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What is the origin of the CNS?
Neural tube (via notochord)
except microglia!!!
What is the origin of the PNS?
Neural Crest
What is the origin of the ANS?
Neural Crest
(CNS) Grey matter
- Neuronal cell bodies / processes
- Astrocytes
- Microglia
- Some oligodendroglia
(Neurons organized by function into nuclei)
(CNS) White Matter
Myelinated axons
(myelin formed by oligodendroglia)
Wiger stains
white matter (black)
gray matter (gray)
FAS Blue stains
stains myelin
Cresyl violet stains
a.k.a. Nissl stains
Stains nissl substance (RER / polysomes)
Histological appearance of neuron in spinal cord gray matter
Motorneuron
• euchromatic nucleus (highly active)
• prominent nucleolus
• abundant Nissl substance (RER / polysomes)
cytoplasm = basophilic
All CNS cell types are derived from neural tube except ________?
Microglia
(bone marrow origin)
CNS Cell Types
- Neurons
- Glia (support cells)
1. Ependymal cells
2. Choroid plexus cells
3. Astrocytes
4. Oligodendrocytes
5. Microglia
Ependymal cells
Lines ventricles of brain / central canal
- Cuboidal cells linked by desmosomes
- Apical microvilli & cilia
- Abundant mitochondria
looks like epithelium (neural tube = ectoderm derived)
Tanycytes
Specialized ependymal cells
(third ventricle)
- Linked to each other and to ependymal cells by tight junctions
- Basal processes form end-feet on blood vessels
Choroid plexus cells
Secrete CSF
- Cuboidal epith. linked by tight junctions
- Apical microvilli
- Infolding of basal plasma membrane
- Abundant mitochondria
Fibrous Astrocytes
White Matter
- long slender processes packed w/ intermediate filaments
- filaments composed of glial fibrillary acidic protein (GFAP)
- use antibodies to GFAP to determine if neural tumor is of astrocytic origin
- structural support for white matter tracts
Protoplasmic Astrocytes
Gray Matter
- short, thick. bushy processes
- fewer intermediate filaments
- stains less intensely w/ GFAP antibodies
- supportive cells for neurons (growth factors)
Astrocyte cytoplasmic processes (end-feet)
End-feet
- Cover neurons (soma / dendrites)
- Create barrier along the pia mater (glia limitans)
- Create barrier around CNS blood vessels (blood-brain barrier)
Oligodendroglia
Myelination of CNS axons
(up to 50 each)
Some act as satellite cells (not myelinating cells)
Microglia
Phagocytic cells
(Bone marrow origin)
- Resting macrophages in CNS derived from monocytes
- Migrate to CNS during development of CNS vasculature
- Respond to CNS injury
Microglial response to CNS injury
Divide and phagocytize injured neurons and glia
- microglial nuclei enlarge / elongate (rod cells)
- increased damage = cells become phagocytic (gitter cells)
Histological features of Cerebellum
Outer layer -> inner layer
- Molecular layer
- Purkinje cell layer
- Granule cell layer
Histological features of Cerebral Cortex
Small neuroglia
Pyramidal cells (apical dendrites)
What are the 3 regions of neurons?
Receptor region
Soma / Nissl bodies / Axon hilock
Conductive region
Axon / Node of Ranvier
Effector region
Telodendron
Where are all the protein synthetic organelles found in a neuron?
Neuronal cell body
Proximal vs. Distal synapses
(Receptive region)
Synapses closer to the cell body have more influence than those more distal
True or False:
Dendrites display an action potential
True
False
FALSE
Inputs (excitatory / inhibitory) summate to cause a graded potential
(i.e. membrane potential becomes more +/ - depending on input)
Axons vs. Dendrites
Dendrites
proximal parts have nissl substance
diameter tapers distally
irregular contours
branches bifurcate @ acute angles
use graded membrane potential
Axons
No nissl substance
uniform diameter
smooth contours
branches @ obtuse angles
use action potential
Molecular structure of axons
Neurofilaments
(maintain axon diameter)
Microtubules
(fast anterograde / retrograde transport)
Neurofilaments are more abundant
Slow Axonal Transport
0.2 - 4 mm/day
Anterograde only
Conveys structural elements
(tubulin / neurofilament proteins / actin)
Removal of materials carried by slow transport
1. Neurofilaments / microtubules are transported as polymers
2. Disassembled @ axon terminal
(due to high Ca
+
environment)
w/o this process, axons will swell (protein accumulation)
Fast Axonal Transport
20 - 400 mm/day
Microtubule dependant
(motor protein)
Anterograde - Kinesin (ATPase)
conveys organelles
(mitochondria / synaptic vesicles / SER)
Retrograde
- Dynein
conveys worn organelle / endocytosed materials
(growth factors / toxins / viruses)
How do neurons grow toward their targets?
Uses fast retrograde axonal transport
Neuron targets make growth factors
(carried back to soma by dynein)
Lipofuscin
Material in retrogradely transported endosomes
Cannot be digested
(lysosomes in soma)
Accumulates w/ age & in some diseases
Types of synapses
1. Chemical
- most common
- excitatory / inhibitory
2. Electrical
(present in some parts of CNS)
- allows neurons to act in unison
- gap junctions
Communication @ synapses
1. Presynaptic membrane depolarizes
2. Induces opening of Ca
+
channels (brief)
3.
Ca
+
influx
promotes exocytosis of synaptic vesicles
4. Release of neurotransmitters (synaptic cleft)
5. Neurotransmitters react with receptors
6. Postsynaptic membrane depolarizes
7. Presynaptic membrane retrieval (coated vesicles)
Dorsal Root Ganglion
Contains sensory neurons that signal:
- pain
- temperature
- touch
- pressure
- vibration
- porprioception
Site of blood-nerve barrier in peripheral nerves
Perineurium
Axatomy Response
Due to loss of target-derived neurotrophic factors
1. cell body swells
2. dissolution of Nissl substance (chromatolysis)
3. nucleus moves eccentrically
4. actin / tubulin genes up-regulated (growth cone)
5. neurofilaments / neurotansmitters down-regulated
Axonal degeneration (injury)
Proximal part = retrograde degeneration
Distal part = anterograde (wallerian) degeneration
Distal part separated from cell synthetic machinery
Axonal growth cone
Motile structure w/ receptors for neurotrophic factors / laminin
(basal lamina surrounds schwann cells)
Author
mnm2186
ID
29824
Card Set
Nervous Tissue
Description
Exam 2
Updated
2010-08-20T16:29:18Z
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