1) In your own words describe an example of a reflex pathway used in the lab tut

Question

1) In your own words describe an example of a reflex pathway used in the lab tutorial.

2) Neurons do not generate an action potential unless the stimulus causes de-polarization at a level called threshold. What would be a potential outcome if the action potential threshold was abnormally low? What would be a potential outcome if the action potential threshold was abnormally high?

3) The lab tutorial uses the example of botulinum toxin. What specific effect does botulinum toxin have on neurons? If we could specifically focus botulinum toxin effect on a neuron which generates IPSPs in a second neuron, what would be a potential outcome for the second neuron?

4) There are different cell membrane channels that act to maintain polarization of the cell membrane and generation of action potentials. Why is it significant that some of these channels are voltage gated, while others are not? How does this contribute to the normal functioning of action potential propagation?

5) Give a brief explanation of the four phases of an action potential including the status of potassium and sodium ion channels during each.

Explanation / Answer

ans 1....reflex pathway.,let us take example of knee reflex pathway.when pateller tendon is striked by hammer,it stimulates the sensory nerves ,the sensory nerve carry the impulses to the spinal cord at L3/L4 level via dorsal root.in the spinal cord these neuron relay on interneurons or motor neurons directly.the motor neuron then carry impulses to quadriceps muscle and leads to its contraction which causes knee reflex

ans 2...if action potential threshold is abnormally low then the cell get stimulated very fast and rapidly.this leads to vigrous contration of the muscle and spasm.the muscle may get rigid

if the action potential is abnormally high,the cell will not be stimulated.there is no electical or physical activity in a muscle.the muscle is flaccid.

ans 3..botulinum toxin block the release of acytyl choline at neuro muscular junction.botulinum toxin generating IPSP in the neuron will lead to no stimulation of the next neuron.this is the reason why this toxin causes paralysis.

ans 4....voltage gated channels open in response to the voltage and the non voltage gated channels open which are also known as ligand gated channels open in response to a ligand or a chemical when it bind to the receptor.the propgation of impulse with a neuron is due to the voltage gated sodium and potassium channel.but the propagation od nerve impulse from one neuron to other is by ligand channel that is by avytyl choline for example.acytyl choline released at synapse and then it attaches at the post synaptic neuron which open the ligand gatee channel which stimulte this neuron.then afterwards volatge gated channel carry the impulse with in the neuron through axon upto the next synapse

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