You are hiking in the mountains on a warm summer day. As you are walking up a st

Question

You are hiking in the mountains on a warm summer day. As you are walking up a steep incline, your leg muscles are working pretty hard. They need to produce a lot more ATP than usual in order to propel you upward. Your breathing becomes deeper and more rapid as you work to bring in more air. You also notice that you are getting warm and starting to sweat. You have water with you and decide to stop for a water and snack break. Your snack consists of a power bar that contains a good mix of carbs, proteins, and lipids - just what your body needs! As you sit and replenish your nutrients and water, you marvel at the beauty of your surrounds and feel a sense of appreciation that your body is healthy and able to adjust its activities to meet your ongoing needs. Answer the following questions based on this scenario:

2. Prior to taking a break, your body was losing water thru sweat.

a. Describe how the kidneys would adjust their activities to reduce the loss of water thru urination, and reduce the potential for dehydration.

b. Describe a regulatory mechanism that would explain how this adjustment would be made.

c. What would happen to blood volume and osmolarity if the kidneys couldn't conserve water when sweating increases and how would that affect cell volume and function?

Make sure to include detail about the anatomical structures involved to provide a thorough picture of the processes taking place and complete pathways for the regulatory mechanisms (i.e. the trigger for the pathway, the control center, the efferent pathway, and the effector/effector response)!!

Explanation / Answer

2. (a) Kidneys are designed in such a way that can regulate the water level in the body. During hiking our body requires more amount of water and the chances of dehydration are more. In such cases the kidneys decrease the amount of water released in the form of urine by making the urine more concentrated. This is done in order to preserve water in the body. Also, the quantity of urine decreases. Not only that the kidneys even increase the amount of reabsorption of water into the bloodstream.

(b) During a situation of dehydration the blood volume decreases and the blood osmolarity increases(Trigger). This activates the Osmoreceptors in the Hypothalamus which activates the thirst center in the hypothalamus and we get a thirsty feeling. If water is not taken then the Hypothalamus which acts as the Control Center releases Anti Diuretic Hormone(ADH) or Vasopressin. This ADH plays a critical role in the amount of water reabsorbed from the collecting ducts and tubules. ADH firstly reduces the blood flow to the more distant extremities of the body and increases the flow to the core of the body. This is done by constricting the arterioles. Next and the more important function of ADH is to insert Aquaporins into the cell membrane. This increases the water permeability of the cells and more water is passed which leads to more reabsorption of water in the bloodstream. The Kidneys act as effectors.

(c) If kidneys couldn't conserve water when sweating increases then the Hypothalamus releases Anti Diuretic Hormone(ADH) which decreases the plasma volume and the blood vlume also decreases. Osmolarity of the blood increases due to high concentration of plasma in the blood. Cell volume will decrease and the overall function of the kidneys will be hampered and long duration of such a situation may even lead to kidney stone.

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