Neurons, Glia, And CNA Histology Flashcards
Neural cel differentiation involves the actions of growth and transcription factors that up-regulate the expression of __________
Pro neural genes
If one progenitor cell responds to pro neural growth factor…
It will begin to differentiate as a neuron
What happens to a progenitor cell at the same time that it differentiates into a neuron
It will being producing adjacent proteins that inhibit pro neural gene expression in adjacent cells
When one porgenitor cell responds to pro neural growth factor it will being to differentiate into a neuron and simultaneously it will being producing proteins that inhibit pro neural gene expression in adjacent cells. What is the this process called ?
Lateral inhibition
This is a transmembrane protein that after binding to ligand encoded by pro neural genes undergoes cleavage of its intracellular domain, which is then translocated to the nucleus, where it inhibits expression of pro neural genes
Notch
What does lateral inhibition involve
Notch signaling pathway
What does microglia originate from?
Bone marrow precursor cells
What does the cell body of a neuron contain
- multiple mitochondria (energy)
- abundant rough ER (protein synthesis)
- Nissl granulation (rough ER can be stained with basophils dyes)
Axon of a neuron
- arrises from hillock
- initial segment
- devoid of ribosomes
- multiple mitochondria
- do not branch proximally
- terminal arbor with terminal boutons (synapses)
Dendrites of a neuron
- multiple
- branched
- neurofilaments and microtubules
- may contain mitochondria
Multipolar neurons
-multiple dendrites, one axon (motor neurons)
Pseudounipolar neurons
One axon with common stem and then sending two branches (sensory neurons)
Bipolar neuron
One dendrite and one axon (specialized senses)
Motor neurons
Somatic and visceral
Sensory neuron
Somatic and visceral
Integration neuron
Connective
Neuroendocrine neurons
Mostly in hypothalamus, release peptide hormones into blood-systemic or portal circulation
How can neurons be classified
- morphologically
- functionally
- by neurotransmitter
Usually pseudounipolar or bipolar composed of a axon that ends peripherally with specific receptors and axon through which they connect with other neurons
Primary sensory neurons
Mechanoreceptros
- Audio-hair cells
- Vibration-pacinian
- Proprioreceptors-muscle spindle, golgi tendon organ
- tactile-meissner corpuscle
- thermoreceptors-free nerve endings
- norireceptors-free nerve endings
What are the classifications of primary sensory neurons
- mechanoreceptors
- chemoreceptors
- photoreceptors
Taste and olfactory
Chemoreceptors
Rods and cones in the retina
Photoreceptors
The process of converting sensory input into a form interpretable by the nervous system is
Transduction
Motor neuronal axons often end in fine branches known as
Terminal arbors
One axon, don’t branch near cell body but terminally they do
Motor neuron
In most motor neurons, each axon terminal is capped with
Terminal boutons
The site at which an axon terminal communicates with a second neuron, or with an effector tissue
Synapse
Contact between part of one neuron (usually its axon) and the dendrites, cell body, or axon of a second neuron
Synapse
Axodendritic
Excitatory or inhibitory
Axospinous
Excitatory synapse
Axosomatic
Excitatory or inhibitory
Axoaxonic
Excitatory or inhibitory, acting to increase or decrease neurotransmitter release by post synaptic terminal (amplifying or suppressing the level of stimulation already occurring inside postsynaptic terminal)
5 steps in transmission
- Synthesis
- Storage
- Transport
- Release
- Reuptake
**
Site of most transcription and translation in neuron
Cell body (soma)
What does the neuron soma produce and send to the dendrites
- membrane receptors
- various post synaptic proteins
- cytoskeleton proteins
What does the neuronal soma send to the axons
Cytoskelatal proteins
Mitochondria
What does the neuronal soma send to the axon terminals
- cytoskeleton proteins
