Pacemaker cells (also known as sinoatrial node cells) are cells that generate rhythmic impulses and set the pace for blood pumping in the heart. These cells have the ability to rhythmically depolarize and initiate action potentials. In pacemaker cells, Ca2+ and Na+ levels are higher in the extracellular environment, while K+ concentration is higher intracellularly. The pacemaker action potentials have three phases: 1-depolarization, where membrane potential reaches -40 mV and voltage-gated Ca2+ channels open, 2-repolarization, where voltage-gated Ca2+ channels close and voltage-gated K+ channels open, and finally 3-gradual depolarization, which is caused by the slow influx of Na+ ions.
Other. Chiropractors are physicians, all physicians are in health care and considered doctors, but not MDs. Vets are no DVMs, and podiatrists are DPMs.
Whole grains contain all parts of the grain kernel. ... But refined grains, like the flour used to make white bread, have had the fiber-dense bran and the nutrient-rich germ processed out, leaving only the starchy endosperm.
