Nervous tissue histology Flashcards
What originates from the Pacinian Corpuscle? What does it do?
The distal process of the dorsal root ganglion neuron. Relays signals from the CNS when pressure upon the skin mechanically stimulates the receptor.
What is the grey matter composed of?
Neurons and supporting cells
What is the white matter composed of?
Myelinated axons
What is the neuropil?
The region of grey matter between cell bodies composed principally of dendrites and axons.
What does the Nissl stain elucidate?
Neuronal cell bodies of grey matter
How do neuronal cell bodies appear on histology?
Round euchromatic nucleus and dark nucleolus
What are Nissl bodies?
Rough ER and free ribosomes in neuronal cytoplasm extending into the bases of dendrites.
What are interneurons?
Small neurons that exist solely in the CNS for interneuronal communication
What are oligodendrocytes?
Supporting cells responsible for elaborating myelin in the CNS. Can be found in white matter.
What cells make myelin in the periphery?
Schwann cells
What is the endoneurium?
Fine reticular fibers that separate individual nerve fibers from one another.
What is a fascicle and what surrounds it?
A fascicle is a bundle of nerve fibers held together by a dense sheath called a perineurium.
What is the epineurium?
Connective tissue that loosely bundles together fascicles. This kind of bundle is what you’ll dissect in GA.
Describe nerve fibers in the parasympathetic ganglia.
Cell bodies are more irregular in shape
Soma usually smaller
Nerve fibers in the bundles between the ganglia are unmyelinated or thinly myelinated.
What cells do neural crest cells become during development?
Neurons, Schwann cells, and satellite cells of the PNS.
What is a major difference between CNS and PNS?
CNS lacks connective tissue
What is the perikaryon?
Rough ER, the cisternae of which are grouped and studded with polyribosomes. Labeled as Nissl bodies as the stain like basophilic clumps under LM.
Each node of Ranvier is associated with a _____ cell.
Schwann
What are dendritic spines? How do they vary?
Focal evaginations of the dendrite and serve as the main receptive structures for axon terminals. Neurons can have many (spinous), some (sparse), or none (aspinous).
What exists in axonal cytoplasm?
Mitochondria, microtubules, neurofilaments NO RIBOSOMES OR RER!
What part of a neuron contains neurotransmitters?
At ends: terminal boutons
Along the length: boutons en passant
What % of neurons in the PNS are surrounded by Scwann cells in one form or another?
ALL!
What are spinal nerves composed of?
Distal to the spinal cord dorsal and ventral roots merge forming “spinal nerves” and thus contain both sensory and motor nerves.
Sympathetic ganglia are positioned close to the _______ (____________) whereas parasympathetic ganglia are located close to, or within, the _______.
spinal cord (paravertebral ganglia),
target structure
What cells protect and encapsulate neuronal cell bodies in peripheral ganglia?
Modified Schwann cells called satellite cells
Given the lack of connective tissue, how are cells in the CNS supported?
Astrocyte cells which contain bundles of intracellular intermediate filaments called glial fibrillary acidic protein (GFAP).
What are the primary immune cells of the PNS?
macrophages & mast cells
What are the primary immune cells of the CNS?
Microglial cells, a phagoycte
What cell organelles are in the terminal buttons?
SER and mitochondria
In what region of the terminal button do synaptic vesicles line up?
Active zones
What are the structures of the sarcolemma that make up the motor endplate?
Junctional folds
Why is calcium critical to release of Ach?
Fusion of synaptic vesicles with the plasma membrane is calcium-dependent.
What is the anterograde reaction to a damaged or crushed peripheral nerve?
Entire neuron distal to the site of injury degenerates and is phagocytosed - “Wallerian degeneration”
What is the retrograde reaction to a damaged or crushed peripheral nerve?
The axon degenerates back to the previous node and the cell body undergoes chromatolysis (i.e. swelling and breaking apart of Nissl bodies). The nucleus moves to the side/periphery (becomes eccentric)
What is critical to connecting a severed nerve in the PNS?
Close proximity of ends, intact connective tissue
What happens when a CNS nerve is damaged?
An astrocytic scar cordons off the area of injured neural tissue and isolates it from the rest of the brain.
What is the black reaction of Golgi?
Figured out how to stain neuronal stains?
What cell organelles do dendrites have?
Mitochondria, RER (larger ones at least), ribosomes
What is a diagnostic feature of nervous tissue?
Nodes of Ranvier
Where in the CNS do oligodendrocytes reside?
White matter
In addition to providing support, what are some major functions of astrocytes?
- Maintain stable microenvironment for neurons (takes up ions and excess neurotransmitters)
- Metabolic support
- Covers most free surfaces of the brain
How do astrocyte nuclei appear?
Small but euchromatic
What are 3 characteristics of epineurium?
- Comprised of dense connective tissue
- Can contain adipose tissue
- Usually no coherent boundary with surrounding tissues
What is the PNS version of astrocytes?
Satellite cell
What cells survive macrophage eating?
Schwann cells
