By T. Jose. Lourdes College. 2018.
Although somewhat less prevalent than down-regula- postreceptor step in the hormone action pathway discount avana 200 mg amex erectile dysfunction statistics uk. Changes in rates of receptor synthesis may also con- a right shift indicates decreased sensitivity and a left shift tribute to long-term down- or up-regulation. Changes in sensitivity reflect (1) an alteration in cells can regulate receptor function. Chronic exposure of receptor affinity or, if submaximal concentrations of hor- cells to a hormone may cause the cells to become less re- mone are present, (2) a change in receptor number. Dose- sponsive to subsequent exposure to the hormone by a response curves may also reflect combinations of changes process termed desensitization. If the exposure of cells to in responsiveness and sensitivity in which there is both a a hormone has a desensitizing effect on further action by right or left shift of the curve (a sensitivity change) and a that same hormone, the effect is termed homologous de- change in maximal biological response to a lower or higher sensitization. If the exposure of cells to one hormone has level (a change in responsiveness). The principal mineralocorticoid in the globulin (CBG) completions of the statement. The ability of hormones to be effective ONE lettered answer or completion that is Aldosterone regulators of biological function BEST in each case. A shift to the right in the biological (D) Cortisol Transport proteins activity dose-response curve for a 4. An index of the binding affinity of a (B) Pleiotropic effects hormone with no accompanying hormone for its receptor can be (C) Signal amplification change in the maximal response obtained by examining the (D) Competitive binding indicates (A) Y-intercept of a Scatchard plot (A) Decreased responsiveness and (B) Slope of a Scatchard plot SUGGESTED READING decreased sensitivity (C) Maximum point on a biological Goodman HM. Basic Medical Endocrinol- (B) Increased responsiveness dose-response curve ogy. Textbook of En- (D) Increased sensitivity and decreased (E) The threshold point of a biological docrine Physiology. New York: responsiveness dose-response curve Oxford University Press, 2000. Within the endocrine system, are synthesized as Clinical Endocrine Physiology. Cell communication: (B) The distance between the (E) Propressophysin The inside story. Williams Textbook of (D) Anatomical connections between (B) Bound to transthyretin Endocrinology. Philadelphia: the endocrine and target cells (C) Free in solution WB Saunders, 1998. The hypothalamic-pituitary axis is composed of the hypo- from the adrenal cortex, to comprise the hypothalamic-pi- thalamus, infundibular stalk, posterior pituitary, and ante- tuitary-adrenal axis. Arginine vasopressin (AVP) and oxytocin are synthesized and emotional stress, AVP, and the sleep-wake cycle. AVP increases water reabsorption by the kidneys in re- the thyroid follicles, to comprise the hypothalamic-pitu- sponse to a rise in blood osmolality or a fall in blood vol- itary-thyroid axis. Oxytocin stimulates milk letdown in the breast in response temperatures, and the sleep-wake cycle. Hypothalamic GHRH increases and hypothalamic SRIF de- sponse to cervical dilation during labor. GH secretion is regulated by the GH, IGF-I, aging, deep thesized in the anterior pituitary and secreted in response sleep, stress, exercise, and hypoglycemia. LHRH stimulates the secretion of FSH and LH from the an- pophyseal portal circulation. Hypothalamic CRH stimulates ACTH release from corti- the ovaries and testes. This Tsecretes an array of peptide hormones that have im- important functional connection between the brain and the portant actions on almost every aspect of body function. Others bring about changes in body function, which enable the individual to grow, reproduce, and re- HYPOTHALAMIC-PITUITARY AXIS spond appropriately to stress and trauma. The pituitary hormones produce these physiological effects by either The human pituitary is composed of two morphologically acting directly on their target cells or stimulating other en- and functionally distinct glands connected to the hypo- docrine glands to secrete hormones, which, in turn, bring thalamus. The pituitary gland or hypophysis is located at about changes in body function.
