pharmacoiogsts 4 Anticholineterases Priysotigmine (obtaned from the deadry calabar bean of South Africa, (where it used to be used for witch mining)],

Anticholineterases Priysotigmine (obtaned from the deadry calabar bean of South Africa, (where it used to be used for witch mining)], neortgrmine and diisopropyt fluorophosphafc (DFP) are substances which can inactivate the enzyme choine esterae'in the motor end plate and thus can prolong the hfe of ACh Therefore, in small doses, chyostirgnines neostifrmine and DFP can produce strorrg muscubf contraction (spasm), but in greater does, they produce depolarting block Physoeigmne (ewnne) and related drugs are used by the ophthafrnc surgeons to produte povierful pupilIary, (ontuctons where such contrartions are needed (e g glaLEoma. foloAirg atropue adminisiration and soonl DFP a popular agent m me ireatnenl of the disease, myasthenia gravrs ( see below N B it should be understood, however that amough phvsostgrnrie causes pupilary constrlction. the muscles for pupillary constriction are smooth muscles Oiganophosphours id organochloinde compounds. These compounds also can inhiblit choline esterase and can prolong the life of ACh in the motor and plate (depolarizing bbcktrs) Theaa ire the major constltuenis of nerve gas.which might be used as a bic logical weapon in apossible future war Examples of commonly used pesticioes contanng them are tic 20 (organopriasphorus compounds), fondoI (organocrilonde compound) Suicide by the se agents by villagers. who Eommonly nave access to these agents, is common r India 6 Myasthenia grans in ITits disease, which literally means grave weakness of me muscles (myo = muscle. asthena = weakness . gravrs = grave), most of the receptors in the neuronmuscular junctions are absent although the motor end plate are apparently normal or sometimes bigger than normal The release of ACh is normal The absence of the receptors, is due to the fact that a circulating anttody which lulls the receptors, develops in the body. Outstanding simttoms are earfy fatigue of the muscles when repeated contractors are attempted, muscular weatoess and even frank neuromuscular Varamission block Besides. DFP. as staled above, heavy dose of cortisol (in the hope of destroying the antibody) is also used for treatment 7 Muscle reLnants Durrg surguil Opferations in the abdomen, muscles should be satistactorily related. as this helps adequate re tiaction of the abdominal wound This, of course can be achieved by deepening me level of anesthesia, but this rs not prefened An artomathe procedure is to use Vie muscle relananfc which (bv ditTerenl mechanisms) can produce a neurorruscular block so mai the tone of all the sketelal muscles (including the muscles of respration) are reduced without using a heavy dO$e Of aneslhesn As can be understood, possiblitly of the respiratory paralysis hat to be guarded agamst recall, me enzyme destoysACh SUMMARY A HIOHUOKTS Onder Ight microscopes, some diflences are seen between skeletal and cardiac muscles, but EM fetfurts ind merhanism of cortractron ualed ratchat or sliding theory) of these two types of muscles are remarkably smilar. Contratlite 0emants are, (i) myosin. and (2) acbn when an AP develops on sarcotemma more ftee Ca++ iors become available within the cytosd of muscle ceil uncovering of the active sites of the actin molecules attachment of the myosin heads into the active sites, occur Now, these heads Totals-x actin filament moves forward (towards the Hzone) the head deattaches -»agam leatlathes lo a new active site and so the sarcomere length reduces and the muscle as a whole shoiteis ATPs are required for The rtation ana deattachment of The heads Neuromuscular Iransmtie is ACh vvhen an AP develops in the motor nerve released from the nerve terminal EPP develops on the post lunctional merricraneif it tneEPP) is of sufficient magnitude, an AP of the muscle develops contraction occurs
omusdJar transmssion can be abolished by auccinyt cholme (depaiarizing, blocter. a twitch followed by pararysis)] curare {(competitive antagonist, not twitch before the paralysis] and so on. 1. Introductory 2. Iratruments for study.3. Some commonly usea terms The properties A