2. Hormones affecting the heart include:

• Adrenaline
• Glucagon
• Adrenocortical hormones
• 5-Hydroxytryptamine
• Thyroxine

Additional Information

Adrenaline (epinephrine) is released from the adrenal medullae. It acts on β₁-adrenoceptors on heart cells and mimics the action of noradrenaline released from sympathetic nerve endings. The effects of adrenaline are to increase heart rate and force of contraction.

Glucagon is secreted by pancreatic islet cells. Its effects are to increase force of contraction and stimulate glycogenolysis.

Adrenocortical hormones such as cortisol (hydrocortisone) increase force of contraction of cardiac muscle cells.

5-Hydroxytryptamine (5-HT or serotonin) increases force of contraction of cardiac muscle cells.

Thyroxine increases heart rate.