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Second messengers are a class of sig- phospholipase C (PLC) on PIP2 discount 0.5 mg dutasteride otc hair loss yeast infection, phosphatidylinositol naling molecules generated inside cells in response to 4 discount 0.5mg dutasteride amex hair loss knit hats for women,5-bisphosphate trusted 0.5 mg dutasteride hair loss patterns. DAG is important for the ac- always available, signal transduction pathways could tivation of protein kinase C, not PLC. The response to a second messenger receptors are activated by the binding of ligands, such varies depending on the cell type because each cell as hormones or growth factors, not by IP3 or DAG. IP3 type differs with respect to the number and comple- can indirectly activate calcium-calmodulin-dependent ment of receptors, effectors, and downstream targets. The activation of tyrosine kinase re- only tyrosine kinase receptors, are coupled to second ceptors often results in a cellular response that is in- messenger generating systems. Cyclic nucleotides are generated by ceptors do not have constitutively active receptors; if 707 708 APPENDICES this were true, there could be no regulation of signal- 7. The activation of ras occurs indirectly by the acti- the ion channel in this example. Ion pumps and Na vation of adapter molecules (Grb2 and SOS) that asso- solute-coupled transporters are examples of active ciate with phosphorylated tyrosine residues in the transport systems, not Na channels. Water exit will lead to a decrease in cell vol- G s subunit remains in its active form and results in in- ume. An influx of Na and synthesis of sorbitol do not creases in adenylyl cyclase activity, intracellular occur during this process because both processes cAMP, and release of growth hormone. If G i is acti- would increase intracellular osmolytes and drive water vated, adenylyl cyclase activity will be decreased. By substituting in the Nernst equa- not increased, growth hormone secretion. Phospholipids have both a polar hy- drophilic head group and a hydrophobic region be- Note that for Cl , the value for z (valence) is 1. Since the hydrophilic and hydrophobic regions are present within the same molecule, phospholipids n R T? Phospholipid molecules can rotate and move laterally within the plane of the lipid bilayer, Chapter 3 but movement from one half of the bilayer to the other is slow because it is an energetically unfavorable 1. Cholesterol is an example of a separate class of in the intracellular fluid relative to the extracellular lipids that do not contain fatty acids. The opposite is true for sodium ion concentra- lipids are distributed unequally between the two halves tion; therefore, there is a strong driving force for potas- of the lipid bilayer. In the red blood cell membrane, for sium to leave the cell and sodium to enter the cell. If example, most of the phosphatidylcholine is in the the permeability to K increases, more potassium outer half. Both ion channels and symporters are mem- would leave the cell, and the cell would become more brane proteins, not phospholipids. Membrane-spanning segments of in- decreases, less sodium would enter the cell, and the cell tegral proteins frequently adopt an -helical confor- would become less positive (hyperpolarize). Voltage-gated potassium channels nities for the polar peptide bonds to form hydrogen open with a delay relative to voltage-gated sodium bonds with one another in the hydrophobic interior of channels in response to depolarization. These segments are composed largely tantly, there is a delay in their closing relative to the of amino acids with nonpolar hydrophobic side chains sodium channels. During the afterhyperpolarization that interact with the surrounding lipids. There are no phase of the action potential, the sodium channels are covalent bonds with cholesterol or phospholipids, and closed, but the potassium channels remain open. An outward calcium cur- membrane potential that develops when a single ion is rent, an outward sodium current, or an inward chloride distributed at equilibrium across a membrane. The current could conceivably hyperpolarize the cell, but Goldman equation gives the value of the membrane these currents are not the basis for this phase of the ac- potential when all permeable ions are accounted for. A specialization occurs in myelinated sure of a solution, and Fick’s law refers to the diffu- axons in which the voltage-gated sodium channels are sional movement of solute. The permeability coeffi- preferentially distributed to the axonal membrane be- cient accounts for several factors that determine the neath the nodes of Ranvier. Intracellular K is high compared action potential jumps from node to node. Active transport always moves solute ance and a decreased capacitance associated with the against its electrochemical gradient. All the other op- myelinated regions of the axon, both of which pro- tions are shared by both active transport and equili- mote the electrotonic spread of the positive charge brating carrier-mediated transport systems.

