Nerve Tissue Flashcards
Nuclei
Collection of neuronal cell bodies in the CNS
Tracks
Collection of axons in the CNS
Ganglion
Colleciton of cell bodies in the PNS
Fibers
Collection of axons in the PNS
What makes myelin?
In the CNS, it’s oligodendrocytes
Int he PNS, it’s Schwann cells
Where are nissl bodies (rough ER, blue dots) in a neuron?
Many in the soma/cell body, some in the dendrites
NONE in the axon
Function of the axon
Initiates action potentials using sodium channels
Function of dendrites
Receives and processes many synapses, usually in dendritic spines
Very branched and gets thinner as it subdivides (unlike axon) in roder to increase the receptive area of the neuron.
Fast vs slow axonal transport
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Fast axonal transport: move vesicles and mitochondria
- Kinesin for anterograde - neurotransmitters to the (+) end
- Dynein for retrograde - growth factors and recycled vesicles to the cell body and (-) ends
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Slow axonal transport: move cytoplasmic proteins and cytoskeletal proteins for the assembly of microtubules and neurofilaments
- Follows the flow of cytoplasm and is not associated with motor proteins
What type of neuron (bipolar, pseudounipolar, multipolar) is typically in sensory organs ?
Ex) retina, vestibular, auditory, visual
Bipolar - if you cut through thecell body, you wouldn’t see dendrites or axons
What type of neuron is the dorsal root ganglion?
Pseudounipolar
Central & peripheral processes of pseudo unipolar neurons
Peripheral processes: sensory
Central processes: actual axon
You’d see a cell body, but no dendrites or axons, and there’d be myelin sheath.
Pathway of touching something and moving - include neuron types
- Info received in the dendrites of a pseudounipolar neuron
- Peripheral process
- DRG
- Central process
- Interneuron (multipolar)
- Motor neuron (multipolar)
Why is the ventrla horn larger than the dorsal horn in the spinal cord?
Ventral horn contains cell bodies
Dorsla horn only contains the axons of the sensory neurons
How does rabies spread to the salivary gland?
- RABV binds the Ach receptor on your neuron –> receptor-mediated endocytosis
- Retrograde axonal transport (dynein) to the cell body supplying the affected muscle
- This virus replicates in the neuron and sheds virions by budding to reach neighboring neurons
- Once it reaches the CNS, anterograde axonal transport (kinesin) by the peripheral nerves to the salivary glands
Drinking water is painful to swallow
The end feet of astrocytes cover ___, ___, and ___.
Astrocytes are the largest and most abundant of the CNS glial cells
Their endfeet cover neurons, pia mater, and every blood vessel of the CNS.
Fibrous vs Protoplasmic astrocytes - which one is which matter? how can you differentiate how they look?
Fibrous astrocytes (white matter) have thinner axons
Prooplasmic astrocytes (gray matter)
Function of astrocytes
Makes up the BBB!
- End feet binds the neurons to capillaries & pia materto transfer ions and molecules from the blood to the neuron
- Forms scar tissue after brain injury
3 components of the blood brain barrier
- Basal lamina (not basement membrane bc it is only contacting nervous tissue, not connective tissue)
- Squamous endothelial cells connected through tight jaxns
- End feet from astrocytes
____ are hard to see on a stin because they have such small/round/dense nucleuses, and CLEAR cytoplasm.
Unlike astrocytes, they don’t have glycogen or GFAP
Oligodendrocytes - one can myelinate several axons in the CNS
Ependymal cells
- Cuboidal cells lining the ventricles of the brain and the central canal of the spinal cord; also seen in the choroid plexus
- Fxn:
- Barrier between brain and CSF
- Cilia or microvilli to move CSF or monitor it
What is this?
Microglia
- Smallest, dense elongated nucleus; motile
- Not usually seen in normal brain tissue
-
Phagocytic cell of the CNS involved in inflammation and repair
- Primary site of HIV-1 infection in the CNS
Schwann cells and axons
Myelinates axons of the PNS, but each axon requires several Schwann cells (SN)
Schwann cells can also just use their cytoplasm (SC) to cover axons without myelinating them
Satellite cells - supports neuron cell bodies in peripheral ganglia
White matter contains ___ axons, ___ cells, and NO ___.
