What kinda of circumstance creats an exited vs. relaxed heart rate?

Question

please help iam i need this for a science fair project and I need to answer this answer. so please help :(

Answer 1

tachycardia (excited) This can happen in response to a decrease in blood volume (through dehydration or bleeding), or an unexpected change in blood flow. The most common cause of the latter is orthostatic hypotension (also called postural hypotension), a sudden drop of blood pressure that occurs with a change in body position (e.g., going from lying down to standing up). When tachycardia occurs for this reason, it is called postural orthostatic tachycardia syndrome (POTS).

Fever and infection leading to sepsis are also common causes of tachycardia, primarily due to increase in metabolic demands and compensatory increase in heart rate.
An increase in sympathetic nervous system stimulation causes the heart rate to increase, both by the direct action of sympathetic nerve fibers on the heart and by causing the endocrine system to release hormones such as epinephrine (adrenaline), which have a similar effect. Increased sympathetic stimulation is usually due to physical or psychological stress (the so-called "fight or flight" response), but can also be induced by stimulants such as amphetamines.

Endocrine disorders such as pheochromocytoma can cause epinephrine release and tachycardia independent of the nervous system. Hyperthyroidism is also known to cause tachycardia.

bradycardia (relaxed)
There are generally two types of problems that result in bradycardias: disorders of the sinus node, and disorders of the atrioventricular node (AV node).

With sinus node dysfunction (sometimes called sick sinus syndrome), there may be disordered automaticity or impaired conduction of the impulse from the sinus node into the surrounding atrial tissue (an "exit block"). It is difficult and sometimes impossible to assign a mechanism to any particular bradycardia, but the underlying mechanism is not clinically relevant to treatment, which is the same in both cases of sick sinus syndrome: a permanent pacemaker.

Atrioventricular conduction disturbances (aka an AV block) may result from impaired conduction in the AV node, or anywhere below it, such as in the His bundle.

Patients with bradycardia have likely acquired it, as opposed to having it congenitally. Also, bradycardia is more common in older patients, since both cardiac and non-cardiac causes are more likely in the elderly.