- enzymes for NT synthesis
- synaptic vesicles
- mitochondria
How are NT and other substances transported within the neuron
Microtubules in both directions
Anterograde transport through microtubules
-away from the cell body through kinesins
Retrograde transport through microtubules
Toward the cell body via dyneins
________ carries substances produced by the neuron to the neuronal synapse
Anterograde transport
What does kinesins use to crawl along the microtubules
ATP
When one head attaches, the other releases and turns 180, literally marches
Fast anterograde transport
- uninterrupted
- carries synaptic vesicles, membrane proteins, NT, mitochondria
Slow anterograde transport
- stop and go
- carries cytosolic proteins (enzymes), cytoskeleton proteins from the cell body to the axon terminals and dendrites
Actually moves very rapidly, but pauses frequently
Retrograde transport along atonal microtubules is driven by
Dyneines
This allows the neuron to respond to growth factors, that are taken up near the axon terminal by either pinocytosis or receptor mediated endocytosis
Retrograde transport
This form of transport functions in the continual recycling of components of an axon terminal, edosomes, damaged mitochondria
Retrograde transport
What uses retrograde transport
Viruses and toxins
Terms describing formations of cell bodies in the CNS (appear grey)
- nucleus
- layers, lamina, stratum
- column
Terms describing formations of neuronal projections in the CNS (white becuuse they have myelin sheath)
- tract, fasiculus, lemniscus
- funiculus (group of parallel tracts)
What is the PNS counterpart to the nucleus
Ganglia
Cell types that are not excitable in CNS
Neuroglia
Neuroglia cells
- astrocytes
- oligodendrocytes
- microglia
- ependimal cells
Support neurons, isolate CNS from other tissues, scar formation
Astrocytes
Proved myelin sheaths to neurons within the CNS
Oligodendrocytes
Immune and inflammatory functions (neural macrophages)
Microglia
Neuroepithelium
Ependimal cells
Astrocytes of the gray matter
Protoplasmic astrocytes
Astrocytes of the white matter
Fibrous astrocytes
Highly branches with multiple processes that give these cells th star like appearance
Astrocytes
Function and structural support that astrocytes provides:
- constant pH, lower EC K+
- secrete growth factors and cytokines (IL-1)
- remove glutamate from synapses
- help metabolism, store some glycogen
Astrocytes retain the ability to ________ in the mature brain
Proliferate
When injury to the CNS results in destruction of neurons, the space created by the breakdown of debris is filled by proliferation and or hypertrophy of astrocytes, resulting i the formation of _______
Astrocytic scar
Astrocytes ability to proliferate
Makes them more likely to evade the control of cell division and explains why the majority of CNS tumors ar of astrocytic origin
Astrocytes-insulation of neural tissue
- they join end feet together and insulate the CNS from other tissues
- every cap in body lined with end feet to separate it from BBB
The surface of the brain and spinal cord, adjacent to the pia mater is covered with several layers of joined end feet called
Glial limiting membrane
All of the components of the true BBB
Neurovascular unit (NVU)
Cellular components of the NVU
- brain endothelial cells and BM
- pericytes, residing on the abluminal surface of the caps
- astrocytes, almost completely ensheath BV
- perivascular macrophages, monitor perivascular spaces of larger vessels
Site of the functional BBB
CNS capillaries comprising a single, non-fenestrated, continuous endothelial cell layer with little or no cytoplasmal inclusions
A physical paracellular barrier is created by what for the BBB
The presence of tight junctions between the brain and the endothelial capillaries
Tight junctions on the capillaries in the CNS (BBB)
Composed of Claudine’s, occludin and junction adhesion molecules and seal the paracellular route between brain endothelial capillaries, don’t allow anything to pass through.
