Histology Flashcards
Fast axonal transport vs. slow axonal
Fast- movement of mitochondria and vesicles along microtubules
Slow- driving cytoplasmic and cytoskeletal proteins mostly for the construction of microtubules and neurofilaments
What is found in gray matter in the CNS? White matter? What does it have to do with Parkinson’s?
Gray matter contains the neuronal cell bodies, dendrites, the initial portion of unmyelinated axons, and glial cells
White matter contains myelinated axons, some unmyelinated, glial cells, but no neurons
Parkinson’s is due to apoptosis of dopamine neuronal cell bodies in the gray matter of the substantia nigra
Axolemma
Plasma membrane of an axon
How do local anesthetics work?
Bind to voltage gated Na+ channels to inhibit action potentials along an axon
Which organelles are found in the axon? What about the perikaryon? The dendrites?
Microtubules, neurofilaments, mitochondria, vesicles
Everything you would expect plus inclusions (lipofuscin). Not really any smooth ER
Everything but Golgi (especially Nissl bodies)
How does excess exocytosed membrane get taken back into the presynaptic cell?
Clathrin mediated endocytosis
What are the three types of axon synapses?
Axosomatic (axon to perikaryon)
Axodendritic (axon to dendritic spine)
Axoaxonal (axon to another axon)
Neuropil
The fine intercellular processes of neurons and glial cells. They make a matrix that looks like collagen.
What are the three structures that astrocytes connect together? What is the glia limitans?
The cytoplasmic processes have end-feet that extend to neurons, capillaries, and the pia mater.
The glia limitans are the joined end-feet covering the pia mater
What is the main component of the blood brain barrier? What two other structure contribute to it?
The tight junctions between endothelial cells are the main barrier with help from the basal lamina of those cells and the perivascular end-feet of astrocytes
What do microglia do? Are they normally found in brain tissue? What does their nucleus look like?
They are the macrophages of the CNS. They are not normally found in the brain and their nucleus is elongate. They are the smallest of the glial cells.
What do satellite cells do? What do they look like on an H&E stain?
They surround and insulate and regulate waste exchange of ganglia in the PNS. They appear as small, dark nuclei around a larger cell body
What is the role of a choroid projection (of the choroid plexus)? What is its general construction?
The projections allow water to diffuse out of the blood into the CSF. The outmost layer is ependymal cells which cover a layer of pia mater which covers a capillary. The center of the projection is loose connective tissue
Unmyelinated axons in the PNS are sometimes sheathed by which cell type?
Schwann cell can sheath up to 12 axons
What are the components of the PNS?
Nerves, ganglia, and nerve endings
What are nerves and tracts?
Nerves and tracts are both collections of axons enclosed by glial cells (PNS vs CNS)
What is myelin made out of? How does it get so spiraled?
The two ends of a Schwann cell cytoplasm come together and form the mesaxon which protrudes down into the cell and wraps around the axon many times. It is made of lipoprotein.
What is the endoneurium? What is it made of?
The connective tissue that surrounds axons. Reticular fibers, fibroblasts, and capillaries
What’s a nerve fascicle? What is perineurium?
Group of axons/Schwann cells surrounded by perineurium. Perineurium is made up of special connective fibrocytes and forms a blood nerve barrier
Epineurium
Irregular fibrous coat that surrounds peripheral nerves
Which types of muscle are striated? Voluntary?
Skeletal muscle is striated and voluntary
Cardiac is striated and involuntary
Smooth is non-striated and involuntary
Define thin filaments, thick filaments, sarcolemma, sarcoplasm, and sarcoplasmic reticulum
Thin filaments- actin
Thick filaments- myosin
Sarcolemma- plasma membrane
Sarcoplasm- cytoplasm
Sarcoplasmic reticulum- smooth ER
What is a muscle fiber? What is a myofibril? What makes up a myofibril?
A muscle fiber is a muscle cell (multinucleated) which is made up of myofibril made from myofilaments
Presence of which proteins can distinguish a quiescent stem cell from an active stem cell?
Pax-7 = quiescent
CD34/MyoD = activated
