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Body Organization and © The McGraw−Hill Anatomy 800 mg viagra vigour overnight delivery erectile dysfunction treatment food, Sixth Edition Organization buy 800 mg viagra vigour amex top 10 causes erectile dysfunction, and the Anatomical Nomenclature Companies, 2001 Human Organism Chapter 2 Body Organization and Anatomical Nomenclature 23 Notochord Dorsal hollow CLASSIFICATION AND nerve cord Primitive eye CHARACTERISTICS OF HUMANS Humans are biological organisms belonging to the phylum Chor- data within the kingdom Animalia and to the family Hominidae within the class Mammalia and the order Primates. Objective 2 List the characteristics that identify humans as chordates and as mammals. Pharynx Objective 3 Describe the anatomical characteristics that set Pharyngeal humans apart from other primates. Our scientific name translates Umbilical bud cord from the Latin to “man the intelligent,” and indeed our intelli- gence is our most distinguishing feature. It has enabled us to Limb bud build civilizations, conquer dread diseases, and establish cultures. We have invented a means of communicating through written Creek symbols. We record our own history, as well as that of other or- ganisms, and speculate about our future. The ever more ingenious ways for adapting to our changing environ- three diagnostic chordate characteristics are indicated in boldface type. At the same time, we are so intellectually specialized that we are not self-sufficient. We need one another as much as we need the recorded knowledge of the past. We are constantly challenged to learn more about our- ferred to as a taxon. As we continue to make new discoveries about our struc- most specific taxon is the species. Humans are species belonging ture and function, our close relationship to other living organisms to the animal kingdom. Phylogeny (fi-loj′˘-nee ) is the science that becomes more and more apparent. Often, it is sobering to realize studies relatedness on the basis of taxonomy. As human organisms, we breathe, eat and digest food, excrete bodily Phylum Chordata wastes, locomote, and reproduce our own kind. These chordate characteristics are development is found throughout nature. The fundamental pat- well expressed during the embryonic period of development and, terns of development of many nonhuman animals also characterize to a certain extent, are present in an adult. Recent genetic mapping of flexible rod of tissue that extends the length of the back of an the human genome confirms that there are fewer than 35,000 embryo. A portion of the notochord persists in the adult as genes accounting for all of our physical traits. By far the majority the nucleus pulposus, located within each intervertebral disc of these genes are similar to those found in many other organisms. The dorsal hollow nerve cord is positioned above the In the classification, or taxonomic, system established by notochord and develops into the brain and spinal cord, which biologists to organize the structural and evolutionary relation- are supremely functional as the central nervous system in the ships of living organisms, each category of classification is re- adult. Body Organization and © The McGraw−Hill Anatomy, Sixth Edition Organization, and the Anatomical Nomenclature Companies, 2001 Human Organism 24 Unit 2 Terminology, Organization, and the Human Organism L4 L5 S1 (a) (b) FIGURE 2. In other chordates, such as humans, embryonic pha- Order Primates ryngeal pouches develop, but only one of the pouches persists, becoming the middle-ear cavity. Spinal nerves exit between vertebrae, and the discs maintain the spacing to avoid nerve damage. A “slipped disc,” resulting from straining the back, is Family Hominidae a misnomer. What actually occurs is a herniation, or rupture, because of a weakened wall of the nucleus pulposus. This may cause severe Humans are the sole living members of the family Hominidae.

