By K. Ugo. The Richard Stockton College of New Jersey.
This arrangement provides for setting the length of because the force exerted by the muscle exactly matches the muscle and tracing a record of force versus time generic sominex 25 mg on-line. In a that of the weight trusted sominex 25 mg, and the mass of the weight does not twitch, isometric force develops relatively rapidly, and sub- vary. The dura- line representing constant force, while the muscle length tions of both contraction time and relaxation time are re- (lower tracing) is free to change. As relaxation begins lated to the rate at which calcium ions can be delivered to (phase 3), the muscle lengthens at constant force because it and removed from the region of the crossbridges, the actual is still supporting the load; this phase of relaxation is iso- sites of force development. During an isometric contrac- tonic, and the muscle is reextended by the weight. When tion, no actual physical work is done on the external envi- the muscle has been extended sufficiently to return to its ronment because no movement takes place while the force original length, conditions again become isometric (phase is developed. The muscle, however, still consumes energy 4), and the remaining force in the muscle declines as it to fuel the processes that generate and maintain force. In almost all situations encountered in daily life, isotonic contraction is preceded Isotonic Contraction. When conditions are arranged so by isometric force development; such contractions are the muscle can shorten and exert a constant force while do- called mixed contractions (isometric-isotonic-isometric). In the simplest conditions, this constant force is traction varies, depending on the afterload. At low after- CHAPTER 9 Skeletal Muscle and Smooth Muscle 159 Isometric twitch Rise of isometric Force force transducer 3 Isometric relaxation Muscle 2 1 4 1 Force is constant during isotonic phases 0 Stimulator Stimulus Isotonic Isotonic shortening relaxation 5 2 3 6 Length is constant during isometric 7 phases Weight 8 Contraction Relaxation 0. The pen at during the final relaxation, conditions are again isometric because the lower end of the muscle marks its length, and the weight at- the muscle no longer lifts the weight. The dotted lines in the force tached to the muscle provides the afterload, while the platform and length traces show the isometric twitch that would have re- beneath the weight prevents the muscle from being overstretched sulted if the force had been too large (greater than 3 units) for the at rest. The first part of the contraction, until sufficient force has muscle to lift.
Genomics cheap 25 mg sominex visa, genes trusted sominex 25mg, and environ- Immediately after rehabilitation begins, diabetes mental interaction: the role of exercise. Clin Sports Med during contraction at a fixed force increase only if endogenous or 2000;19:273–286. J Appl Physiol cells are required to perform the same insulin-independent glucose uptake 2001;90:2166–2171. Exer- (D) Oxidative energy-producing is reduced in active muscles cise training in coronary artery disease systems are up-regulated 16. N Engl J Med in the top five of her statewide high the following is a predictable effect of 2000;343:632–641. Role of exercise in preventing Encouraged, she redoubles her training pregnancy? Rheum Dis intensity, only to find that her (A) Increased average gestational Clin North Am 2001;27:131–141. After finally visiting her doctor, (B) Increased fetal weight at term and the immune system: regulation, in- her serum estrogen levels are found to (C) Decreased risk of maternal tegration, and adaptation. Potential benefits (A) Dynamic exercise endurance less (E) Decreased neonatal responsiveness and hazards of physical activity and ex- than an untrained person scores ercise on the gastrointestinal tract. CASE STUDIES FOR PART VIII • • • appears dazed, and his answers to questions are coherent CASE STUDY FOR CHAPTER 29 but slow. Blood sam- Heat Exhaustion with Dehydration ples are drawn, and an intravenous drip is started. The lab- oratory report shows serum [Na ] of 156 mmol/L (normal A Michigan National Guard infantry unit was sent at the end of May to Louisiana for a field training exercise. Two liters of normal saline in Michigan was cool, but during the exercise in Louisiana, (0. Well before the the temperature reached at least 30 C (86 F) every after- end of the infusion, the patient is alert, his nausea disap- noon.
