bio for josh-ppttake 2

8/6/2019 Bio for Josh-ppttake 2

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Dendrite Morphology and ItsEffects

By Prion and Rhinovirus



An Overview of Neurons

Dendrite

Soma

Node of

Ranvier

Axon Terminal

Schwann Cell

Meylin SheathNucleus

Axon



Informative Background



What is Dendrite

Morphology?

� Dendrite Morphology - study on how a

dendrite changes shape and length

� changes in response to multiple

psychological stimuli, such as chronic or

short term stress

� Important because it changes the

frequency with which neurons fire



Synapse



Burst Firing

� rapid spikes followed by periods of inactivity

� occurs in CNS and spinal cord

� Tonic Firing: the state in which neurons are

constantly firing, but at lower frequencies



Effects of Burst Firing

Seizures occur when the electricalimpulses firing between these neurons

misfire or begin to fire much too

rapidly. When contradictory signals are

sent at the same time, it causes a

seizure.



History of Research� Valentin was the first to describe the cells of nervous

tissue, nucleus and nucleolus of neurons, in 1836.

� 1837: Purkinje described subtle elongated fiber-like

processes which seemed to be peculiar to the nervoussystem.

� 1863: Deiters saw clear and complete images of

neuron cells, and found that there were two different

kinds of branching processes attached to the soma:tree like, short branches, and a long fiber he called an

³axis cylinder.´

�20 years later, dendrites were named.



� Gerlach proposed that nerve impulses

traveled from cell to cell through the

filaments, and that the brain was formed by

giant nets, or reticula, with a huge number

of such interconnected filaments.

� Bowditch: All neural functions could be the

result of transmission of electric charges

sent throughout the web of neurons.



The First of the Articles: Impact of

Dendritic Size and Dendritic Topology on

Burst Firing

� Used a computational model to evaluate the

impact of changes in dendrite

� Length: Pruning the branches

� Size: Condensing and Expanding

� Topology: Rearranging Branches



Results

� Length: degree of bursting decreases as

length decreases

� Size: burst firing disappears as lengthdecreases; only a certain range in which

burst firing is exhibited (too large, no

bursting)

� Implies that small change in length can causebig change in firing pattern



� Topology:

Remodeling

topology can

change firingstate of cell;

also influences

degree of

bursting



The Second of the Articles: Burst Firing

and Epilepsy� Point of experiment: to show that the loss of

function of dendrites plays an important role

in generation of absence seizures.

� Method: took rat brain slices from rats

afflicted with a seizure disorder and used

dendritic and somatic stimulation while

taking readings using an electrocorticogram.

� Electrocorticogram: A record of

electrical activity derived directly from

the cerebral cortex.



results

They found that

dendrites play a key rolein absence seizures. A

reduction in dendrites

modifies the action

potential output of pyramidal neurons that

caused increased burst

firing.



Studying in Further Areas

� Direct experimentation on Neurons

� With a Focus On...

� Manipulating dendrite characteristics

� Direct experimentation on Neurons affected by

psychological stresses

� With a focus on...

� Rehabilitating lost dendrite length and size

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