By Y. Hjalte. North Central College.
The result is that Ann O’Rexia’s admission laboratory the concentration of ketone bodies rises in the blood (Fig buy 100mg modafinil with visa. The brain begins to studies showed a blood glucose take up these ketone bodies from the blood and to oxidize them for energy order modafinil 100 mg with amex. There- level of 65 mg/dL (normal fasting blood glucose 80 100 mg/dL). Her serum ketone body concentration was Glucose is still required, however, as an energy source for red blood cells, and 4,200 M (normal ~70 M). The Ketostix the brain continues to use a limited amount of glucose, which it oxidizes for energy (Bayer Diagnostics, Mishawaha, IN) urine test and uses as a source of carbon for the synthesis of neurotransmitters. Overall, how- was moderately positive, indicating that ever, glucose is “spared” (conserved). Less glucose is used by the body, and, there- ketone bodies were present in the urine. In her fore, the liver needs to produce less glucose per hour during prolonged fasting than starved state, ketone body use by her brain is during shorter periods of fasting. The amino acid pool, produced by the 5 90 breakdown of protein, continues to serve as a major source of carbon for gluconeo- 4 Glucose 70 genesis. A fraction of this amino acid pool is also being used for biosynthetic func- 3 50 tions (e. However, as a result of the decreased bodies 4 rate of gluconeogenesis during prolonged fasting, protein is “spared”; less protein 3 is degraded to supply amino acids for gluconeogenesis. Consequently, because glucose 0 2 4 6 8 production decreases during prolonged fasting compared with early fasting, urea Days of starvation production also decreases (Fig. Role of Adipose Tissue During Prolonged Fasting in the blood during prolonged fasting. During prolonged fasting, adipose tissue continues to break down its triacylglycerol Death by starvation occurs with stores, providing fatty acids and glycerol to the blood.
Varicose veins—swelling and loss of function in super- d cheap modafinil 100 mg mastercard. Breathing—changes in pressure move blood toward ficial veins generic modafinil 100mg visa, usually in legs and rectum (hemorrhoids) heart Questions for Study and Review Building Understanding Fill in the blanks 1. Capillaries receive blood from vessels called . The specific part of the brain that regulates blood pres- 5. The flow of blood into an individual capillary is regu- lated by a(n) . How does the structure of the blood vessels correlate b. Trace a drop of blood from the left ventricle to the: d. Trace a drop of blood from capillaries in the wall of 13. The main process by which substances move the small intestine to the right atrium. What is the pur- between the cells and the capillary blood is pose of going through the liver on this trip? What physiological factors influence blood pressure? Describe three mechanisms that promote the return c. What are some symptoms of arteriosclerosis and how 14. The stomach, spleen, and liver receive blood via are these produced?
Hepatic Pancreas It is only through and between the cells portal vein of these thin-walled vessels that the Superior necessary exchanges can occur cheap 100 mg modafinil overnight delivery. Looking again at Figure 15-11 modafinil 200 mg on line, one can see how this fluid serves as “middleman” between the capillary membrane and the neigh- boring cells. As water, oxygen, and other necessary cellular materials pass through the capillary walls, they enter the tissue fluid. Then, these substances Descending make their way by diffusion to the colon Ascending cells. At the same time, carbon dioxide colon and other end products of metabolism Small leave the cells and move in the oppo- intestine site direction. These substances enter 15 the capillaries and are carried away in Figure 15-10 Hepatic portal system. Veins from the abdominal organs carry blood to the hepatic portal vein leading to the liver. Diffusion does not require transporters or The purpose of the hepatic portal system is to trans- cellular energy. For example, when food is digested, most of the blood into the tissues is the pressure of the blood as it end products are absorbed from the small intestine into flows through the capillaries. Blood pressure is the force the bloodstream and transported to the liver by the portal that filters, or “pushes” water and dissolved materials out system. In the liver, these nutrients are processed, stored, of the capillary into the tissue fluid. Fluid is drawn back and released as needed into the general circulation. Os- Checkpoint 15-12 The hepatic portal system takes blood from motic pressure is maintained by plasma proteins (mainly the abdominal organs to what organ? These processes result in the constant exchange of fluids across the capillary wall. The movement of blood through the capillaries is rel- ◗ The Physiology of Circulation atively slow, owing to the much larger cross-sectional Circulating blood might be compared to a train that trav- area of the capillaries compared with that of the vessels els around the country, picking up and delivering passen- from which they branch.