It’s ___ in the brain and ___ in the spinal cord.
-
Myelinated axons, glial cells, and NO neurons
- Neuropil: non-neuron component
- Deeper in the brain
- Peripheral in the spinal cord
Gray matter- composition, location
-
Neurons, dendrites, and the initial unmyelinated portions of axons, and glial cells
- Will see cell bodies!
- Brain: Makes up the cerebral and cerebellar cortex and forms islands in white matter called nuclei
- Spinal cord: Makes up deeper, H-shaped region containing the central canal
Neuropil
The non-neuronal component: synapses, dendrites, and axons
Eosinophilic
Cerebral cortex is full of
Pyramidal neurons; integrates sensory info and initiates voluntary motor responses
The cerebellar cortex coordinates muscular activity throughout the body and is composed of what 3 layers?
Molecular layer (ML): mostly neuropil and scattered neuronal cell bodies
Purkinje cells (P): large neurons that project into the medulla (M); coordinates movement
Granular layer (GL): densely packed interneurons
Where are the axons and dendrites of Purkinje cells?
Axons go through GL into the medulla
Dendrites go into the ML
Ventral vs lateral vs dorsal horn of gray matter in spinal cord
Ventral - motor neurons
Lateral - sympathetic neurons
Dorsal - sensory neurons
What horn of the spinal cord is this?
Large motor neurons –> ventral
Meninges of the brain (outer to inner)
- Dura mater: dense irregular connective tisue
- Arachnoid: simple, squamous epithelium that sends fibrous trabeculae into the subarachnoid space to connect to the pia
-
Subarachnoid space: CSF that communicates with ventricles; contains blood vessels
- Subdural hemorrhage
- Pia mater: loose connective tissue; vascular
Choroid plexus - location, composition, function
-
Location:
- Roof of 3rd and 4th ventricles (V)
- Walls of lateral ventricles
-
Composition: loose connective tissue and blood vessels (C); covered by special ependymal cells (E)
- Cells have microvilli and cilia
- Function: the ependymal cells make CSF
CSF formed by ependymal cells of choroid plexus passes to ventricles then subarachnoid space then venous circulation through
Arachnoid villi
Nerve fibers
Axons surrounded by sheaths of ectodermal origin
Unmyelinated fibers in the PNS vs CNS
In the PNS, each Schwann cell can continuously sheathe many unmyelinated axons
In the CNS, there are a lot of unmyelinated and unsheathed axons
Myelinated fibers
Multiple sclerosis
Microglia phagocytose and degrade myelin –> numb muscles and coordinated issues
Nerves
Groups/bundles of nerve fibers covered by connective tissues
Layers of connective tissues (outer to inner) surrounding nerves
- Epineurium: dense connective tissue
- Perineurium: flattened epithelial-like cells that wrap around each bundle (Fascicle) of nerve fibers
- Endoneurium: loose connective tissue; type 3 collagen (reticular fibers) surrounds each individual nerve fiber
Ganglia
Encapsulated groups of neurons + glial cells + connective tissue
Sensory or autonomic
Sensory ganglion
Pseudounipolar neurons surrounded by satellite cells
Receives and transmits afferent impulses to the gray matter
Autonomic ganglion
Multipolar neurons in the walls of organs (GI tract)
Smaller, unmyelinated, fewer satellite cells, no connective tissue capsule
Pyramidal cells are what kind of neurons?
Multipolar neurons in the cerebral cortex
what kind of ganglion is this?
Smaller, less satellite cells, can kinda see dendrites
–> autonomic ganglion
What type of collagen is in endoneurium surrounding the nerve fibers?
type 3
(asterisks)
Tetanus toxin is a protease that blocks the release of ___ at spinal synapses –> jaw spasms (trismus), exaggerated reflexes, respiratory failure
inhibitory mediators
