By R. Hauke. Lake Forest Graduate School of Management.
The decreased range of motion subsequently leads to fixed joint contractures discount top avana 80mg otc sudden onset erectile dysfunction causes, even when there are no structural joint deformities order 80 mg top avana with mastercard erectile dysfunction at 20. Joint Motor Mechanics Often, the mechanics of a single joint are based on the specifics of the in- volved joint; however, the only active way to move a joint is by the muscle attached to that joint. These muscle–tendon units attach in the bone and work by creating a moment through a moment arm. An excellent example of this is the knee, where the hamstring muscles attach to the tibia by being posterior to the joint’s center of motion. A moment arm is created and a ten- sion force is applied to create a moment that may cause motion. The mo- ment created is called the strength of the hamstring in clinical scenarios (Figure 7. The amount of strength, or joint moment, that is created in- cludes the percent of the muscle’s contraction, the cross-sectional area of the muscle, the position of the muscle fiber length on the Blix curve, the direc- tion and velocity of the change in the muscle fiber, and the moment arm of the muscle. Another variable is muscle fiber configuration with the degree of pennation of the fibers to the line of action of the muscle. In the hamstring muscles, this variable is of no significance because of a very low pennation angle. Some of these variables can be actively altered, and others are struc- tural variables. The variables that can be actively altered are the percent of muscle firing, the moment arm length, the position on the Blix curve, and the velocity of length change. The variables with the structural characteristics that can change over time are the diameter of the muscle through muscle Figure 7. To understand the force-gener- ating ability of the muscle, it is very impor- tant to understand the concept of stable ver- sus changing moment arms. An example is the quadriceps, which has a relatively con- sistent moment arm length independent of the joint position. The hamstrings, on the other hand, have a moment arm that is very dependent on joint position with the moment arm being very short at knee extension and very long at full knee flexion. Thus, the im- pact of a hamstring contracture very quickly becomes more significant as the degree of knee flexion increases. Single-Joint Muscles From the perspective of the central program generator, muscle activation that crosses a single joint requires consideration of the impact of at least three variables, including the percent of motor units to activate, the current length of the fiber that will define the moment arm and the Blix curve location, and the velocity of muscle fiber shortening. The system also has to consider its longer-term organization caused by structural alterations. From the treatment perspective, the major alterations are made in the structural variable. A major element in the clinical assessment of children is trying to understand if these structural changes are positive to the function of the joint and the whole- body motor system or if this structural change is now part of the pathology of the impairment that is increasing the disability. The intellectual under- standing of muscles that cross single joints, such as the short head of the biceps femoris, is relatively easy. The force generated is easily modeled, lead- ing to a clear understanding of the effects; however, in children with CP, these single joint crossing muscles cause far fewer problems than the muscles that cross multiple joints. Multiple-Joint Muscles Multiple-joint muscles, such as the rectus femoris and the gastrocnemius, comprise most of the problematic muscles. With these muscles, it is ex- tremely hard to conceptualize a clear understanding of an individual muscle’s function at a specific time in the gait cycle of a child. For example, the long head of the biceps femoris crosses the hip and knee joints; therefore, the number of variables in the control algorithm more than doubles, because now the hip position and knee position have to be considered for each vari- able (Table 7. This complexity is relatively apparent, and it is easy to understand why control of these muscles is most problematic for the central program generators of children with CP. These multiple-joint muscles tend to function predominantly as energy transfer muscles and in deceleration; this means multiple-joint muscles are used predominantly in situations that require eccentric contraction. In approaching these muscles as a treating physician, an attempt needs to be made to understand as many of the vari- ables in the control scenario as possible. However, dynamic control theory seems to work better to understand the process. Factors that have to be controlled during a contraction of the semitendinosus compared with the vastus.
They are slowly excreted in the bile and feces cheap top avana 80 mg on-line zopiclone impotence, and (e 80 mg top avana visa erectile dysfunction 18 years old. The lowest dose effects are probably associated with thymic atrophy and decreased immune Suggested References response, chloracne and related skin lesions, and neoplasia (cancer). Dioxins can cross Nomenclature of chemical compounds. Most undergraduate organic textbooks provide a more detailed into the placenta to cause developmental account of the nomenclature used for organic molecules, including the R,S nomenclature for chiral and reproductive effects, decreased prenatal centers. Good literature reviews for many environmental toxins are published by the U. Department of Health and Human Services: Public Health Service Agency for Toxic Substances and Disease Registry, including: Toxicological Profile for Chlorinated Dibenzo-p-dioxins, 1998, and the Toxicological Profile for 4,4 -DDT, 4,4 -DDE, 4,4 -DDD (Update), 1994. REVIEW QUESTIONS—CHAPTER 5 Directions: Select the single best answer for each of the questions below. Base your answers on your knowledge of nomenclature. You need not recognize any of the structures shown to answer the questions. Which of the following is a universal characteristic of water-soluble organic compounds? CH OH–CH –CH –COO 2 2 2 A patient was admitted to the hospital emergency room in a coma. Laboratory tests found high levels of the compound shown above in her blood. On the basis of its structure (and your knowledge