Isometric contraction results when an activated muscle is chains of the myosin molecule cheap 100 mg avana free shipping impotence in men over 60, which is then free to inter- prevented from shortening and force is produced without act with actin. The contractions of smooth muscle are considerably shortens against an external force (or load). The external slower than those of skeletal muscle, but are much more load determines the force that the muscle will develop, and economical in their use of cellular energy. A crossbridge the developed force determines the velocity of shortening. The length-tension curve describes the effect of the resting muscles to maintain contraction for extremely long periods length of a muscle on the isometric force it can develop. Smooth muscle tissues, especially those in the walls of dis- normal length of the muscle in the body, is determined tensible organs, can operate over a wide range of lengths. This chapter treats muscles as organized tissues, ated with the extra metabolic requirements of the terminal, beginning with the events leading to membrane activation are also plentiful. Here the mem- brane is formed into postjunctional folds, at the mouths of ACTIVATION AND CONTRACTION which are located many nicotinic ACh receptor molecules. OF SKELETAL MUSCLE These are chemically gated ion channels that increase the cation permeability of the postsynaptic membrane in re- Skeletal muscle is controlled by the central nervous system sponse to the binding of ACh. Between the nerve and mus- (CNS), which provides a pattern of activation that is suited cle is a narrow space called the synaptic cleft. The resulting contraction is further choline must diffuse across this gap to reach the receptors shaped by mechanical conditions external to the muscle. Also located in the synaptic The connection between nerve and muscle has been stud- cleft (and associated with the postsynaptic membrane) is ied for over a century, and a fairly clear picture of the the enzyme acetylcholinesterase (AChE). While the process functions amaz- ingly well, its complexity means that critical failures can Chemical Events at the Neuromuscular Junction. When the wave of depolarization associated with a nerve action potential spreads into the terminal of a motor axon, Impulse Transmission From Nerve to Muscle several processes are set in motion. The lowered membrane Occurs at the Neuromuscular Junction potential causes membrane channels to open and external calcium ions enter the axon. The rapid rise in intracellular The contraction of skeletal muscle occurs in response to ac- calcium causes the cytoplasmic vesicles of ACh to migrate tion potentials that travel down somatic motor axons orig- to the inner surface of the axon membrane, where they fuse inating in the CNS. The transfer of the signal from nerve to with the membrane and release their contents. Because all muscle takes place at the neuromuscular junction, also the vesicles are of roughly the same size, they all release called the myoneural junction or motor endplate. When the ACh molecules arrive at the postsynaptic The Structure of the Neuromuscular Junction. On membrane after diffusing across the synaptic cleft, they reaching a muscle cell, the axon of a motor neuron typically bind to the ACh receptors. When two ACh molecules are branches into several terminals, which constitute the presy- bound to a receptor, it undergoes a configurational change naptic portion of the neuromuscular junction. The termi- that allows the relatively free passage of sodium and potas- nals lie in grooves or “gullies” in the surface of the muscle sium ions down their respective electrochemical gradients. Soon ACh diffuses away and is hydrolyzed by AChE into choline and acetate, terminating its function as a trans- mitter molecule, and the membrane permeability returns to Axon terminal Schwann cell the resting state. The choline portion is taken up by the presynaptic terminal for resynthesis of ACh, and the ace- Synaptic vesicles tate diffuses away into the extracellular fluid. These events take place over a few milliseconds and may be repeated many times per second without danger of fatigue. Synaptic cleft Schwann cell process Electrical Events at the Neuromuscular Junction. The binding of the ACh molecules to postsynaptic receptors ini- muscle cell tiates the electrical response of the muscle cell membrane, and what was a chemical signal becomes an electrical one. The stages of the development of the electrical signal are Nicotinic acetylcholine shown in Figure 9.
Intercostal and thoracic transverse colon muscles safe avana 100 mg erectile dysfunction urologist, and pleurae Suprarenal aa. Transverse colon, descending colon, sigmoid colon, and rectum Common iliac aa. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 568 Unit 6 Maintenance of the Body FIGURE 16. Two branches arise from the external arterial blood to the gluteal muscles and the organs of the iliac artery, however, before it passes beneath the inguinal liga- pelvic region (fig. An inferior epigastric artery branches from the external the iliolumbar and lateral sacral arteries. The internal vis- iliac artery and passes superiorly to supply the skin and muscles ceral organs of the pelvis are served by the middle rectal and of the abdominal wall. The deep circumflex iliac artery is a the superior, middle, and inferior vesicular arteries to the small branch that extends laterally to supply the muscles at- urinary bladder. The muscles of the buttock are femoral triangle on the upper medial portion of the thigh served by the superior and inferior gluteal arteries. At this point, it is close to the surface the upper medial thigh muscles are supplied with blood from and its pulse can be palpated. The internal pudendal artery of the in- femoral artery to serve the thigh region. The largest of these, ternal iliac artery serves the musculature of the perineum and the deep femoral artery, passes posteriorly to serve the ham- the external genitalia. The lateral and medial femoral circumflex ar- blood for vascular engorgement of the penis in the male and teries encircle the proximal end of the femur and serve clitoris in the female. