibitory)
4. Granule cell layer- innermost layer between the purkinje layer and the white matter composed of small neurons

Front 24

Meninges

Back 24

-3 layers of CT: dura matter, arachnoid, pia matter
-pia and arachnoid are very closely associated

Front 25

Dura Matter

Back 25

-thick, fibrous outer layer that provides protection and contains the venous sinuses

Front 26

Arachnoid

Back 26

-spider web-like and bridges the CSF-filled subarachnoid space

Front 27

Pia matter

Back 27

-extremely thin layer lying on the outisde surface of the brain and spinal cord

Front 28

CSF circulation

Back 28

-reabsorbed from the subarachnoid space through the arachnoid villi