EXAM2_HE14_15_Nervous_Tissue Flashcards
4 stains used for Nervous tissue & ex
- HE
- NISSL (base-like-cell bodies)
- Golgi (silver based- processes & bodies)
- Myelin- lipid in myelin
3 types of neurons and function of each
- Multipolar (motor efferent)-interneurons
- Pseudounipolar (Sensory afferent)- post root ganglia & CN sensory ganglia
- Bipolar (most rare)- single dendrite- Retina, CNI,VIII
- Multipolar neuron features
- Euchromatic prominent nucleolus
- Basophilic
- Nissl Bodies (toluidine blue nissl stain)
Nissl bodies
collections of RER & FREE Ribosomes arranged as polyribosomes (polysomes)
Cytoplasmic components & functions of neurons
Lots of Nissl bodies and polyribosomes- PROTEIN SECRETION of NTM- lots of intracellular proteins
Dendrite structure
larger diameter than axon- not myelinated- Proximal parts have cytoplasmic organelles- Nissl bodies and golgi complexes
Axon basic structure
originates from cell body at axon hillock
-no nissl bodies/golgi
-no protein production
-
Initial segment
1st part of axon after axon hillock-
no nissl bodies or golgi
Site where AP is generated
- What does presence of mitochondria indicate in axon?
- Where are protein components of microtubules and neurofilaments synthesized?
- What is the function of the neurofilaments?
- Transport
- Polysomes in cell body
- tensile strength
AXONAL transport- 2 types and direction. What do viruses do?
-Req ATP
-MT’s & motor proteins (kinesin/dynein)
-transport organelles, synaptic vessels
1. Anterograde- away from cell body to MT/Kinesins
2. Retrograde- toward cell body MTs and Dyneins.
virus-use retrograde-toward cell body
Collaterals & Terminals
neurons can branch to other axon terminals (boutons)
cardiac muscle doesn’t have boutons
Internodal segments- nodes of Ranvier-
What stain used?
What appearance in HE stain?
Silver stain
segments of myelinated axon
gaps between internodal segments are nodes of ranvier
pale/white “moth eaten” w/ HE- high lipid content of myelin
Myelin formation
Glial cell + its cytoplasm wrap around neuron pushing nucleus to outside.
-phospholipid structure
Non-myelinated axons
Smaller diameter axons
slower conduction velocities (no myelin)
axon enveloped by glial cell+plasma membrane but NO wrapping
3 types of synapses
- axosomatic (axon to cell body)
- Axodendritic (axon to dendrite or dendritic spine)
- Axoaxonic (axon to axon)
Where is CNS neurons and glia derived from?
PNS neurons and glia?
When do neuropores close?
CNS- Neuroectoderm- neurotube
PNS-Neuroectoderm-neurocrest
Week 4 neuropores close
how do you classify neurons if they are CNS or PNS?
by developmental origin
and location of cell obdy
CT of CNS- what called? what does it line? 3 types
MENINGES: lines cavities of CNS
- Dura Mater- DIRCT (toughest)
- Arachnoid mater- Subarachnoid space
- Pia Mater- LCT (remains outer surface only- not in grey /white matter)
Grey Mater-Structure-Location
White Mater
What’s Unique to both GM and WM?
GM- CNS nuronal cell bodies (Nuclei)
WM- myelinated axons (Tracts)
NO CT IN GM OR WM
Nuclei
Tracts
N- collections of related neuronal cell bodies
T- collections of related nerve processes (axons)
Neuropil- What is it? What 3 things does it contain? how do you identify it? What could you confuse it with at LM?
The “Feltwork” around nuclei in the grey matter:
1. unmyelinated neuronal cell processes
2. glial cell bodies & processes
3. small blood vessels
Looks like LCT but ther is NO CT in GM or WM
Astrocytes- Origin, Locations, 4 functions
CNS Glial Cells- Neural Tube- in GM and WM
many cell processes radiate from cell body
1. guide migrating neurons during CNS development
2. Glia Limitans; Regulate ionic environment in ECM
3. Support blood/brain barrier
4. Proliferate at sites of injury (gliosis)
Glia Limitans
Thin barrier of astrocyte FOOT PLATES associated with parenchyma basal lamina surrounding the brain and spinal chord.
SEPARATES PIA & CNS TISSUE
regulates movement of small molecules and cells into brain and supports blood-brain barrier.
Astrocytes can regulate endothelial cells to adjust the leaky ability of the blood vessels
Layers of the head
Scalp>Cranium (skull)>Dura>Arachnoid>subarachnoid space> Pia>Glia limitans>cerebral cortex
What is the Blood brain barrier formed by? What is the most common and most aggressive malignant primary brain tumor and where is it derived from?
tight junctions between capillary endothelial cells
Glioblastoma multiforme- GBM
Astrocytoma of glial cells - astrocytes
Oligodendrocytes- Origin-location-function-
What is demyelinating disease of oligodendrocytes?
CNS glial cells- Neural tube- found In WM
- myelination of CNS axons
- can myelinate more than one axon
- multiple internodal segments per axon
- MS of CNS oligodentrocytes
Microglia- Origin? Pathway? Location? Function?
