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    By O. Aschnu. Saint Andrews Presbyterian College.

    The septal cartilage forms the anterior portion of the nasal septum generic detrol 4mg visa, and the paired lateral carti- lages and alar cartilages form the framework around the nostrils discount detrol 1mg without a prescription. The nasal vestibule is the anterior expanded portion of the nasal fossa (fig buy 2mg detrol visa. There are several openings into the nasal cavity, including the openings of the various paranasal sinuses, those of the nasolacrimal ducts that drain from the eyes, and those of the audi- tory tubes that drain from the tympanic cavities. Respiratory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 606606 Unit 6 Maintenance of the Body Simple squamous epithelium (lining pulmonary alveoli) FIGURE 17. The roof of the nasal cavity is formed anteriorly by the frontal bone and paired nasal bones, medially by the cribriform plate of the ethmoid bone, and posteriorly by the sphenoid bone (see figs. In the trachea and bronchi, there are The anterior openings of the nasal cavity are lined with stratified squa- about 300 cilia per cell. The cilia move mucus-dust particles toward mous epithelium, whereas the conchae are lined with pseudostratified the pharynx, where they can either be swallowed or expectorated. Mucus-secreting gob- let cells are present in great abundance throughout both regions. Dust, pollen, smoke, and other fine particles are trapped • The nasal epithelium covering the conchae serves to warm, along the moist mucous membrane lining the nasal cavity. The nasal epithelium is highly vascular and covers an extensive surface • The olfactory epithelium in the upper medial portion of area. This is important for warming the air but unfortu- the nasal cavity is concerned with the sense of smell. Respiratory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 Chapter 17 Respiratory System 607 FIGURE 17. There are several drainage openings into the nasal cavity (see Pharynx fig. An excessive secretion of tears causes the nose to run as the tears drain into the nasal cavity. The supporting walls of the pharynx are com- accessory connections, it is no wonder that infections can spread so posed of skeletal muscle, and the lumen is lined with a mucous easily from one chamber to another throughout the facial area. To avoid causing damage or spreading infections to other areas, one membrane. Within the pharynx are several paired lymphoid or- must be careful not to blow the nose too forcefully. Commonly referred to as the “throat” or “gul- let,” the pharynx has both respiratory and digestive functions. Paranasal Sinuses The pharynx is divided on the basis of location and function into three regions (see fig. Paired air spaces in certain bones of the skull are called paranasal • The nasopharynx serves only as a passageway for air, be- sinuses. These sinuses are named according to the bones in cause it is located above the point of food entry into the which they are found; thus, there are the maxillary, frontal, body (the mouth). It is the uppermost portion of the phar- sphenoidal, and ethmoidal sinuses (fig. Each sinus com- ynx, positioned directly behind the nasal cavity and above municates via drainage ducts within the nasal cavity on its own the soft palate. These sinuses are responsible ditory (eustachian) tubes connect the nasopharynx with for some sound resonance, but most important, they function to the tympanic cavities. The pharyngeal tonsils, or ade- decrease the weight of the skull while providing structural noids, are situated in the posterior wall of the nasal cavity.

    Those primarily responsible for transmitter release belong to the N (a1B) order detrol 2 mg otc, P/Q (a1A) and R classes (a1E) detrol 2mg cheap. So far order detrol 4 mg otc, no pharmacological agents capable of uniquely modifying Ca2‡ channels involved in transmitter release have been described (other than polypeptide toxins). These, and other (L-type, T-type), Ca2‡ channels are also variably present in neurons somata and/or dendrites, where they contribute to the regulation of neural activity in other ways (see below). REGULATION OFCa2‡ CHANNELS BY NEUROTRANSMITTERS N and P/Q channels are susceptible to inhibition by many neurotransmitters and extra- cellular mediators that act on receptors coupling to Pertussis toxin-sensitive G-proteins (primarily Go) Ð for example, noradrenaline (via a2 receptors), acetylcholine (via M2 and M4 muscarinic receptors), GABA (via GABA-B receptors), opioid peptides (via m=d receptors) and adenosine (via A2 receptors) (see Fig. Inhibition results from the release of the bg subunits of the trimeric (abg) G-protein following its activation by the receptor. The bg subunit then binds to the Ca2‡ channel in such a way as to shift its voltage sensitivity to more positive potentials, so that the channels do not open as readily during a rapid membrane depolarisation. One interpretation of this is that the binding of the bg subunits is itself voltage- dependent. This is thought to provide the principal mechanism responsible for presynaptic inhibition, whereby neurotransmitters inhibit their own release (autoinhibition) during high-frequency synaptic transmission. This process can be replicated by applying exogenous transmitters or their analogues (see Fig. Records show intra- axonal recordings from (a) a regenerating sciatic nerve axon following nerve crush; (b) a normal sciatic nerve axon; and (c) a demyelinated ventral root axon after treatment with lysopho- sphatidylcholine. Note that 4-AP prolongs the action potential in (a) and (c) but not in (b). Thus, current through 4-AP-sensitive K‡ channels contributes to action potential repolarisation in premyelinated or demyelinated mammalian axons, whereas in normal myelinated axons repolarisation is entirely due to Na‡ channel inactivation. Ion Channel Organization of the Myelinated Fiber, p 48±54 (1990) with permission from Elsevier Science 40 NEUROTRANSMITTERS, DRUGS AND BRAIN FUNCTION Figure 2. Currents were evoked by two successive 10 ms steps from 770 mV to 0 mV, separated by a prepulse to ‡90 mV. Note that the transient inhibition produced by NA (mediated by the G-protein Go) and the tonic inhibition produced by the G-protein b1g2 subunits were temporarily reversed by the ‡90 mV depolarisation. Note that pretreatment with Pertussis toxin (PTX), which prevents coupling of the adrenoceptor to Go, abolished inhibition. Reproduced with permission) CONTROL OFNEURONAL ACTIVITY 41 and suppressed by blocking the presynaptic receptors with antagonist drugs, which thereby selectively enhance the release of individual transmitters. ION CHANNELS AFFECTING THE PATTERN AND FREQUENCY OF ACTION POTENTIAL DISCHARGES The opening of Na‡ ion channels for the initiation of neuronal depolarisation and action potential generation, as described above, can be induced by excitatory neuro- transmitters acting on receptors that are directly linked to cation channels. These include glutamate AMPA receptors (Chapters 3 and 10) and ACh nicotinic receptors (Chapter 6). The inhibitory neurotransmitter GABA has an opposing effect through receptors (GABAA) that are directly linked to the opening of chloride channels, inducing an influx of Cl7 ions and subsequent hyperpolarisation (Chapters 1 and 11). There are, however, a number of other ion channels, generally for K‡ or Ca2‡, that have a more subtle controlling effect on neuronal activity. Their opening may be initiated by (or dependent on) preceding changes in membrane potential and ion flux, but they can be affected indirectly by various neurotransmitters, e. The role of these channels in controlling the overall activity of neurons is clearly important and needs to be considered. However, most nerve cells possess other K‡ channels which are opened during nerve cell discharges but which stay open much longer. These do not contribute much to the repolarisation of individual action potentials but instead affect the excitability of the neuron over periods of hundreds of milliseconds or even seconds. Two principal types of channel having this effect have been identified and their properties are summarised in Table 2. This means that they are activated by the Ca2‡ influx through voltage-gated Ca2‡ channels when these are opened during a somatic or dendritic action potential, or during trains of action potentials.

