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tatuchka [14]
2 years ago
7

Tamara's muscle weakness and fatigue becomes progressively worse over the course of the day. This is a hallmark sign of myasthen

ia gravis, an autoimmune disorder that affects the ability of a motor neuron to communicate with a muscle fiber. What synaptic events must happen first for excitation to occur?
A. The action potential travels down the T tubules in the sarcolemma and triggers the release of calcium ions from the sarcoplasmic reticulum.
B. Calcium binds to tropomyosin, shifting it from the active site on actin, allowing cross bridge formation to occur as myosin binds to the active site.
C. Acetylcholine is released from the axon terminal and diffuses across the synapse to bind to a receptor in the surface of the motor end plate.
D. Sodium ions from the extracellular fluid diffuse into the cytosol of the muscle fiber, triggering the generation of an action potential in the sarcolemma.
Biology
1 answer:
zubka84 [21]2 years ago
3 0

Answer:

C. Acetylcholine is released from the axon terminal and diffuses across the synapse to bind to a receptor in the surface of the motor end plate.

Explanation:

The contraction of muscle fibers needs nerve impulses to be initiated. Nervous stimuli release acetylcholine in the synaptic clefts, depolarizing muscle cells, after which the calcium cation (Ca²⁺) channels open. Calcium forms a set of proteins that trigger the reactions between myosin and actin.

These reactions promote sarcomere (fibrillar and globular protein complex) shortening, and when several sarcomeres shorten at the same time, muscle contraction occurs.

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Which of the following will NOT cause mass extinction?
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Answer:

D. None of the above

Explanation:

<u>Reason that Drastic Change in weather may cause mass extinction</u>

Weather plays an important role in the survivability & the growth/diminish of the population. For example, animals that need large amounts/bodies of water (for example fishes), will not survive when the area is hit with a heat wave & drought, which would cause fishes to surface, and die.

<u>Reason that Geological change would play a large role in mass extinctions</u>

While the Geography is constantly changing, large abrupt changes would cause a upheaval and may upset the population, leading to a depletion of resources or even a sudden destruction of part/all of the population. For example, an earthquake may kill large amounts of animals, and the destruction of the greenery in the area may severely limit the amount of food/decrease the primary consumer's populations, leading to a starvation.

~

8 0
3 years ago
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A plant has the genotype AAbbCcDDEeff, where each letter represents a different gene. This plant is crossed with another whose g
scoundrel [369]

Answer:

The fraction of the offspring that will show the phenotype produced by the recessive c allele is 1024/4096 = 0.25 A-BbccDdE-Ff = 25%

Explanation:

You can calculate the fraction of the offspring that will show the phenotype produced by the recessive c allele by making the punnet square for each gene and then multipling the phenotypic proportions, like this:

Cross) AAbbCcDDEeff     x      AaBBCcddEEFF

Cross For each gene by separately:

  • Parental )        AA    x    Aa

       Gametes)  A    A         A    a

        F1)             2/4 AA  

                          2/4 Aa

  • Parental )        bb    x    BB

         Gametes)  b    b         B   b

          F1)                   4/4 Bb

  • Parental )        Cc    x    Cc

        Gametes)  C    c         C    c

         F1)             1/4 CC

                           2/4 Cc

                            1/4 cc

  • Parental )        DD    x    dd

       Gametes)  D    D          d    d

        F1)             4/4 Dd

  • Parental )        Ee    x    EE

        Gametes)     E     e      E     E

         F1)             2/4 Ee

                           2/4 EE

  • Parental )        ff    x    FF

         Gametes)     f     f      F     F

          F1)             4/4 Ff

So, fraction of the offspring that will show the phenotype produced by the recessive c allele is:

4/4 A-  x  4/4 Bb   x   1/4 cc   x   4/4 Dd   x  4/4 E-   x   4/4 Ff =  

1024/4096 = 0.25 A-BbccDdE-Ff =25%  

6 0
3 years ago
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The moment it is exposed into the environment
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2 years ago
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Answer:

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3. The throat (pharynx and larynx) is a ring-like muscular tube that acts as the passageway for air, food and liquid. It is located behind the nose and mouth and connects the mouth (oral cavity) and nose to the breathing passages (trachea [windpipe] and lungs) and the esophagus (eating tube).

4. The main function of the epiglottis is to seal off the windpipe during eating, so that food is not accidentally inhaled.

5. The heart pumps blood to the lungs for oxygenation and the lungs then give the heart back oxygen rich blood to be transmitted to the whole body

Explanation:

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2 years ago
The forelimb structur seen in both bat wings and human arms is very similar to that of an extinct land animal called eusthenopte
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<span>b.Eusthenpteron might be a common ancestor of bats and humans.

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