- Supportive - Protective (cushion and ideal chemical environment) - Regulatory - Electrically Insulated

Module B-01 Flashcards by hasina ashraf

2 major cell types in CNS and PNS

1) Neurons

2) Glia

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Functions of Glia

Supportive
Protective (cushion and ideal chemical environment)
Regulatory
Electrically Insulated

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Define Neurites

axons and dendrites

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Describe neuronal cell membrane

Phospholipid bilayer with ion channels , receptors and other protein complexes

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Describe neuronal nucleus

bilayered porous membrane that contains DNA

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Nissl substance consists of_______ and produces______

RNA granules ; Proteins

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Location of Nissl substance

Cell body and proximal regions of dendrites

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describe mitochondria

Bilayered organelle involved in energy generation

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Function of Golgi apparatus

vesicular packaging

- modification and transport of products of Nissl substance

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Lysosomes

scavenger vesicles loaded with degratory enzymes

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3 types of Cytoskeleton filaments

1) Microtubules
2) Neurofilaments/Intermediate Filaments
3) MIcrofilaments

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Functions of Cytoskeleton filaments

Change shape during cell growth and regenration
Maintain shape in Mature cell
Transport of material

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Microtubules are polymers of___________

alpha, Beta and Gamma tubulin

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How do microtubules grow?

-addition of tubulin dimers which are the cross linked by Tau protein (alzheimer’s)

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Function of microtubules

Forms Tracts for the 2 axonal transport

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Anterograde transport aka

orthograde

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Protein involved in anterograde axonal transport is ________ and retrograde is ________

Kinesin; Dynein

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In which direction does Kinesin move on along the microtubules?

towards the positive end of the micortubule and becomes inactivated at nerve ending

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What type of proteins are Kinesin and Dynein?

ATPases

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In which direction does Dynein move on along the microtubules?

towards negative end of microtubule and becomes inactivated at the soma

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Function of Retrograde transport

NGF transport after endocytosis at teh nerve terminal towards the soma
recycled vesicles and lysosomes

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3 Types of Neurofilaments/Intermediate filaments

GFAP (glial fibrillary acidic protein)
nestin
vimentin

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Function of Neurofilaments/Intermediate filaments

create scaffolding of cytoskeleton

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Structure of Neurofilaments/Intermediate filaments

Highly polymerized with little turnover

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Number of Neurofilaments/Intermediate filaments in neurons is dependant on _________

Axonal Diameter (radial development)

_________ is similar to myosin of muscle in that it has binding sites for large structures

Kinesin

Actin is a type of __________

Microfilament

Function of Microfilament

- participates in advancement of Growth Cone | - synaptic vesicle endocytosis during vesicle recycling (actin)

Location of Microfilaments

forms a network just below the cell membrane

How is dendritic transport different from axonal?

microtubule are in mixed orientation for selective movement to dendrites rather than axons

Rate of Axoplasmic flow

1mm/day

neuron with multiple dendrites

Multipolar

Multipolar neuron with long axons are called ________ and those with short axons are called ________

Golgi type I (Motor) ; Golgi type II (inhibitory)

Neurons with elongated cell body and two processes

Bipolar

Function of Bipolar

Special sensory systems like retina and CN 8 (visual and auditory)

neurons with 2 axonal processes that diverge from a stalk of the cell body

Pseudounipolar

Example of Pseudounipolar

sensory neurons that form the Dorsal Root ganglia and cranial nerve ganglia

Class A fibers

Myelinated neurons

Class C fibers

Unmyelinated neurons

Myelination _______ speed of conduction

increases

categorization of neurons according to myelination

Class A and C

Categorization of neurons according to Axonal diameter

Class I, II, III and IV

Class I

Largest diameter and most rapid conducting

Class II and III

intermediate diameter and intermediate conduction speeds

Class IV

Smallest, unmyelinated and slowest (Class C)

How do inhibitory neurons inhibit

release transmitter that polarize and stabalize membrane

What dictates whether a neuron has inhibitory or excitatory effect?

