By D. Connor. Marygrove College.
These colliculi form the cerebellum in situ has an upper or superior surface order indinavir 400mg visa medicine of the future, as “tectum indinavir 400mg with visa treatment plan template,” a term often used; a less frequently seen in this photograph, and a lower or inferior surface used term for these colliculi is the quadrigem- (shown in the next illustration). The pineal, a glandular structure, known as the vermis. The lateral portions are called the hangs down from the back of the diencephalon cerebellar hemispheres. Sulci separate the folia, and some of the deeper sulci • Although not quite in view in this illustration, are termed ﬁssures. The primary ﬁssure is located on the the trochlear nerves (CN IV) emerge posteriorly superior surface of the cerebellum, which is the view seen at the lower level of the midbrain, below the in this photograph. The horizontal ﬁssure is located at inferior colliculi (see Figure 10). Using these sulci and ﬁssures, the cerebellar cortex has This view also shows the back edge of the cerebral pedun- traditionally been divided into a number of different lobes, cle, the most anterior structure of the midbrain (see Figure but many (most) of these do not have a distinctive func- 6 and Figure 7). The pathway for discriminative touch sensation, BRAINSTEM 6 called the gracilis tract (or fasciculus) continues up the posterior aspect of the spinal cord and synapses in the nucleus of the same name; the pathway then continues up BRAINSTEM AND CEREBELLUM: DORSAL to the cerebral cortex. Beside it is another nucleus for a similar pathway with the same func- This is a photograph of the same specimen as Figure 9A, tion, the nucleus cuneatus (see Figure 10). These nuclei but the specimen is tilted to reveal the inferior aspect of will be discussed with the brainstem cross-sections in the cerebellum and the posterior aspect of the medulla. The medulla ends and the The posterior aspect of the pons is still covered by the spinal cord begins where the C1 nerve roots emerge. The posterior aspect of the The cerebellar lobules adjacent to the medulla are midbrain can no longer be seen. The upper end of the known as the tonsils of the cerebellum (see ventral view thalamus is still in view. The tonsils are found just The horizontal ﬁssure of the cerebellum is now clearly inside the foramen magnum of the skull. The vermis of the cerebellum is clearly seen between the hemispheres. Just below the vermis is an Should there be an increase in the mass of tissue occupy- opening into a space — the space is the fourth ventricle ing the posterior cranial fossa (e. This would and Figure 21) The opening is between the ventricle and force the cerebellar tonsils into the foramen magnum, the subarachnoid space outside the brain (discussed with thereby compressing the medulla. The compression, if Figure 21); the name of the opening is the Foramen of severe, may lead to a compromising of function of the Magendie. The complete syndrome is known as tonsillar herni- men is the medulla, its posterior or dorsal aspect. This is a life-threatening situation that signiﬁcant structure seen here is a small elevation, repre- may cause cardiac or respiratory arrest. Both can be seen in the ventral view of the BRAINSTEM 7 brainstem (see Figure 7). Details of the information car- ried in these pathways will be outlined when the functional aspects of the cerebellum are studied with the motor sys- BRAINSTEM: DORSAL VIEW — CEREBELLUM tems (see Figure 55). The superior cerebellar peduncles REMOVED convey ﬁbers from the cerebellum to the thalamus, passing through the roof of the fourth ventricle and the midbrain This diagram shows the brainstem from the dorsal per- (see Figure 57). This peduncle can only be visualized from spective, with the cerebellum removed. This dorsal perspective is useful (see also Figure 6 and Figure 7). The lower part of the fourth ventricle separates the MIDBRAIN LEVEL medulla from the cerebellum (see Figure 21). The special structures below the fourth ventricle are two large protu- The posterior aspect of the midbrain has the superior and berances on either side of the midline — the gracilis and inferior colliculi, as previously seen, as well as the emerg- cuneatus nuclei, relay nuclei which belong to the ascend- ing ﬁbers of CN IV, the trochlear nerve. The posterior ing somatosensory pathway (discussed with Figure 9B, aspect of the cerebral peduncle is clearly seen.
