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 nice mix of carbs, proteins, and lipids. Just what your body needs! As you sit and replenish your energy 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.

2. Prior to taking a break, your body was losing water thru sweat. Describe how the kidneys would adjust their activities to reduce the loss of water thru urination, and reduce the potential for dehydration. Describe a regulatory mechanism that would explain how this adjustment would be made.

3.The nutrients in the power bar and the water are taken in thru the digestive tract to help meet your body's energy needs and help to keep you hydrated. Describe where in the digestive tract each of the nutrients is broken down into an absorbable form and where the nutrients and water are absorbed. Describe a hormonal regulatory mechanism that would help to make the digestion of these nutrients possible.

Explanation / Answer

Answer:

Describe how the kidneys would adjust their activities to reduce the loss of water thru urination, and reduce the potential for dehydration. Describe a regulatory mechanism that would explain how this adjustment would be made.

Sweat production is highly variable: low for sedentary people exposed to moderate temperature, it can reach several liters per day during intense physical activity, high ambient temperature, and/or high humidity. The body adapts sweat production to maintain body core temperature. Sweat is produced in the dermis by sweat glands. It comes from interstitial water and is filtered deep in the sweat gland tubule before being reabsorbed distally. Sweat is usually 99% water, with a pH between 5 and 7. It contains approximately 0.5% of minerals (potassium and sodium chloride) and 0.5% of organic substances (urea, lactic acid). As seen previously, the kidneys have the ability to widely adapt the quantity of excreted water, while maintaining stable solute excretion. Depending on body hydration state and fluid intake, metabolic waste is therefore excreted in a more or less concentrated urine.

The excretion of water by the kidney is indeed regulated to maintain a constant composition and concentration of extracellular fluids and in particular a constant plasma osmolarity. This is made possible thanks to a feedback system based on the anti-diuretic hormone (ADH) or vasopressin.

In the case of water deficit, osmolality of the extracellular fluids, in particular of plasma, increases above its normal value (about 280 mOsmol/kg H2O). This increase, which in practice means an increase in plasma sodium concentration, is detected by osmoreceptors that stimulate the release of ADH. ADH is synthetized in the hypothalamus and stored in the posterior pituitary gland. Once ADH released, it is transported via the blood to the kidneys, where it increases the permeability of the distal tubules and collecting ducts to water. The increased water permeability causes increased water reabsorption and excretion of a small volume of concentrated urine. Water is therefore conserved in the body, while sodium and other solutes continue to be excreted. This causes the dilution of the extracellular fluids and therefore corrects the plasma osmolality.

The maintenance of body water balance therefore depends on different physiological processes: the renal regulation, thirst and drinking behavior, but also sweating. The relative importance of those physiological processes and their interactions depend upon the prevailing activities

Describe where in the digestive tract each of the nutrients is broken down into an absorbable form and where the nutrients and water are absorbed.

Digestive enzymes are enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption by the body. Digestive enzymes are found in the digestive tracts of animals. Digestive enzymes are diverse and are found in the saliva secreted by the salivary glands, in the stomach secreted by cells lining the stomach, in the pancreatic juice secreted by pancreatic exocrine cells and in the intestinal (small and large) secretions, or as part of the lining of the gastrointestinal tract.

In the mouth, carbohydrates are broken down by amylase into maltose (a disaccharide) and then move down the esophagus, which produces mucus for lubrication, but no digestive enzymes. Then the in duodenum, disaccharides are broken down into monosaccharides by enzymes called maltases, sucrases, and lactases, the monosaccharides produced are then absorbed into the bloodstream and transported to cells to be used in metabolic pathways to harness energy.

In the stomach, proteins are broken down into peptides, which are then broken down into single amino acids that are absorbed in the bloodstream though the small intestine. Lipids are digested mainly in the small intestine by bile salts through the process of emulsification, which allows lipases to divide lipids into fatty acids and monoglycerides. The monoglycerides and fatty acids enter absorptive cells in the small intestine through micelles; they leave micelles and recombine into chylomicrons, which then enter the bloodstream. Fat-soluble vitamins are absorbed in the same manner as lipids; water-soluble vitamins can be directly absorbed into the bloodstream from the intestine.

Describe a hormonal regulatory mechanism that would help to make the digestion of these nutrients possible

Hormones are chemical substances produced by endocrine cells. Once released, the hormone enters the bloodstream and is transported to its specific site of action. Once the target cell has been stimulated, it responds in a variety of different ways such as producing new proteins, activating or deactivating enzymes within the cell or allowing the passage of substances into or out of the cell.

Gut hormones: The gut hormones work in association with the gut’s extensive nervous system (enteric nervous system) and play a co-ordinating role in the control of appetite, the digestion of food, the regulation of energy balance and the maintenance of blood glucose levels. The gut continuously sends information to the brain regarding the quality and quantity of the food that is consumed.

The role that some of these hormones play in digestive system is described below

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