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==MyMCAT==
MyMCAT is designed to utilize the power of community development much like Wikipedia. However, because learning requires more than just reading, the project has been expanded to include personalized resources such as tests and quizzes.

==Resources==
As well as a continually growing encyclopedia of review text, MyMCAT also has topic tests, passage tests, and quizzes throughout the text. In the next few months, we hope to add learning games, flashcards, and personalized score tracking.

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You really saved my skin with this infromatoin. Thanks!

2011-02-26T18:42:57Z

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Welcome

Finally, a free site to help you prepare for the Medical College Admission Test (MCAT). Read through our [[Site_Map|review text]], practice [[:Category:Section_Tests|sample questions]], or even try complete [[:Category:Passages|passages]] - MyMCAT has hours of content all geared to helping you do better on the MCAT. 
 

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<li>[[Image:Blue_goto_arrow.png|link=Site_Map]] Check out our review directory for a complete list of mcat review materials</li>
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What's New

20/02/11 - A new mcat passage on neurological lesions has been added, [[Passage:Motor Neurone Disease]]. 

05/08/10 - A new section test on work and energy has been add, [[Section Test:Work]]. 

28/07/10 - A new genetics page on [[Hardy-Weinberg Genetics]] and a new test which covers the concepts seen on the mcat, [[Section_Test:Hardy-Weinberg Genetics]], have been added. 

22/07/10 - MyMCAT is getting a facelift, we hope you like the changes and we hope it helps your mcat studies. 

For the complete history of pages/items added, please visit [[MyMCAT:News]].

2011-02-26T17:40:10Z

WikiAdmin:

Passage:Sickle Cell Anemia

2011-02-26T17:34:52Z

WikiAdmin: Created page with '== Passage Information == This sample MCAT passage covers topics in general biology and genetics. == The Passage == <quiz display…'

== Passage Information ==
This sample MCAT passage covers topics in general [[Category:Biology|biology]] and [[Category:Genetics|genetics]].

== The Passage ==

<quiz display=simple>
{question1.
|type="()"}
- ...
- ...
+ ...
- ...
|| some answer explanation.

[[Category:Passages]]

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2011-02-26T15:29:42Z

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2011-02-26T15:29:07Z

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Passage:Motor Neurone Disease

2011-02-21T12:59:11Z

WikiAdmin:

The primary motor pathway is typically composed of the same neuronal architecture throughout the body. Upper motor neurons (UMNs), originating in the CNS travel down the spinal cord where they synapse lower motor neurons (LMNs). These lower motor neurons connect the spinal cord to muscle fibers, bringing nerve impulses from the upper motor neurons out to the muscles.

At the end of the lower motor neuron's axon are the neuromuscular junctions which act as specialized synapses for muscle fibres. Here LMNs release acetylcholine into the synaptic cleft where the postsynaptic receptors of the muscle cell membrane, respond by activating ion channels effectively signaling the muscle to contract.

When lesions occur in the motor pathway, the symptoms are often widespread, depending most importantly on where the lesion occurs. Nerve fibers usually originate in the primary motor cortex, pass via the corona radiata to gather in the internal capsule before crossing over to the opposite side in the medullary pyramids and proceeding down the spinal cord to meet lower motor neurons in the anterior horn. When damage occurs somewhere along this UMN pathway, control of muscles is often lost or diminished while reflexes persist.

Myasthenia gravis is an autoimmune disorder, in which muscle weakness is caused by antibodies targeting the receptors found on the post-synaptic muscles of neuromuscular junctions.

Amyotrophic lateral sclerosis (or ALS) is a form of a motor neuron disease. ALS is a progressive, fatal, and neurodegenerative disease caused by the degeneration of motor neurons in the central nervous system that control voluntary muscle movement. The defining feature of ALS is the death of both upper and lower motor neurons in the motor cortex of the brain, the brain stem, and the spinal cord. Prior to their destruction, motor neurons develop proteinaceous inclusions in their cell bodies and axons. There is no known cause for ALS however some cases have been shown to be due to a hereditary factor.

