Carbon dioxide :)
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Answer;
Retinohypothalamic path
A small branch of the optic nerve, known as the retinohypothalamic path extends directly from the retina to the SCN.
Explanation;
The SCN is an abbreviations for suprachiasmatic nucleus or nuclei; which is a region in the hypothalamus. that is responsible for controlling circadian rhythms.
Retinohypothalamic path is a neural input pathway that extends directly from the retina to the SCN.
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Exocytosis is ana ctive transport method and does not include any transport protein. whereas calcium ions pass through the membrane with the help of trans- membrane protein. These proteins make pores inside hydrophobic membrane and allow the ions to pass though it.
The correct answer is this one: "A.When actin filaments are pulled toward the center of the sarcomere, the fiber shortens." The statement that accurately describes the way in which a muscle moves is when actin filaments are pulled toward the center of the sarcomere, the <span>fiber shortens</span>