Question

Tetrodotoxin (TTX) is a poison produced by puffer fish which acts as a neurotoxin by blocking voltage-gated sodium channels. Which of the following is the reason that TTX can kill you?

		TTX inhibits the action of neurotransmitters at the synaptic cleft
		TTX prevents repolarization of the membrane during neuron resting potentials
		TTX prevents depolarization of the membrane during neuron action potentials.
		TTX disrupts the diffusion of sodium needed to establish neuron resting potentials
		TTX allows action potentials to move backwards down an axon.

Which of the following might happen in individuals that had a nonsense mutation in the middle of the gene for growth hormone (GH) ?

		Their hypothalamus would secrete low levels growth hormone-releasing hormone (GH-RH)
		Their hypothalamus would secrete low levels of somatostatin
		Their liver would secrete high levels of somatomedins
		Their anterior pituitary would secrete high levels of growth hormone (GH)
		They would grow larger than normal

Which two factors help establish the resting potential?

		Diffusion of sodium ions into the cell and diffusion of potassium ions out of the cell.
		Sodium-potassium pump and voltage-gated sodium channels.
		Sodium-potassium pump and diffusion of potassium ions out of the cell.
		Diffusion of potassium ions out of the cell and diffusion of anions into the cell.
		Sodium-potassium pump and diffusion of sodium ions into the cell.

Answer 1

1. The poison Tetrodotoxin (TTX) blocks the voltage gated Sodium ion channels,which is responsible for the blocking of development of action potential can kill us,now-

a. Release of neurotransmitters at synaptic cleft is not affected by the action of the voltage dependent Na+ channel, actually the Ca++ plays a role in the release of neurotransmitters.So this statement is incorrect.

b. The repolarization phenomena is done by the entry of K+ in the cell in exchange of Na+ through the Na-K ATPase pump.So this statement is incorrect.

c. The depolarization is occured by the opening of voltage dependent Na+ channels,and produces action potential in the cell. So by the blocking of these Na+ channels will prevent the depolarization restrict these phenomena.So this statement is correct.

d. The Na+ is not responsible for establishing the resting membrane potential rather it produces action potential.So this statement is incorrect.

e. The TTX does not prevent the voltage dpendent Na+,which means it does not allow the cell to produce the action potential in the postsynaptic membrane.So this statement is incorrect.

The correct option is-(c)

2. The GH is released from the anterior pituitary which releasing signals comes from the hypothalamus.This GH helps in the ceellular growth. So mutation in the GH gene may results in-

a. The releasing of the GH-releasing hormone (GH-RH) is not affect by the mutation of the GH gene as the the gene of the GH and thee GH-RH are completely different.So this statement is incorrect.

b. The releasing of the somatostatin is associated with the inhibition of GH.But the releasing of the somatostatin is not associated with the release of thr somatostatin.So this statement is incorrect.

c. The release of somatomedine acts by inhibiting the GH,but the GH gene is responsible for abnormalities for GH sysnthesis from the anterior pituitary.So this statement is incorrect.

d. The mutation in the GH gene may cause to relaese high level of GH from the anterior pituitary.So this option is correct.

e. The release of GH hormone relsults in abnormal growth,so mutation off the GH gene is not directly affected with the GH gene mutation.So this statement is incorrect.

The correct answeer is-(d)

3. Resting potential is established by the influs of the K+ inexchange for Na+.

a. Diffusion of the Na+ into the cell and K+ out of the cell will cause to produce development of action potential.So this option is incorrect.

b. Na-K pump acts by removing two K+ in exchange of three Na+,and the volatge gated Na+ channels will hephs in establishing the resting membrane potential by the influx of the K+ and removal of thee Na+.So this satement is correct.

c. Sodium-potassium pump and diffusion of potassium ions out of the cell will cause development of the action poteential.So this statement is incorrect.

d.  Diffusion of potassium ions out of the cell and diffusion of anions into the cell will not helps in the establishment of the resting membrane potential,as the K+ is being removed from the cell.So this statement is incorrect.

e. Sodium-potassium pump and diffusion of sodium ions into the cell will lead to increase positivity inside the cell.So this statement is incorrect.

The correct answer is-(b)