By M. Boss. Adrian College. 2018.
Peak discharge occurred when the monkey moved its hand to the right and toward itself buy 60mg alli with visa, its PD of movement order 60mg alli free shipping. We examined two possible ways in which the anisotropic properties of limb movement might influence the activity of individual neurons discount alli 60mg fast delivery. First alli 60 mg discount, cells with PDs associated with movements requiring greater power may show larger variations in their discharge than cells with preferred directions associated with movements requiring less power. However, we found no correlation between this mean discharge rate and the corresponding total peak joint power (R2 = 0. A second possibility is that variations in the mechanics of limb motion in different spatial directions may result in a nonuniform distribution of PDs across the cell sample. There was a wide range in the number of neurons associated with each movement direction, from 27 to 1. One would Copyright © 2005 CRC Press LLC A 3 4 2 5 1 6 8 7 100 50 0 -500 0 500 1000 Time (ms) Preferred Direction (PD) of Cell B 90 0 deg 180 10 spikes/s PD 270 FIGURE 6. The thick line denotes the mean and the thin lines denote one standard deviation based on five repeat trials. Copyright © 2005 CRC Press LLC A A 30 r2= 0. Each dot reflects the PD of an individual neuron and all dots forming a line reflect neurons with PDs in a given direction of movement (16 divisions of 22. However, the diagram graphically illustrates that the distribution is not uniform when compared to a bimodal distribution. The non- uniform distribution of PDs was also observed based on neural activity only during the reaction time period prior to the onset of movement, suggesting that such biases were not simply a result of afferent feedback. The strong bias in the distribution of PDs during reaching has two profound effects on population vectors (Figure 6. Second, the nonuniform distribution resulted in large variations in the magnitude of the population vector ranging from 56 to 145% of the mean vector length. This modulation in the magnitude of the population vector occurred although movements were of similar magnitude and with similar peak hand veloc- ities. The neural trajectory did not predict the direction of movement from the very beginning of hand motion. Criticisms have been raised about these observed deviations between the popu- lation vector and movement direction. How- ever, reanalysis of our data using the direction of movement for the entire limb movement (from movement initiation to the end of movement) still resulted in the majority of population vectors not predicting the direction of hand movement (11 of the 16 directions). We used a technique comparable to weighting function 8 in the study of Georgopoulos et al. Popu- lation vectors for each movement are shown as grey arrows and corresponding hand path is attached to the base of the arrow. The two large, dashed, light grey circles denote start (right) and target (left) spatial locations. Each sequential value is added vectorally to previous data points and then scaled to match the spatial trajectories in the diagram. The size of the circle denotes a significant difference between population vector and instantaneous hand motion. Population vectors are shifted in time such that the first vector that is statistically tuned is aligned to movement onset. As stated by Georgopoulos,70 “Eight points are insufficient to estimate accurately intermediate points for an intensely curved tuning function. While the article states that PDs were uniformly distributed, it is not stated whether the distribution was tested against both a unimodal and a bimodal distribution. The present study illustrates that nonhuman primates are capable of generating movements of the hand to spatial targets even though population vectors constructed Copyright © 2005 CRC Press LLC from neural activity in M1 do not point in the direction of hand movement. This certainly does not disprove that some neural activity in M1 may convey information related to the hand. It is important to note that while the present study suggests that limb mechanics has a strong influence on the activity of neurons in M1, it does not mean that neural activity at the single cell or population level is explicitly coding joint power. The covariation between the distribution of PDs and joint power can be viewed as a reflection of the internal model of the motor periphery used to guide and control limb movement.