Receptors on postsynaptic neurons , not the transmitter

6 types of glia

- Astrocytes - Microglia - Oligodendrocytes - Ependymal cells - Tanycytes - Choroidal epithelial cells

Most numerous cell type in CNS

Astrocytes

Functions of Astrocytes

- Maintain ionic homeostasis - Maintain synaptic homeostatis - Regulate cerebral blood flow - Protect neurons from oxidative damage - Supply lactate to glucose-deprived neurons - Direct differentiation of neuronal precursors (releasing growth factors) - Release cholesterol (a component of the lipid structure of membranes) - Increase numbers of synapses - Release gliotransmitters - Uptake of excess K+ through ion channels

What transmitters do astrocytes take up at the synaptic cleft?

glutamate, glycine and monoamines

What Gliotransmitters do Astrocytes release?

Glutamate, D-serine and ATP

Which 2 types of glial cell forms Gliotic scar (gliosis) during Brian and Spinal cord damage?

Astrocytes and ependymal cells

Effect of high extracellular K+ levels on neuron

Depolarizes the neuron

What is spatial buffering or potassium siphoning?

When astrocytic K+ ion channels that take up the excessive extracellular ions for shunting to neighboring astrocytes via gap junctions

__________ are Neuronal, astrocytic and oligodendrocytic progenitors

Radial Glia

2 locations where Radial glia persist

- Bergman glia in cerebellum | - Müller cells of the retina

Function of Microglia

Immunocompetent and phagocytic - Protect neurons from micro-organisms and toxic effects of cellular debris - Secrete neurotrophic or neuron survival factors upon activation - contribute to initiation of pathological neuronal degernation - Release cytotoxic molecules

Types of cytotoxic molecules released by microglia

o Proinflammatory cytokines o Reactive oxygen intermediates o Proteases

_________ myelinate axons of CNS neurons

Oligodendrocytes

Function of ependymal cells

Produce CSF form CSF-brain barrier produce neurons and glial cells after stroke

Location of Ependymal cells

walls of ventricles

Function of Choroid plexus epithelial cells

- Secrete cerebrospinal fluid (CSF) | - transfer molecules from blood into CSF

Tanycytes are derived from

Radial Glia

Function of Tanycytes

Interface between CSF and Blood | allow sampling by homeostatic areas

Where do Schwann cells originate from

neural crest cells (both myelinated and unmyelinated)

Functions of Schwann cells

- myelination in PNS | - clearing cellular debris by phagocytosis

What happens to schwann cells of damaged axons

regress to immature state to support regeneration

Enteric glial cells are similar to _______

astrocytes

Where are satellite glia found?

in sensory, sympathetic and parasympathetic ganglia

what type of glia are schwann cells, satellite and enteric glial cells?

PNS glia

Function of satellite cells

surround neurons to to regulate chemical environment

What happens during axonal transection of PNS

o Distal axonal segment degenerates o Proximal axonal segment may form sprouts o Schwann cells Proliferate, forming a guide tube  Release nerve growth factors, encouraging axonal regeneration  Re-myelinate the regenerating axon  Target cells may die unless reinnervated within denervated cells may die after 3 weeks

Rate of axon growth in remyleination

about 2 mm/day

Define Chromatolysis

Post traumatic neuronal swelling and dilution of of organelles

Anterograde transneuronal degeneration

death of denervated (postsynaptic) cell or neuron

Retrograde transneuronal degeneration

death of the cell presynaptic to the damaged cell

Wallerian degeneration

degeneration of the disconnected axon and terminal

Why doesn't regeneration occur in CNS?

- not enough NGF is secreted by the glial cells - oligodendrocytes don't form guide tubes as Schwann cells - Gliotic scars block axonal regrowth

All Tumors of the PNS are_________

Schwannomas

__ of tumors of brain and ____ of spinal cord are glial origin

50%; 25%

2 demyelinating autoimmune diseases

- Guillain Barre Syndrome (peripheral demyleinating) | - Multiple Sclerosis