Introduction to Nervous Systems Flashcards
E.g. of circuitry problems
Schizophrenia
Autism
Depression
Addiction
e.g. of cellular biological problems
Alzheimer’s disease, which becomes almost an epidemic disease
Parkinson’s disease
Both are degenerative diseases
Multiple sclerosis
What is an unipolar neuron ?
Usually, a sensorial neuron that connect receptors to the spinal cord of the brain. The soma is linked to the axon. They don’t have dendrites.
What is a multipolar neuron ?
The typical neuron, one axon, many dendrites
What is a bipolar neuron ?
1 dendrite and 1 axon, usually retinal neurons (the soma is in the centre, and one dendrite links receptors eg photoreceptors to the cell body)
What are the timescales for diffusion in a cell ?
T=x^2/D
And D=[m]^2/t
D= diffusion coefficient
A larger value indicates a higher rate of jiggling around of the molecule. It’s value is determined by the velocity of the molecules and the meantime between collisions.
It is inversely proportional to the viscosity of the medium.
The lowest D would be, the longer the time it takes to a molecule to travel from A to B.
That means, the longer the distance is, the longer is the time it takes.
Diffusion is in 3D -> t=x^2/(6D)
What is the solution to the diffusion problem ?
Active transport.
Use of proteins such as Dynein and kinesin involved in active transport in a cell.
The pulse chase radio labelling paradigm is used to study axonal transport
It’s an ATP-dep process
What is the pulse chase radiolabelling paradigm ?
Measurement of radioactivity (radiolabelled amino acids are injected in the vicinity of neuronal cell bodies of an adult animal and are then incorported by newly synthesised proteins.
Once synthesised, they are then transported into axons and distal synapses by endogenous processes)
The movement of these protein is then inferred (=deduct) by analysing sequential axonal segment over incremental time-periods.
How does the active transport work ?
It is an ATP-dep mechanism involving microtubules where motor proteins (Dynein and kinesine) work along.
Microtubules are dynamic structures that undergo continual assembly and disassembly within the cell. They determine cell shape and are involved in cell movement.
It is a polar structure with two distinct ends: a fast-growing + end and a slow-growing - end. This polarity determines the direction of motor proteins movement. It is similar to actin filaments that define the direction of myosin.
In dendrites, MT are anti parallel. In axons, there are parallel.
Define kinesin transport type
Anterograde transport. It goes from minus toward +
From the centre of the cell toward the periphery.
define Dynein transport type
Retrograde transport
It goes from + to -
From the periphery toward the centre of the cell.
Which are the two possible mechanism for kinesin transport ?
The hand-over-hand mechanism:
It’s a walking mechanism. The kinesin heads step past one another, alternating the lead position as it was walking
The inchworm mechanisms:
One kinesin head always leads, moving forward a step before the trailing head catches up.
The hand-over-hand is more likely to occurs.
Dynein follows a mechanism similar to the hand-over-hand mechanism.
