Name ____________________________

Water Balance – 50 Informal PointsIntroduction

Bill’s friends throw a summer picnic to celebrate his 40th birthday. Bill spends the day playing touch football and chasing around after his kids. It’s almost 100°F outside and he is doing what he can to stay cool. Cold beer seems to work so he drinks many over the course of the day. Other than running to the bathroom all afternoon, Bill feels fine. But the next morning when he wakes up, he feels awful. He’s nauseous, dizzy and wishing he had stuck to water at the party. He wonders what is causing this horrific hangover.

Water balance is key to human survival. If you have ever competed in a vigorous athletic event or have been out in the heat for too long a time, you have probably experienced the signs and symptoms of dehydration. You become weak, nauseous, and may even pass out. Your body’s urinary system is designed to help you conserve water, but if no new water is coming in and your body is losing water through exercise or sweat, a balance cannot be maintained. The volume of urine that we excrete is a reflection of how much fluid and salt our bodies have to spare. Your body will give you warning signs, but sometimes they come a bit too late!

Like most processes in the body, water balance is regulated by hormones. These chemical messengers help control how much water is retained or removed from the body. In fact, your endocrine system, your nervous system, and your urinary system work together to signal thirst and to effectively manage a water shortage. In this activity, you will explore how the body monitors water levels and calls the kidneys into action. Your job is to help Bill understand how the events of the day affected his ability to maintain homeostasis. Why is poor Bill feeling so bad? What has happened to the water balance in his body? How does this lack of water link to his symptoms and how can he find some relief? Explore the feedback loops in the body that work to keep a water balance and investigate how substances such as alcohol can directly affect the release of hormones.

Procedure1. Research the area of the brain that senses and controls thirst. The sensation of thirst and your body’s

ability to maintain a proper water balance are controlled by communication between the nervous system, the endocrine system and the urinary system.

Area of brain that controls thirst: ______________________________

2. Review effects of vasopressin (antidiuretic hormone (ADH)) on water balance in the blood by the monitoring of blood pressure. Use the figure below to help write a 2-3 paragraph essay describing how the renin-angiotensin feedback loop raises blood pressure when it is too low. You may either type this or hand write it on separate paper.

3. Use the figure and your essay to help create a negative feedback loop that shows how your body uses ADH to maintain a water balance.

o Start by thinking about how the brain detects high or low levels of sodium or water in the blood.

o Your feedback loop descriptions should include the following words: thirst, ADH, hypothalamus, neuron, pituitary gland, nephron, kidney, urine, reabsorption, osmoreceptors.

o Your feedback loop should show the involvement of the nervous system, the endocrine system and the urinary system in restoring a water balance. Make sure to reference key regions in the brain, specific glands and their target organs as well as indicate how the nephron is affected.

o You may need to do a bit of additional research to include all the necessary key terms and fully understand the physiology.

o Create your feedback loop a Body system organizer to show where each step is taking place in the body.

4. Continue to research the effects of alcohol on ADH and your body’s water balance and answer the following questions about Bill.

Why did Bill keep running to the bathroom?

Alcohol is a diuretic. Alcohol also reduces the production of a hormone called vasopressin, which tells your kidneys to reabsorb water rather than flush it out through the bladder. With the body's natural signal switched off, the bladder is free to fill up with fluid.

What is happening to his body since he is producing so much urine?

Bill is becoming increasingly dehydrated.

How are changed in the ADH hormone linked to Bill’s symptoms?

Alcohol also reduces the production of a hormone called vasopressin, also known as ADH (anti-diuretic hormone), which tells your kidneys to reabsorb water rather

than flush it out through the bladder. With the body's natural signal switched off, the bladder is free to fill up with fluid.

5. Note that another hormone, aldosterone, helps maintain a water balance. However, the way in which this hormone works differs from the mechanism of ADH. Research the way in which aldosterone affects the nephron. Make sure to reference the effect of aldosterone on electrolytes and note the gland that is responsible for the release of the hormone. Describe in the space below:

Aldosterone also causes water to be reabsorbed along with sodium; this increases blood volume and therefore blood pressure. Thus, aldosterone indirectly regulates blood levels of electrolytes (sodium, potassium and hydrogen) and helps to maintain the blood pH.

6. In the space below, create a Venn diagram that compares and contrasts the action of the two hormones ADH and aldosterone.

7. Return to your Maniken® and use clay to create an adrenal gland. Use images you find on the Internet to help you locate this gland and design and build a replica. Find the pituitary gland you built earlier in the year. Both of these glands help maintain the body’s water balance.