It is likely that impaired tracheobronchial clearance of the abnormal secretions leads to widespread mucous plugging of airways buy indinavir 400mg with mastercard medicine 2020, resulting in secondary bac- terial infection buy discount indinavir 400mg on-line treatment 5th metatarsal stress fracture, persistent inflammation, and consequent generalized bronchiectasis. Extrapulmonary manifestations may also suggest the diagnosis of CF. Prominent among these findings are pancreatic insufficiency with consequent steatorrhea, recurrent par- tial intestinal obstruction caused by abnormal fecal accumulation (the so-called meco- nium ileus equivalent), heat prostration, hepatic cirrhosis, and aspermia in men. The diagnosis can be established by abnormal results on a sweat test performed in a quali- fied laboratory using pilocarpine iontophoresis. In persons younger than 20 years, a sweat chloride level exceeding 60 mEq/L confirms the diagnosis; a value exceeding 80 mEq/L is required for diagnosis in persons 20 years of age or older. With the identifica- tion of the gene for CF, genetic screening has become available. A 53-year-old man with a 60-pack-year history of cigarette smoking presents with complaints of pro- ductive cough and dypsnea. He reports that for the past 3 months, he has been treated for bronchitis with antibiotics, but his symptoms have not resolved. Over the past several weeks, he has experienced progressive dypsnea on exertion. He denies having any chest discomfort or any other significant med- ical history. His lung examination shows wheezing that resolves with expectoration of phlegm. Arterial blood gas measurements are as follows: PaO2, 75 mm Hg; alveolar carbon dioxide tension (PACO2), 55 mm Hg. Which of the following is NOT true for this patient? If this patient continues to smoke, his FEV1 value will continue to decrease two to three times faster than normal B. If this patient stops smoking, the rate of decline in expiratory flow reverts to that of nonsmokers, and there may be a slight improve- ment in FEV1 during the first year C. This patient would be expected to have evidence of extensive panacinar emphysema D. This patient would be expected to have increased RV, increased FRC, and normal or increased total lung capacity (TLC) E. This patient is at risk for right-sided heart failure Key Concept/Objective: To understand the progression of chronic bronchitis and emphysema 12 BOARD REVIEW Panacinar emphysema is common in patients with α1-antitrypsin deficiency. Centriacinar emphysema is commonly found in cigarette smokers and is rare in non- smokers. Centriacinar emphysema is usually more extensive and severe in the upper lobes. In most cigarette smokers, a mixture of centriacinar and panacinar emphysema develops. In healthy nonsmokers, FEV1 begins declining at about 20 years of age and continues at an average rate of about 0. In smokers with obstructive lung disease, FEV1 decreases, on average, two to three times faster than normal. When per- sons with mild to moderate airflow obstruction stop smoking, the rate of decline in expiratory flow reverts to that observed in nonsmokers, and there may be a slight improvement in FEV1 during the first year. Measurement of lung volumes uniformly reveals an increased RV and a normal to increased FRC. RV may be two to four times higher than normal because of slowing of expiratory flow and gas trapping behind pre- maturely closed airways. One group of patients (type A) exhibit dyspnea with only mild to moderate hypoxemia (PaO2 levels are usually > 65 mm Hg) and maintain normal or even slightly reduced PACO2 levels. The other clinical group of patients (type B) are some- times called blue bloaters; they typically exhibit cough and sputum production, fre- quent respiratory tract infections, chronic carbon dioxide retention (PACO2 > 45 mm Hg), and recurrent episodes of cor pulmonale. In the type B patient, both alveolar hypoxia and acidosis (secondary to chronic hypercapnia) stimulate pulmonary arterial vasoconstriction, and hypoxemia stimulates erythrocytosis. Increased pulmonary vas- cular resistance, increased pulmonary blood volume, and, possibly, increased blood vis- cosity (resulting from secondary erythrocytosis) all contribute to pulmonary arterial hypertension.
