STUDY OF THE EFFECT OF VARIOUS DRUGS AND IONS ON THE FROG

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STUDY OF THE EFFECT OF VARIOUS DRUGS AND IONS
ON THE FROGS HEART
Li Jingxin Physiologcal Department
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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?

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• 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 .

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• 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 .

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• 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.

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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.

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

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

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PROCEDURE

• 1.Expose the frogs heart
• As compared to human heart, in the frogs 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 frogs
  heart

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• a. The parietal layer of the membranous
  pericardium if easily removable but the visceral
  layer is firmly attached to the heart muscle.
• b. The wall of single ventricle is thicker than
  that of atria.
• c. The truncus arteriosus lies anteriorly to the
  ventricle near it base and divides into two
  aorta.
• d. Sinus venosus lies posteriorly and superior
  and inferior vena cava empty into it.
• e. The color of the ventricle is seen to become
  pale during contraction.

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f. During contraction, size of the ventricle is
decreased and during relaxation size is increased
due to distension g. The two atria are separated
from the ventricle by atrio-ventricular
groove. h. A careful observation will show a
white line at the junction of the sinus and
atria. i. Sequence of heartbeat is the sinus,
atria, ventricle and finally the truncus
arteries. If we remove the heart from the
animals body and immerse it in Ringer solution
placed, the various parts of the heart are seen
to continue to beat in the usual regular
sequence. This indicates that the heartbeat
originates from the heart itself.
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PROCEDURE

• 2. Connect the heart clip with the apex of the
  ventricle. Lift the heart gently by raising the
  lever and adjust its position so that the beating
  heart produces good movements. Pour Ringer
  solution on the heart from time to time .
• 3. Adjust the velocity and sensitivity ,record
  normal curve.

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PROCEDURE

• 4. Pour 0.65 NaCl solution(deficiency of calcium
  ) on the frogs heart and record its effect on
  the cardiac activity.
• 5. 1KCl solution
• 6. 1CaCl2 solution
• 7.1/10000 acetylcholine solution
• 8. 1/10000adrenalin solution