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What foramina are three of its structural examples of diseases or skeletal conditions structures pass through these openings? Describe where imbalance of any of these three essential immediately these two components articulate purchase dutasteride 0.5 mg with amex hair loss cure news june 2014. The most common surgical approach to a (b) inferior to the frontal sinus order 0.5mg dutasteride amex hair loss 4 months after delivery. How are these processes similar generic 0.5mg dutasteride fast delivery hair loss cure 4 cancer, team of archaeologists recently completed (b) the tympanic part and how do they differ? Explain how an examination of 18 skeletons from (c) the mastoid part radiographs can be used to determine people buried under tons of volcanic ash (d) the petrous part normal bone growth. Explain the process of endochondral the scientists were able to determine the which bone? Why is it sex, physical health (including a partial (a) the sphenoid bone important that a balance be maintained medical history), approximate age, and (b) the ethmoid bone between osteoblast activity and osteoclast even the general profession of each of the (c) the palatine bone activity? Describe the curvature of the vertebral examination of a preserved skeleton yield 9. Skeletal System: The © The McGraw−Hill Anatomy, Sixth Edition Appendicular Skeleton Companies, 2001 Skeletal System: The Appendicular Skeleton 7 Pectoral Girdle and Upper Extremity 173 Pelvic Girdle and Lower Extremity 178 CLINICAL CONSIDERATIONS 189 Clinical Case Study Answer 191 Developmental Exposition: The Appendicular Skeleton 192 Chapter Summary 194 Review Activities 194 Clinical Case Study A 12-year-old boy was hit by a car while crossing a street. He was brought to the emergency room in stable condition, complaining of severe pain in his left leg. Radiographs revealed a 4- inch fracture extending superiorly from the distal articular surface of the tibia into the anterior body of the bone. With the radiographs in hand, the orthopedic surgeon went into the waiting room and conferred with the boy’s parents. He told them that this kind of injury was more serious in children and growing adolescents than in adults. He went on to say that future growth of the bone might be jeopardized and that surgery, although recommended, could not guarantee normal growth. The parents asked, “What is it about this particular fracture that threatens future growth? FIGURE: Currently, physicians have an array of techniques available to treat fractured bones. It wasn’t so long ago that the only procedure used was to align the parts of a broken bone and then immobilize the area with a tightly bound splint. The spine of the scapula is a prominent diagonal bony tive for freedom of movement and extensive muscle attachment. The spine strength- ens the scapula, making it more resistant to bending. Above the Objective 1 Describe the bones of the pectoral girdle and spine is the supraspinous fossa, and below the spine is the infra- the articulations between them. This process serves for the attach- Objective 2 Identify the bones of the upper extremity and list the distinguishing features of each. On the anterior sur- Two scapulae and two clavicles make up the pectoral (shoulder) face of the scapula is a slightly concave area known as the sub- girdle (fig. As an axial bone, the ster- The superior edge is called the superior border. Lacking a poste- der is nearest to the vertebral column, and the lateral border is rior attachment to the axial skeleton, the pectoral girdle has a directed toward the arm. Because it is not weight-bearing, it is the superior and medial borders; the inferior angle, at the junc- structurally more delicate than the pelvic girdle. The primary tion of the medial and lateral borders; and the lateral angle, at function of the pectoral girdle is to provide attachment areas for the junction of the superior and lateral borders. It is at the lateral the numerous muscles that move the shoulder and elbow joints. Along the superior border, a distinct depression called the scapu- Clavicle lar notch is a passageway for the suprascapular nerve. Clinically, the pectoral girdle is significant be- joint away from the trunk to permit freedom of movement.

