Phenergan

By C. Joey. Augustana College, Rock Island Illinois.

Direct measurements of intracellular Na+ and intracellular Ca2+ and effect of ouabain block of the sodium pump phenergan 25 mg amex. This figure shows the astoundingly steep dependence of contractile force on intracellular Na+ generic phenergan 25mg free shipping. This loss amounts to only a few millimoles at the time the peak therapeutic inotropism is attained and has nothing to do with the desired inotropic effect of the drug. If excessive glycoside is administered however, K+ loss increases and this loss is responsible for the appearance of toxic electrophysiological effects of the digitalis compounds. When cells exposed to digitalis progress to the toxic state, they lose substantial intracellular K+, which tends to accumulate in narrow extracellular spaces outside cells. This increases the [K]o/[K]i ratio (bringing it closer to unity), and, as described by the Nernst equation, makes the resting membrane potential less negative. The maximum diastolic potential of automatic Purkinje cells is thus brought closer to threshold. The diminished negativity of the resting membrane reduces the rate of opening of the fast Na channels so that the rate of rise of the action potential spike is decreased. In summary, the digitalis glycosides produce their desired inotropic effect through their ability to inhibit the cellular Na-K pump and thereby induce an increase in [Na]i that in turn, leads to stimulation of Ca2+ influx through a transsarcolemmal Na-Ca exchange system. The toxic effects of the drug also relate to the Na-K pump inhibition but are attributable, at least in part, to the losses of K+ induced by the inhibition. The concept of an equilibrium potential, and how it is important for determining ion fluxes across cell membranes C. The relationship between an ion’s equilibrium potential and conductance in determining the cell’s membrane potential at any instant in time. It is actually not all that messy and provides a good basis for understanding ion fluxes across membranes. If you understand the following three equations, you will have a pretty good understanding of the bases for these fluxes. Goldman-Hodgkin-Katz equation: Similar to the Nernst equation, tells you where the membrane potential will rest when more than one ion is involved. Pion = the permeability of the membrane for an ion Nernst Potential and Osmosis - Daniel Madison, M. A round cell has equal concentrations K+ and Cl- inside, equal concentrations of Na+ and Cl- outside. Consider also that you are recording the electrical potential difference (voltage) between the inside and outside of the cell. In this condition, the voltage across the membrane will be zero, because all charges in this system are fully compensated (i. When given the opportunity, K+ will flow down its concentration gradient from the inside to the outside of the cell. For an uncharged species, this flow would continue until the concentration gradient is fully dissipated. However, since K+ is charged, it’s movement will result in the separation of + and – charges across the membrane, since the Cl- ions are not free to follow K+ out of the cell. This voltage, also known as the membrane potential, will resist the further net flow of K+ out of the cell (the uncompensated negative charges will slow the efflux of K+ charges out of the cell). Thus, there are now two forces acting on the K+ ion; a) the concentration gradient pulling K out, and b) the membrane potential resisting its outward flow. Eventually, as K+ flows out, the inward force of this voltage will grow to exactly compensate the outward concentration force. At this point, the system will be in equilibrium, with outward and inward rates of K+ flow being equal. The value of the equilibrium potential depends on the size of the concentration gradient. Seriously, they are all names for the same thing – the value of the membrane potential where an ion is in equilibrium. Equilibrium potential, because its value tells you where the ion is in equilibrium. Reversal potential, because knowing this value lets you predict which direction ions will flow across the membrane. The concept of a reversal potential is one of the most important parts of understanding the electrical behavior of cells such as heart cells. But if you perturb that equilibrium by injecting charges into the cell (never mind how, for now), you will change the voltage across the membrane. Injection of positive charges will dissipate the membrane potential (or depolarize it).