8. Use the Internet to research answers to the questions listed below.

o The kidneys themselves also serve as an endocrine gland. What hormones are produced by the kidney and what function do they serve? What other human body system do these hormones regulate?

Hormones that are produced by the kidney are Erythropoietin, which is the vital hormone forthe production of red blood cells (regulate cardiovascular system), Calcitriol, which is vital for calcium homeostasis (regulate Skeletal system), and acts to raise plasma calcium levels, and Renin, which forms a vital part in the renin-angiotensin-aldosterone system, a complex system of hormones and enzymes which raise blood pressure when stimulated by hypotension.

o Describe the role of at least two other organs or structures that help the body deal with an influx of alcohol.

The liver metabolizes the alcohol using an enzyme known as alcohol dehydrogenase to break down the alcohol into acetate, where it is further broken down into carbon dioxide and water.The kidney handles the excess, diluted urine caused by the diuretic effect of alcohol.

Conclusion Questions1. Would blood ADH levels be higher or lower than normal in a person who just completed a three mile run

without drinking any water? Explain.

The blood level of ADH would be higher than normal after a 5km run, due to loss of body water in sweat, since ADH is anti-diuretic and the person is trying to conserve as much water as possible.

2. Is the ADH feedback loop an example of positive or negative feedback? Explain.

Negative because the opposite is attempting to happen. ADH is attempting to conserve water to increase blood volume and raise blood pressure when the blood pressure is too low. Hypotension is currently in place, so blood pressure is trying to increase.

3. How did the events of Bill’s day impact his body’s ability to conserve and balance water?

Bill became dehydrated because ADH (vasopressin) was suppressed by the alcohol, causing his homeostasis to become out of whack since he was releasing more water than he should have, causing him to become increasingly dehydrated.

4. Explain the role of sweating in the body. What effect did sweating have on Bill’s water balance?

Sweating causes a person to lose water and salt, causing them to become dehydrated if they are not taking in enough water and salt to make up for this loss. This also contributed to Bill’s dehydration and subsequent hangover.

5. How could Bill have prevented his horrible hangover? Explain.

Limited the amount of alcohol he drank; drink water instead of alcohol or at least switch between alcohol and water

Not ran around so much so that there would have been less sweating

Drink Gatorade to replenish both water and electrolytes

Find cooler shelter reduce sweating

6. Diuretics are often prescribed to treat high blood pressure. Given the name of the class of drug, how do you think diuretics affect the kidney, the fluid and electrolyte balance in the body and overall blood pressure?

Diuretics cause the kidneys to remove more sodium and water from the body, which helps to relax the blood vessel walls, thereby lowering blood pressure.

7. Explain how drinking too much water can throw off the electrolyte balance in your blood. How does this imbalance specifically affect the nervous system and the muscular system? Hint: Think back to what happens at the plasma membrane for a nervous signal to be communicated and to the ions that are required for muscle contraction.

This is EXTERMELY rare:Water intoxication is the extreme result of a bodily imbalance between electrolytes (the minerals in your blood and body fluid that carry an electric charge) and water, a condition called "hyponatremia." Chemically speaking, an electrolyte is any substance that ionizes, i.e. gains or loses an electron or electrons, when dissolved in a solvent like water. A classic example is table salt, chemical formula NaCl, which dissociates into a positively charge sodium ions and negatively charged chloride ions when dissolved in water.In severe cases of hyponatremia, the kidneys – which help, among other things, to regulate water and electrolyte levels in the body – become overwhelmed. At rest, under normal conditions, your kidneys are a supremely efficient filtration system.Consume water at a faster rate than the kidneys can process it, however, and the excess is driven by osmosis to regions of the body with high electrolyte concentration, beginning with the blood and eventually seeping into the salt-rich interiors of cells throughout the body. The cellular influx of water is manifest as swelling known as edema; the cells of your body become turgid, ballooning and distending with their newly acquired water weight.

8. Explain how a shortage of water affects the health of your cells. Make sure to use words such as osmosis, hypertonic solution, hypotonic solution, or isotonic solution in your answer.

Cell size responds to tonicity. Osmosis is the passive movement of water across a cell membrane.

When body cells are in isotonic solutions the net movement of water is zero, creating a healthy, stable cell. This means the amount of water moving into the cell matches that of the amount of water moving out of the cell.

When body cells are in hypertonic solutions the net movement of water is out of the cell, causing it to shrink and shrivel. This is bad because the internal components of the cell will not have enough water to function properly. This can be reversed and typically is not as harmful as hypotonic solutions.

When body cells are in hypotonic solutions the net movement of water is into the cell, causing it to expand. This could be deadly if it happens to swell so large that it bursts.