CNS Glial cell- found in GM & WM
Monocytes>BBB>CNS>divide into microglia
Function as resident macrophage and Immune defense of CNS.
Ependymal Cells- Origin? Location? Function? What is the main component of Ependymal cells?
CNS glial cell- originate from Neural Tube- Cuboidal- Makes CSF-
- Line the central canal of spinal cord & ventricular system of brain
1. A component of choroid plexus- Produce & circulate CSF
What are the 4 Glial cells of the CNS? Functions? All three are derived from which place? where is the 4th glial cell derived from?
- Astrocytes (form glia limitans/support BBB)
- Oligodendrocytes (myelinate axons)
- Microglial (phagocytosis macrophages bone marrow)
- Ependymal (make and circulate CSF)-Choroid plexus
NEURAL TUBE DERIVED EXCEPT
MICROGLIA (macrophages in bone marrow)
Where is CT in the grey/white matter of CNS? Why only 3 places? Is there a external lamina?
CT COVERINGS (outer surfaces) 1. Dura 2. Arachnoid 3. Pia Glia limitans present so no CT or external lamina with grey or white matter.
What are Tracts? where located?
Tracts are myelinated axons of glia in the White Matter
What are Nuclei? where located?
Nuclei are neuron cell bodies in the Grey Matter
Origin of brain/spinal cord/ neurons & glia ?
Neural tube
Origin of Neurons & nerve processes & glia outside brain and spinal cord?
Neural Crest
Collections of functionally-related neuronal cell bodies
Ganglion
Collections of functionally-related nerve fibers
Peripheral nerves
What does silver stain highlight? What about Myelin stain?
highlights the cell bodies and processes. the grey matter.
highlights the lipids of myelin shows reverse of silver stain. highlights the white matter
What make up the Grey matter in the CNS? Functionally related nerve processes? what do they make up?
Nuclei (cell bodies of neurons)
Tracts (axons of the nuclei) - make up the white matter
What is the dead give away that you are looking at a neuron in grey matter?
Nissl bodies (usually around a bullseye)- its the neuron cell bodies (nissl)
What occurs in brain damage repair?
What happens if repair goes too far?
What repairs better CNS or PNS? Why?
Gliosis at brain injury
- astrocytes proliferate creating a bridge and gap over that area
- Too much astrocyte proliferation creates a GLIAL SCAR & prevents regeneration of axons
- cns doesn’t regenerate as well as pns
GBM
neoplastic changes to astrocytes that create malignant tumors
External lamina functions? needed in CNS?
adherence, filtration barrier;
not needed b/c we have astrocytes that do this
Round cells with euchromatic nuclei, prominent nucleolous, Lots of cytoplasm with tiny cells forming complete ring around the cells. What does a LMN look like in conjunction?
chocolate Malt balls
pseudounipolar neurons
-satellite cells around cell body- glial- Neural Crest
Lower Motor Neuron of CNS (has nissl bodies w/ bullseye in middle)
Pseudounipolar cells what are the two parts?
- Central process (into cns) and
- Peripheral process (to muscles)
Posterior Root Ganglion
No synapses. Has a pseudounipolar neuron for sensory and a Lower Motor Neuron for action
Nerve fibers less bundled- Neuronal cell bodies less densely packed- more scattered. Tiny cells form incomplete ring around the cells . Euchromatic nuclei, nucleolus. Why cells so spread apart?
Motor ganglia- autonomic: sympathetic & parasympathetic
Synapses occur here!
4 types of peripheral nerves
Axons-
- Cranial nerves & branches
- Spinal roots, nerves, rami & branches
- Sympathetic & Parasympathetic nerves
- Visceral sensory nerves
Epineurium- Structure? What does it surround? Function?
DiRCT/TypeI collagen/ ELASTIC FIBERS
- Surrounds entire peripheral nerve
- interacts w/ adjacent neurovasuclar structures
Perineurium- Structure? What does it surround? Function?
DiRCT but less dense/still Elastic
-Surrounds bundles of axons called Fascicle
Endoneurium- Structure? what does it surround?
What makes ECM? Is CT found in CNS?
LCT & Reticular TypeIII collagen
-surrounds individual myelinated & unmyelinated axons
-ECM made by fibroblasts & schwann cells (glial cells)
NO CT IN CNS!
Thick black border around cells what is it? what surrounds these cells?
myelin around cells- endoneurium
SCHWANN CELL- origin? Functions? disease? What advantage over oligodendrocyte in CNS?
SECRETORY! from Neural crest (PNS)
- Reticular fibers (type III collagen into endoneurium)
- External lamina (TypeIV, PGs’)(separates schwann cell from endoneurium)-blood nerve barrier
- external lamina guides repair
- one schwann cell wraps only one internodal segment on one axon
NO EXTERNAL LAMINA IN CNS-
What did you forget about schwann cells?
They envelop unmyelinated axons- think about what this will look like at TEM
Sensory Ganglia- What type of neurons? what part of functional nervous system?
Sensory ganglia- Posterior root ganglia- Pseudounipolar neurons- Somatic reflex
NO SYNAPSES occur within the ganglia
Motor ganglia- what type of neurons?
Autonomic- multipolar neurons- visceral reflex
Has synapses