Unlike uptake 2 in the PNS viagra vigour 800mg with amex erectile dysfunction and testosterone injections, glial uptake of cate- ter enters the synaptic vesicles and is made available for re- cholamines has many characteristics of uptake 1 800 mg viagra vigour fast delivery impotence when trying to conceive. In peripheral noradrenergic synapses (the sympa- The catecholamines differ substantially in their interac- thetic nervous system), the neuronal uptake process tions with receptors; DA interacts with DA receptors and NE described above is referred to as uptake 1, to distinguish it and EPI interact with adrenergic receptors. Up to five sub- from a second uptake mechanism, uptake 2, localized in types of DA receptors have been described in the CNS. Of the target cells (smooth muscle, cardiac muscle, and gland these five, two have been well characterized. In contrast with uptake 1, an active are coupled to stimulatory G proteins (G ), which activates transport, uptake 2 is a facilitated diffusion mechanism, adenylyl cyclase, and D2 receptors are coupled to inhibitory which takes up the sympathetic transmitter NE, as well as G proteins (G ), which inhibit adenylyl cyclase. Activationi the circulating hormone EPI, and degrades them enzymat- of D2 receptors hyperpolarizes the postsynaptic membrane ically by MAO and COMT localized in the target cells. A third subtype of DA the CNS, there is little evidence of an uptake 2 of NE, but receptor postulated to modulate the release of DA is local- 54 PART I CELLULAR PHYSIOLOGY ized on the cell membrane of the nerve terminal that releases 5-Hydroxytryptamine is stored in vesicles and is re- DA; accordingly, it is called an autoreceptor. The major Adrenergic receptors, stimulated by EPI and NE, are lo- mode of removal of released 5-HT is by a high-affinity, cated on cells throughout the body, including the CNS and sodium-dependent, active uptake mechanism. There are the peripheral target organs of the sympathetic nervous several receptor subtypes for serotonin. Activation results in an in- as either or , based on the rank order of potency of cat- crease in sodium and potassium ion conductances, leading echolamines and related analogs in stimulating each type. The remaining well-characterized receptor sub- The analogs used originally in distinguishing - from - types appear to operate through second messenger sys- adrenergic receptors are NE, EPI, and the two synthetic tems. Both glutamate (GLU) and der: ISO was most potent and EPI either more potent or aspartate (ASP) serve as excitatory transmitters of the equal in potency to NE. These dicarboxylic amino acids are important sub- guished these two classes of receptors: -receptors were strates for transaminations in all cells; but, in certain neu- stimulated by PE, whereas -receptors were not. Serotonin or 5-hydroxytryptamine (5-HT) is leased by exocytosis, stimulate specific receptors in the the transmitter in serotonergic neurons. Since mission in these neurons is similar in several ways to that GLU and ASP are readily interconvertible in transamina- described for catecholaminergic neurons. Tryptophan hy- tion reactions in cells, including neurons, it has been diffi- droxylase, a marker of serotonergic neurons, converts tryp- cult to distinguish neurons that use glutamate as a transmit- tophan to 5-hydroxytryptophan (5-HTP), which is then converted to 5-HT by decarboxylation (Fig. Glutamate (5-HT) is synthesized by the hydroxylation of (GLU) is synthesized from -ketoglutarate by tryptophan to form 5-hydroxytryptophan (5-HTP) and the de- enzymatic amination. Upon release into the synaptic cleft, GLU carboxylation of 5-HTP to form 5-HT. The removal of GLU is prima- synaptic cleft, 5-HT can bind to a variety of serotonergic recep- rily by transport into glial cells, where it is converted into gluta- tors on the postsynaptic cell. Glutamine, in turn, is transported from glial cells to the when 5-HT is transported back into the presynaptic terminal for nerve terminal, where it is converted to glutamate by the enzyme repackaging into vesicles. CHAPTER 3 The Action Potential, Synaptic Transmission, and Maintenance of Nerve Function 55 ter from those that use aspartate. Three of these, named for the syn- compounded by the fact that GLU and ASP stimulate thetic analogs that best activate them—kainate, common receptors. Accordingly, it is customary to refer to quisqualate, and N-methyl-D-aspartate (NMDA) recep- both as glutamatergic neurons. Activation of the kainate and quisqualate re- mitochondrial conversion of -ketoglutarate derived ceptors produces EPSPs by opening ion channels that in- from the Krebs cycle (Fig. Activation of the NMDA 2 vesicles and released by exocytosis, where it activates spe- receptor increases Ca conductance. This receptor, how- 2 cific receptors to depolarize the postsynaptic neuron. Thus, the NMDA receptor can be thought of transmitter by re-storage in vesicles and re-release. Cal- cells (particularly astrocytes) contain a similar, high-affin- cium gating through the NMDA receptor is crucial for the ity, active transport mechanism that ensures the efficient development of specific neuronal connections and for neu- removal of excitatory neurotransmitter molecules from ral processing related to learning and memory.

