Nervous System Pt.2

Question 1

Describe the ventricular system.

Answer 1

-ependymal cells
-communicates with subarachnoid space
-both circulate CSF

Question 2

Describe CSF.

Answer 2

-made in choroid plexus (modified ependymal cells)
-formed & renewed 3x a day
-sampled for tests
FUNCTION:
-filtration system medium -> remove metabolic waste
-exchange of bio molecules in and out of brain
-maintain extracellular environment of brain (homeostasis)
-cushions CNS for impact

Question 3

Describe the choroid plexus.

Answer 3

-CSF formed as plasma & filtered from blood through choroid plexus ependymal cells
-made by active secretion of Na+ into ventricles and water following the osmotic gradient
-microvilli (brush border -> increases SA)
-tight junctions
-cuboidal
-capillaries (fenestrated & no tight junctions)
-loose CT
-blood CSF barrier
-cells secrete cytokines (normal brain homeostasis & neuroinflammatory process)
-4 choroid plexuses (1 in each hemisphere of brain)
>all parts of ventricular system
>except cerebral aqueduct, frontal horn, occipital horn, lateral ventricles

Question 4

Describe CSF reabsorption and production.

Answer 4

Made in choroid plexus.
Absorbed in subarachnoid space.

Question 5

Describe the BCB.

Answer 5

-separate blood from CSF & CSF from brain tissue
-at choroid plexus -> arachnoid membrane
FUNCTIONS:
-prevents blood into brain
-transport substances into brain
-remove brain metabolites & metabolic waste into blood
-modulates entry of leukocytes

Question 6

Describe the cerebellum (with arbor vitae).

Answer 6

1. Molecular layer - basket cells
2. Ganglionic cell layer - purkinje cells
3. Granular cell layer - granule cells in stratum granulosum

White matter core & grey matter periphery
(Sulcus & gyrus present)

Question 7

Describe the fetal cerebellum.

Answer 7

Additional exterior cortical lamina (external granular cell layer) that will populate the internal granular cell layer during postnatal development.

Question 8

Describe the nucleus in CNS.

Answer 8

-cluster of neurons in CNS
-located deep in cerebral hemispheres & brainstem

Question 9

Describe the spinal cord.

Answer 9

-central canal = remnant of lumen of embryonic neural tube
-ependymal cells
-grey matter =
1. anterior (bottom) horn
>motor neurons - axons make up ventral roots
2. posterior (top) horn
>receive sensory fibers from neurons in spinal ganglia - dorsal roots

[Spinal cord neurons = lg & multipolar esp in anterior horns - lg motor neurons]

Question 10

What are the functional PNS divisions?

Answer 10

A. Somatic =
-one neuron
-innervates voluntary skeletal muscle
-OR somatosensory receptors of skin, muscle, joints
B. Autonomic =
-2 neurons
-efferent
-innervates cardiac, smooth muscle, & glands
-involuntary
1) sympathetic (thoracolumbar)
2) parasympathetic (craniosacral)

Question 11

Describe nerves.

Answer 11

-axons & dendrites outside of CNS
-axons, dendrites, blood vessels, glial, CT

Endoneurium, perineurium, epineurium

Cells present in a nerve:
-Endothelial cells, fibroblasts, Schwann cells

Question 12

Describe ganglia.

Answer 12

-cell bodies outside CNS
-cells of ganglion: neurons, neuroglia cells (amphicytes)
-schwann cells, endothelial cells, axons
-2 types of ganglia
1. Sensory (craniospinal)
2. Autonomic

Question 13

Describe glial cells in PNS.

Answer 13

1. Schwann cells
   -enveloped nerve fibers
   -myelin sheath around 1 axon (14th week of fetal development)
   -regen of damaged fibers
   -plasma membrane of glial cells (20% protein & 80% lipid)
2. Satellite glial cells (amphicytes)
   -surround neurosomas in ganglia of PNS
   -electrical insulation around soma
   -regulate chemical environment of neurons

Question 14

Describe the myenteric plexus.

Answer 14

-between inner & outer longitudinal layers of tunica muscularis -
-control peristaltic movement of GI