By V. Altus. Friends University.
It also helps to coordinate im- transmitter may be removed by several methods: pulses within the CNS 80 mg top avana sale. The spinal cord is contained in and protected by the vertebrae order 80mg top avana, which fit together to form ◗ It may slowly diffuse away from the synapse 80mg top avana visa. The column of bone again discount 80mg top avana with mastercard, a process known as Reuptake. This disparity in growth continues to increase, so that in Checkpoint 9-9 Chemicals are needed to carry information adults, the spinal cord ends in the region just below the across the synaptic cleft at a synapse. THE NERVOUS SYSTEM: THE SPINAL CORD AND SPINAL NERVES 187 Brain C1 C2 Cervical Brain stem C3 Spinal cord C4 plexus Cervical C5 Cervical nerves C6 (C1—8) C7 Brachial enlargement C8 plexus T1 Radial nerve T2 T3 Spinal T4 cord T5 Median nerve T6 Ulnar nerve T7 Thoracic T8 nerves Intercostal T9 nerves T10 9 (T1—12) T11 Phrenic nerve T12 Lumbar L1 enlargement L2 L3 Lumbar L4 Lumbosacral nerves L5 plexus (L1—5) Femoral nerve S1 Sacral S2 S3 nerves Sciatic nerve S4 (S1—5) S5 Coccygeal CO1 nerve A B Figure 9-11 Spinal cord and spinal nerves. ZOOMING IN Is the spinal cord the same length as the spinal column? How does the number of cervical vertebrae compare with the number of cervical spinal nerves? Structure of the Spinal Cord commissure (KOM-ih-shure). In the center of the gray commissure is a small channel, the central canal, that The spinal cord has a small, irregularly shaped internal contains cerebrospinal fluid, the liquid that circulates section of gray matter (unmyelinated tissue) surrounded around the brain and spinal cord. A narrow groove, the by a larger area of white matter (myelinated axons) (Fig. The internal gray matter is arranged so that a col- left portions of the posterior white matter. A deeper umn of gray matter extends up and down dorsally, one on groove, the anterior median fissure (FISH-ure), separates each side; another column is found in the ventral region the right and left portions of the anterior white matter. These two pairs of columns, called the dor- sal horns and ventral horns, give the gray matter an H- shaped appearance in cross-section. The bridge of gray Ascending and Descending Tracts The spinal matter that connects the right and left horns is the gray cord is the pathway for sensory and motor impulses trav- 188 CHAPTER NINE Dorsal root Dorsal root of Central canal Posterior median sulcus ganglion spinal nerve Dorsal horn Gray commissure Spinal nerve Ventral horn A Ventral root of Anterior median fissure White matter spinal nerve Central canal Posterior median sulcus Dorsal horn Gray matter Gray commissure Ventral horn Anterior median fissure White matter B Figure 9-12 The spinal cord. These impulses are carried in The Reflex Arc the thousands of myelinated axons in the white matter of the spinal cord, which are subdivided into tracts (groups As the nervous system functions, it receives, interprets, and of fibers). Sensory (afferent) impulses entering the spinal acts on both external and internal stimuli. The spinal cord cord are transmitted toward the brain in ascending tracts is also a relay center for coordinating neural pathways. Motor (efferent) impulses traveling complete pathway through the nervous system from stim- from the brain are carried in descending tracts toward ulus to response is termed a reflex arc (Fig. The basic parts of a reflex arc are the following (Table 9-2): 1. Receptor—the end of a dendrite or some specialized Checkpoint 9-10 The spinal cord contains both gray and white matter. Sensory neuron, or afferent neuron—a cell that trans- Checkpoint 9-11 What is the purpose of the tracts in the white matter of the spinal cord? Sensory impulses enter the dorsal horn of the gray matter in the spinal cord. THE NERVOUS SYSTEM: THE SPINAL CORD AND SPINAL NERVES 189 5. Effector—a muscle or a gland out- side the CNS that carries out a re- sponse. At its simplest, a reflex arc can in- volve just two neurons, one sensory and one motor, with a synapse in the CNS. Few reflex arcs require only this minimal number of neurons. The many intricate patterns that make the nervous system so responsive and adaptable also make it difficult to study, and investigation of the nervous system is one of the most active areas of research today. Reflex Activities Although reflex pathways may be quite complex, a simple reflex is a rapid, uncompli- cated, and automatic response involv- ing very few neurons. Reflexes are spe- cific; a given stimulus always produces the same response.