Adherens junctions of the capillaries in the CNS (BBB)
Sit albuminal to tight junctions and consist of VE-cadherin dimers that mediate cell to cell membrane adhesion and bind to the actin cytoskeleton via catenins
This is the pathway for transport of plasma macromolecules such as albumin and LDL to brain
Trans cytosol
Brain endothelial cells have extremely low rates of ______creating a barrier to hydrophilic molecules
Transcytosis
Brain endothelial cells use _________ to regulate the influx of nutrients and effluent of metabolic wast and toxins between the blood and the brain parenchyma
Transporters
CNS immune surveillance
-BECs also express very low levels of leukocyte adhesion molecules (LAMs) limiting CNS immune surveillance by impeding the binding immune cells to BECs and then their migration into the CNS
Healthy brain is immune privileged
Small cells with relatively few processes that are usually aligned in rows between axons. The processes wrap around a portion of an axon, for me in an internodal segment of myelin
Oligodendrocytes
What produces and maintains the myelin sheath in the CNS?
Oligodendrocytes
Interruptions between the myelin segments
Nodes of ranvier
Where does the propagating of the action potential occur
At the node of ranvier
This method is faster and requires much less energy than having ionic exchanges occur continuously along the length of the axon
Saltatory conduction
What kind of disease is multiple sclerosis
Demyelinating disease
The smallest cells in the neural tissue, scattered throughout it that arise from myeloid granulocyte-monocytes progenitor cells
Microglia
What are the immune cells of the CNS
Microglia, normally they are quiescent
When do microglia activate
They possess processes through which they can sample their environment, if a foreign antigen or cellular debris are detected, they activate.
Microglia and infection
Form long rod cells closely AP posed to affected neurons
Microglia and tissue injury
They become motile, ameboid phagocytes capable of migrating to the site of injury and proliferating. They phagocytize tissue debris
What happens when migroglgia are stimulated
Secrete cytokines, which range from neurotoxic mediators of inflammation to neuro protective mediators of tissue repair
What are the proinflammatory cytokines released from microglia
Interleukines and tumor necrosis factor-a, arachidonic acid derivatives-prostaglandins E2
What are some of the thrombogenic cytokines released from microglia
Platelet activating factor
What are some of the protective cytokines released from the microglia
Growth factors (brain derived neurotrophic factor)
This virus is transported in retrograde direction to the cell bodies of the neurons innervation the muscle. Produce and shed copies of virus, which are taken up by the terminals of adjacent cells. Causes behavioral changes. Travels from CNS to salivary gland anterograde, innervating these glands. The infected salivary gland in turn sheds the virus
Rabies
Transported retrograde direction in nerve cells whose axons terminate at the site of infection. Toxin is released from nerve cell body and taken up by terminals of neighboring neurons. Toxin is diluted as it passes from cell to cell. Range of neurological defects
Tetanus
No treatment, just vax
Virus resides latent in sensory ganglia and can reactivate. Painful vesicular rash
Varicella zoster (chicken pox/shingles)
Virus resides latent in sensory ganglia and can reactivate. Painful vesicular rash. Can cause encephalitis destroying temporal lobes
Herpes simplex
A microtubules assembly protein-Tau-is dysfunctional possibly by B-amyloid
Alzheimer’s disease
Mutant protein-Huntington-disrupts atonal transport
Huntington disease
What does microglia secrete during BM, especially after abx
Overstimulated to secrete IL-1B
What does IL-1B do
Acts on endothelial cells to loosen their tight junctions, allowing leukocytes and blood plasma to enter CNS tissue, escalating the inflammation to a level that can be fatal
How do you improve the survival rate of bacterial meningitis
Administering steroids prevents this secondary inflammation and the survival rate goes up
Infection involving the meninges of the brain
Bacterial meningitis
How does bacterial breach BBB
B strep can weaken BBB integrity by suppressing tight junction protein expression and causes BM
Th-1 and BBB
Activated Th1 cells can sneak through BBB and induce autoimmune response
- TH1 lymphocytes trigger inflammation (increases permeability)
- inflammatory demyelination in MS
Most common benign brain tumor in adults
Meningioma
CNS lymphoma
- metastatic high grade B cell non-hodgkin lymphomas
- occur in AIDs
- ring enhancing lesions with contrasted border
Most common brain malignnacy
**
Metastases
*****
-lung, breast, skin, kidney, GI, prostate
