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Chapter 1 Cells, Glial cells, Neurons, Cellular components, Cellular…
Chapter 1
Cells
Glial cells
Support signaling functions
Define synaptic contacts
Maintain signaling abilities of neurons
Functions
Aiding (sometimes impeding) recovery from neural injury
Stem cells
Give rise to
Glia
A neuron in a few instances
Only stem cells in mature brain
Prevent regeneration
Maintain ionic mileu of nerve cells
Modulating rate of nerve signal propagation
Modulating synaptic action
Controlling uptake and metabolism of neurotransmitters
At or near the synaptic cleft
Scaffold for some aspects of neuronal development
Interface between brain and immune system
Facilitating convective flow of brain interstitial fluid
While sleeping
Wash out metabolic waste
Additional filament proteins
Glia
Greek for "glue"
19th century assumption
Bind nerve cells together
As abundant as neurons
Types
Mature nervous system
Astrocytes
CNS
Brain & Spinal cord
Give cells starlike "astrall" appearance
Functions
Maintain appropiate chemical environment
For neuronal signaling
Including the blood-brain barrier
Providing
Myelin
Oligodendrites
CNS
Some axons
Speed of transmission electrical signals
Schwann cells
PNS
Microglial cells
Derived from
Primarily hematopoetic precursor cells
Sometimes neural precursor cells
Share many properties with macrophages
Scavenger cells
Remove debris
From sites of injury
Number of microglial cells increases dramatically
Proliferate from microglia in the brain
From macrophages that enter the brain
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From normal cell turnover
Secrete signaling molecules
Wide range of cytokines
Local inflammation
Influence whether other cells survive or die
Glial stem cells
Proliferate & generate
Additional precursors of glia
Differentiated glia
Sometimes neurons
Categories
Astrocytes
Primarily near the
Ventricles in the subventricular zone (SVZ)
Give rise to more
Stem cells
Neurons
Mature
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Adjacent to ventricular zone blood vessels
Oligodendrocyte precursors
In the white matter
Polydendrocytes
Give rise to
Mature
Oligodendrocytes
Some astrocytes
In vitro neurons
Neurons
Specialization for communication
Generating electric signals
Branching
Axon
Most have only one
May have branches
Divergence
Number of targets
Synaptic contact
Sometimes with cell bodies
Synapse
Communitation
Presynaptic
Extracellular proteins
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Presynaptic terminal
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Synaptic cleft
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Types
Chemical synapses
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Electrical synapses
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Mostly with dendrites
Can be meters
Distinct cytoskeleton
Sometimes not present
Action potential
Electrical signals
Spikes
Units
Electric potential
All-or-nothing changes
Voltage
Across membrane
Conveys information
Self-regenerating wave
Synaptic transmission
Information from action potential to a target cell
Via synapse
Dendrites
Synaptic input
Integrated
"Read out"
Origin of the axon
Many ribosomes
Specific cytoskeletal proteins
Tubulin
Actin
Spines
Some neurons lack these
Limits integration of information
Convergence
Number of inputs of a single neuron
From 1 to 100,000
Elaborate branches?
Greater integration of information
Organelles
Endoplasmatic reticulum
Not in axons or dendrites
Mitochondria
Concentrated at synapses
Proteins
Myosin
Distinctive organisation
Stability & Function
Synaptic junctions
Neuronal processes
Actin
Tubulin
Several others
Types
Interneuron
Local circuit
Short axon
Local branching
Multiple post-synaptic sites on many neurons
Afferent neuron
Information from periphery
toward
the brain or spinal cord
Efferent neuron
Information
away
from the brain of spinal cord
Projection neuron
Extented axon
E.g. spinal cord to foot
Cellular components
20th century
Techniques
Light microscopes
Golgi staining
Electron microscopy
Features of neurons
Mitochondrion
Endoplasmatic reticulum
Nucleus
Soma
Golgi apparatus
Ribosomes
Axon
Dendrites
Neuron Doctrine
Santiago Ramón y Cajal
No continuity
Discrete enities
Specialised contacts
Charles Sherrington
Synapses
19th century
Reticular theory
Camillo Golgi
Golgi apparatus
Golgi staining
Continuous directly interconnected
Protoplasmatic links
Specialised intercellular continuities
Gap junctions
Direct signal transfer
Electrical
Chemical
Techniques
Less good microscopes
Less good staining techniques
Cellular diversity
Visualization techniques
Golgi staining
Silver salts
Individual nerve cells
Processes
Fluorescent dye injection
Processes
Single nerve cells
Cresyl violet dye
RNA
Nucleolus (not the nucleus
Ribosome-rich ER
Blank unstained dendrites
Nissl staining
Lamination
Different densities
Cerebral cortex
Olfactory bulbs
Distibution of cell bodies
DNA and RNA
Cell bodies
Ribosomes
Antibody staining
Label specific components
In situ hybridization
Nucleic acid probe
mRNA
Enzyme injection
86 billion neurons and at least that many glia
Greater range of distinct cell types
Morphology
Molecular identity
Physiological role
Many different gene expression
Cognition
Higher order brain functions
Perception
Memory
Language
Attention
Emotions
Thinking
Genomics
Human genome
Gene
DNA sequence
Regulatory
Introns
Promotors
Coding
Exons
mRNA
Protein
Mutated genes
Neurological & Psychological disorders
Disruption of brain development
Single gene mutation
Microcephaly
Failure of growth
Diminished brain function
Degenerative disorders
Huntington's disease
Parkinson's disease
20,000 genes
Nervous system
14,000 genes
6,000 only nerves
8,000 all cells
Different regulation
Diversity & Complexity
Brain structure & function
Splice variants