The United States has a much higher C-section rate than any other developed country order viagra vigour 800mg mastercard erectile dysfunction causes mental, with no improvement in birth outcomes cheap viagra vigour 800mg with mastercard erectile dysfunction drugs and hearing loss. Similarly, the rate of false-positive 218 Anderson mammograms in the United States is twice that in other developed coun- tries, again without improving the cancer detection rate. In another example of litigation-biased decision making, cardiac surgeons have been accused of gaming risk selection of patients to improve outcome data, limiting surgical access for the highest risk patients (44). Even ignoring the emotional burden and the damage caused by liti- gation-scared physicians practicing angry or hurt, the dollar costs are enormous. In 1996, Kessler and McClellan (45) estimated the cost of defensive medicine at $50 billion and argued that extending current malpractice reforms to all the states would reduce health care costs by 5 to 9%. More recently, the Department of Health and Human Services calculated the savings at $60 to $108 billion per year (2). Although these may be the best estimates available, they are extremely conservative. These numbers reflect the reduced cost of health care in states with effective tort reform compared to states lacking such reforms. Califor- nia, inherently a litigious state, has a frequency of malpractice litigation that is about 50% above the national average (16), despite MICRA. Although the data indicate that effective tort reforms reduce the practice of defensive medicine, it is clearly not eliminated. This would suggest that the true costs are considerably higher than indicated by this meth- odology. Because financing the cost of health care in the United States today is a zero-sum game, these direct and indirect costs of the malpractice crisis must be subtracted from funds available to fund the care of the uninsured and underinsured (2,5,31), and for medical research and innovation. Reasonable limits on noneconomic damages, by reducing both the direct costs of malpractice insurance and the cost of defensive medicine, would save enough money to fund a prescription drug ben- efit for Medicare beneficiaries and facilitate insurance coverage for millions of uninsured Americans (2). Access to Care As direct and indirect cost drivers increase the price of health care, it becomes unaffordable for an incremental number of patients. As the cost of malpractice insurance increases, it becomes unaffordable for an incremental number of doctors, other health care providers, and medical institutions, effectively preventing them from delivering medical services. As the fear of malpractice litigation and the conse- quent increase in malpractice insurance rates affect physician behav- ior, doctors become incrementally more averse to high-risk procedures, difficult patients, and more litigious venues. They also become incre- Chapter 15 / The Case for Legal Reform 219 mentally more susceptible to practices with more benefit in litigation avoidance than patient care. The same pressures will incrementally affect the choice of specialties by medical students and investment in medical facilities and medical research (46). None of this would appear to be particularly controversial; however, for several reasons it is difficult to be precise about the magnitude of these effects or to define the exact tipping point for individual physi- cians, specialties, facilities, or communities. Third, there are no adequately defined and scaled metrics for analysis as costs and their consequential pressures continue to rise. Moreover, there is an important personal factor in evaluating the access to care issue that goes beyond statistical analysis. If it is your obstetri- cian who is unavailable, then you have an access to care crisis. If the trauma center closest to the scene of your accident is closed, then you have an access to care problem. If there is no neurosurgeon available in your community following your head injury, then you have an access to care issue. The Florida Select Task Force looked carefully at access to care because they felt it to be the most important reason for reform of laws governing medical malpractice litigation. Again, their conclusion was unequivocal: “The concern over litigation and the cost and lack of medical mal- practice insurance have caused doctors to discontinue high-risk procedures, turn away high-risk patients, close practices, and move out of the state. In some communities, doctors have ceased or dis- continued delivering babies and discontinued hospital care” (22). On the other hand, with effective tort reform: “Physicians and hospitals will not be compelled to reduce or elimi- nate services, particularly those involving high risk. Lower malpractice insurance rates increase the willingness of physicians and hospi- tals to provide treatments that carry a relatively high risk of failure but offer the only real prospect of success for seriously ill patients” (22).

