Describe the physiological basis for the positive inotropic effect of digoxin on the heart. How does this explain the therapeutic benefit of the drug?

Digoxin is a sodium potassium adenosine triphosphatase (Na+/K+ ATPase) inhibitor.

Digoxin is a group of drug that has most effects on cardiac tissues. Digoxin was first isolated from the plant Digitalis lantana that was found to be a sodium potassium adenosine triphosphatase (Na+/K+ ATPase) inhibitor. This drug when taken through mouth, gives a 60 to 80% bioavailability .

This drug blocks the sodium potassium adenosine triphosphatase (Na+/K+ ATPase) pumps of the myocardium. When the sodium pumps are closed, this leads to the increase in extracellular levels of sodium.

As the extracellular sodium increase, this indirectly blocks the sodium calcium exchanger which in normal conditions exchange 1 intracellular calcium in exchange of 3 extracellular sodium ions.

As this pump is blocked, this leads to increase in intracellular levels of calcium. This calcium levels also increase in the sarcoplasmic reticulum. Thus, the contractibility of the heart muscles per beat increase which helps to pump blood more effectively. Thus, the effect seen is positive intropic effect.

fertilization, pictured in figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. the egg and sperm each contain one set of chromosomes. to ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. in mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. when a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. in placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in figure 24.23b. the fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. the nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

explanation:

tsd is temerature dependent sex determination.

tsd: it is a type of environmental sex determination in which the temperature experienced during embryonic/ larval development (ambient temperature for development) determine the sex of the offspring.

crocodile displays the tsd where the ambient temperature of the developing egg determines the individual's sex. for example in the american alligator's eggs, incubation at 33 ºc produces mostly males, while incubation at 30 ºc produces mostly females. so if the american alligator's egg will get the ambient temperature (33 degree celcius)during embryonic development from egg, the offspring will be male and same for the female sex determination.