The drug can reduce body temperature and generic phenergan 25 mg free shipping, depending on circumstances in experiments buy phenergan 25mg with visa, either raise or lower heart rate and blood pressure. Researchers find that the substance interferes with recognizing common items shown in distorted pictures; such trouble is considered evidence of the brain suffering from weakened ability to understand what the eyes see. Because of adverse impact on mental clarity and physical performance, people are advised to avoid operating dan- gerous machinery (such as cars) for at least 48 hours after using lorazepam. Driving tests have shown the drug to reduce vehicle control skill while in- creasing risk-taking. Other tests demonstrate worsened attention, slower re- action time, and delay in reasoning out the solution to a problem. An experiment demonstrated that users may be unaware of how much the drug is interfering with their abilities. Typically a dose has greater impact on the elderly, and all persons risk falling down until the drug wears off. A case report notes that lorazepam can eliminate a person’s interest in sexual activity. An unusual case report tells of someone who was hearing noises in an ear, and the noises became musical hallucina- tions of popular songs when the person began taking lorazepam. Other case reports tell of visual hallucinations after taking the compound, and that re- sponse was also observed in 3 children among 112 who were given the drug. Although lorazepam is used to reduce anxiety, case reports and formal ex- perimentation show that the substance can increase aggressiveness (perhaps because people are less afraid to do things). A schizophrenic who received the drug lost enough inhibitions to start acting out violent impulses, and similar reports exist. In formal experimentation volunteers receiving lorazepam be- came more aggressive but did not realize they were angrier than other persons in the experiment. Among persons who already have a history of drug abuse (a population prone to like drugs much more than nonusers do), some results indicate lorazepam has about the same addictive potential as diazepam or meprobamate; some results simply show lorazepam to have an unspecified amount of appeal; and in one experiment abusers found the drug about as attractive as a placebo (indicating low addictive potential). If a person takes lorazepam enough to develop dependence on it, suddenly quitting the drug Lorazepam 227 can produce a withdrawal syndrome. If drug use has been heavy the with- drawal can include confusion, depression, perspiration, cramps, tremors, vom- iting, mania, and convulsions. Lighter use can produce lighter withdrawal such as insomnia and generally feeling out of sorts. Symptoms can be avoided altogether if a person gradually takes smaller and smaller doses rather than stopping abruptly. If a person taking lorazepam simultaneously ingests other depressants (alcohol, barbiturates, opiates) the total depressant effects deepen. Although we might expect stimulants to counteract lorazepam’s actions, re- search has found that cocaine can boost some of them, with sleepiness becom- ing particularly greater. Thus cocaine users receiving lorazepam for medical treatment may require lower doses than normal. Mice having fetal exposure to lorazepam exhibit lasting neu- rochemistry abnormalities, and rats with fetal exposure demonstrate brain dif- ficulty. Extrapolating from rat test results, two researchers concluded that fetal exposure to the drug may result in male offspring having more anxiety than normal and females having less than normal. Pregnant rabbits receiving lor- azepam in an experiment produced more birth defects than usual. Persuasive evidence indicates that the drug passes from a pregnant woman into the fetus. Analysts examining thousands of medical records concluded that lorazepam does not necessarily cause birth defects but found that the drug may be in- volved with a deformity blocking an infant’s anal opening. Fetal exposure to lorazepam is suspected of slowing development of infants’ abilities to move and think. Case reports say that infants can have withdrawal symptoms if the mother used the drug during pregnancy, symptoms accompanied by abnor- mal muscle tone and trouble with eating. Nursing mothers are told to avoid lorazepam, as infants might be drugged from the amount of lorazepam that passes into milk. As drug effects go away, users may experience weariness and muscle aches accompanied by depression. Users coming off the drug may also be short- tempered, suspicious of others, and nervous. Typically the effects desired by a user decline with repeated use of the drug, while undesired postintoxication effects increase. The per- centage of fatalities among abusers is small, but the size difference between a recreational dose and a serious overdose can vary tremendously between in- dividuals. What one person can tolerate without apparent ill effect can send another person to a hospital. Not enough scientific information to report about tolerance, dependence, or withdrawal. Although not a true amphetamine, methylphenidate has properties similar to (including appetite suppression and sleep disruption) but is less potent. Limited success is seen in experimental usage of the drug to help autistic children.