Despite ity to communicate with others effective alli 60mg, increases the degree of the apparent overlap of effects with stimulant drugs 60mg alli otc, intimacy one feels toward others in the surroundings 60mg alli amex, in- however buy alli 60 mg without prescription, there is no cross-tolerance with the CNS stim- creases self-esteem and mood, and generally appears ulants such as amphetamine. One during drug abstinence, nor is there a tremendous crav- residual effect of abuse is the MDMA hangover, which ing for drug during the drug-free period. Therefore, is the occurrence on the second day after abuse of clearly no dependence is attributed to the hallucinogens. Typically, a dose of 75 mg produces the pri- mary psychotomimetic effects, while a dose of 150 mg Treatment Strategies produces LSD-like effects, and a dose of 300 mg pro- The difference between the abused and the lethal dose duces amphetaminelike CNS stimulation. The amphet- of LSD is very large, so little pharmacological interven- aminelike stimulation of the CNS and periphery is tion is necessary. The effects Treatment of PCP intoxication also involves limiting that can be produced by stimulatory doses of hallucino- external stimuli, minimizing lighting, noise, and unneces- gens include tachycardia, hypertension, and arrhyth- sary physical contact. It induces a wide variety of psychotomimetic and hallucinatory effects during emergence from anes- Mechanism of Action thesia. At a low dose, individuals believe they are thinking the hallucinogens is the activation of the 5-HT2-receptor. Other happiness, though (especially at higher doses) the indi- drugs, such as MDMA, induce the release of endogenous vidual can vacillate between euphoria and depression. At higher doses the stimulatory effects are more pronounced and the likelihood of tremendous mood swings more likely. INHALANTS At near anesthetic doses, it produces more typical de- pressant effects, including motor incoordination, Volatile chemicals and gases that produce behavioral ef- catalepsy, vacant stare, or even amnesia. The two derivatives are referred to as drugs in that it is confined primarily to juveniles and China White and are 900 and 1,100 times as potent as young adults. Meperidine has also been used as a template trous oxide by young medical professionals who have for preparing synthetic heroin, the end product being ready access to this agent. However, MPPP is sometimes contaminated with the Deaths occur occasionally by individuals inhaling ni- side reaction product 1-methyl,4-phenyl-1,2,3,6-tetra- trous oxide alone. Volatile organic solvents are usually hydropyridine (MPTP), which produces a parkinsonian aliphatic and aromatic hydrocarbons. Several substi- stances such as gasoline, paint and lacquer thinners, tuted derivatives of amphetamine have also been called lighter fluid, degreasers (methyl chloride and methylene designer drugs. The most widely known of this group is chloride), and the solvents in airplane glue, typewriter the hallucinogen MDMA (ecstasy). Judgment and perception of reality are impaired, ANABOLIC STEROIDS and hallucinations may be produced. The mechanism by Historically, drugs used to increase the ability of an which inhalants produce their behavioral effects are athlete to perform in a given sport included the use of poorly understood, but there are some indications that stimulants to diminish the onset of fatigue or opiates to their actions are similar to those of other centrally acting diminish the pain of exertion. Toxicity depends on the bolic–androgenic steroids (derivatives of testosterone) properties of the individual solvents. They are used to increase muscle size and of inhaling these substances can be severe, for they have definition (in the case of body-building competitors) been implicated in producing cancer, cardiotoxicity, neu- and are sometimes coabused with other growth en- ropathies, and hepatotoxicity. In sports in which mass, physical size, or even total strength (a func- tion of total muscle mass) is important, the abuse of an- DESIGNER DRUGS abolic steroids provides a shortcut to attainment of the In an effort to avoid federal regulations, chemists in physical stature that might otherwise require much clandestine laboratories adopted the strategy of synthe- more extensive training and exercise. Although misconception to believe that anabolic steroid abuse is these drugs are technically not illegal until scheduled, limited to professional athletes and body builders. Efforts to make synthetic adult men and women who are not athletes, who are heroin led to the synthesis of at least six chemicals that blue-collar and white-collar workers, and by male and are structurally similar to fentanyl. These agents gained female athletes at the college, high school, and junior considerable attention because their increased potency high school levels. A 28-year-old man, a long-term opioid user, is hostility and tells you that he is being pursued by brought to the emergency department with typical strangers. A patient is brought into the emergency depart- (D) He abuses heroin and should be prescribed ment on Saturday night exhibiting paranoia and methadone maintenance. The lack of (C) People who abuse drugs today choose heroin availability is a major reason these compounds are and cocaine over barbiturates. The abstinence syndrome in chronic al- (C) Heroin cohol or barbiturate users consists of hallucinations, (D) Alcohol tremors, hyperthermia, and autonomic hyperactiv- (E) Amphetamine ity.
