In humans, the quadriceps muscle is a skeletal leg muscle under voluntary control. As such, it contracts in response to signals from the motor cortex in the cerebrum. If such a muscle contracts involuntarily, that indicates:

The correct answer is - operation of reflex arc.

Explanation:

The reflex arc is a unique and special type of neural pathway that starts with a sensory neuron and ends with a motor neuron. In this operation sensory neuron acts as the receptor and motor neuron is effector. This type of neural circuit helps in faster response.

Voluntary muscles like quadriceps muscle are normally in control voluntarily however, such muscle may contract involuntary due to reflex arc. This type of contraction takes place before the signal has even reached the brain.

In this response the sensory neuron takes the signal to the spinal cord and then motor neuron to the effector muscle for faster response.

Thus, the correct answer is - operation of reflex arc.

you are certainly talking about this picture:

a: is the label of the white square, it is showing the  replication fork, formed by helicase (d) ==> so it is the site of dna separation and replication 

b: is a new dna brand that is following directly the replication fork, so it is continuous ==> built continuously from 5' to 3

c: dna polymerase cannot replicate dna on its own, it needs the of their proteins, and one of them plays the role of a clamp which fixes  the dna with the dna template and increases  the processivity of the enzyme. ==>   stops polymerase from falling off the  template.

d: is the enzyme responsible for forming the replication fork (helicase) ==> unwinds and separates dna into two strands

e: is the delayed strand, it is built  in the opposite sense of the helicase, so dna will be built in fragments ==> built  fragments from 5' to 3 joins

and finally f: is the enzyme that builds  the new dna strand (dna polymerase) ==>   adds nucleotides to make a new dna helix.

credit: gradman555p98x9p

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