The equations of the medial and lateral femoral spheres expressed in the femoral coordinate system of axes were written as: 2 2 2 fxy purchase indinavir 400mg on line symptoms vitamin b deficiency, = – r – x– h – y – + (1 discount indinavir 400mg on line treatment 12mm kidney stone. The equations of the medial and lateral tibial planes expressed in the tibial coordinate system of axes were written as: g(x′, y′) = my′ + c (1. Initially, a two-point contact situation is assumed with the femur and tibia in contact on both medial and lateral sides. In the calculations, if one contact force becomes negative, then the two bones within its compart- ment are assumed to be separated, and the single-point contact situation is introduced, thus maintaining contact in the other compartment. The contact condition requires that the position vectors of each contact point in the femoral and the → → tibial coordinate systems, Rc and rc, respectively, satisfy Eq. Since contact occurs at points identiﬁable in both the femoral and tibial articulating surfaces, we can write at each contact point: zc = f(xc, yc) (7. Satisfying these equations at some given point will ensure that it is a contact point. Thus, in the two-point contact version of the model, Eqs. The geometric condition of compatibility of rigid bodies requires that a single tangent plane exists to both femoral and tibial surfaces at each contact point. This condition also implies that the normals to the femoral and tibial surfaces at each contact point are always colinear, and their cross product must vanish. In order to express the geometric compatibility condition in a mathematical form, the position vector of the contact point in the femoral coordinate system (Eq. Cross product of these two tangent vectors is then employed to determine the unit vector normal to the femoral surface,nˆ f , at the contact point. Thus, for each contact point, two independent scalar equations are written generating four scalar equations to represent the geometric compatibility conditions in the two-point contact situation and two scalar equations to represent the geometric compatibility conditions in the one-point contact situation. Ligamentous Forces In this analysis, external loads are applied, and ligamentous and contact forces are then determined. The model includes 12 nonlinear spring elements that represent the different ligamentous structures and the capsular tissue posterior to the knee joint. Four elements represent the respective anterior and posterior ﬁber bundles of the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL); three elements represent the anterior, deep, and oblique ﬁber bundles of the medial collateral ligament (MCL); one element represents the lateral collateral ligament (LCL); and four elements represent the medial, lateral, and oblique ﬁber bundles of the posterior part of the capsule (CAP). The coordinates of the femoral and tibial insertion sites of the different © 2001 by CRC Press LLC ligamentous structures were speciﬁed according to the data available in the literature. The spring elements representing the ligamentous structures were thus assumed to be line elements extending from the femoral origin to the tibial insertion. These elements were assumed to carry load only when they are in tension, that is, when their length is larger than their slack, unstrained length, Lo. Ligaments exhibit a region of nonlinear force-elongation relationship, the “toe” region, in the initial stage of ligament strain, then a linear force-elongation relationship in later stages. The magnitude of the force in the jth ligamentous element is thus expressed as: ε ≤ j 2 Fj = K1j Lj − Lo j ; 0 j 2 1 (1. The strain in the jth ligamentous element, εj, is given by L j − o j ε = (1. Values of the stiffness coefﬁcients of the spring elements used to model the different ligamentous structures were estimated according to the data available in the literature21,23,30,93-96,109,118,129,130,133 and are listed in Table 1. The slack length of each spring element is obtained by assuming an extension ratio e at full extension and using the following relation:j © 2001 by CRC Press LLC TABLE 1. The values of the extension ratios were speciﬁed according to the data available in the literature20,60 and are listed in Table 1. Contact forces are induced at one or both contact points. These forces are applied © 2001 by CRC Press LLC normal to the articular surface. Thus, the contact force applied to the tibia is expressed as: Ni = Nnˆ where i i N is the magnitude of the contact force, andi nˆi is the unit vector normal to the tibial surface at the contact point, expressed in the femoral coordinate system. In the two-point contact situation, i = 1, 2 and in the single-point contact situation, i = 1. Equations of Motion The equations governing the three-dimensional motion of the tibia with respect to the femur are the second order differential Newton’s and Euler’s equations of motion. Newton’s equations are written in a scalar form, with respect to the femoral ﬁxed system of axes, as: 2 12 F ex x ix jx m ˙˙xo (1. Euler’s equations of motion are written with respect to the moving tibial system of axes which is the · · tibial centroidal principal system of axes (x′, y′ and z′).
