Ass gned as Homework Problem Set Q3 Which has a faster acceleration: Calanoid Co

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Ass gned as Homework Problem Set Q3 Which has a faster acceleration: Calanoid Copepod or the Porsche 918 Spyder? Data for the copepod are presented in the lecture you will have to use the internet to find data on the car. Responses Reply Showing All Responses ordered by Newest Responses* Assigned as Problem Set Q4 You have gone fishing and caught some squid. Before making delicious calamari, you dissect out the giant axon, and study it in your neurophysiology laboratory. Your piece of giant axon is 3cm long and 1mm in diameter, with =10um and ' ms. You placerecord ng electrodes at 0.5cm intervals along the length of the axon. You decide to simultaneously stimulate the axon at both ends with a 1ms depolarizing current pulse. Draw a plot of membrane potential along the length of the axon 40ms after stimulation. Responses Reply Showing All Responses ordered by Newest Responses Assigned as Problem Set Q5 In terms of resistance and capacitance, why does myelination increase conduction velocity? Are these the same reasons for why the squid giant axon has a fast conduction velocity?

Explanation / Answer

Answer to Problem Set Q5:

The myelin sheath increases the conduction speed by decreasing the capacitance of cell membrane. In myelinated fibres impulses hop or propagate by saltatory conduction. Myelin decreases capacitance and increases electrical resistance through out the cell membrane(axons). Voltage gated sodium channels are absent in the myelin sheath but at the Nodes of Ranvier where myelin is not present, voltage gated sodium channels are present which allows enough sodium inside the axon to generate action potential. This action potential jumps from one Nodes of Ranvier to other nodes of Ranvier and hence conduction of nerve impulse is fast.

Squid axon is large in diameter but it is unmyelinated. Therefore because of large axon diameter, it conducts action potential faster because large diameter means large membrane area and more ion channels and hence faster conduction.

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