ACh/synaptic nerve question, very important..?

Ok people I have a test shortly that basically decides whether I get into University or not. A question like this is expected to come up. Can someone tell me how I work it out, without giving me just the answer?? Please guys I really need your help.

A nerve impulse travels along a presynaptic nerve. When the nerve impulse arrives at the nerve ending a chemical, acetylcholine, is released which diffuses across a gap known as a synapse and stimulates receptors on a postsynaptic nerve. The nerve junction where the presynaptic and postsynaptic nerves meet is known as a ganglion. When the acetylcholine receptors in the ganglion are stimulated a nerve impulse is generated which passes along the postsynaptic nerve. When this nerve impulse reaches the postsynaptic nerve ending acetylcholine is released which diffuses across the gap and stimulates receptors on some smooth muscle, causing the muscle to contract.

Drug N stimulates the acetylcholine receptors on the postsynaptic nerve. Drug C stimulates the acetylcholine receptors on both the postsynaptic nerve and the smooth muscle. Drug H attaches to the acetylcholine receptors on the postsynaptic nerve without stimulating them and prevents acetylcholine from gaining access to them. Drug A attaches to the acetylcholine receptors on the smooth muscle without stimulating them and prevents acetylcholine from gaining access to them. Drug L prevents the transmission of nerve impulses.

Which of the following statements is most consistent with the information given?

a Drug C will inhibit the muscle contraction induced by drug A

b Drug A will inhibit the muscle contraction induced by drug N

c Drug H will inhibit the muscle contraction induced by drug C

d Drug A will inhibit the muscle contraction induced by drug H

e Drug N will inhibit the muscle contraction induced by drug C

4 Answers

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  • 10 years ago
    Best Answer

    This is quite an easy question chief lol. Drugs N and C are the only drugs that stimulate. Therefore we can ignore statements a, and d by the last part of the statements; as drugs A and H do not cause a reaction.

    Drugs N and C stimulate so statements a and e can be ignored due to the first part of the statement.

    This only leaves statements b and c.

    All you have to do is work out which statement has an inhibitor and a MUSCLE stimulant in it.

    Statement b begins with a muscle inhibitor but does not end with a muscle stimulant.

    Statement c begins with a drug that inhibits the propagation of an action potential past the post synaptic membrane. It is also the only relevant statement to end with a drug that can stimulate the smooth muscle.

    Alternatively, Drug C is the only drug that can stimulate muscle, this eliminates all statements but c and e.

    Statement e begins by saying Drug N will inhibit. We know that drug N is a stimulant not an inhibitor and can therefore rule out statement e.

    Both leave the same answer.

    Hope this helps

  • 10 years ago

    take note first that acetylcholine stimulates the receptors on the smooth muscle causing the muscle to contract.

    we will analyze each drug one at a time:

    Drug N stimulates the ACh receptors on the POSTSYNAPTIC NERVE. - this may cause muscle contraction.

    Drug C stimulates the ACh receptors on BOTH POSTSYNAPTIC and SMOOTH MUSCLE. - this may cause muscle contraction.

    Drug H attaches to the ACh receptors on the POSTSYNAPTIC NERVE and PREVENTS ACh from attaching to the ACh receptors on the postsynaptic nerve. - no contraction will happen if drug H is present

    Drug A attaches to the acetylcholine receptors on the SMOOTH MUSCLE and PREVENT ACh from gaining access to the ACh receptos on the smooth muscle - no contraction will happen if drug A is present.

    Drug L prevents the transmission of nerve impulses. - no contraction will happen if drug L is present.

    So back to the choices given above.

    Choice A is already NOT consistent with the information give above. Why? because drug C stimulates and may cause muscle contraction.

    Choice B is not consistent because drug A attaches on the ACh receptors on the SMOOTH muscle and drug N stimulates the ACh receptors on the POSTSYNAPTIC NERVE, NOT on the smooth muscle.

    Choice C is CONSISTENT with the information because drug H attaches to the ACh receptors on the POSTSYNAPTIC NERVE which inhibits muscle contraction. The drug that stimulates these ACh receptors on the postsynaptic nerve is drug C.

    Choice D is NOT consistent because drug H does not induced muscle contraction. It prevents muscle contraction by attaching to the ACh receptors on the postsynaptic nerve.

    Choice E is NOT consistent because drug N does not inhibit muscle contraction but it stimulates the ACh receptors on the postsynaptic nerve which may cause muscle contraction.

  • 10 years ago

    Figure it out. L is not in issue, so ignore it. N+C stimulate, H+A inhibit. You need an inhibition between the stimulation and the muscle.

  • 4 years ago

    It makes the neural nets in your brain work. Without it we wouldn't even have bugs, there would be no animals anywhere (or insects).

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