During an anatomical class, Dr. Hales removes the heart of a frog and places it in a beaker of oxygenated Ringer's solution. He
then instructs his health care trainees to observe how the muscles of the frog's heart continue to contract even without external stimulation. What property of the muscles of the heart is Dr. Hales asking his students to observe? Autorhythmicity
Bradycardia
Tachycardia
Biorhythmicity
It is the study of the characteristics features of the cardiac muscle cells with the ability to initiate action potential at certain level without connection to any external stimulus which the heart beats constantly and rhythmically. Cardiac muscle cells controls the rate of contraction of heartbeats.
This is a unique future of cardiac muscles of the heart.It is the ability of these muscles to generate and fire action potential spikes at a fixed rate without an external stimulus ; the spread of these potential to all the cells of the heart, with consequent contraction heart as a single unit , or rhythmically.
This process is mediated by nervous and endocrine system, and the action potential generated is conducted through the heart by the myocardial conduction cells.
Autorhythmicity is the due to lack of membrane potential in the myocardial conduction cells. This is because, the sodium channels did not close up but allow continuous influx of sodium ions, with the rise in the membrane potential from -60mv to 40mv. Consequently,pre-potential depolarization sets in. This is followed by influx of Ca+ ions, though the voltage-gated Calcium channels; leading to generation of action potential and therefore spread to all parts of the heart,leading to autorhythmicity.
The greenhouse effect is a natural process that warms the Earth's surface. When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. The absorbed energy warms the atmosphere and the surface of the Earth.
The amount of lipids stored as an energy reserve far exceeds the energy stored as glycogen since the human body is simply not capable of storing as much glycogen compared to lipids. Lipids yield 9 kcal of energy per gram while carbohydrates and proteins yield only 4 kcal of energy per gram.