Using the understanding of Wolff’s law buy top avana 80 mg on-line, it is clear that the growth plate tries to decrease this sheer force as a summated effect over time top avana 80 mg amex. Using this assumption buy top avana 80mg, three-dimensional finite element modeling of the proximal femoral growth plate has confirmed that the femur will grow into varus if a child is in a regular weightbearing stable hip environment and will grow into valgus if the child does not have a balanced hip abductor generic 80 mg top avana amex. Therefore, when a baby is born with a 150° neck shaft angle, as she gets to the age of 1 year and starts to walk, the abductor muscle power is increasing. As the abductor muscle force increases, it causes a joint reaction force vector that points the femoral head into the center of the acetabulum. As the abductors get stronger, the femoral neck shaft angle will drop into more varus as the hip joint reaction force vec- tor goes into more varus. This process is totally independent of neurologic control or genetic modeling, as demonstrated by patients who have a com- pletely normal development with normal neck shaft angles up to age 2 years, and then through accidents or other reasons, become nonambulatory and have a change in their pathomechanics (Case 10. The femoral neck shaft angle will follow the pathomechanics, not the genetic program that appears to have been present. For nonambulatory children, the resultant joint reac- tion force vector becomes almost vertical with the femoral shaft because the hip abductors are either at a disadvantage or are being overpowered by the hip adductors. Both the adducted hip and the severely abducted hip de- velop a high degree of femoral neck shaft angle or coxa valga because the resultant hip joint reaction force vector tends to be very nearly parallel with the femoral shaft. Understanding the pathomechanics of the valgus neck shaft angle also explains why there is no impact on the neck shaft angle from having chil- dren weight bearing, such as in a standing frame. This type of weight bear- ing does not impact the degree of femoral neck shaft valgus because these children are usually not using a functioning abductor muscle against the body mass area to cause a more horizontal joint reaction force vector that drives the hip medially, which is needed to cause the femoral neck shaft an- gle to go into varus or to stay in varus (Figure 10. This also demonstrates why, when varus osteotomy is performed in young children, especially those at age 2 years or younger, that all the femoral neck shaft angle will recover to where the mechanical system is determining it should be. This ability for remodeling the femoral neck shaft angle starts to diminish substantially in late childhood. By the adolescent growth spurt, the ability for the femoral neck shaft angle to remodel itself either into varus or recover back into coxa Case 10. A radiograph of his hip at the time of the initial injury demonstrated a normal hip (Fig- ure C10. By age 7 years, 5 years after the insult, the hip had the typical appearance of the valgus femoral neck with spastic hip subluxation (Figure C10. This process is totally independent of neurologic control or genetic modeling, as demonstrated by this boy who had completely normal development with normal neck shaft angles up to age 2 years. Because the proximal femoral epiphysis determines femoral neck shaft angle and it responds by trying to decrease princi- pal shear stress, weight bearing in a stander or walking with a walker is not likely to im- pact the femoral neck shaft angle. This angle can only be impacted if the hip abductor has a forceful contraction against a fixed limb in which the abductor moment arm causes the hip joint reaction force to medialize. Weight bearing in the stander or walking in a walker does cause bone stress and should increase the bone mass even if it does not impact the shape of the proximal femur. Natural History The natural history of the internal rotation deformities, which include both femoral anteversion and the spastic internal rotator muscles, is fairly con- sistent. Often, the internal rotation is noted in young children, and as these children start standing and walking, it may cause substantial difficulty be- cause both knees are hitting together and they will trip. Children who gain the ability to do independent walking often have sufficient motor control and will start attempting to correct the anteversion. This muscular attempt at correcting the internal rotation sends mechanical messages to the bone, caus- ing the bone to derotate as it grows, and this is the means by which infantile femoral anteversion is corrected in normal children. Most of this internal ro- tation will be corrected by the age of 5 to 7 years. However, some children have such severe femoral anteversion that their ability to continue making progress toward walking independence becomes blocked as young as age 4 years. This failure to progress is often a combination of motor control and femoral anteversion, which is especially a problem if some internal tibial tor- sion is combined with the femoral anteversion. Hip 623 that femoral anteversion can recur, especially if it is corrected in children younger than age 4 years22; however, in our experience, the anteversion will not recur if it is corrected after age 5 to 7 years. The internal rotation pos- ture may recur due to spastic or contracted internal rotator muscles. Because of this natural history of responsiveness of the bone to torsional change, it is better to correct anteversion later and, if at all possible, try to avoid cor- recting it before age 5 to 7 years.
