Histo: Nervous Tissue Flashcards
What are the two principal cell types of the nervous system?
- neurons
- neuroglia
CNS neurolglia
- ependymal cells
- oligodendrocytes
- astrocytes
- microglia
PNS neurolglia
- satellite cells
- schwann cells
3 functional classifications of neurons
- sensory neuron: info coming at CNS
- interneuron: helps process info coming in from multiple sources which affects motor neurons
- motor neuron: info exiting CNS
3 parts of a neuron
- Dendrites: collect electrical signals from other neurons
- Cell body: makes proteins, integrates incoming signals and generates outgoing signals to axons
- Axon: passes electrical signals to dendrites of another cell to cells of effector organs
Neuron parts
Green: dendrites
Gray: cell body
B: axon
How are structural classifications of a neurons determined?
They are named after the number of processes coming off of the cell body
Structural classifications of a neuron
Bipolar:
- 1 axon and 1 dendrite (2 processes, separated by cell body)
- found in sensory organs (ex: retina of eye)
Pseudo-unipolar:
- 2 axons: peripheral and central (1 process off of the cell body that branches immediately)
- peripheral axons have dendrites
- found in PNS
Multipolar:
- 1 axon and many dendrites (3+ processes)
- found in CNS
Another name for cell body?
Perikaryon
Cell body image
- Light staining = euchromatin = active
- Most organelles are located in cell body (lots of RER for protein production)
Cell body image nissl-stained
B arrows: nissl bodies
R arrows: golgi (shows up clear)
Dendrites:
- Transmit information to the cell body
- Contain the same organelles as the cell body EXCEPT GOLGI
- Are supported by microtubules and intermediate neuro filaments (neurofibrils)
- Unmyelinated
- Branch
- Larger in diameter than axons
Dendrite labeled on image
What are dendritic spines:
- evaginations on dendrites that increase the SA of the cell membrane
- synapses occur on the spines
- can be added or taken off as needed
Dendritic spine image
Axons:
- 1 axon per neuron
- originates from axon hillock
- has neurofibrils
- usually myelinated
- lacks nissl substance
- action potentials originate at the initial segment (right at axon hillock)
Axon image
Looks clearish and off to the edge of cell body
Axon in EM
- locate axon hillock
- initial segment
- myelin
Image of chemical synapse
- locate presynaptic neuron
- locate postsynaptic neuron
- locate synaptic cleft
Image of chemical synapse
Satellite cells (PNS neuroglia)
- surround neuron cell bodies in ganglia
- regulate O2, CO2, nutrients, and neurotransmitter levels around neurons in ganglia
Schwann cells (PNS neuroglia)
- surrounds axons in PNS
- responsible for myelination of peripheral axons
- participate in repair process after injury
Oligodendrocytes (CNS neuroglia)
- myelinate CNS axons
- provide structural framework
Astrocytes (CNS neuroglia)
- maintain blood-brain barrier
- regulate ion, nutrient, and gas concentrations
- absorb and recycle neurotransmitters
- form scar tissue after injury
Microglia (CNS neuroglia)
- remove cell debris, wastes, and pathogens by phagocytosis
Ependymal cells (CNS neuroglia)
- line ventricles and central canal
- assist in producing and monitoring CSF
Satellite cell and schwann cell on peripheral cell body
Satellite cell image
darker nuclei = more heterochromatin = less active
Schwann cell with myelin sheath
T/F: schwann cells only myelinate a small segment of an axon
T
Peripheral nerve image:
- locate schwann cell
- locate nerve fibers
What are nodes of ranvier?
- gaps formed between the myelin sheath where the axons are left uncovered
- allow the generation of a fast electrical impulse along the axon
Node of ranvier image:
Node of ranvier EM:
What are Schmidt-Lanterman Clefts?
small pockets of cytoplasm left behind during the Schwann cell myelination process
What are the arrows pointing to?
Nodes of ranvier
3 roles of astrocytes:
- modulation of communication
- nutrient transport from blood to neuron
- supporting myelin coverage of neurons
What 2 things do astrocytes come into contact with?
- blood vessels
- neurons
Oligodendrocyte in white matter
“fried egg” appearance
What is unique about oligodendrocytes?
They can myelinate multiple sections of an axon AND multiple axons
Microglia
- smallest of the CNS glia
- can function as macrophages with their phagocytosis
- release cytokines to modulate synaptic transmission
- can cleave spines of dendrites
oligodendrocyte in scanning EM
Microglia with silver stain
Note spindly processing coming from cell body
Microglia with H&E
Note rod-shaped nucleus
Ependymal cells
- can be squamous or columnar
- can be ciliated (beat to circulate CSF)
- line central cavities of brain and spinal column
Ependymal cell image
Ependymal cell image
Autonomic (postganglionic) ganglia
- multipolar cell bodies surrounded by satellite cells
- located intramurally within certain organs
- preganglionic nerves synapse here
Sensory ganglia
- unipolar cell bodies surrounded by cuboidal capsule cells
- associated with cranial and spinal ganglia
- no synapse
sensory ganglia
circular neuron with central nucleus
autonomic ganglia
nuclei on side of cell
CT components layers of spinal nerve
epineurium
perineurium
endoneurium
endoneurium and perineurim
endoneurium perineurim and epineurium
What is the cerebral cortex?
outermost layer of gray matter making up the superficial aspect of the cerebrum
3 major parts of the brain?
cerebrum
cerebellum
brainstem
3 layers of the cerebellum
molecular layer
purkinje cell layer
granule cell layer
cerebellum image: identify 3 layers
ID
multipolar neurons
ID
multipolar neuron
ID
dorsal root ganglion
ID the small brown dots
satellite cells
ID the pink dot
- nissl substance
- psedounipolar at axon hillock
ID the type of neuron
multipolar
Is there blood in the endoneurium?
NO
Perineurium and epineurium labeled
endoneurium are brown and surrounding each little circle