Homologous chromosomes contain genes for the same characteristic at the same locus purchase viagra vigour 800mg without prescription erectile dysfunction wiki. One allele of each pair originates from the female parent and the other from the male cheap 800mg viagra vigour mastercard erectile dysfunction treatment ppt. The shape of a person’s ears, for example, is determined by the kind of allele re- ceived from each parent and how the alleles interact with one another. Alleles are always located on the same spot (called a locus) on homologous chromosomes (Fig. For any particular pair of alleles in a person, the two alleles are either identical or not identical. Two par- If the alleles for a particular trait are homozygous, the char- ents with unattached (free) earlobes can have a child with attached earlobes. If the alleles for a particular trait are heterozygous, phenotypes of the individuals would be free earlobes resulting from however, the allele that expresses itself and the way in which the the presence of a dominant allele in each genotype. A person who genes for that trait interact will determine the phenotype. The inherited two recessive alleles for earlobes would have the geno- allele that expresses itself is called the dominant allele, the one type ee and would have attached earlobes. The various combinations of Thus, three genotypes are possible when gene pairing in- dominant and recessive alleles are responsible for a person’s volves dominant and recessive alleles. Only In describing genotypes, it is traditional to use letter symbols two phenotypes are possible, however, because the dominant al- to refer to the alleles of an organism. The dominant alleles are sym- lele is expressed in both the homozygous dominant (EE) and bolized by uppercase letters, and the recessive alleles are symbolized the heterozygous (Ee) individuals. Thus, the genotype of a person who is homozygous for pressed only in the homozygous recessive (ee) condition. Refer to free earlobes as a result of a dominant allele is symbolized EE; a figure 22. In both of these instances, the trait may be expressed in a child of parents who are heterozygous. Developmental © The McGraw−Hill Anatomy, Sixth Edition Development Anatomy, Postnatal Companies, 2001 Growth, and Inheritance 784 Unit 7 Reproduction and Development Phenotypes of the parents dark hair dark hair free free earlobes earlobes FIGURE 22. Any of the combinations of genes that have a D and chart, and the female gametes (ova) at the top, as in figure 22. Three of the possible combinations The four spaces on the chart represent the possible combinations have two alleles for attached earlobes (ee) and at least one allele for of male and female gametes that could form zygotes. Three of the combina- bility of an offspring having a particular genotype is 1 in 4 (. These are indicated with a for homozygous dominant and homozygous recessive and 1 in 2 square (I). The remaining possibility has the genotype eedd for at- tached earlobes and light hair. Normal color vision (designated C) are followed from parents to offspring is referred to as a dihybrid dominates. The term hybrid refers to an offspring de- depends entirely on the X chromosomes. The genotype possibili- scended from parents who have different genotypes. The al- C c X X Normal female carrying the recessive allele lele for red-green color blindness, for example, is determined by a c c X X Color-blind female In order for a female to be red-green color-blind, she must have the recessive allele on both of her X chromosomes. Her fa- Punnett square: from Reginald Crundall Punnett, English geneticist, 1875–1967 ther would have to be red-green colorblind and her mother Van De Graaff: Human VII. Developmental © The McGraw−Hill Anatomy, Sixth Edition Development Anatomy, Postnatal Companies, 2001 Growth, and Inheritance Chapter 22 Developmental Anatomy, Postnatal Growth, and Inheritance 785 would have to be a carrier for this condition. A male with only concern for developmental anatomy are such topics as ectopic one such allele on his X chromosome, however, will show the pregnancies, so-called test-tube babies, multiple pregnancy, fetal characteristic.