<quiz display=simple>
{Which of the following is the most likely source of left-sided paralysis in both the arm and leg?
|type="()"}
- a lesion on the right side of the spinal cord at L3.
|| This cannot be the answer since the lesion is also affecting the arm and L3 is too far down.
+ a lesion on the right side of the brainstem.
- a lesion in the left side of the cerebrum.
|| The motor neurons in question are contralateral, meaning that the right side of the brain controls the left, thus a left sided lesion will not affect the left in such a way.
- a lesion on the right side of the spinal cord at C5.
|| This would produce the correct symptoms but on the wrong side as the fibers at this level have already crossed.

{Which of the following symptoms would not be seen in a lower motor neuron lesion?
|type="()"}
- decreased or absent reflexes
|| In LMN diseases, reflexes are destroyed since the efferent fibers to the muscles have been damaged.
- weakness
|| for the same reason above, the efferent fibers directly innervating muscle are damaged and so the muscles do receive adequate signal to respond correctly.
- muscle wasting
|| When muscle is not stimulated it undergoes atrophy, in LMNs, the lack of stimuli cause muscles to waste.
+ increased tone (increased residual muscle tension)
|| For the same reason that the muscles are not stimulated, the lack of continuous stimuli will cause reduced tone, NOT increased tone (this is an UMN disease symptom).

{Which of the following would not be possible approaches to treating myasthenia gravis.
|type="()"}
- An acetylcholine esterase inhibitor.
|| This is correctly the recommended treatment and is effective because it effectively increases the amount of available neurotransmitter in NMJs when stimulation occurs by preventing the signaling molecules breakdown.
- An immunosuppresant
|| myasthenia gravis is an autoimmune disease and so immunosuppresants would decrease the rate of destruction of NMJs.
+ intravenous acetylcholine injections.
|| Acetylecholine does not exist in the blood and is rapidly degraded. It is found only in neutransmitter vesicles in neurons and made directly by these cells. External administration would be increase the availibility of the transmitter to neurons.
- Plasmapheresis
|| an alternative to an immunosuppresant would be to remove antibodies from the blood to reduce the immune response.

{An animal with a dysfunctional cerebellum would have a major deficit in?
|type="()"}
- visual acuity
- taste
- memory
+ coordination
|| the cerebellum is a region of the brain that plays an important role in the integration of sensory perception, coordination and motor control. In order to coordinate motor control, there are many neural pathways linking the cerebellum with the cerebral motor cortex and the spinocerebellar tract.

{Which of the following should have the slowest conduction velocity?
|type="()"}
- an unmyelinated, small-diameter nerve
- an unmyelinated, large-diameter nerve
- a myelinated, small-diameter nerve
+ a myelinated, large-diameter nerve
|| myelin sheaths increase conduction velocity by allowing the signal propagation to "jump" between nodes of ranvier (which occurs because of the insulation effect on the membrane).
|| Secondly, large diameter fibres conduct more rapidly because of the increased movement/flow of ions that occurs.

{Grey matter consists of ___________?
|type="()"}
- nerve cells
- nerve cell bodies
+ nerve cell bodies and dendrites
- nerve cell bodies, dendrites and axons
|| Grey matter consists of all the neuronal components found in the CNS without the axons. It is the axons which, when bundled together and wrapped in myelin are seen as white under the microscope (and hence called the white matter).

{Ganglia are present in _______________?
|type="()"}
+ the dorsal root of spinal cord
- the ventral root of spinal cord
- both a and b
- neither a nor b

{The nodes of Ranvier are ________________?
|type="()"}
- covering of the nerve fibre
- swelling along the nerve fibre
+ gaps in the cover of the nerve fibre
- collection of nerves in the heart

{In ALS, one would not expect to see
|type="()"}
+ initial muscle weakness confined to trunk and later the arms and/or legs
|| Because ALS is destructive along the whole length of the motor neuron system, those neurons which are longest are more likely to show signs first, thus the initial effects are often confined to the arms and legs. Thus this is the answer.
- reduced cognitive abilities
|| cognitive abilities (stemming from the cerebrum) are generally untouched as they do not make up the motor neuron tracts.
- reduced sense of touch.
|| sensory neurons are not affected by ALS, only motor neurons to voluntary muscles.
- loss of muscle control but preserved reflexes
|| this would be a sign of UMN disease, but ALS is indifferent to its destruction, damaging both UMNs and LMNs.

</quiz>

[[Category:Passages]][[Category:Biology]]

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2011-02-21T02:08:30Z

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2011-01-27T03:07:37Z

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