Nervous

Question 1

Explain the different components of neuron.

Answer 1

• dendrites radiate from the soma and branch numerous times with dendritic spines synapsing with axons from other neurons (loss of these spines is a noticable problem in down syndrom)
• somas are the location of the darkly stained nucleus, with Neissel bodies (clumps of rER) and the organnelles of a cell.
• axon hillock: an area with a dense concentration of sodium channels and a low threshold for AP. there is only one per soma.
• axons are the extension of the axon hillock with an initial segment starting it and the terminal button being the end.
• terminal buttons form the synapse with either the soma (axosomatic), another axon (axoaxonic), or most likely a dendrite (axodendritic)

Question 2

Types of Neurotransmitters

Answer 2

Excitatory - Glutamate, Aspartate, & ACh (on nAChR)

Inhibitory - Glysine & GABA

Modulatory - DA & 5-HT

Question 3

T/F

There are more neurons than glial cells

Answer 3

False

There are as many as 10 glia per 1 neuron

Question 4

Describe Schwann Cells

Answer 4

• Schwann cells are the myelinating glia of the PNS, in myelinated axons they wrap their myelin sheath around a single axon.
• A transmembrane protein compresses all of the layers, which pushes all of the cytosol into one of these four locations: inner collar, outer collar, Schmidt Lanterman clefts, or perimodal areas. The cytosol is still used to support the sheath, and is directed by a peripheral nucleaus.
• Multiple unmyelinated axons are enveloped by a single Schwann cell, which is key in organization of axons, debris cleanup & nueronal regeneration (Wallerian degredation)

note: saltatory conduction & nodes of Ranvier

Question 5

Describe Satellite Cells

Answer 5

Satellite cells are insulating cuboidal cells that surround the somas of dorsal root and chain ganglion neurons.

DRG have more satellite cells and have centrally located nuclei in clusters of soma.

Chain ganglion are not tightly clustered and have eccentrically located nuclei.

Question 6

Describe Oligodendrocytes

Answer 6

• Oligodendrocytes are the myelinating glia of the CNS
• Aside from their location, they differ with Schwann Cells by one oligodendocyte surrounding either multiple areas of a single axon, or multiple different axons

Question 7

Describe Astrocytes

Answer 7

• ​Astrocytes are the servant cells of the CNS, and they perorm various functions. There are two types of astrocytes, the protoplasmic (in gray matter) and fibrous (in white matter - 80% of brain tumors)
• First, they connect capillaries to neurons through transport to and from perivascular and perineural feet (supply nutrients).
• Second, they play a central role in propoer functioning of the blood-brain-barrier (BBB), by secreting RF’s that alter the tight junctions and fenestrations of the BBB.

note: O2/CO2 pass diffusably through BBB, while glucose, AA, proteins require carrier proteins. WBC can exit capillaries, which is how viruses infect CNS (trojan horse)

Question 8

Describe Microglia

Answer 8

• Microglia are the phagocytotic cells of the CNS.
• They proliferate and are active in regions where trauma or infection has occurred.
• They are important in establishing neural networks in development.
• Research suggests that early life disease/trauma/infection could lead to the over-responsive macrophages later in life.. causing brain disorders

Question 9

Describe Epidymal Cells

Answer 9

• Epidymal cells are the cells lining the central canal and/or ventricals, and possess cilia/microvilli to secrete CSF into the sub arachnoid space (SAS).
• They form the choroid plexus in the pia mater, in combination with the capillary loops

Question 10

Explain the function of the meninges outside of the spinal cord and their organization of nerve bundles.

Answer 10

• The epineurium (extension of dense irregular CT of dura mater) surrounds and in between the nerve bundles.
• The perineurium (an extension of the arachnoid, with squamous cells) ensheaths the individual bundles
• The endoneurium (an extension of the pia mater, composed of Schwann cells) is the layer between/around each axon fiber.

Question 11

Explain the process of nerve regeneration upon injury to the distal portion of a peripheral nerve.

Answer 11

1. Walleran degradation occurs, which involves macrophage mediated degeneration of the distal part of injured nerve.
2. The proximal nerve sends an axon to the Schwann cell (myelinated tube or unmyelinated hole)
3. The extending axon will follow the architecture of the Schwann cell to the mucle, and reinnervate the atrophied muscle.