Thus discount 80 mg top avana with mastercard, dur- ing mild and moderate-intensity exercise generic 80 mg top avana fast delivery, the release of lactate diminishes as the aerobic metabolism of glucose and fatty acids becomes predominant generic top avana 80mg without prescription. Blood Glucose as a Fuel At any given time during fasting purchase top avana 80 mg otc, the blood contains only approximately 5 g glu- cose, enough to support a person running at a moderate pace for a few minutes. Therefore, the blood glucose supply must be constantly replenished. The liver per- forms this function by processes similar to those used during fasting. The liver pro- duces glucose by breaking down its own glycogen stores and by gluconeogenesis. The major source of carbon for gluconeogenesis during exercise is, of course, lac- tate, produced by the exercising muscle, but amino acids and glycerol are also used (Fig. Epinephrine released during exercise stimulates liver glycogenolysis and gluconeogenesis by causing cAMP levels to increase. During long periods of exercise, blood glucose levels are maintained by the liver through hepatic glycogenolysis and gluconeogenesis. The amount of glucose that the liver must export is greatest at higher work loads, in which case the muscle is using a greater proportion of the glucose for anaerobic metabolism. With increasing duration of exercise, an increasing proportion of blood glucose is supplied by gluconeogene- sis. However, for up to 40 minutes of mild exercise, glycogenolysis is mainly respon- sible for the glucose output of the liver. However, after 40 to 240 minutes of exercise, the total glucose output of the liver decreases. This is caused by the increased utiliza- tion of fatty acids, which are being released from adipose tissue triacylglycerols (stim- ulated by epinephrine release). Glucose uptake by the muscle is stimulated by the increase in AMP levels and the activation of the AMP-activated protein kinase, which stimulates the translocation of GLUT4 transporters to the muscle membrane. The hormonal changes that direct the increased hepatic glycogenolysis, hepatic glu- coneogenesis, and adipose tissue include a decrease in insulin and an increase in glucagon, epinephrine, and norepinephrine. Plasma levels of growth hormone, cortisol, and thyroid-stimulating hormone (TSH) also increase and may make a contribution to 876 SECTION EIGHT / TISSUE METABOLISM Remember from Chapter 1 that a 2. One gram of glucose Glycogen can give rise to 4 kcal of energy, so at a rate of consumption of 500 Calories per hour we 1. In the fasting state, blood glucose levels are approximately 90 mg/dL, or 900 mg/L. Glycerol If not replenished, that amount of glucose Pyruvate Amino acids would only support 2. Amino acids Lactate 25% Lactate 23% 45% 40 min 240 min Basal Exercise Fig. Production of blood glucose by the liver from various precursors during rest and during prolonged exercise. The shaded area represents the contribution of liver glycogen to blood glucose, and the open area represents the contribution of gluconeogenesis. Metabolic Adaptation to Prolonged Phys- ical Exercise. The activation of hepatic glycogenolysis occurs through glucagon and epinephrine release. Hepatic gluconeogenesis is activated by the increased supply of precursors (lactate, glycerol, amino acids, and pyruvate), the induction of gluconeogenic enzymes by glucagon and cortisol (this only occurs in pro- longed exercise), and the increased supply of fatty acids to provide the ATP and NADH needed for gluconeogenesis and the regulation of gluconeogenic enzymes. Free Fatty Acids as a Source of ATP The longer the duration of the exercise, the greater the reliance of the muscle on free fatty acids for the generation of ATP (Fig. Because ATP generation from 100 Muscle glycogen 75 Blood–borne fatty acids 50 Blood–borne glucose 25 Exhaustion 0 1 2 3 4 Hours Fig. The pattern of fuel utilization changes with the dura- tion of the exercise. CHAPTER 47 / METABOLISM OF MUSCLE AT REST AND DURING EXERCISE 877 free fatty acids depends on mitochondria and oxidative phosphorylation, long-dis- tance running uses muscles that are principally slow-twitch oxidative fibers, such as the gastrocnemius.
