<p>this is my weakest subject: nuerons + muscle contractions…</p>
<p>ummm my answer would be skipped but if i guessed it’d be D</p>
<p>I would say D as well.</p>
<p>Could anyone list a few examples of Negative Feedback please? = D</p>
<p>also hate that as well^^^^^</p>
<p>I have no clue, I need to study neurons.</p>
<p>If K+ leaves the neuron then it becomes hyperpolarized, so D</p>
<p>yearsofwisdom: i hope not!!!</p>
<p>@olleger - most things in the body are regulated via negative feedback. Think of insulin release (which lowers blood sugar). When said blood sugar gets <em>too</em> low, then glucagon (which heightens blood sugar) is released into the blood (both the latter and the former are produced by the liver, by the way) and insulin production comes to a halt. This is termed negative feedback because when something happens in response to a chemical, said chemical ceases being produced.
And another…tetanus is a bacteria whose toxins released cease inhibitory chemicals from reaching the mandible muscles’ PNS network. Thus, without any negative feedback, and only positive feedback circulating back to the CNS, and no respective inhibitions to the muscle contractions, one develops a conditioned known colloquially as lock jaw.</p>
<p>There is a lot of negative feedback in the body; most things are. Blood glucose levels, blood calcium levels, body temperature, …</p>
<p>Positive feedback is much less common. The only thing I can think of is the contractions that occur at birth. A contraction causes more contractions with greater severity until the baby is born.</p>
<p>positive feedback one that i know of is that if your injured. more platelets will be sent to your wound… i don’t know the mechanism for that but it happens.</p>
<p>Positive feedback also occurs during sex and when a baby is suckling. I believe oxytocin is released in the latter case causing the mother to produce more milk, but it could be prolactin. Doubt it though.</p>
<p>Lol, I read that as “…occurs during sex when a baby is suckling” and was like…what?</p>
<p>Negative feedback can be shivering when cold/sweating when hot.</p>
<p>There’s negative feedback with insulin right?</p>
<p>idk.,… i just know that thats part of homeostasis.</p>
<p>^yes there is. When there is too much insulin it will stoop it.</p>
<p>What is the curve for this test and how many points are needed for a 5?</p>
<p>Hey guys! Since I still have merely couple hours until the AP exam, I was wondering if I should spend the time to cover the senses or not (such as structure of the eye, ear, etc) since they are fairly detailed. Thanks!</p>
<p>^ </p>
<p>Nope. I don’t think you have to know anything about the structure of those types of semi-external organs. Focus of the heart, neuron, and muscle cells.</p>
<p>Can someone please help me out and explain muscle contractions? I only have Barron’s book, don’t have Cliffs (stupid mistake) and it hardly says anything about muscle contractions :(</p>
<p>You’re in luck, I just took PR notes on them:</p>
<p>• When acetylcholine (a type of neurotransmitter that can be broken down by the enzyme acetylcholinesterase) is released by a motor neuron, it binds with receptors on a muscle fiber and causes an action potential.
• The impulse stimulates the release of calcium ions from the sarcoplasmic reticulum. Calcium ions bind to troponin molecules, exposing the myson-binding sites on the actin filaments.
• ATP (which is bound to the myosin head) is split. Myosin, now cocked, binds to the exposed site on the actin molecules and actin-myosin cross bridges form. In creating these cross bridges, myosin pulls on the actin molecule, drawing it towards the center of the sarcomere. Then the actin-myosin complex binds ATP and myosin releases actin.</p>
<p>In short:</p>
<p>Summary of Muscle Contraction:</p>
<ol>
<li> A nerve impulse is sent to the skeletal muscle.</li>
<li> The neuron sending the impulse releases a neurotransmitter onto the muscle cell.</li>
<li> The muscle depolarizes.</li>
<li> Depolarization causes the sarcoplasmic reticulum to release calcium ions.</li>
<li> These calcium ions cause the actin and myosin filaments to slide past each other.</li>
<li> The muscle contracts.</li>
</ol>
<p>i was reviewing my cliffnotes practice test…and this confused me:
(page 277)
5. what will be the effect on the reaction if the enzyme if heated to 100 degrees C. before being mixed with the substrate?</p>
<p>i chose C.) The reaction will not occur</p>
<p>but the answer is B) the reaction will occur at a slower rate.</p>
<p>why?
shouldn’t all of the enzymes have been denatured by the high heat?
so…wouldn’t they NOT perform any reaction at all?</p>
<p>i’m so confused.
please help :)</p>