rifts between eastern us and western africa
Answer:
false
Explanation:
individuals from different populations can be genetically more similar than individuals from the same population.
Answer:
Because the English measurement system has been in use for a very long time, it will be costly and time consuming to change from the English to SI units. Many technological measurements, products, and tools were developed in English units.
The cost of converting all measurements to SI units will be costly and will require a long period of time. Conversions between the English and the SI system of units appear to be more cost-effective than hardware changes.
Example:
It will be costly to convert designs for bridges, tunnels, locomotives, automobiles, and other hardware to the SI system. Although new designs are being performed in SI units, much useful hardware based on English units still remain.
Eventually, it is likely that complete conversion from English to SI units will happen, albeit slowly.
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.
