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By Y. Owen. Franklin W. Olin College of Engineering. 2017.

This Nearly all of the dietary nutrients and approximately 95 to mode of absorption order 25mg benadryl amex, called solvent drag, is responsible for 98% of the water and electrolytes that enter the upper small a significant amount of the Na absorption by the duode- 508 PART VII GASTROINTESTINAL PHYSIOLOGY Stomach most of the monosaccharides and amino acids have already Parietal cell been absorbed by the small intestine (Fig. Sodium chloride is transported via two exchangers located at the brush border membrane. The downhill move- Vitamin B12 ment of Na into the cell provides the energy required for the uphill movement of the H from the cell to the lumen. Similarly, the downhill movement of HCO3 out of the cell provides the energy for the uphill entry of Cl into the Intrinsic enterocytes. The Cl then leaves the cell through facili- factor Intrinsic factor/ tated transport. This mode of Na uptake is called vitamin B12 Na /H -Cl /HCO3 countertransport. There is no sugar- or amino acid–coupled Na transport because most Ileum Lumen sugars and amino acids have already been absorbed. Sodium is also absorbed here via Na -selective ion channels in the apical cell membrane (electrogenic Na absorption). Absorption takes place throughout the intestine by passive H+ + HCO - H CO CO + H O Blood Vitamin B released into blood 3 2 3 2 2 12 Cl- Transcobalamin/ Glucose, + Na+ + Na H Transcobalamin vitamin B amino 12 complex acids H2CO3 Cl- HCO - FIGURE 27. CO2 + H2O 3 Na+ Metabolism ATP K+ A num and jejunum, but it probably plays a minor role in Na absorption by the ileum and colon because more distal re- Blood gions of the intestine are lined by a “tight” epithelium (see Chapter 2). CO + H O H CO In the jejunum, Na is actively pumped out of the baso- 2 2 2 3 lateral surface of enterocytes by a Na /K -ATPase (Fig. The result is low intracellular Na concentration, and the luminal Na enters enterocytes down the electro- chemical gradient, providing energy for the extrusion of H into the lumen (via a Na /H exchanger). The H + + - - Cl- Na+ Na H HCO3 Cl then reacts with HCO3 in bile and pancreatic secretions in the intestinal lumen to form H2CO3. The CO2 readily diffuses H CO 2 3 across the small intestine into the blood. Another mode of Cl- Na uptake is via a carrier located in the enterocyte brush CO + H O 2 2 + + border membrane, which transports Na together with a Na Na monosaccharide (e. K+ K+ B In the ileum, the presence of a Na /K -ATPase at the basolateral membrane also creates a low intracellular Na Blood concentration, and luminal Na enters enterocytes down the electrochemical gradient.

However buy 25mg benadryl with visa, periods of inade- ture of the brainstem exhibits the most precise autoregula- quate blood flow to the heart muscle caused by experimental tion, with good but less precise regulation of blood flow in flow reduction do stimulate collateral enlargement in healthy the cerebral cortex. It is assumed that in humans with coronary vascular tory ability has clinical implications because the region of disease who develop functional collateral vessels, the mech- the brain most likely to suffer at low arterial pressure is the anism is related to occasional or even sustained periods of in- cortex, where consciousness will be lost long before the au- adequate blood flow. Whether or not routine exercise aids in tomatic cardiovascular and ventilatory regulatory functions the development of collaterals in healthy humans is debat- of the brainstem are compromised. However, there is no doubt that cal that causes cerebral autoregulation has not been possible. States will, at some time during their lifetimes, require Despite, the multiple treatments available to deal with ex- medical or surgical intervention because of atherosclero- isting coronary artery blockage, the ideal treatment is to avoid sis of the coronary arteries. Excessive intake of cholesterol-rich food, seden- rupture of the endothelial layer over an atherosclerotic tary lifestyles that tend to raise low-density lipoproteins (LDL) plaque, followed by a clot that occludes or nearly oc- and lower high-density lipoproteins (HDL), and obesity lead- cludes a coronary artery. About 10% of these incidents ing to insulin resistance are key problems leading to acceler- result in death before the patient reaches the hospital. Two of the three can be ad- For those who reach a coronary care facility, about 70% dressed with a lowered cholesterol and calorie-restricted diet will be alive 1 year later, and about 50% will be alive in 5 to promote loss of body fat. If the patient does not have a risk of bleeding, the approximately 30 minutes, 3 days a week, has consistently clot can be dissolved by administering tissue plasmino- been shown to lower LDL and raise HDL, as well as aid in body gen activator or streptokinase. Pharmacological blockade of cholesterol synthesis in restored within a few hours, the damage to the heart the liver with the statin family of compounds is effective to muscle can be minimal. In some cases, advancing a both prevent second heart attacks and lower the risk of a first catheter into the blocked artery to expand the vessel and heart attack. These drugs are so effective that in the near fu- remove the clot is the best approach. In a few cases, ture, most persons older than age 50 may be advised to follow emergency replacement of the blocked artery is required; a dietary and exercise plan complemented with statin therapy. However, increasing concentra- fore, some aspect of sympathetic nerve activity other than tions of any of these chemicals causes vasodilation and in- the routine regulation of vascular resistance is important for creased blood flow.

Hearing nosed hearing loss may speak too loudly by bone conduction is evaluated by plac- and may require increased volume to hear ing a vibrating tuning fork in different the television and radio generic 25 mg benadryl with amex. Both conductive viduals with suspected hearing loss to and sensorineural impairments can be de- obtain evaluation and treatment. Abnormal test re- resistance to these recommendations is sults warrant further testing and evaluation. When problems with hearing are iden- tified, referral for additional testing may be made. For further testing and evaluation, Physical Examination individuals may be referred to an audiol- ogist, a person with a master’s or doctoral Physicians may be the first to recognize degree in audiology who specializes in the or be consulted about a potential hearing evaluation and rehabilitation of individ- loss. If testing by for hearing loss should be part of every the audiologist reveals that medical inter- physical exam. Various check sheets and vention is necessary, referral is made to an questionnaires may be used initially to otolaryngologist (physician who special- elicit the signs and symptoms associated izes in diagnosis and treatment of condi- with hearing loss. Rudimentary auditory Audiometric testing measures the degree screening may also be performed in the of hearing loss with an electronic device physician’s office. An audiologist usual- Physicians sometimes use tuning forks in ly performs the test. Tests routinely used routine physical examinations in their by audiologists attempt to define three offices as an initial screening method for major aspects of hearing: hearing impairments. This method can help differentiate between conductive or • The degree of hearing sensorineural hearing loss; however, it • The type of hearing loss does not quantify the degree of impair- • The ability to understand speech ment, if one exists. Because of the gross under various conditions Diagnostic Procedures 153 PURE TONE AUDIOGRAM Frequency in Hertz (Hz) Weber L R L R L R L R L R 125 250 500 1000 2000 4000 8000 10 0 Normal Hearing 10 Sensitivity 20 30 40 50 60 70 80 90 100 110 Left Ear Right Ear Figure 5–2 Pure-Tone Audiogram. A complete audiometric evaluation usu- responses to calibrated tones are plotted as ally includes pure-tone air audiometry, bone thresholds. Numbers across the top of the conduction audiometry, speech audiometry, audiogram represent pure-tone frequen- and acoustic immittance measurement. The audiogram illustrates the degree of Pure-Tone Air Audiometry hearing loss.