In the human body, the hormone which is secreted into the blood and which controls the rate of the heart beat is?

The correct answer is Adrenaline.
Key Points

• Adrenaline is secreted in response to stress of any kind and during emergency situations and is called emergency hormones or hormones of Fight Fright and Flight(Triple F hormone).
• Key actions of adrenaline include:-
  • Controlling the heart rate.
  • Increasing blood pressure.
  • Expanding the air passages of the lungs.
  • Enlarging the pupil in the eye. 
  • Redistributing blood to the muscles, and altering the body's metabolism, so as to maximize blood glucose levels (primarily for the brain).

Important Points

• Thyroxine
  • Thyroxine is the main hormone secreted into the bloodstream by the thyroid gland.
  • It plays a vital role in digestion, heart and muscle function, brain development, and the maintenance of bones.
• Insulin
  • ​Insulin is a peptide hormone and it regulates glucose homeostasis.
  • Insulin acts mainly on hepatocytes and adipocytes (cells of adipose tissue) and enhances cellular glucose uptake and utilization.
  • Insulin also stimulates the conversion of glucose to glycogen (glycogenesis) in the target cells.
• Testosterone
  • Testosterone is responsible for the development of male sexual characteristics.
  • Testosterone regulates fertility, muscle mass, fat distribution, and red blood cell production.