of the nomenclature of functional groups), you identify the compound as (A) methanol (wood alcohol). A patient was diagnosed with a deficiency of the lysosomal enzyme -glycosidase. The name of the deficient enzyme sug- gests that it hydrolyzes a glycosidic bond, which is a bond formed (A) through multiple hydrogen bonds between two sugar molecules. CHAPTER 5 / STRUCTURES OF THE MAJOR COMPOUNDS OF THE BODY 71 4. A patient was diagnosed with a hypertriglyceridemia. This condition is named for the high blood levels of lipids composed of (A) 3 fatty acyl groups attached to a glycerol backbone. A patient was diagnosed with a sphingolipidoses, which are congenital diseases involving the inability to degrade sphin- golipids. All sphingolipids have in common (A) a glycerol backbone. Genes are tran- scribed by enzymes called RNA polymerases that generate a single-stranded RNA identical in sequence (with the exception of U in place of T) to one of the strands of the double-stranded DNA. The DNA strand that directs the sequence of nucleotides in the RNA by complementary base-pairing is the template strand. The RNA strand that is initially generated is the primary transcript. The DNA template is copied in the 3 to 5 direction, and the RNA transcript is Other synthesized in the 5 to 3 direction. RNA polymerases differ from DNA poly- regulatory Coding sequences Promoter region merases in that they can initiate the synthesis of new strands in the absence of of gene a primer. Specific sequences on DNA, called promoters, determine where ment of DNA that functions as a unit to gener- the RNA polymerase binds and how frequently it initiates transcription. Other reg- ate an RNA product or, through the processes ulatory sequences, such as promoter-proximal elements and enhancers, also of transcription and translation, a polypeptide affect the frequency of transcription. The transcribed region of a gene con- In bacteria, a single RNA polymerase produces the primary transcript precur- tains the template for synthesis of an RNA, sors for all three major classes of RNA: messenger RNA (mRNA), ribosomal RNA which begins at the startpoint. Because bacteria do not contain nuclei, ribo- includes regions of DNA that regulate produc- tion of the encoded product, such as a pro- somes bind to mRNA as it is being transcribed, and protein synthesis occurs moter region.
The facilitative transporter most responsible for transporting fructose from the blood into cells is which of the following? An alcoholic patient developed a pancreatitis that affected his exocrine pancreatic function 80 mg top avana for sale erectile dysfunction age 36. He exhibited discomfort after eat- ing a high-carbohydrate meal order 80mg top avana with mastercard erectile dysfunction treatment comparison. The patient most likely had a reduced ability to digest which of the following? A type I diabetic neglects to take his insulin injections while on a weekend vacation. Cells of which tissue would be most greatly affected by this mistake? After digestion of a piece of cake that contains flour, milk, and sucrose as its primary ingredients, the major carbohydrate products entering the blood are which of the following? A patient has a genetic defect that causes intestinal epithelial cells to produce disaccharidases of much lower activity than nor- mal. Compared with a normal person, after eating a bowl of milk and oatmeal sweetened with table sugar, this patient will exhibit higher levels of which of the following? It is com- posed of glucosyl units linked by -1,4 glycosidic bonds, with -1,6 branches occurring roughly every 8 to 10 glucosyl units (Fig. The liver and skeletal muscle contain the largest glycogen stores. The formation of glycogen from glucose is an energy-requiring pathway that begins, like most of glucose metabolism, with the phosphorylation of glucose to glucose 6-phosphate. Glycogen synthesis from glucose 6-phosphate involves the formation of uridine diphosphate glucose (UDP-glucose) and the transfer of glu- cosyl units from UDP-glucose to the ends of the glycogen chains by the enzyme glycogen synthase. Once the chains reach approximately 11 glucosyl units, a branching enzyme moves six to eight units to form an (1,6) branch. Glycogen degradation is a phospho- rolysis reaction (breaking of a bond Glycogenolysis, the pathway for glycogen degradation, is not the reverse of the using a phosphate ion as a nucle- biosynthetic pathway. The degradative enzyme glycogen phosphorylase removes ophile). Enzymes that catalyze phosphorolysis glucosyl units one at a time from the ends of the glycogen chains, converting them reactions are named phosphorylase. Because to glucose 1-phosphate without resynthesizing UDP-glucose or UTP. A debranch- more than one type of phosphorylase exists, ing enzyme removes the glucosyl residues near each branchpoint. To generate glucose, the the enzyme, such as glycogen phosphorylase glucose 1-phosphate produced from glycogen degradation is converted to or purine nucleoside phosphorylase. Glycogen is composed of glucosyl units linked by -1,4-glycosidic bonds and -1,6-glycosidic bonds. The branches occur more frequently in the center of the molecule, and less frequently in the periphery. The anomeric car- bon that is not attached to another glucosyl residue (the reducing end) is attached to the protein glycogenin by a glycosidic bond. Glucose 6-phosphatase, an enzyme found only in liver and kidney, converts glucose 6-phosphate to free glucose, which then enters the blood. Glycogen synthesis and degradation are regulated in liver by hormonal changes that signal the need for blood glucose (see Chapter 26). The body main- tains fasting blood glucose levels at approximately 80 mg/dL to ensure that the brain and other tissues that are dependent on glucose for the generation of adeno- sine triphosphate (ATP) have a continuous supply. The lack of dietary glucose, signaled by a decrease of the insulin/glucagon ratio, activates liver glycogenoly- sis and inhibits glycogen synthesis. Epinephrine, which signals an increased uti- lization of blood glucose and other fuels for exercise or emergency situations, also activates liver glycogenolysis. The hormones that regulate liver glycogen metabo- lism work principally through changes in the phosphorylation state of glycogen synthase in the biosynthetic pathway and glycogen phosphorylase in the degrada- tive pathway.
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