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What is the link between electrical activity of the heart and its contraction?

The electrical current is produced in the SA node (the primary pacemaker of the heart) and travels to the AV node via fibres in the walls of the atria. These impulses cause the muscular walls of the atria to...
SM
Answered by Stephen M. • Biology tutor
7088 Views

Can you explain the oxygen dissociation curve.

What is the graph telling us? On the graph, we can see two axes. We have partial pressure of oxygen on the X axis and Hb saturation on the Y axis. Partial pressure is another way of saying how much oxygen th...
TK
Answered by Thomas K. • Biology tutor
3076 Views

How do stars form?

A star is formed from a nebulae, which is a cloud of dust and gas. The dust and gas particles are drawn together by the gravitational attraction between them. As the nebulae contracts, the dust and gas parti...
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Answered by Stephen S. • Physics tutor
2865 Views

Show the sum from n=0 to 200 of x^n given that x is not 1, is (1-x^201)/(1-x) hence find the sum of 1+2(1/2)+3(1/2)^2+...+200(1/2)^199

Let the first term of a geometric progression be 'A', define the geometric sum, which we will call 'S', of 'Ax^n' for each integer n to be the sum from n=0 to r of 'Ax^n'. Hence S=A+Ax+Ax^2+...+Ax^r. Conside...
JB
Answered by Jordan B. • Maths tutor
3567 Views

What is the difference between sentirse and sentir?

Both sentirse and sentir mean to feel, but aren't used interchangeably. Sentirse is used to describe how you feel, and is followed by and adjective (e.g. feliz, triste). Sentir is used to describe what you f...
EH
Answered by Eva H. • Spanish tutor
9228 Views