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 Right lung Left lung Diaphragm muscle Heart Inferior vena cava Right kidney Left renal artery Celiac trunk Left kidney Common hepatic Abdominal aorta artery Inferior mesenteric Superior mesenteric artery artery Right common iliac artery Right external iliac artery Right external iliac vein FIGURE 16. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 570 Unit 6 Maintenance of the Body FIGURE 16. To At the ankle, the anterior tibial artery becomes the dor- prevent a victim from bleeding to death, it is important to know sal pedal artery that serves the ankle and dorsum (superior where to apply pressure to curtail the flow of blood (fig. The pressure points for the appendages are the brachial artery on the portion) of the foot and then contributes to the formation of medial side of the arm and the femoral artery in the groin. Clinically, palpation of the dorsal plied pressure to these regions greatly diminishes the flow of blood to pedal artery can provide information about circulation to the traumatized areas below. A tourniquet may have to be applied if foot; more important, it can provide information about the bleeding is severe enough to endanger life. These vessels traverse the anterior oneal, artery to serve the peroneal muscles of the leg. At the and posterior aspects of the leg, respectively, providing blood to ankle, the posterior tibial bifurcates into the lateral and medial the muscles of these regions and to the foot. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 Chapter 16 Circulatory System 571 FIGURE 16. The structures within the femoral triangle are shown in (a); the boundaries of the triangle are shown in (b). PRINCIPAL VEINS OF THE BODY Digital arteries arise from the plantar arch to supply the toes After systemic blood has passed through the tissue, this oxy- with blood. Knowledge Check Objective 18 Describe the venous drainage of the head, 17. Describe the clinical significance of the brachial and radial Objective 19 Describe the venous drainage of the thorax, arteries. Describe the arterial pathway from the subclavian artery to Objective 20 Describe the vessels involved in the hepatic the digital arteries. List the arteries that supply blood to the lower abdominal wall, the external genitalia, the hamstring muscles, the In the venous portion of the systemic circulation, blood flows knee joint, and the dorsum of the foot. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 572 Unit 6 Maintenance of the Body Superficial temporal artery Facial artery Subclavian artery Common carotid artery Brachial Radial artery artery Femoral Popliteal artery artery Dorsal pedal artery FIGURE 16. Veins are more numerous than arteries and are both neck regions is drained by the external jugular veins (fig. Superficial veins generally can be seen just These vessels descend on the lateral sides of the neck, superficial beneath the skin and are clinically important in drawing blood to the sternocleidomastoid muscle and deep to the platysma mus- and giving injections. They empty into the right and left subclavian veins, located ies and are usually similarly named.
The assessment takes place before the attorney ever meets you and is based on what you have written in your medical records discount 50mg avana with mastercard age related erectile dysfunction causes. The attorney looks to see if you are honest and forthcoming, which is not something he or she wants to see in a potential defendant. If you share your concerns with the patient when there is a complication, that openness will be a very effec- tive deterrent to a plaintiff lawyer. You may feel you are raising a red flag by documenting that something is wrong. However, you may be keeping your patient from going to an attorney for answers, and you will be showing what a wonderful doctor (and witness) you will be if there is a lawsuit. Your goal is to minimize the chances of your patient seeking legal aid to get answers. Your goal is also to be successful if all that occurred was a complication rather than a deviation from the standard of medi- cal care. Hopefully, this chapter helps you understand some simple ways of accomplishing these goals. Chapter 4 / Physician As a Witness 41 4 The Physician As a Witness Joel A. Mattison, MD, FACS SUMMARY This chapter is a personal reflection on the role of the physician as an expert witness in medical malpractice litigation. It looks at both the individual experience and professional obligations of the expert from both the medical and the legal perspectives. A number of practical suggestions for courtroom preparation and deportment are presented. Key Words: Expert witness; courtroom strategy; courtroom deport- ment; cross-examination. INTRODUCTION When a physician has either the opportunity or the obligation to testify as an expert witness, the reaction often passes through a cascade of several phases. Teddy Roosevelt once commented that the bravest man he had ever known was the one who followed him up San Juan Hill. Although this came from a hero, the arrogance of such a remark is apparent even, or espe- cially, when subtle. You must be willing to learn this carefully from the attorney who has engaged you. Everything in life has associated risks, and the courtroom is often a battleground. If this vulnerability frightens you, then think twice before you agree to tes- tify or even to review a case. Very little, because most effective experts tend to want to avoid shar- ing their strategies. My wife’s reaction to my writing this chapter was, “Are you going to give away all your trade secrets? More- over, not all of these strategies will be equally effective for everyone. Gather a lot of strategy but be careful not to try to use all of it in the same case. SOME PRELIMINARY ADVICE The following is a list of basic things to remember as you prepare for litigation in a malpractice suit. Remember that although this may be your first time, it is a well- understood and familiar arena to those who are involved in it weekly or monthly. You are not likely to come up with any new or clever answers that have not already been heard by the judge, opposing counsel, and some of the jury. This will take your adversaries by surprise and is a useful arrow in your quiver. If you cannot control your feelings and be objective, then this task is not for you. Remember that the judge is deserving of the respect of his or her office and of his or her civil authority.
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