Nt1310 Unit 4 Assignment

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Please answer these questions using a computer program for the text, and use a spellchecker- I often have trouble reading handwriting. Images can be easily scanned or created in powerpoint.
Question 1 (25 points): Draw (and explain) a scheme where water is moved (transcellularly) from the interstitial compartment to the luminal compartment with chloride as the key osmolite and using NKCC1 and KCC2. Include other transporters or ion channels that may also be necessary to support chloride movement. Through Na/K pumps on the basolateral membrane, the Na gradient would be inwardly directed- driving the uptake of chloride by NKCC1 transporters on the basolateral membrane. Chloride would be pumped into the lumen via KCC2 and expression of conductance
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In class, we discussed the relationships of length-tension of muscle as well as the differences between fast twitch and slow twitch muscle fibers. All of the above has been combined to produce the following points:
• Generally speaking, in skeletal muscle the tension generated is a function of the magnitude of overlap between actin and myosin myofilaments. In individual muscle fibers, the amount of tension created depends on the cross-bridges formed. This is influenced by the frequency neural stimulation. The amount of force created by this tension varies. This gives muscles the ability to move both light objects and heavy objects.
• Energy is required for muscle contraction to occur. When ATP is cleaved, it activates the myosin head which can then easily bind and form a cross bridge to actin (shortening the sarcomere). Once bound, ADP is released pulling the actin filament over myosin. In order for the cycle and muscle contraction to continue, ATP is required. If the amount of ATP available is reduced or not properly replenished, this can and likely will effect then tension