I believe the answer is C.
because when the dinosaurs thrived they ate most of the mammals which were small animals but when the dinosaurs went extinct the mammals grew larger in size and started to thrive.
Answer:
The correct answer is 3: "<em>High levels of Ca2+ are expected to be found </em><em>within the sarcoplasmic reticulum</em>".
Explanation:
Muscular contraction is a highly regulated process that depends on free calcium concentration in the cytoplasm. Amounts of cytoplasmic calcium are regulated by <u>sarcoplasmic reticulum</u> that functions as a storage of the ion.
When a nerve impulse reaches the membrane of a muscle fiber, through acetylcholine release, the membrane depolarizes producing the entrance of calcium from <u>extracellular space</u>. The impulse is transmitted along the membrane to the sarcoplasmic reticulum, from where calcium is released. At this point, <em>tropomyosin is obstructing binding sites for myosin on the thin filament</em>. The calcium channel in the sarcoplasmic reticulum controls the ion release, that activates and regulates muscle contraction, by increasing its cytoplasmic levels. When <em>calcium binds to the troponin C</em>, <em>the troponin T alters the tropomyosin by moving it and then unblocks the binding sites,</em> making possible the formation of <em>cross-bridges between actin and myosin filaments.</em> When myosin binds to the uncovered actin-binding sites, ATP is transformed into ADP and inorganic phosphate.
Z-bands are then pulled toward each other, thus shortening the sarcomere and the I-band, and producing muscle fiber contraction.
Answer:
B
Explanation:
The whole point of natural selection is for animals to compete to survive in that specific environment
Hope this helps!
Answer:
regulation of the diameter of blood vessels and control of blood pressure
Explanation:
Skeletal muscles are the multinucleated muscles with striations and are attached to the bones (skeleton). The main function of skeletal muscles is to generate the voluntary movement of the body or body parts. The skeletal muscles of face, rectum, and urinary bladder generate their voluntary movement as per the will of the organism. On the other hand, blood vessels are lined with smooth muscles with spindle-shaped cells.
For example, the muscles present in the subcutaneous layer of the skin of the face are responsible for various facial expressions. Contraction of these facial muscles brings about the movement of skin of the face to generate a wide variety of emotions. Smooth muscles of blood vessels are involuntary in nature.
Vasodilation and vasoconstriction as brought about by smooth muscles of blood vessels are regulated by the autonomic nervous system. Under the conditions of lower blood pressure, contraction of smooth muscles of blood vessels restore the reduced blood pressure. On the other hand, when the blood pressure rises above the normal range, the smooth muscles of blood vessels relax to dilate them and to lower down the blood pressure.