can someone tell me about regulation of cardiac output?

Answer 1

Practically speaking, cardiac output is regulated at the most proximate level by the heart cells themselves, in response to low oxygen. This may occur at the sinoatrial node, atrial cells, atrioventricular node, or ventricular cells -- the ventricular cells are the most sensitive to hypoxia and most likely to fire out of rhythm, which will alter stroke volume, rate, and output.

Outside of the heart, various locations of baroreceptors, volume receptors, and pH receptors are able to alter cardiac output by increased adrenergic/cholinergic tone -- for example, in response to low blood pressure, baroreceptors in the carotid sinuses will increase cardiac output by increased adrenergic output to the SA-node, which will effectively increase heart rate. The opposite happens when blood pressure gets too high.

Answer 2

Cardiac Output is a function of Stroke Volume and Heart Rate

CO = SV x HR

(ie. the volume that the heart pumps out each beat, times heart rate per minute, gives you a volume per minute output).

These are in turn regulated by a series of interesting physiological detection and feedback mechanisms that would be very difficult to describe here.

Let me give you some places to start looking and learning about it.