By J. Narkam. New School University. 2017.
Normal range of operation Total force Active force (systolic) Resting force (diastolic) Muscle length FIGURE 10 cheap viagra sublingual 100 mg with mastercard. The limit to force is provided by the afterload; the limit to lated cardiac muscle. A, isometric contraction physiologically significant lengths includes a resting force com- phase; B, isotonic shortening phase; C, isometric relaxation ponent. Because the mus- and, thus, interacts with the particular afterload chosen. It is important to real- In physical terms, the area enclosed by this pathway rep- ize that during isotonic shortening, the muscle force is lim- resents work done by the muscle on the external load. If the ited by the magnitude of the afterload and not by the afterload or the starting length (or both) is changed, then a length-tension capability of the muscle. The area shortening at a given afterload that is limited by the length- enclosed will differ with changes in the conditions of con- tension property of the muscle; this is a very important con- traction, reflecting differing amounts of external work de- sideration when measuring cardiac performance under con- livered to the load. In a typical skeletal muscle contraction, ditions of changing blood pressure and filling of the heart as shown in Fig. Such a contraction does no net external ior is the key to autoregulation (self-regulation) by cardiac work, and no area is enclosed by the pathway. Each case in Figure length at rest, the active contraction results in a greater 10. This allows the heart to adjust Cardiac muscle contraction cycle Long starting length 4 High load 3 B 2 C A 1 D 0 Skeletal muscle contraction cycle Low afterload 2 3 4 5 Muscle length 4 4 4 Short Long 3 3 3 Afterload B 2 B 2 B 2 C C A C A D A 1 1 1 D D 0 0 0 2 3 4 5 2 3 4 5 2 3 4 5 Muscle length Muscle length Muscle length FIGURE 10. Left: Cardiac muscle contraction amount of shortening possible, as does decreasing the starting cycles. The horizontal box shows the effect of starting at two dif- length; in both cases, the limit to shortening is determined by the ferent initial lengths at the same afterload. Right: The contraction cycle of skeletal the effect of two different afterloads on shortening that begins at muscle. CHAPTER 10 Cardiac Muscle 183 its pumping to exactly the amount required to keep the cir- particular afterload is chosen (in this case, 0. Again there is a dif- Under a wide range of conditions, the contractile behavior ference in shortening velocity at a constant afterload, but of skeletal muscle is fixed and repeatable.
Personality disorders describe disorders characterized by inﬂexible or maladaptive Factitious Disorders behaviors that have usually lasted a long time and that impair interpersonal or Although not severely disabling buy 100 mg viagra sublingual otc, a vari- occupational functioning or cause subjec- ety of other types of mental disorders may tive distress (American Psychiatric Asso- interfere with effective functioning. They may assume the sick role (American Psychiatric rationalize their actions, blaming others Association, 2000). A factitious disorder for their situation or misfortune without differs from malingering (in which indi- examining their own responsibility for the viduals also produce symptoms intention- situation at hand. When a personality disorder exists in combination with other mental Dissociative Disorders disorders, the prognosis is more guarded, and treatment and management of the Conditions in which individuals expe- personality disorder are more difﬁcult. At rience an alteration in memory, conscious- times, these individuals may not have a ness, or identity for no organic reason are full-blown personality disorder but rather called dissociative disorders. Dissociative maladaptive personality traits that may fugue is a condition in which individuals interfere with the treatment or diagnosis leave their environment and assume a of the concomitant disorder. The diagnosis of mental conditions is The most commonly used intelligence often an art as well as a science. It requires tests are the Wechsler Intelligence Scale for skill and experience on the part of those Children-Revised, the Wechsler Preschool evaluating individuals’ symptoms and and Primary Scale of Intelligence, the interpreting the results of the various tests Stanford-Binet, and the Wechsler Adult designed to measure psychological or intel- Intelligence Scale-Revised. Many professionals may The limitations of intelligence testing be involved in testing and evaluation; psy- originate from: chiatrists and clinical psychologists are fre- • the difﬁculty of tapping all aspects of quently involved in the diagnosis of intellectual ability mental disorders. Diagnosis is usually • the individual’s ability to take the test based on information from a variety of dif- • the degree to which the test measures ferent sources. There is considerable individual can be obtained through psychological variability in abilities, however, and results testing. Psychological tests may be used to of intelligence tests, like results of other evaluate intelligence, personality, or forms of psychological tests, must be eval- behavior.