    Her blood you request an angiogram of her abdominal pressure is markedly elevated today generic detrol 2mg on line, and in arteries generic 4 mg detrol mastercard. How can the renal artery stenosis stethoscope buy 1 mg detrol fast delivery, which corresponds to her heart- (narrowing) seen in the adjacent beat. Lab work shows very low serum potas- angiogram cause high blood pressure? Discuss the impact that this condition low potassium, so you start her on potassium may have on the opposite renal artery supplementation. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 Chapter 16 Circulatory System 599 Chapter Summary Functions and Major Components of the (c) The heart contains right and left (b) Veins have venous valves that direct Circulatory System (pp. The circulatory system transports oxygen and bicuspid valves, respectively); a compressed by the skeletal muscle and nutritive molecules to the tissue cells pulmonary semilunar valve; and an pumps. Capillaries are composed of endothelial from tissue cells; it also carries hormones 2. They are the basic functional and other regulatory molecules to their are the pulmonary and the systemic; in units of the circulatory system. Principal Arteries of the Body protect the body from infection, and (a) The pulmonary circulation includes (pp. The components of the circulatory system right ventricle through the lungs, and the brachiocephalic trunk, the left are the heart, blood vessels, and blood, from there to the left atrium. The brachiocephalic system, and the lymphatic vessels and other arteries, capillaries, and veins trunk divides into the right common lymphoid tissue and organs of the in the body. These vessels carry blood carotid artery and the right subclavian lymphatic system. Blood, a highly specialized connective (c) The myocardium of the heart is external carotid arteries and the vertebral tissue, consists of formed elements served by right and left coronary arteries. Erythrocytes are disc-shaped cells that coronary sinus collects and empties the paired vertebral arteries, which lack nuclei but contain hemoglobin. Contraction of the atria and ventricles is surrounding the pituitary gland. Leukocytes have nuclei and are classified the atria and then enter the 3. The upper extremity is served by the as granular (eosinophils, basophils, and atrioventricular (AV) node. Leukocytes defend the conducted by the atrioventricular the axillary artery and then the body against infections by bundle and conduction myofibers brachial artery as it enters the arm. During contraction of the ventricles, the the radial and ulnar arteries, which cytoplasmic fragments that assist in the intraventricular pressure rises and causes supply blood to the forearm and formation of clots to prevent blood loss. Erythrocytes are formed through a process the pulmonary and aortic valves close 4. The abdominal portion of the aorta has called erythropoiesis; leukocytes are because the pressure is greater in the the following branches: the inferior formed through leukopoiesis. Closing of the AV valves causes the first renal, suprarenal, testicular (or ovarian), sac, liver, and spleen. In the adult, red sound (lub); closing of the pulmonary and and inferior mesenteric arteries. Heart murmurs are commonly internal and external iliac arteries, which caused by abnormal valves or by septal supply branches to the pelvis and lower Heart (pp. The wall of the heart consists of the conduction is called an electrocardiogram Principal Veins of the Body epicardium, myocardium, and (ECG or EKG). Blood from the head and neck is drained (a) The right atrium receives blood from Blood Vessels (pp. Arteries and veins have a tunica externa, blood from the brain is drained by the and the right ventricle pumps blood tunica media, and tunica interna. Arteries ventricle pumps blood into the transport blood away from the heart. Circulatory System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 600 Unit 6 Maintenance of the Body 3.

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