2.3 Adrenaline

2.3.1 Site of production of adrenaline

• Adrenal glands are found above the kidneys.

• Adrenaline is produced by the adrenal medulla which is found within the adrenal glands.

• Adrenaline is a “fight or flight” hormone – produced when one is afraid, angry, anxious or stressed.

2.3.2 Release of adrenaline

2.3.3 Effects of adrenaline

• Increases blood glucose levels by speeding up the breakdown of glycogen to glucose in the liver and muscles. This allows more glucose to be available for muscle cells for respiration to release more energy/ATP.

• Increases metabolic rate. This means more energy is released during tissue respiration.

• Increases the rate of heartbeat and causes a rise in blood pressure so that oxygen and glucose can be transported to the skeletal muscles for respiration to occur.

• Increases the rate and depth of ventilation. This increases the oxygen concentration gradient between alveolar air space and blood capillaries. Rate of diffusion of oxygen from alveolar air space into red blood cells in blood capillary increases.

• Constricts skin arterioles, thus more blood can be sent to the skeletal muscles to prepare for 'fight or flight' response.

• Causes pupils to dilate to enhance vision to identify flight route and source of danger, anxiety or stress.

• Hair erector muscles contract and hair stands on the skin resulting in "goose pimples".