The usual site for thoracentesis is the posterior lateral aspect of the back over the di- aphragm but under the fluid level cheap alli 60mg free shipping. Confirm the site by counting the ribs based on the x- ray and percussing out the fluid level discount 60mg alli free shipping. Avoid going below the eighth intercostal space because the risk of peritoneal perforation is great purchase 60 mg alli with amex. Use a hemostat to measure the 14–18-gauge thoracentesis needle to the same depth as the first needle buy alli 60mg with visa. Make sure that you “march” over the top of the rib to avoid the neurovascular bun- dle that runs below the rib (see Fig. With the three-way stopcock attached, ad- vance the thoracentesis catheter through the needle, withdraw the needle from the chest, and place the protective needle cover over the end of the needle to prevent injury to the catheter. This may result in hypotension or the development of pulmonary edema due to reexpansion of compressed alveoli. This maneuver increases intrathoracic pressure and decreases the chances of a pneumotho- rax. Optional lab studies are cytology if you suspect a malignancy, amylase if you suspect an effusion secondary to pancreatitis (usually on the left) or esophageal perforation, and a Sudan stain and triglycerides (>110 mg/dL) if a chylothorax is suspected. Complications • Pneumothorax, hemothorax, infection, pulmonary laceration, hypotension, hypoxia 13 due to ventilation–perfusion mismatch in the newly aerated lung segment Differential Diagnosis of Pleural Fluid For a more complete differential, see Chapter 3. Transudate is usually associated with nephrosis, CHF, cirrhosis; an exudate is associated with infection (pneumonia, TB), malig- nancy, empyema, peritoneal dialysis, pancreatitis, chylothorax. URINARY TRACT PROCEDURES Bladder Catheterization Indications • Relieving urinary retention • Collecting an uncontaminated urine specimen for diagnostic purposes • Monitoring urinary output in critically ill patients • Performing bladder tests (cystogram, cystometrogram) Contraindications • Urethral disruption, often associated with pelvic fracture • Acute prostatitis (relative contraindication) 13 Bedside Procedures 307 Materials • Prepackaged bladder catheter tray (may or may not include a Foley catheter) • Catheter of choice (see Fig. Red rubber catheter (Robinson): Plain rubber or latex catheter without a balloon, usually used for “in-and-out catheterization” in which urine is removed but the catheter is not left indwelling. Each insertion of a catheter implants bacteria into the bladder, so strict aseptic tech- nique is mandatory. Have the patient lie supine in a well-lighted area; females with knees flexed wide and heels together to get adequate exposure of the meatus. Inflate and deflate the balloon of the Foley catheter to ensure its proper function. In females, use one gloved hand to prep the urethral meatus in a pubis-toward-anus di- rection; hold the labia apart with the other gloved hand. With uncircumcised males, re- tract the foreskin to prep the glans; use a gloved hand to hold the penis still. The hand used to hold the penis or labia should not touch the catheter to insert it; a dis- posable forceps in the kit can be used to insert it. In the male, stretch the penis upward perpendicular to the body to eliminate any inter- nal folds in the urethra that might lead to a false passage. Any signifi- cant resistance encountered may represent a stricture and requires urological consulta- tion. Some tricks used to get a catheter to pass in a male are to make sure that the penis is well stretched and to instill 30–50 mL of sterile water-based surgical lubricant (K-Y jelly) into the urethra with a catheter-tipped syringe prior to passage of the catheter. Viscous lidocaine jelly for urologic use can help lubricate and relieve the discomfort of difficult catheter place- ment. Allow at least 5 min after instillation of the lidocaine jelly for the anesthetic ef- fect to take place. These maneuvers ensure that the balloon inflates in the bladder and not in the urethra. After inflation, pull the catheter back so that the balloon comes to rest on the bladder neck. If a large amount of lubricant jelly was placed into the urethra, the catheter may need to be flushed with sterile saline to clear the excess lubricant.
