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Investigation of neurons

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Investigation of neurons

Postby inayat » Wed Sep 10, 2008 7:53 pm

I have been given the question below and have come up with an answer but I am really not sure of my answer. But this is the best I could do after looking through all the resources I had access to. Can someone please look at my answer and see if what I have written makes sense and if its right? Thanks very much.

[b]How is the later differentiation of different types of motor neuron determined? Suggest an experiment that could be used to investigate the effects of different target muscles on the properties of the motor neurons that innervate them. You should also identify what property(s) of the neurons you might investigate and name an appropriate technique to determine it.

Motor neurons innervate specific target muscles. The different types of motor neuron express different combinations of further regulatory genes. The specific regulatory genes expressed by different motor neurons is determined by the signals that the neural precursors receive according to their position within the spinal cord as well as the signals they receive as their processes grow out of the spinal cord. The time at which the neural precursors withdraw from the cell cycle and differentiate also determines the signals received by the developing motor neurons. After correct positioning in the developing nervous system, the motor neurons need to form connections with their target cells. Growth cones at the tip of the growing axons are specialised structures which move and sense environmental signals. The growth cone extends and retracts filopodia repeatedly which have lamellipodia between them. Chemoattractive or chemorepulsive stimuli, detected by receptors in the growth cone, direct the growth of the axon towards its target skeletal muscle. Long range cues are usually diffusible signals while short range cues are usually contact –mediated. Once the axons of the motor neurons reach the tissues they will innervate, they form synapses with the target cells.

An experiment to investigate the effects of different target muscles on the properties of motor neurons that innervate them could be done through transplantation. Developing motor neurons can be transplanted into different muscle types. The neurons can be labelled with tracers to distinguish them from the host muscle cells and the effect of a particular muscle type on the neuron can be investigated. A property of motor neurons such as the quantity of neurotransmitter release by the neuron in the case of each muscle type can be determined and the results compared. If there are significant differences between the amount of neurotransmitter release in each type, this would show that different muscles have different effects on the motor neurons. The amount of neurotransmitter release could be measured by electrophysiological techniques.
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