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3. A patient suffering from hypertension may receive drugs that decrease the heart's output, dilate arterioles, or increase urine production. In each case, how would the drug treatment help relieve hypertension? Diane
Hypertension is elevated blood pressure, which can result from or is contributed to by many different factors. Essential or primary hypertension is commonly caused or exacerbated by poor dietary choices and/or a sedentary lifestyle which usually results in overweight. In its simplest terms, increase body mass means increased workload on the heart to get the blood where it needs to go. Secondary hypertension results from other health problems or medications, though lifestyle is still usually a contributing factor. Because high blood pressure contributes to stroke, heart attack or failure, and kidney failure among other problems (p177), doctors tend to try to get it under control as quickly as possible.
There are five basic types of medications for treating blood pressure: diuretics, beta blockers, ACE (angiotensin converting enzyme) inhibitors, angiotensin II receptor antagonists, and calcium channel blockers (www.healthsquare.com/hbp5.htm). Each medication acts differently within the body to help lower blood pressure, and some act than one way.
Medications that “decrease the heart’s output” generally fall into the classification of beta blockers (which block epinephrine and norepinephrine, and cause relaxation of smooth cardiac muscles), and some of the older calcium channel blockers (which block the entry of calcium into the heart muscles thereby slowing contractions). They actually decrease the force of heart’s contractions which in turn pumps less blood into the arteries. Lower volume of blood in the vessels reduces the pressure on them.
Medications that “dilate arterioles” are ACE (angiotensin converting enzyme) inhibitors, newer calcium channel blockers, ARBs (angiotensin-receptor blockers), direct-acting vasodilators. The kidneys secrete rennin which produces angiotensin I, which is then converted to angiotensin II which causes contraction of the muscles around the blood vessels and stimulates production of the hormone adrenal (which also raises blood pressure). The renin-angiotensin I-angiotensin II cycle is referred to as the RAA system. ACEs limits the body’s production of angiotensin II. ACE medications prevent angiotensin I from converting to angiotensin II; ARBs prevent the arterioles (small blood vessels) from receiving the angiotensin II) (http://www.medicinenet.com/script/main/art.asp?articlekey=18025 ). Calcium-channel blockers and the direct vasodilator hydralazine relax the smooth muscles in the arteries to prevent them from constricting (http://www.cvpharmacology.com/vasodilator/vasodilators.htm ). By preventing vascular constriction or by causing the blood vessels to expand, the blood can travel more freely through them which decreases blood pressure.
Diuretics “increase urine production” by increasing the kidney’s secretion of sodium and water which decreases the volume of fluid in the bloodstream and therefore pressure on the blood vessels. There is less for the heart to have to pump and the arteries to carry, which eases the blood pressure. The diuretic has been in use the longest of all the anti-hypertensive agents, and has the largest body of research behind it (www.cardiologychannel.com/hypertension/pharm.shtml ), including recent studies. “The latest findings stem from a landmark investigation based at the UT School of Public Health, which in 2002 established that diuretics were “as good or better” than three other classes of medications for high blood pressure during a multi-center, randomized, double-blind, clinical trial. The investigation is called ALLHAT - Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial” (http://www.sciencedaily.com/releases/2008/01/080128165704.htm ).
Before prescribing any hypertension medication, doctors consider all contributing lifestyle factors and any other health issues to ensure best results with fewest side effects. The long-term effectiveness of any anti-hypertensive medication is limited by lifestyle issues. Medications will treat the symptoms (high blood pressure) but not the varied causes (obesity, lack of exercise, underlying heart problems, diabetes, etc.), so changes in diet and exercise levels are critical to controlling high blood pressure.


9. When Jason runs his marathon, what energy sources are going to be readily available for his muscle contraction? Where will the muscles of his legs get their steady energy supply? Would it make sense for him to take nutrients during the marathon? Diane

Lots to talk about on this one, since it covers pretty much the scope of cellular metabolism. But the short answer: the most readily available sources of energy will be ATP stored in the muscle cells. Unfortunately, that supplies energy for only about ten seconds, so the cells must begin to produce ATP from other sources including creatine phosphate (creatine-P), glycogen, glucose, and fatty acids (p130). Creatine-P provides less than a minute’s burst of high-energy, and then for the next 3-5 minutes, the cells draw on their store of glycogen which can be broken down anaerobically. The glucose can be drawn out without oxygen (which produces lactic acid). Since oxygen is not required, this is why you don’t usually start to breathe heavily until a few minutes after you start exercising.
Once the cell’s stored glycogen has been anaerobically processed into glucose, the steady, long-term energy supply will come from aerobically catabolized glucose, fatty acids, and other high-energy molecules (p.130).
Here I had to dig for answers, starting with Wikipedia. After 18-22 miles, many runners hit “the wall” – a feeling of overwhelming fatigue (a feeling many college students can relate to after two days of studying without sleep in preparation for exams!). Marathoners work hard at conditioning the muscles to work most efficiently for the longest period of time, but “hitting the wall” is nearly because the body can only store a certain amount of glycogen. Once that is used up, the cells start to draw on stored fat which is not as efficient an energy source as glycogen. (Wikipedia, http://en.wikipedia.org/wiki/Marathon_(sport)#During_the_race )
My first guess is that intake of some nutrients help the body work more efficiently, depending on the type and amount of nutrients consumed. The Wikipedia page on marathon running indicates that replacing salt along with water helps avoid excessive dilution of sodium in the blood (hyponatremia, article in Science Daily here: http://www.sciencedaily.com/releases/2008/01/080109195002.htm ). Consuming high-concentrate carbohydrates with some potassium and sodium (anybody remember the sodium-potassium pump??) and sometimes caffeine, periodically throughout the race provides a quick energy source and helps minimize the impact of “hitting the wall.”
I found a really great article on “the wall” at Marathon & Beyond. If you’re interested in, it is at http://www.marathonandbeyond.com/choices/latta.htm and has a LOT of information presented in a very accessible fashion.