Later cheap alli 60mg with visa, Hepatic when this oxygenated blood is pumped Spleen veins to capillaries in other parts of the body buy alli 60mg cheap, it unloads the oxygen and picks up car- bon dioxide and other substances gen- Liver erated by the cells (Fig buy discount alli 60mg on line. For example purchase alli 60mg, when food is digested, most of the blood into the tissues is the pressure of the blood as it end products are absorbed from the small intestine into flows through the capillaries. The movement of blood through the capillaries is rel- ◗ The Physiology of Circulation atively slow, owing to the much larger cross-sectional Circulating blood might be compared to a train that trav- area of the capillaries compared with that of the vessels els around the country, picking up and delivering passen- from which they branch. The lymphatic system, discussed in Chapter 16, can be regulated by changing the size of the blood vessels collects this extra fluid and protein and returns them to supplying that organ. A vasomotor center in the medulla of the brain stem regulates vasomotor activities, sending The Dynamics of Blood Flow its messages through the autonomic nervous system. Some organs, a precapillary sphincter of smooth muscle that encircles such as the brain, liver, and kidneys, require large quan- the entrance to the capillary (see Fig. Return of Blood to the Heart Blood leaving the capillary networks returns in the venous system to the As evidence of these effects, if a person stands com- heart, and even picks up some speed along the way, de- pletely motionless, especially on a hot day when the su- spite factors that work against its return. Blood flows in a perficial vessels dilate, enough blood can accumulate in closed system and must continually move forward as the the lower extremities to cause fainting from insufficient heart contracts. The force of ventricular nally, the force of gravity works against upward flow from contraction starts a wave of increased pressure that begins regions below the heart. During inhalation, the di- but if a heartbeat is abnormally weak, or if the artery is 15 To heart To heart Proximal Proximal valve opens valve closes Skeletal Skeletal muscle muscle contracts relaxes Vein Vein Distal Distal valve closes valve opens A B Figure 15-12 Role of skeletal muscles and valves in blood return. The basic heart rate is set internally by the SA ing a pulse, it is important to gauge the strength as well node, but can be influenced by the autonomic nervous as the regularity and rate. The sympathetic nervous sys- ◗ The pulse is somewhat faster in small people than in tem can stimulate more forceful heart contractions to large people and usually is slightly faster in women than increase ejection of blood. Because the effects of resistance are whereas during strenuous exercise, the rate may go up seen mostly in small arteries and arterioles that are at a to well over 100 beats/minute. For a person in good distance from the heart and large vessels, this factor is condition, the pulse does not go up as rapidly as it does often described as peripheral resistance. More pressure is generated as you Blood pressure is the force exerted by the blood against the blow, and the balloon is a lot harder to inflate than a walls of the vessels. Just as a milkshake is harder to suck through a straw than milk is, increased Cardiac Output As described in Chapter 14, the out- blood viscosity will increase blood pressure. Increased put of the heart, or cardiac output (CO) is the volume of numbers of red blood cells, as in polycythemia, or a loss of plasma volume, as by dehydration, will increase blood viscosity. The Blood pressure hematocrit test described in Chapter increases 13 is one measure of blood viscosity; it measures the relative percentage of packed cells in whole blood. Blood vessel diameter ◗ Total blood volume, the total Heart rate Cardiac Peripheral Vessel elasticity amount of blood that is in the vascu- Stroke volume output resistance Blood viscosity lar system at a given time. BLOOD VESSELS AND BLOOD CIRCULATION ✦ 321 To summarize, all of these relationships are expressed ◗ Diastolic pressure, which occurs during relaxation of together by the following equation: the heart muscle, averages about 80 mmHg. Because blood pressure decreases as the slowly lets air out of the cuff until the first pulsations are blood flows from arteries into capillaries and finally into heard. They measure two variables: mercury, but alternate types display the readings on a dial, or measure blood pressure electronically and give a ◗ Systolic pressure, which occurs during heart muscle digital reading. Blood pressure is reported as systolic contraction, averages about 120 and is expressed in pressure first, then diastolic pressure, separated by a millimeters of mercury (mmHg). Typically, the monary disorders such as shock, pericarditis, congenital right internal jugular vein is used because it is the shortest heart disease, and heart failure. However, it may persist in sclerosis a number of conditions, including the following: Although medical caregivers often place emphasis on ◗ Kidney disease and uremia (excess nitrogenous waste the systolic blood pressure, in many cases, the diastolic in the blood) or other toxic conditions pressure is even more important. The total fluid volume ◗ Endocrine disorders, such as hyperthyroidism and in the vascular system and the condition of small arteries acromegaly may have a greater effect on diastolic pressure. Table 15- ◗ Arterial disease, including hardening of the arteries 1 lists degrees of hypertension as compared with normal (atherosclerosis), which reduces elasticity of the vessels blood pressure values. BLOOD PRESSURE CLASSIFICATION (ADULTS)* It is important to treat even mild hypertension because this condition CATEGORY SYSTOLIC (mmHg) DIASTOLIC (mmHg) can eventually: Optimal 120 80 ◗ Weaken vessels and lead to saclike Normal 130 85 bulges (aneurysms) in vessel walls High normal 130–139 85–89 Hypertension that are likely to rupture. Drugs used to treat hypertension include the following: ◗ Diuretics, which promote water loss ◗ Drugs that limit production of renin ◗ Drugs that relax blood vessels Checkpoint 15-19 What is meant by hypertension and hy- potension?