In the design of this safety system order phenergan 25 mg otc, the possibility has been considered that the bag may be triggered during normal driving order 25 mg phenergan free shipping. If the bag were to remain expanded, it would impede the ability of the driver to control the vehicle; therefore, the bag is designed to remain expanded for only the short time necessary to cushion the collision. If, however, the impact is sudden, as in a rear-end collision, the body is accelerated in the forward direction by the back of the seat, and the unsupported neck is then suddenly yanked back at full speed. Here the muscles do not respond fast enough and all the energy is absorbed by the neck bones, causing the well-known whiplash injury (see Fig. It was found in these cases that the body made about a 1-m-deep depression in the surface of the snow on impact. The credibility of these reports can be verified by calculating the impact force that acts on the body during the landing. It is shown in Exercise 5-6 that if the decelerating impact force acts over a distance of about 1 m, the average value of this force remains below the magnitude for serious injury even at the terminal falling velocity of 62. In the normal course of daily activities our bodies are subject mostly to smaller repetitive forces such as the impact of feet with the ground in walking and running. A still not fully resolved question is to what extent are such smaller repetitive forces particularly those encountered in exercise and sport, damaging. Osteoarthritis is the commonly suspected damage resulting from such repetitive impact. Chapter 5 Exercises 71 Osteoarthritis is a joint disease characterized by a degenerative wearing out of the components of the joint among them the synovial membrane and cartilage tissue. As a result of such wear and tear the joint loses flexibility and strength accompanied by pain and stiffness. After the age of 65, about 60% of men and 75% of women are to some extent affected by this condition. Over the past several years a number of studies have been conducted to determine the link between exercise and osteoarthritis. The emerging conclu- sion is that joint injury is most strongly correlated with subsequent develop- ment of osteoarthritis. Most likely this is the reason why people engaged in high impact injury-prone sports are at a significantly greater risk of osteo- arthritis. Further, there appears to be little risk associated with recreational running 20 to 40 km a week (∼13 to 25 miles). It is not surprising that an injured joint is more likely to be subsequently subject to wear and tear. A joint injury usually com- promises to some extent the lubricating ability of the joint leading to increased frictional wear and osteoarthritis. This simple picture would lead one to expect that the progress of osteoarthritis would be more rapidly in the joints of peo- ple who are regular runners than in a control group of non-runners. Osteoarthritis seems to progress at about the same rate in both groups, indicating that the joints possess some ability to self- repair. If the bones of one arm absorb all the kinetic energy (neglecting the energy of the fall), what is the minimum speed of the runner that will cause a fracture of the arm bone? Assume that the object is hard, that the area of contact with the skull is 1cm2, and that the duration of impact is 10−3 sec. Calculate the duration of the collision between the passenger and the inflated bag of the collision protection device discussed in this chapter. In a rear-end collision the automobile that is hit is accelerated to a veloc- ity v in 10−2/sec. What is the minimum velocity at which there is danger of neck fracture from whiplash? Use the data provided in the text, and assume that the area of the cervical vertebra is 1 cm2 and the mass of the head is 5 kg. Calculate the average decelerating impact force if a person falling with a terminal velocity of 62. Assume that the person’s mass is 70 kg and that she lands flat on her back so that the area of impact is 0. Assuming that the moving part of his hand weighs 5 kg, calculate the rebound velocity and kinetic energy of the bag. In particular, we will consider the hovering flight of insects, using in our calculations many of the concepts introduced in the previous chapters. The parameters required for the computations were in most cases obtained from the literature, but some had to be estimated because they were not readily available. A complete discussion of flight would take into account aerodynamics as well as the changing shape of the wings at the various stages of flight. Differences in wing movements between large and small insects have only recently been demonstrated.