12.8 : 影响心率的因素

Cardiac output determines the pulse rate, so factors impacting cardiac output affect the pulse rate.

Some factors are age, body temperature, posture, acute pain, chemicals, hormones, electrolyte imbalance, and medications.

Age influences the pulse rate for newborns and children, which is rapid compared to adults.

Body temperature is also an influencing factor; hyperthermia or fever increases the pulse rate, and hypothermia decreases it.

Posture influences the pulse rate; standing and sitting positions cause increased heart rates compared to lying down.

Acute pain triggers sympathetic stimulation, raising the pulse rate.

The influence of circulating chemicals and electrolyte imbalances, such as low potassium, depresses cardiac function, causing an irregular pulse rate.

High carbon dioxide levels, or hypercapnia, raise the pulse rate. It's often due to hypoxia.

Hormones like adrenaline and noradrenaline increase and decrease the pulse rate, respectively.

The baroreceptors on the aortic and carotid sinus walls are sensitive to arterial pressure and influence the pulse rate.

Medications such as antihypertensives and beta-adrenergic antagonists decrease the pulse rate.