Most of these papers report physical therapy being used in conjunction with other treatments quality 80mg top avana, such as surgical hip recon- structions or lower extremity reconstructions for gait improvement cheap 80 mg top avana, or fol- lowing dorsal rhizotomy and Botox injections order top avana 80 mg line. Many of these reports are case series without controls to evaluate the index procedure buy discount top avana 80mg on-line, and most make no objective attempt to evaluate the impact of the therapy program sepa- rately from other modalities. The number of reports attempting to evaluate the impact of specific therapy programs is increasing; however, many con- tain few patients and no control groups. Many reports presume that physical therapy is like medication in that it can be evaluated by having a control group with no treatment. This research approach has some merit if no effect is found, such as the evaluation of therapy in infant stimulation programs. Recognizing these complex interactions has led to recommending more complex and global evaluations using multivariate analysis in research protocols. For example, a treat- ment protocol where physical therapy modalities along with casting and Botox are used to treat gait abnormality in young children cannot be rea- sonably evaluated by any other means. Recognizing the complex interaction of physical therapy in its own right will lead to improved research techniques for other treatments as well. The long history of physical therapy has been predominated by different theories of development and specific protocols to impact childhood devel- opment. In this theory the spinal cord-mediated activities, such as single synapse reflexes and spasticity, have to be corrected first be- fore the more primitive higher reflexes can be addressed. These primitive reflexes then have to be corrected before high-functioning cortical motor 5. Therapy, Education, and Other Treatment Modalities 153 activities, such as walking, can develop properly. This hierarchical theory of neurologic development has some base in animal studies. For example, the need for the eye to function properly before the optical cortex will organize and function appropriately is well documented. The scope of this text, however, makes it impossible to give a full discription of these techniques. In the 1990s, the theory of neurologic development was slowly changing to a more complex, circular theory in which subsystems are recognized to interact. In this the- ory, the psychologic state and behavior of children are also recognized as be- ing important in their motor function. Complex interactions exist between lower reflexes and cortical motor movement patterns, in which the inter- actions and impacts are both from the higher function to the lower function and vice versa. However, this change in approach is not universally adapted, because neurologic pediatric physical therapy is a small subspecialty of the much larger physical therapy discipline. In gen- eral, physical therapists tend to have clinical aptitudes that are similar to those of orthopaedic surgeons. Clinicians with a treatment approach like to identify a specific problem, then apply a cure to make the problem go away. This approach was feasible in the early therapy protocols based on the hier- archical development theory; however, it often frustrated the child, the family, and the therapist. Developing a concept where the child, family, physician, and therapist are one team whose goal is to make the child as in- dependent as he or she can be when growing up is a much more functional approach. With this approach, an experienced therapist is the ideal head coach of the team, because this is the individual who knows the child best from a medical perspective and has the best relationship with the child, family, educators, and physicians. Unfortunately, because of frequent changes in therapists, this role of head coach often falls to the family. For some fam- ilies, this works well, but for others, it does not. The therapist who takes on the role of coach of a child’s motor impair- ment management team has to develop a good relationship with the family and child. In general, this relationship does not work well if the parent or child does not like the therapist. Also, the therapist has to have some under- standing of behavior management techniques to get the most cooperation from a child.