Home Assignment 1

Exercise 1
Part 1
Ex1Part2

Part 2
Ex1Part1

Exercise 2
a)

Gray matter is the main component of the Central Nervous System consisting of Neuronal Cell bodies, Neurites, glial cells, synapses and capillaries.

the White matter consists mostly of glial cells and myelinated axons that transmit signals.

So we can remark that the main difference between Gray and White matter is that Gray matter mainly consists of numerous cell bodies and relatively few myelinated axons, while the White matter consists, on the other hand, of a wide range of myelinated axon and few cell bodies.

b)

We could say that a neuron has two mainly distinguishable parts:

  • The Cell body, which is also known as Soma, that contains the cell nucleus.
  • Neurites, which are thin tubes that radiate away from the central region. There are two types:
    • Axons, usually one per neuron. An Axon has uniform diameter and any branches from it and  they can extend over great distances in the body. It’s believed to be the “wire” that carry the output of the neurons and in its final, known as Axon Terminal, it’s carried out the communication in a process called Synapsis.
    • Dendrites, commonly much shorter than Axons. Many of them extend from the Soma. It’s believed to be the “antennae” of the neuron which receives incoming singals.

neuron.png
c)

  • Myelin

It’s a white and fatty substance that surrounds the axon forming a layer. It is essential for a proper functioning of the Nervous System.

  • cidpDiseaseInfoReceptor

The cell who receives the information in the Synapse process is known as Receptor.

  • Interneuron

The Interneurons are the neurons which serve as connection point between the other sensory and motor neurons. They are exclusively found in the central Nervous System, that means that they are located in the brain and in the spinal cord but not in the peripheral segments of the Nervous System.

interneuron.jpg

  • Pyramidal Cell

One of the methods in order to classify the cells are by its own shape. A Pyramidal Neuron is a neuron whose dendrites are arranged in a pyramidal way.

Sobo_1906_33

d)

Neurons are the most well-known  cells in the Nervous System. Nevertheless, there are approximately the same number of Neurons and Glia and Glia takes quite important functions as well.

Glia, or Glial Cells, are the ones in charge of insulating, supporting and nourishing neighboring neurons.

i.e. Imagine Stracciatella Ice cream. The chocolate bits would be the Neurons and the rest of the Ice cream would be the Glia. The Glia is the one that keeps all the neurons stuck. In fact, the word “Glia” comes from the Greek word for “glue”.

stracciatella

 

Exercise 3

We chose the joint Nobel prize winners Alan Hodgkin and Andrew Huxley. They built a mathematical model of a neuron describing it as a electrical circuit. Using this model, one can tell quite accurately the electrical properties of a neuron (a part of a neuron, called compartment) by calculating differential equations. The voltage difference compared to the inside and outside of the compartment relies on the operation of the ion channels. A great upside of this model is that it can be extended by any number of ion channels with different mechanism, so the accuracy of the resulting model is adjustable (simulation time versus accuracy).

Hodgkin-Huxley Model

A drawing of the electrical circuit model of a neuron from Wikipedia.

Hodgin and Huxley received their Nobel prize, because they voltage clamped – kept the membrane potential at a given value, and by occasionally changing this value, they can observe the reactions of the neuron to such changes –  a giant squid’s nerve cell and fit a model on the recorded data. The findings are still valid and actively used in computational simulations – e.g. MOOSE – thus the findings were incredibly important as this is one of the most accurate electrical model of neurons ever created.

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