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Neurons And Glia (The Building Blocks Of The Brain) Notes

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This is an extract of our Neurons And Glia (The Building Blocks Of The Brain) document, which we sell as part of our Neurology Notes collection written by the top tier of Bristol University students.

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Lecture 5 Neurons and glia are the building blocks of the brain

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Structure of neurons o General
? Electrically excitable, use electricity to relay messages
? Polarised (dendrites- input; axons- output)
? Terminally differentiated (don't divide- postmitotic)

* When neurons die, don't produce more. Fewer when die than born
? Actual CNS neuron: axon length >0.5m
? In peripheral nervous system= longer o Structural classes of neurons
? Polarity refers to number of processes coming from the cell body (i.e. dendrites and axons)
? UNIPOLAR

* E.g. Dorsal root ganglion sensory neuron (primary afferent)
? BIPOLAR

* E.g. Retinal bipolar cell (special senses)
? MULTIPOLAR

* E.g. Spinal motor neuron
? NB. May also be described structurally according to shape (e.g. pyramidal cells, granule cells, stellate cells) Ionic basis of electrical activity o (Resting) Membrane potential
? Neurons maintain (negative inside, ~-70mV) membrane potential at rest
? Key determinant of membrane potential

* Ionic conc. gradient

* Ionic electrical gradient (2 together= electrochemical gradients)

* Selective membrane ionic permeability
? Key charged ion species

* Na; K; Cl; Organic ions (largely protein), Ao Sodium-potassium ATPase establishes electrochemical gradient
? 3 Na out; 2 K in
? Critical for balance of osmotic pressures
? ATPase so requires energy (ATP)
? Energy efficiency is problem for NS. Human brain (-2% body mass) consumes

* 15% CO

* 20% total body oxygen consumption

* 25% total body glucose utilisation under low physical exertion o In average neuron at rest
? Ion Intracellular Extracellular Out/In Na 15mM 145mM 10 K 155mM

4.5mM

0.03 Ca

0.0001mM 1mM 10000 Cl 5mM 120mM 6 o Nernst Equation

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