Histology - Nervous System

Question 1

Answer 1

Question 2

Nueroglial cells

Aka glia

Answer 2

Non-conducting cells located close to neurons

CNS central neuroglia - oligodendrocytes, microglia, astrocytes, and ependymal cells

PNS peripheral nuerolgia - Schwann cells and satellite cells

Fx - providing physical support and protection for neurons

Insulating nerve cell bodies and processes (myelin)

Reparising neuoranal injury

Regulating the internal fluid environment of the CNS

Clearing neurotransmitters from synaptic clefts

Facilitating metabolic exchange between the vascular system and neurons

Question 3

Nissl bodies

Answer 3

Rough ER and polyribosomes - appear as clumps of basophilic material

Question 4

Neuronal type of dorsal root ganglia

Answer 4

Pseudo-unipolar neurons

Question 5

Neuronal cell type of the retina

Answer 5

Bipolar neurons

Question 6

Purkinje and pyramidal cells

Answer 6

Found within the CNS

Question 7

Afferent processes of neurons

Answer 7

Dendrites - they receive information from other neurons or from the environment

Dendrites are generally unmyelinated

Lack golgi but otherwise organelle profile similar to that of the cell body

Question 8

Dendritic spines

Answer 8

Increase surface area and are the sites of synapses

Question 9

Efferent processes of neurons

Answer 9

Axons - initial segment located below or distal to the axon hillock (where action potentials are generated)

Question 10

Recurrent axonal branching

Answer 10

Near the cell body

Question 11

Collateral axonal branching

Answer 11

Near the target

Question 12

Organelle profile of axons

Answer 12

Arrays of microtubules and neurofilaments

Mitochondria

Vesicles

Derivatives of smooth ER

Question 13

Direction of axonal transport

Answer 13

Biderectional

Anterograde - via kinesin motors - moves organelles and secretory vesicles along microtubules

Retrograde - moving endosomes via dynein motors

Question 14

Types of synapses

Answer 14

Axosomatic

Axodendritic

Axoaxonic

Question 15

Most common form of synapse in humans

Answer 15

Chemical synapses

Question 16

Excitatory synapses

Answer 16

Allow Na+ to enter postsynaptic cells, dpolarizing the membrane and causing an action potential

Question 17

Inhibitory synapses

Answer 17

Allow Cl- to enter postsynaptic cells, hyperpolarizing the membrane and making acxtion potentials less likely

Question 18

Astrocytes

Answer 18

Provide physical and metabolic support for neurons and form the blood-brain barrier.

Fibrous astrocytes are found in white matter, while protoplasmic astrocytes are found in gray matter

Question 19

Oligodendrocytes

Answer 19

Produce myelin and myelinate CNS axons

Question 20

Microglia

Answer 20

Resident macrophages in the CNS, derived from monocytes

Note the elongated nuclei of microglia

Question 21

Ependymal cells

Answer 21

Line the ventricles in the brain and the central canal of the spinal cord. These columnar, epithelial-like cells absorb cerebrospinal fluid. In the choroid plexus, ependymal cells are modified to secrete CSF.

Question 22

Satellite cells

Answer 22

Provide physical and metabolic support for cell bodies in ganglia

Question 23

Schwann cells

Answer 23

Myelinate axons and support both myelinated and unmyelinated axons in the PNS

Question 24

Protoplasmic astrocytes

Answer 24

Gray matter - form BBB

Question 25

Fibrous astrocytes

Answer 25

White matter - processes are longer and thinner than protoplasmic astrocytes - also contribute to the BBB

Question 26

What accounts for ~80% of primary brain tumors?

Answer 26

Tumors originating from fibrous astrocytes

Question 27

What embryonic cell population are Schwann cells derived from?

Answer 27

Neural crest cells

Question 28

What type of cells do Schwann cells support?

Answer 28

Both myelinated and unmyelinated cells of the PNS

Question 29

Difference between myelination of axons by oligodendrocytes in CNS and Schwann cells in PNS?

Answer 29

Schwann cells only myelinate portions of one axon whereas oligodendrocytes may myelinate segments of more than one axon

Question 30

Answer 30

Arrow - node of Ranvier (where two Schwann cells meet - unmyelinated portion of axon) Circle - Schmidt-Lanterman clefts appear as pink arrow heads with the white bubbles of myelin - remaining cytoplasm of Schwann cells - likely play a role in nourishment of the myelinated axons

Question 31

Guillain-Barre syndrome

Answer 31

Acute inflammatory demyelinating polyradiculoneuropathy Large accumulations of lymphocytes, macrophages, and plasma cells around nerve fivers within nerve bundles (fascicles). Large segments of myelin are damaged, leaving the axons exposed to the extracellular matrix. **T-cell mediated immune response directed against myelin**, causing its destruction - slowing or blocking nerve conduction Pt exhibits sxs of muscle paralysis, loss of muscle coordination, and loss of sensation

Question 32

Multiple sclerosis

Answer 32

Attacks myelin in CNS. Characterized by immune-mediated damage to myelin which **becomes detached** from the axon and is eventually destroyed. **Destruction of oligodendrocytes** occurs, so new myelin cannot be made. **Myelin basic protein** appears to be the major autoimmune target of this disease. Chemical changes in the lipid and portein constituents of myelin produce irregular, **multiple plaques throughout the white matter of the brain.** Sxs depend on the area in the CNS that is damaged. Typically characterized by distinct episodes of neurologic defects such as unilateral vision impariment, loss of cutaneous sensation, lack of muscle coordination and movement, and loss of bladder/bowel control.

Question 33

Endoneurium

Answer 33

Loose CT that surround individual nerve fibers **Collagen type III** secreted by Schwann cells Occasionally fibroblasts, mast cells, and macxrophages are in the endoneurium

Question 34

Perineurium

Answer 34

Specialized CT that surrounds nerve fascicles Metabolically active diffusion barrier that maintains the ionic milieu of the ensheathed nerve fibers, contributes to the BBB Perineural cells have characteristics of both fibroblasts and smooth muscle cells

Question 35

Epineurium

Answer 35

Dense irregular CT that surrounds and binds nerve fascicles into a common bundle Often associated with adipose Often blends with tunica adventitia of blood vessels

Question 36

Answer 36

Question 37

Answer 37

Question 38

Answer 38

Cerebrum: gray matter of cerbral cortex and its distinct layers

Question 39

Answer 39

Question 40

Answer 40

Purkinje cells

Question 41

Molecular layer of the cerebellum

Answer 41

Mostly dendrites of Purkenje cell bodies

Question 42

Where are pseudounipolar neurons typically found?

Answer 42

The dorsal root ganglion

Question 43

Answer 43

Fibrous astrocytes stained with glial fibrillary acidic protein (GFAP) Cells with blue stained nuclei - oligodendrocytes ## Footnote Remember: Fibrous astrocytes - white matter Protoplasmic astrocytes - gray matter

Question 44

Answer 44

Cells with large nuclei - oligodendrocytes

Question 45

Answer 45

Left - microglial Right - oligodendrocytes

Question 46

Answer 46

Ependymal cells (at the lateral ventricle)