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Xochitecatl is located in a dominant position upon the summit of a 4 km-wide extinct volcano that forms a range of hills that rises approximately 200 meters above the floor of the Puebla-Tlaxcala Valley; the so-called Atlachino-Nativitas-Xochitecatl block, which is located in the centre of the valley.
It contains a sprawling palace with vibrantly colored murals painted in Maya style. The nearby site of Xochitecatl was a more public ceremonial complex associated with Cacaxtla. Cacaxtla and Xochitecatl prospered 650–900 CE, probably controlling important trade routes through the region with an enclave population of no more than 10,000 people.
The later is burnished and principally used for storing liquids. Most of the pieces are made either molds or with the use of a potters' wheel. [3] In San Damian Texoloc makes pottery heavily influenced by that which was made in the sites of Xochitecatl and Cacaxtla. [3] [13]
In a healthy heart, the SA node continuously produces action potentials, setting the rhythm of the heart (sinus rhythm), and so is known as the heart's natural pacemaker. The rate of action potentials produced (and therefore the heart rate ) is influenced by the nerves that supply it.
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In the pacemaking cells of the heart (e.g., the sinoatrial node), the pacemaker potential (also called the pacemaker current) is the slow, positive increase in voltage across the cell's membrane, that occurs between the end of one action potential and the beginning of the next.
In heart pacemaker cells, phase 0 depends on the activation of L-type calcium channels instead of the activation of voltage-gated fast sodium channels, which are responsible for initiating action potentials in contractile (non-pacemaker) cells. For this reason, the pacemaker action potential rising phase slope is more gradual than that of the ...
The action potential passes along the cell membrane causing the cell to contract, therefore the activity of the sinoatrial node results in a resting heart rate of roughly 60–100 beats per minute. All cardiac muscle cells are electrically linked to one another, by intercalated discs which allow the action potential to pass from one cell to the ...