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Because of pressure diuresis buy dutasteride 0.5mg without prescription hair loss cure university pennsylvania, as long as mean arterial Atrial natriuretic peptide (ANP) is a 28-amino acid pressure is elevated generic dutasteride 0.5mg amex hair loss in men exercise, salt and water excretion will exceed the polypeptide synthesized and stored in the atrial muscle normal rate; this will tend to lower extracellular fluid vol- 298 PART IV BLOOD AND CARDIOVASCULAR PHYSIOLOGY Intervention CARDIOVASCULAR CONTROL DURING STANDING Arterial pressure Salt and An integrated view of the cardiovascular system requires an increase water output understanding of the relationships among cardiac output discount 0.5mg dutasteride fast delivery hair loss cure oct 2015, decrease venous return, and central blood volume and how these re- lationships are influenced by interactions among various neural, hormonal, and other control mechanisms. Consid- Cardiac output Plasma volume eration of the responses to standing erect provides an op- portunity to explore these elements in detail. When a person is recumbent, pressure in the veins of the legs is only a few mm Hg above the pressure in 8 the right atrium. The pressure distending the veins—trans- mural pressure—is equal to the pressure within the veins of the legs because the pressure outside the veins is atmos- 6 pheric pressure (the zero-reference pressure). When a person stands, the column of blood above the lower extremities raises venous pressure to about 50 mm 4 Hg at the femoral level and 90 mm Hg at the foot. A higher output of salt and water in response to increased arterial pressure reduces blood volume. The curve on the left shows the relationship in a person with normal blood pressure. The curve on the right shows the same relationship in an individual who is hypertensive. Note that the hypertensive individual has an elevated arterial pres- sure at a normal output of salt and water. As discussed earlier in this chapter and in Chapter 15, a decrease in blood volume reduces stroke volume by lowering the end-diastolic filling of the ventricles. Pressure diuresis persists until it lowers blood volume and cardiac output sufficiently to return mean arterial pressure to a set level. A decrease in mean arterial pressure has the opposite effect on salt and water excretion. Reduced pressure diuresis increases blood volume and cardiac output until mean arterial pressure is re- turned to a set level. Pressure diuresis is a slow but persistent mechanism for regulating arterial pressure. In this example, standing rial pressure is above or below a set level, it will eventually places a hydrostatic pressure of approximately 80 mm Hg on the return pressure to that level. Right atrial pressure is lowered because of the reduction in curve shown in Figure 18. The negative pressures above the heart with salt and water excretion are normal at a higher arterial pres- standing do not actually occur because once intravascular pressure sure. If this were not the case, pressure diuresis would inex- drops below atmospheric pressure, the veins collapse. CHAPTER 18 Control Mechanisms in Circulatory Function 299 the transmural (distending) pressure because the outside liter of blood. It follows that an adequate cardiovascular re- pressure is still zero (atmospheric). Because the veins are sponse to the changes caused by upright posture—or- highly compliant, such a large increase in transmural pres- thostasis—is absolutely essential to our lives as bipeds (see sure is accompanied by an increase in venous volume. The arteries of the legs undergo exactly the same in- The immediate cardiovascular adjustments to upright creases in transmural pressure. However, the increase in posture are the baroreceptor- and cardiopulmonary recep- their volume is minimal because the compliance of the sys- tor-initiated reflexes, followed by the muscle and respira- temic arterial system is only 1/20th that of the systemic ve- tory pumps and, later, adjustments in blood volume. Standing increases pressure in the arteries and veins of the legs by exactly the same amount, so the added pressure has no influence on the difference in pressure driv- Standing Elicits Baroreceptor ing blood flow from the arterial to the venous side of the and Cardiopulmonary Reflexes circulation. The decreased central blood volume caused by standing in- cludes reduced atrial, ventricular, and pulmonary vessel Standing Requires a Complex volumes. These volume reductions unload the cardiopul- monary receptors and elicit a cardiopulmonary reflex. Re- Cardiovascular Response duced left ventricular end-diastolic volume decreases stroke When a person stands and the veins of the legs are dis- volume and pulse pressure as well as cardiac output and tended, blood that would normally be returned toward the mean arterial pressure, leading to decreased firing of aortic right atrium remains in the legs, filling the expanding veins. The combined reduction in For a few seconds after standing, venous return to the heart firing of cardiopulmonary receptors and baroreceptors re- is lower than cardiac output and, during this time, there is sults in a reflex decrease in parasympathetic nerve activity a net shift of blood from the central blood volume to the and an increase in sympathetic nerve activity to the heart.

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