Histology Of The Nervous System

Question 1

Multipolar neurons

Answer 1

Single axons w/ two or more dendrites

Most common type of neurons on the body

• all motor neurons of CNS/PNS
• all CNS interneurons

Question 2

Pseudounipolar

Answer 2

Single axon that bifurcates

• peripheral process goes to targets
• central process goes to CNS

No dendrites

Makes up most of the primary sensory neurons in the spinal ganglion

Question 3

Unipolar neurons

Answer 3

Single axon that doesnt bifurcate

No dendrites

Specific cells only (cerebellum and dorsal cochlear nucli/nerves)

Question 4

Bipolar nerouns

Answer 4

Single axon

Single dendrite

Special primary sensory neurons

• retina
• olfactory
• vestibular

Question 5

Anaxonic

Answer 5

No axon

Multiple dendrites

Don’t produce action potential and instead helps regulate electrical activity in other neurons
- common most in retina

Question 6

Parts of the cerebellum from superficial to deep

Answer 6

1) molecular layer
- contains stellate and basket neurons
- contains parallel fibers and Purkinje dendrites

2) Purkinje cell layer
- Purkinje cell bodies locations

3) granular layer
- golgi and granule neurons
- mossy fibers synapse
- contains primarily granular cells

4) sub cortical white matter
- deep cerebellar nuclei
- purkinjie cell axons
- mossy and climbing fibers

• note: 1-3 are found in the Cortex of the cerebellum*

Question 7

Pyramidal neurons

Answer 7

Present in all layers of the cerebral cortex except layer 1
- most common in 2/3/5

Histologically contains

• pyramid-shaped cell body
• single apical dendrite that goes upward
• multiple basal dendrites that go laterally
• single axon that descends and exits the cortex (efferent fiber)

Question 8

Different axon fibers found in the cerebral cortex

Answer 8

Association fibers
- travel to and terminate in the cortex of the ipsilateral cerebral hemisphere

Callosal fibers
- decussate in the corpus callosum and terminate in the contralateral cerebral hemisphere

Projection fibers
- descend to sub cortical targets in the forebrain/brainstem/cerebellum and spinal cord.

are virtually the only output of the cerebral cortex

Question 9

Cell types in the PNS and its histologically shapes

Answer 9

Schwann cells

• possess larger nuclei
• Are large oval shaped cells and nuceli
• make up the myelin sheath
• are surrounded by myelin

Fibroblasts

• possess smaller nuceli
• generate CT of the endoneurium
• are surrounded by myelin
• are small spindle shaped cells and nuclei

Question 10

Differences between epineurium perineurium and endoneurium

Answer 10

Epineurium
- outer most layer of a a nerve and its Connective tissue

Perineurium
- underlies the epineurium and houses the nerve fascicle

Endoneurium

• innermost layer that surrounds each individual nerve fiber
• is always myelinated

Question 11

Why is the external capsule of a nerve ganglion more vascularized than a nerve?

Answer 11

Requires more metabolic demand due to having to synthesize most of the cellular components (nerves dont need to do this)

Question 12

What is the soma or perikaryon?

Answer 12

Individual Neuronal cell body

Question 13

What are satellite cells?

Answer 13

Small cells that surround cellular bodies

Function to:

• support cells
• provide protection and insulation
• transfer metabolites
• modify ECM

Derived from neural crest cells

Question 14

How is lipofuscin distinguished in histologically slides?

Answer 14

It is brown-ish in color

It is a build up of enzymatically digested materials that are unable to be removed from the cells

Question 15

What kind of general neurons are found in the anterior horn of the gray matter in the spinal cord?

Answer 15

Somatic efferent neurons That are multipolar

Question 16

What kind of general neurons are found in the lateral horn (IML) of the gray matter in the spinal cord?

Answer 16

Visceral efferent neurons and presynaptic sympathetic neurons

Multipolar neurons are most common

Question 17

What kind of general neurons are found in the posterior (dorsal) horn of the gray matter in the spinal cord?

Answer 17

Somatic and visceral afferent neurons and secondary sensory neurons

Neurons are multipolar

Question 18

What type of cells line the lumen of the central canal of the spinal cord?

Answer 18

Ependymal cells

note these aren’t epithelium cells since they got no basement membrane to anchor cells to

Question 19

What is the most common type of glial cell isn’t he gray matter of the CNS?

Answer 19

Astrocytes

Question 20

Parkinson’s disease

Answer 20

A slowly progressing disorder that caused by a gradual loss of dopamine-producing neurons within the substantia Nigra

Treated with L-dopa injections which are precursors to dopamine

Question 21

Local anesthetics

Answer 21

Low molecular weight molecules that bind to voltage-gated sodium channels of the axolemma

They interfere with sodium influxes and inhibit action potentials responsible for nerve impulses

Question 22

Selective serotonin reuptake inhibitors (SSRIs)

Answer 22

A class of drugs that help treat depression and anxiety disorders.

They inhibit reuptake of serotonin at the presynaptic membrane which increases levels of serotonin postsynaptically

Question 23

Astrocytoma

Answer 23

Tumors Derived from fibrous astrocytes

Distinguished pathologically by overexpression of GFAP

Question 24

Alzheimer’s disease

Answer 24

Abnormal build up of neuorfibrillary tangles (accumulations of tau proteins) and neurotic plaques (dense aggregates of B-amyloid proteins)

These build ups affect the synapses and neuronal perikarya in the cerebrum overtime

Question 25

Multiple sclerosis

Answer 25

Autoimmune disorder where the immune system attacked the myelin sheaths around affected neurons and produces various neurological problems
- specifically T lymphocytes and microglia

This slows conduction down of these neurons and causes multiple neurologic defects.