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Science-Related Homework Help High School Level Science Topic started by: princess001 on Feb 22, 2013



Title: In a class experiment, the strength of a neural stimulus and the resulting muscle contraction are ...
Post by: princess001 on Feb 22, 2013
In a class experiment, the strength of a neural stimulus and the resulting muscle contraction are compared. A single motor neuron that synapses with a muscle fibre is suspended. The other end of the muscle fibre is attached to a mass. If an electrical stimulus is sufficient to cause an impulse in the neuron, the muscle will contract and lift the mass. The following data were obtained from the experiment. Analyze the data, and answer the following questions.











Strength of stimulus (mV)                                Mass lifted by muscle contraction (g)
                1                                                                                0
                2                                                                              10
                3                                                                               ?
                4                                                                               ?

a) Define "threshold potential". What is the minimum size of the stimulus required to reach the threshold potential for this motor neuron?
b) Explain the all-or-none response. Then predict the mass that could be lifted at 3mV of stimuli and at 4mV of stimuli.
c) Choose a specific example of a sensory neuron, and explain neural stimulation and impulses in terms of the threshold potential and the all-or-none response.


Title: In a class experiment, the strength of a neural stimulus and the resulting muscle contraction are ...
Post by: bio_man on Feb 22, 2013
Use this towards your answers :nerd:

A neuronal membrane is said to be depolarized if the transmembrane potential is reduced to less than the resting potential of −70 mV. If, for any reason, the membrane at a node of Ranvier becomes depolarized to −55 mV, a dramatic change occurs in the membrane. This change is called an action potential. (As you will see later, this depolarization is usually caused by an action potential that has just occurred at an adjacent node of Ranvier.) An action potential is called an “all-or-none” event because a depolarization to between −70 mV and −55 mV has no effect. Any depolarization to −55 mV, or any other amount up to 0, will produce identical action potentials. The potential difference of −55 mV is therefore called the threshold potential. Threshold potentials can vary slightly, depending on the type of neuron, but they are usually close to −55 mV. When the transmembrane potential at a node of Ranvier reaches threshold, special structures in the membrane called voltage-gated sodium channels open and make the membrane very permeable to sodium ions. The sodium ions on the outside of the axon suddenly rush into the axon, driven by their concentration gradient and the potential difference across the membrane. Within a millisecond or less, enough positively charged sodium ions have crossed the membrane to make the potential difference across the membrane in that tiny region of the axon +35 mV.

Use the attachment to supplement the content shown here ^^


Title: In a class experiment, the strength of a neural stimulus and the resulting muscle contraction are ...
Post by: princess001 on Feb 22, 2013
Thanks this really helps.

By any chance would you know this question. I think it is D but I still want to make sure.

An Olympic downhill skier, attempting to win a bronze medal, is midway through the race. Which row now describes accurately the effects of the sympathetic nervous system on the skier's body components?

a) Blood vessles in the skin constrict, sphincters of the digestive tract contracted, bronchioles dilated
b) Blood vessles in the skin constricted, sphincters of the digestive tract relaxed, bronchioles constricted
c) Blood vessles in the skin dilated, sphincters of the digestive tract contracted, bronchioles constricted
d) Blood vessles in the skin dilated, sphincters of the digestive tract relaxed, bronchioles dilated


Title: In a class experiment, the strength of a neural stimulus and the resulting muscle contraction are ...
Post by: traviscorp on Sep 23, 2013
Thank you! this was a big help.


Title: In a class experiment, the strength of a neural stimulus and the resulting muscle contraction are ...
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Title: In a class experiment, the strength of a neural stimulus and the resulting muscle contraction are ...
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Title: In a class experiment, the strength of a neural stimulus and the resulting muscle contraction are ...
Post by: bio_man on Nov 13, 2013
Thanks this really helps.

By any chance would you know this question. I think it is D but I still want to make sure.

An Olympic downhill skier, attempting to win a bronze medal, is midway through the race. Which row now describes accurately the effects of the sympathetic nervous system on the skier's body components?

a) Blood vessles in the skin constrict, sphincters of the digestive tract contracted, bronchioles dilated
b) Blood vessles in the skin constricted, sphincters of the digestive tract relaxed, bronchioles constricted
c) Blood vessles in the skin dilated, sphincters of the digestive tract contracted, bronchioles constricted
d) Blood vessles in the skin dilated, sphincters of the digestive tract relaxed, bronchioles dilated


What response did you get for this?


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