Nervous Tissue Flashcards
Be able to describe the principle constituents of nervous tissue and how they vary in terms of distribution in the CNS vs. PNS?
a
Be able to describe a unipolar, pseudounipolar, bipolar, and multipolar nerve cell.
a
Be able to explain the distinction(s) between gray matter and white matter.
a
Be able to describe the cytology of a ‘generalized’ neuron.
Plasma membrane: crucial for developing action potentials
pigments: lipofuson (wear and tear pigment), end product of lysosomal degradation; neuromelanin Rough endoplasmic reticulum (Nissl)
Be able to differentiate between encapsulated and unencapsulated receptors.
encapsulated: meissner’s corpuscle, pacinian corpuscle
unencapsulated: free/naked, merkel’s disks, hair follicle plexus
Be able to explain the basis for naming different types of synapses.
Axo-dendritic Axo-somatic Axo-axonal Serial (e.g., axo-axo-dendritic) dendrodendritic
Be able to describe the structure of a chemical synapse.
Pre-synaptic structure -Neurotransmitter containing vesicles -Pre-synaptic dense projections -Neurofilaments -Mitochondria Synaptic cleft Post-synaptic structure
Be able to explain what synaptic vesicle recycling and renewal mean.
a
Be able to explain the difference types of axonal transport. Be able to explain what dyneins and kinesins do and what orthograde and retrograde transport mean.
Slow component:
- Rate: 0.5-3 mm/day
- Only in orthograde direction
- Materials transported:
- Non-packaged molecules
- Cytoskeletal components
- Mechanism not clear
Fast component
-Rate:
~Orthograde: 400 mm/day
~Retrograde: 1/2 to 2/3 speed of orthograde rate
`Materials transported
~Orthograde:
synaptic vesicles; mitochondria, etc
Membrane associated proteins (acetylcholinesterase)
~Retrograde
Worn out membranes of synaptic vesicles; mitochondria; etc.
Clinical, developmental, and experimental significance
Orthograde motor: kinesin (ATPase)
Retrograde motor: dynein (ATPase)
Be able to describe the basic structure and function of the following glial (neuroglial) cell:
astrocytes
Fibrous & protoplasmic versions
Golgi staining vs H&E staining
Cell processes:
-Pervasive; terminate in “end-feet”
-End on blood vessels
~Form layer outside basement membrane of endothelial cells
~May help induce formation of tight junctions between endothelial cells
-External & internal glial limiting membranes
Probable functions
- Structural support
- Uptake of excess potassium from extracellular spaces during intense or prolonged neuronal activity
- Phagocytosis & scar formation (gliosis) after injury
- Isolation of nerve terminals from each other
- Regulation of entry of substances into interneuronal space
Be able to describe the basic structure and function of the following glial (neuroglial) cell:
oligodendrocytes
Functions
Myelination of CNS axons
black and small on a stain
Be able to describe the basic structure and function of the following glial (neuroglial) cell:
microglial cells
< 5% of all glial cells
Monocyte ancestry
Function: phagocytosis
Be able to describe the basic structure and function of the following glial (neuroglial) cell:
ependymal cells
Line central canal of spinal cord and ventricles of brain
Simple cuboidal to columnar epithelium that is ciliated
Functions
- Cilia help move the CSF
- Transport of substances from CSF into brain
- Secretion into ventricles
Choroidal epithelium
- Roof of four ventricles
- Covers the choroid plexus
- Control composition of CSF produced by choroid plexus
- Cells attached to each other via tight junctions
Be able to describe the different connective tissue coats of a peripheral nerve.
Epineurium: around fascicles of axons
Perineurium: around bundles of axons
Endoneurium: around individual fibers
Be able to differentiate between an unmyelinated and a myelinated axon.
Unmyelinated Nerves (PNS): Axons (less than 1 m in diameter) Sheath of Schwann (neurilemma) Definitions -Mesaxon -Bundle of Remak -C fibers Occurrence: -Axons of post ganglionic autonomic neurons -Axons of small sensory neurons in dorsal root -ganglia
Myelinated Nerves (PNS) Axon; myelin; sheath of Schwann Myelin composition: 80% lipid; 20% protein Nodes of Ranvier Internodes Schmidt-Lantermann clefts A & B fibers are myelinated
Be able to explain how
axons become myelinated in the PNS and CNS.
Jelly-Roll Theory
Intraperiod line
-lighter line, where material gets squeezed to
Major dense line
dark line, where things get stuck as cytoplasm is squeezed out
Internal & external mesaxons
node of
Ranvier
unmylenated areas of axons
Schwann cell
a
mesaxon
a
internode
a
Schmidt-Lantermann cleft
a
Be able to describe the structural similarities and differences of a typical sensory ganglion and typical autonomic ganglion.
Sensory ganglia
- Dorsal root ganglia; sensory ganglia of cranial nerves V, VII, VIII, IX, and X
- Nerve cells are pseudounipolar; cell bodies are in the ganglia
- A to C fibers
- Light and dark cells
- No synapses in ganglia
- Satellite cells (capsule cells)
- Fibroblasts
- C.t. capsule
Autonomic ganglia
-Sympathetic ganglia
~Discrete structures with capsules: superior cervical, celiac, superior mesenteric, etc.
Parasympathetic ganglia
-Small and encapsulated in head; elsewhere simply isolated clusters of cells: ciliary or otic ganglia in head; submucosal and myenteric plexi of gut
-Preganglionics synapse with cell bodies of postganglionic neurons
-Cell bodies of postganglionic neurons
~multipolar neurons
~Eccentric nuclei; sometimes binucleate
~Axons terminate on effector organs (smooth muscle; cardiac muscle; glands)
-Myelination
~Preganglionics are small, myelinated B fibers
~Postganglionics are small, unmyelinated C fibers
-Connective tissue and fibroblasts are present
-Neurotransmitters
~Acetylcholine: at termination of preganglionics of both sympathetic and parasympathetic fibers
~Acetylcholine: at termination of postganglionic parasympathetics
~Norepinephrine: at termination of postganglionic sympathetics except for acetylcholine for sympathetic innervation of sweat glands
Be able to explain what satellite cells are
Autonomic ganglia
Satellite cells and Schwann cells
-Represent the glia of the PNS
-Satellite cells form incomplete covering of cell bodies
-Schwann cells associated with nerve fibers running through ganglia
Be able to describe some of the basic characteristics of degenerative and regenerative processes of
nerves cells.
degeneration
Wallerian (Orthograde) Degeneration
- Axon, axon terminals, myelin disintegrate
- Schwann cell sheath and c.t. layers remain in PNS; no CNS counterpart
- Phagocytosis of debris (Schwann cells & macrophages)
Retrograde degeneration
Degeneration of axon and myelin sheath in direction of cell body
Chromatolysis
Death of cell (with or without chromatolysis)
Severity levels: cell type; site of lesion; nature of injury; age of individual
