Neuroscience: Neurons & Glial Cells

Front 1

Cell Types of the CNS and PNS

Back 1

1) Neurons
2) Glial Cells
-Astrocytes
-Microglial cells
-Oligodendrocytes
-Ependymal cells
-Cells of choroid plexus
-Schwann cells
-Satellite cells

Front 2

Function of the Neuron

Back 2

CNS & PNS
1. impulse formation
2. impulse conduction
3. information processing

Front 3

Function of Astrocytes

Back 3

CNS
housekeeping cell:
1. maintain internal milieu in CNS
2. help form blood-brain barrier
3. phagocytosis of nonfxning synapses
4. scar formation in CNS
5. absorb excess NT and K+

Front 4

Function of Microglial Cells

Back 4

CNS
specialized for phagocytosis and Ag processing:
-brain macrophages
-part of mononuclear phagocyte system

secrete cytokines and growth factors

Front 5

Function of Oligodendrocytes

Back 5

CNS
-form myelin sheaths in CNS

Front 6

Ependymal cells Function

Back 6

CNS
-line cavities in CNS

Front 7

Cells of choriod plexus fxn

Back 7

CNS
-secrete cerebral spinal fluid

Front 8

Schwann Cells fxn

Back 8

PNS
-form myelin sheaths in PNS

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Satellite Cells fxn

Back 9

PNS
-modified schwann cell
-surrounds cell body of neurons in PNS ganglia

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Parts of the neuron

Back 10

only 10% cells in brain
-Dendrite
-Soma
-Axon hillock
-Myelin sheath
-Node of Ranvier
-Axon
-Presynaptic Terminal
-Synapse

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Dendrites

Back 11

-highly branched outgrowths from cell body
-surface area over 90% of neuronal surface for synaptic contact
-synapses where signals are received from other neurons

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Cell Body (Soma)

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-contain nucleus & genetic info for protein synthesis
-axoplasmic transport: materials move from cell body along microtubules/neurofilaments

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Axon

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-single process extending from cell body that carries AP away from cell body
-can undergo branching
-can be myelinated (conduct AP at higher velocity) or unmyelinated (pain fibers)

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Myelin

Back 14

-formed by glial cells (not considered part of neuron itself)

Front 15

Nodes of Ranvier

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-spaces bw myelin-forming cells, sites of voltage-gated Na and K channels for propagation of AP

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Axon collaterals

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-branches of axon enable neuron to activate more than one effector cell at a time

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Axon terminals

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-contain synaptic vessicles of chemical substances (NT) for transmitting signal at synapse

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Post-synaptic neuron

Pre-synaptic neuron

Back 18

Post: 1 neuron synapses w/ another, neuron that is activated

Pre: neuron that causes the synapse/action

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What determines the post-synaptic action?

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-the NT receptors
-NT can be excitatory/inhibitory
ex: Ach = excite skeletal muscle BUT inhibit cardiac muscle

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Hyperpolarize

Depolarize

Spatial and Temporal summation

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-ion channels that allow negatively charged ions flow into cell (inhibit cell)

-allow positively charged ions to enter cell will excite

-summary of excite/inhibit AP received of the post-synaptic cell

Front 21

Neuron Types

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1. Unipolar: invertebrates
2. Pseudounipolar: peripheral sensory afferent, 2 axons (1 central & 1 peripheral) ex: cutaneous, joint recept, muscle spindles & tendon organs
3) Bipolar: special sensory (Ex: retina, auditory, vestibular)
4) Multipolar: large dendritic trees (ex: spinal motor neuron, purkinje cells in cerebellum) receive input from mult. sources

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3 Fxnal classes of neurons

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1) afferent: recept. at peripheral endings that respond to physical/chemical changes in environment & cause elect. signals to generate in neuron, and transmit to other neurons in CNS
2) efferent: transmit electrical signal from CNS out to effector cells (muscle or gland cells)
3) interneurons: found entirely w/ CNS, account ~99% all neurons, integrate inputs from many sources & imp. in reflex pathways & pattern-generating circuits

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Groups of neurons

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1. Nuclei: fxn related groups of neuronal cell bodies, large cluster of gray matter in CNS
2. Ganglion: cluster of neuron cell bodies (dorsal root gang/autonomic gang)
3.Tract/Fasciculus/lemniscus:bundles of axons (white matter)
4. Grouped by action of NT

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Types of NT action neurons

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-noradrenergic
-cholinergic
-dompaminergic
-serotonergic
-glutaminergic
-GABAergic
-Glycinergic
-Peptidergic

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Glial Cells

Back 25

-90% of CNS
-supportive cells of CNS
-do not conduct APs (astrocytes may be excitable)

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Oligodendrocytes

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-form myelin sheath in CNS
-secreate protein called Nogo-A, inhibitory to growth of axons

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Astrocytes

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-surround every CNS BV and provide structural support for neurons
-secrete growth factors vital for neurons
-infiltrate sites of CNS injury/infarct, produce astrocytic scar (impedes regen.)
-regulate ionic concen. & pH in extracell. space & remove metabolic waste
-participate in NT metabolism
-respond to stim. by adjacent neurons or other astrocytes: communicate (gap jxn), stim astrocyte spread (wave Ca), release NT

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Ependymal Cells

Back 28

-line ventricles, cerebral aqueduct & canal of spinal cord, produce som SCF

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Microglia

Back 29

-resident macrophages of CNS
-1st line of defense
-mobilize in acute pathological events that might affect CNS, convert phagocytes in response to cell-death
-act as scavenger cells to destroy bacterial/viral intruders

Front 30

Supportive Cells of the PNS

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-Schwann cells (myelin): form myelin sheath in PNS
-SC (nonmyelin): "terminal" S-cells, provide trophic support to regenerate motor axons in PNS (induce nerve sprouting)
-satellite cells: surround cells bodies of neurons in sens & autonomic ganglia

Front 31

Tumors of Glial

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Glial: can cause neurological deficits, depned on locat, compromise fxn on important brain SC regions
-Gliomas
-oligodendrocytomas
-ependymomas
-astrocytomas

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Tumors of Schwann Cells

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-tumors of periphery: easily removed
-Schwannomas: painful condition and loss of fxn in pNS
-Neurofibromas: difficult to remove bc infiltrate nerve fibers