In some indi- nucleus may or my not receive innervation from the cortex viduals best 400mg indinavir treatment knee pain, there is a predominantly crossed of both sides or only from the opposite side makes inter- innervation indinavir 400mg free shipping treatment viral conjunctivitis. A lesion affecting the hypoglossal nucleus ﬁbers inﬂuence all the brainstem motor nuclei, or nerve is a lower motor lesion of one-half of the tongue particularly the reticular formation, including (on the same side) and will lead to paralysis and atrophy the red nucleus and the substantia nigra, but not of the side affected. The cortico-retic- © 2006 by Taylor & Francis Group, LLC Functional Systems 127 Fronto-pontine ﬁbers Cortico-bulbar (and Temporo-pontine ﬁbers cortico-spinal) ﬁbers Parieto-pontine ﬁbers Occipito-pontine ﬁbers FIGURE 46: Cortico-Bulbar Tracts — Nuclei of the Brainstem © 2006 by Taylor & Francis Group, LLC 128 Atlas of Functional Neutoanatomy intermingled with the lateral cortico-spinal tract (see Fig- FIGURE 47 ure 68 and Figure 69). RUBRO-SPINAL TRACT The rubro-spinal tract is a well-developed pathway in some animals. In monkeys, it seems to be involved in ﬂexion movements of the limbs. Stimulation of this tract VOLUNTARY/NONVOLUNTARY MOTOR in cats produces an increase in tone of the ﬂexor muscles. CONTROL NEUROLOGICAL NEUROANATOMY The red nucleus is a prominent nucleus of the midbrain. It gets its name from a reddish color seen in fresh dissec- The location of this tract within the brainstem is shown tions of the brain, presumably due to its high vascularity. The tract is said to continue throughout the tion with large neurons more ventrally located. The rubro- length of the spinal cord in primates but probably only spinal pathway originates, at least in humans, from the extends into the cervical spinal cord in humans. The ﬁbers of CN III (oculomotor) exit through the The red nucleus receives its input from the motor areas medial aspect of this nucleus at the level of the upper of the cerebral cortex and from the cerebellum (see Figure midbrain (see Figure 65A). The cortical input is directly onto the projecting cells, thus forming a potential two-step pathway from motor CLINICAL ASPECT cortex to spinal cord. The rubro-spinal tract is also a crossed pathway, with The functional signiﬁcance of this pathway in humans is the decussation occurring in the ventral part of the mid- not well known. The number of large cells in the red brain (see also Figure 48 and Figure 51B). The tract nucleus in humans is signiﬁcantly less than in monkeys. The ﬁbers then course in the lateral portion adequately described. Although the rubro-spinal pathway of the white matter of the spinal cord, just anterior to and may play a role in some ﬂexion movements, it seems that the cortico-spinal tract predominates in the human. The role of this circuit in motor control will be explained with the cerebellum (see CRANIAL NERVE NUCLEI Figure 54–Figure 57). The motor cranial nerve nuclei and their function have DESCENDING TRACTS AND CORTICO- been discussed (see Figure 7 and Figure 8A), and their location within the brainstem will be described (see Figure PONTINE FIBERS 64–Figure 67). Only topographical aspects will be The descending pathways that have been described are described here: shown, using the somewhat oblique posterior view of the brainstem (see Figure 10 and Figure 40), along with those • CN III — Oculomotor (to most extra-ocular cranial nerve nuclei that have a motor component. These muscles and parasympathetic): These ﬁbers pathways will be presented in summary form: traverse through the medial portion of the red nucleus, before exiting in the fossa between the • Cortico-spinal tract (see Figure 45): These cerebral peduncles, the interpeduncular fossa ﬁbers course in the middle third of the cerebral (see Figure 65A). At the lowermost part of the before exiting posteriorly (see Figure 10 and medulla (Figure 7), most of the ﬁbers decussate Figure 66A). The slender nerve then wraps to form the lateral cortico-spinal tract of the around the lower border of the cerebral pedun- spinal cord (see Figure 68 and Figure 69). The term also includes those cortical could not be depicted from this perspective. These are also located sion): The ﬁbers to the muscles of facial expres- in the middle third of the cerebral peduncle and sion have an internal loop before exiting. The are given off at various levels within the brain- nerve loops over the abducens nucleus, forming stem. It should from the lower portion of the red nucleus decus- be noted that the nerve of only one side is being sates in the midbrain region and descends shown in this illustration. In the spinal cord, the • CN IX — Glossopharyngeal and CN X- ﬁbers are located anterior to the lateral cortico- Vagus (motor and parasympathetic): The ﬁbers spinal tract (see Figure 68). CORTICO-PONTINE FIBERS • CN XI — Spinal Accessory (to neck muscles): The ﬁbers that supply the large muscles of the The cortico-pontine ﬁbers are part of a circuit that involves neck (sternomastoid and trapezius) originate in the cerebellum.