Tetanus toxin poisons neurons BUT leads to over stimulation of skeletal muscle c

Question

Tetanus toxin poisons neurons BUT leads to over stimulation of skeletal muscle contraction by preventing neurotransmitter release. This could only occur if it blocked ________.

A. inhibitory post-synaptic potentials

B. voltage-gated Ca2+ channels

C. voltage-gated Na+ channels

D. excitatory postsynaptic potentials

Which of the following is common to graded potentials but NOT action potentials?

A. only produce depolarizing electrical potentials

B. are self-propagating

C. posses a refractory period

D. can be summed together

Explanation / Answer

1 A. Inhibitory post synaptic potential.

Tetanus toxin (tetanospasmin) inhibit release of Inhibitory Neurotransmitter (GABA) so there is no inhibitory effect on neuron and thus it fires impulse nonstop (ie it does not repolarize). This causes spasm of muscles.

2. D) Can be summed together.

Action potential can Not be summed as they follow ALL or NONE law (either action potential is elicited or it is not elicited at all).

Graded potential can be summed (either spatial summation or by temporal summation). Their summation may lead to action potential

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