Interorgan Flux of Amino Acids in the part order 100mg modafinil amex, changes in the rate of protein synthesis Postabsorptive State and degradation take place over a span of hours purchase 200mg modafinil free shipping. The fasting state provides an example of the interorgan flux of amino acids neces- sary to maintain the free amino acid pool in the blood and supply tissues with their What changes in hormone levels required amino acids (Fig. During an overnight fast, protein synthesis in the and fuel metabolism occur during liver and other tissues continues, but at a diminished rate compared with the an overnight fast? Gluco- 1 3 4 and other functional nitrogen corticoid levels also increase in the blood. Fatty acids are released from adipose metabolites triacylglycerols and are used as the major 5 ATP 7 fuel by heart, skeletal muscle, liver, and 6 Urea N 2 ATP other tissues. The liver converts some of the (urine) fatty acids to ketone bodies. Liver glycogen stores are diminished and gluconeogenesis 8 Glucose Glycogen NH+ Lipid becomes the major support of blood glucose 4 levels for glucose-dependent tissues. The Dietary major precursors of gluconeogenesis glucose include amino acids released from skeletal muscle, lactate, and glycerol. Dietary protein (1) and degradation of endogenous protein (2) provide a source of essential amino acids (those that cannot be syn- thesized in the human). The synthesis of new protein is the major use of amino acids from the free amino acid pool. Compounds synthesized from amino acid precursors are essential for physiologic functions. Many of these compounds are degraded to N-containing urinary metabolites and do not return to the free amino acid pool. In tissues, the nitrogen is removed from amino acids by transamination and deamination reactions. The nitrogen from amino acid degradation appears in the urine primarily as urea or NH , the ammonium ion. Ammo- 4 nia excretion is necessary to maintain the pH of the blood.
PEROXISOMAL OXIDATION OF VERY-LONG-CHAIN FATTY ACIDS do not contain polyunsaturated fatty acids that can be used for synthesis of eicosanoids Peroxisomes are present in greater number in the liver than in other tissues cheap modafinil 100mg overnight delivery. Peroxisomes also contain catalase and are capable of detoxifying hydrogen peroxide cheap 200 mg modafinil. Very-long-chain fatty acids of C20 to C26 or greater are activated to CoA deriv- atives by very-long-chain acyl CoA synthetase present in the peroxisomal mem- brane. The very-long-chain acyl CoA derivatives are then oxidized in liver peroxi- somes to the 8-carbon octanoyl CoA level. In contrast to mitochondrial -oxidation, the first enzyme in peroxisomal -oxidation introduces a double bond and gener- ates hydrogen peroxide instead of FAD(2H). The remainder of the cycle, however, remains the same, releasing NADH and acetyl CoA. Peroxisomal catalase inacti- vates the hydrogen peroxide, and the acetyl CoA can be used in biosynthetic path- ways such as those of cholesterol and dolichol synthesis. The octanoyl CoA that is the end-product of peroxisomal oxidation leaves the peroxisomes and the octanoyl group is transferred through the inner mitochondrial membrane by medium-chain-length acylcarnitine transferase. In the mitochondria, it enters the regular -oxidation pathway, beginning with medium-chain-length acyl CoA dehydrogenase (MCAD). Zellweger’s (cerebrohepatorenal) syndrome occurs in individuals 3. PEROXISOME PROLIFERATOR ACTIVATED RECEPTORS with a rare inherited absence of peroxisomes in all tissues. Patients accumu- The peroxisome proliferator activated receptors (PPAR) play an important role in late C26-C38 polyenoic acids in brain tissue liver metabolism. These receptors obtained their name from the finding that certain owing to defective peroxisomal oxidation of agonists were able to induce the proliferation of peroxisomes in liver. These ago- the very-long-chain fatty acids synthesized nists included hypolipidemic agents, nonsteroidal anti-inflammatory agents, and in the brain for myelin formation. The receptors that bind these agents, the PPAR, are members bile acid and ether lipid synthesis are of a nuclear receptor family and, when activated, stimulate new gene transcription. Fatty acids are an endogenous ligand for PPAR , such that when the level of fatty acids in the circulation is increased (with a concurrent increase in the fatty acid content of hepatocytes), there is increased gene transcrip- tion for those proteins involved in regulating fatty acid metabolism (Table 46.