List the categories of corticosteroids and identify the zones of the adrenal cortex that secrete these hormones order sominex 25 mg visa. Excessive stimulation of the adrenal medulla can result in de- pletion of the body’s energy reserves cheap sominex 25mg overnight delivery, and high levels of corti- costeroid secretion from the adrenal cortex can significantly impair Van De Graaff: Human V. Endocrine System © The McGraw−Hill Anatomy, Sixth Edition Coordination Companies, 2001 474 Unit 5 Integration and Coordination FIGURE 14. These changes are elicited by neural impulses from the hypothalamus that directly influence body tissues and by impulses to the adrenal medulla that secondarily influence the same body tis- sues through the release of epinephrine. The gonads are mixed glands in that they produce GONADS AND OTHER both sex hormones and sex cells, or gametes (see chapters 20 ENDOCRINE GLANDS and 21). The gonads produce sex hormones that control the development and function of the male and female reproductive systems. Addi- Testes tionally, many other organs secrete hormones that help regulate The interstitial cells of the testes produce and secrete the male digestion, metabolism, growth, and immunity. Testosterone controls the development Objective 16 Discuss the endocrine functions of the gonads. It also promotes the male secondary sex Objective 17 Describe the structure and location of the characteristics (see chapter 20) and somewhat determines the pineal and thymus glands and their endocrine functions. The The endocrine function of the ovaries is the production of the male gonads are called testes and the female gonads are called female sex hormones, estrogens and progesterone. Endocrine System © The McGraw−Hill Anatomy, Sixth Edition Coordination Companies, 2001 Chapter 14 Endocrine System 475 Melatonin H H H O CH3O C C N C CH3 N H H H Pineal gland Day Inhibition Sympathetic neurons Night Retinohypothalamic Stimulation tract Superior cervical Suprachiasmatic nucleus ganglion (the “biological clock”) FIGURE 14. The secretion of melatonin by the pineal gland is stimulated by sympathetic axons originating in the superior cervical ganglion. Activity of these neurons is regulated by the cyclic activity of the suprachiasmatic nucleus of the hypothalamus, which sets a circadian rhythm. They are also produced in the placenta, adrenal cortex, and even in the testes of the male. It Progesterone is produced by the corpus luteum and is pri- begins to regress in size at about the age of 7, and in the adult it marily associated with pregnancy in preparing the uterus for im- appears as a thickened strand of fibrous tissue. Although it lacks direct nervous connection to the rest of Most cultures of the world practice birth control, or contra- the brain, the pineal gland is highly innervated by the sympa- ception, in one form or another. It has a long history, dating back to the ancient Egyptians who used various substances to inhibit thetic division of the ANS from the superior cervical ganglion.
To do so purchase sominex 25mg without prescription, how- treatment for bleeding problems through- ever order sominex 25mg line, individuals must be able to calculate out the individual’s life. With proper care the appropriate dose and mix and admin- and treatment, however, individuals with ister the concentrate intravenously. Home hemophilia can manage their chronic dis- therapy is appropriate for mild bleeding ease, and their life expectancy approach- but is not sufficient when major bleeding es normal (Teitel et al. Major bleeding requires medical To prevent damage from abnormal bleed- evaluation. There are therapies that involve intravenous infu- over 100 comprehensive hemophilia treat- sion, there is the chance of the transmis- ment centers throughout the country that sion of infection such as hepatitis and help individuals with hemophilia manage human immunodeficiency virus (HIV) their condition physically and psycholog- (Parish, 2002). These care centers emphasize early should always be sterile and never shared. Individuals who Because there is no cure for hemophil- receive blood products intravenously can ia, treatment is directed toward prevent- also develop an allergic reaction to the in- ing any injury that could precipitate fusion. Such reactions should be reported bleeding and toward controlling bleeding to a physician promptly. Conditions Affecting the Blood or Immune System 239 Individuals with bleeding into a joint being unable to control bleeding may may require joint immobilization for sev- result in passivity and inactivity. At oth- eral days in addition to replacement ther- er times, if individuals have had difficul- apy. Joint pain may be treated with anti- ty adjusting to the condition, are uncer- inflammatory medications and analgesics. Although replacement therapy and home Physical therapy or prescribed exercise car- treatment have done much to improve ried out at home may be necessary to main- the lives of individuals with hemophilia tain the range of motion of the affected and to decrease the disability resulting joints. If the joints undergo severe degen- from the condition, treatments are very eration, reconstructive orthopedic surgery, expensive. This expense may be an addi- such as joint replacement, may also be tional source of stress. Individuals Individuals with hemophilia may expe- with hemophilia should always wear a rience both acute and chronic pain if there Medic Alert identification bracelet or has been bleeding into the joints. Conse- necklace to alert others to their condition quently, pain medications are frequently in case of an emergency. If medications are not carefully used and monitored, drug dependence may Psychosocial Issues in Hemophilia result, sometimes necessitating drug reha- bilitation.
