BM3501 12/02/02

DESCRIBE THE FACTORS (INCLUDING CIRCULATION FACTORS AND NEURAL INPUTS) WHICH CAN ALTER THE INOTROPIC AND CHRONOTROPIC STATE OF THE HEART.

Cardiac output is defined as the frequency of beats per minute multiplied by the volume of blood expelled per stroke. If the cardiac output is to be transformed, then it stands to reason that there are only two methods of achieving this, altering the frequency of the beats (chronotropism), or varying the volume of blood expelled per stroke (inotropism).

The chronotropic state of the heart is regulated by the Sino Atrial Node (SAN) or pacemaker, the inotropic condition of the heart is dependant on the contractility of the myocardium.

The SAN gives off an inherent frequency of 100 beats per minute (BPM) but the SAN is under constant influence of circulating drugs and neuronal control, therefore the heart has a great capacity to change its chronotropic value. Both sympathetic and parasympathetic neurones converge on the SAN and influence the heart rate, with the parasympathetic innervation far outnumbering the sympathetic. Paras

The Bainbridge reflex is the response to a sudden increase in volume load entering the heart. If the right side of the heart is suitably distended by and increased pressure the heart elicits a tachycardic response to increase the cardiac output. However if the heart is already beating at and elevated rate then a degree of bradycardia is noted.

Some topics in this essay:
Kinase Ca2+, Acetylcholine Ach, Left Vagus, BPM SAN, HEART Cardiac, Medulla Oblongata, Node SAN, heart rate, vagus nerve, BPM Parasympathetic, Christopher Dawson, cardiac output, CHRONOTROPIC HEART, innervation heart, inotropic chronotropic, via vagus, effects heart, chronotropic heart, inputs alter inotropic, neuronal control, control heart, inotropic chronotropic heart, alter inotropic chronotropic, neural inputs alter, neuronal control heart,