山东大学：《医学机能学实验》课程教学课件（PPT讲稿）05 STUDY OF THE EFFECT OF VARIOUS DRUGS AND IONS ON THE FROG’S HEART

STUDY OF THE EFFECT OFVARIOUSDRUGSANDIONSONTHE FROG'SHEART

STUDY OF THE EFFECT OF VARIOUS DRUGS AND IONS ON THE FROG’S HEART

THEORYIons1.The fluids perfusing the heart must contain aproper balance of the three essential ions i.e.sodium ions, potassium ions and calcium ions2. If these three ions are present properproportions, the heart is able to maintain itsincontractilityforhoursnormalanoxygenated environment.3. If the concentrations of ions are abnormal.then the heart will what happen?

THEORY Ions 1.The fluids perfusing the heart must contain a proper balance of the three essential ions i.e. sodium ions, potassium ions and calcium ions. 2. If these three ions are present proper proportions, the heart is able to maintain its normal contracti1ity for hours in an oxygenated environment. 3. If the concentrations of ions are abnormal, then the heart will what happen?

1). If concentration of these ions isaltered then heart rate andcontractility are changed.e.g. excess of potassium ions in thefluids perfusing the heart causesthe heart to become dilated andslows the heart rate and may stopheart during diastole

1). If concentration of these ions is altered then heart rate and contractility are changed. e.g. excess of potassium ions in the fluids perfusing the heart causes the heart to become dilated and slows the heart rate and may stop heart during diastole

2).An excess of sodium ionsdepresses cardiac function likepotassium ions excess but for anentirely different reason. Sodiumions compete with the calcium ionsat the same point in the excitatoryor contractile process of the heartmuscle

2).An excess of sodium ions depresses cardiac function like potassium ions excess but for an entirely different reason. Sodium ions compete with the calcium ions at the same point in the excitatory or contractile process of the heart muscle

3).Excess calcium ions in the fluidsenhance myocardial contractility .When large amount of calciumions are infused into theexperimental animals, the heartrelaxes less during diastole andeventually stops in systole(calcium rigor). A deficiency ofcalcium ions causes cardiacflaccidity

3).Excess calcium ions in the fluids enhance myocardial contractility . When large amount of calcium ions are infused into the experimental animals, the heart relaxes less during diastole and eventually stops in systole (calcium rigor). A deficiency of calcium ions causes cardiac flaccidity

Drugs1.The intrinsic properties of theheart are influenced byautonomic nervous systemSympathetic and parasympatheticnerve2.Various drugs acting on specificreceptors present in the heart alsoinfluence the cardiac activity

Drugs 1.The intrinsic properties of the heart are inf1uenced by autonomic nervous system. Sympathetic and parasympathetic nerve 2.Various drugs acting on specific receptors present in the heart also influence the cardiac activity

: Acetylcholine(Ach) acts onthe M- receptors present in theheart and causes the decreasein the heart rate and cardiaccontractility

• Acetylcholine(Ach) acts on the M- receptors present in the heart and causes the decrease in the heart rate and cardiac contractility

: Adrenalin (Adr) acts on alphaand beta-adrenergic receptorsIt has positive chronotropic(increased heart rate) andpositive inotropic (increasedforce of contraction)effects

• Adrenalin (Adr) acts on alpha and beta-adrenergic receptors. It has positive chronotropic (increased heart rate) and positive inotropic (increased force of contraction)effects

PROCEDURE1.Expose the frog's heart: As compared to human heart, in thefrog's heart, there are five chambersie one ventricle, two atrium, onesinus venosus ,one truncus arteriosus: There is no special conducting tissue? There is no coronary circulation inthe frog's heart

PROCEDURE 1.Expose the frog’s heart • As compared to human heart, in the frog’s heart, there are five chambers ie one ventricle, two atrium, one sinus venosus ,one truncus arteriosus • There is no special conducting tissue. • There is no coronary circulation in the frog’s heart

Truncus arteriosusventricleatriumventriclesinus venosus

ventricle Truncus arteriosus atrium sinus venosus ventricle