Question

what is the magnetic force on ions during a nerve pulse

Answer 1

As we know that blood in the nerve is negatively charged solution, as blood is moving during the nerve pulse, a current is developed in opposite direction of the flow of the blood, because negative charge is moving inside the nerve. Due to this current a magnetic field will get develop.

that will vary as per the ampere law of magnetism,

$\oint Bdl=\mu_o I$