The adrenal gland produces the hormone adrenaline. Describe two effects of adrenaline on the human body.

Adrenaline is released from the adrenal glands in times of stress, fear, or excitement, triggering the "fight or flight" response. This response prepares the body for vigorous physical activity. Key effects include: - **Increased heart rate:** The heart beats faster, pumping more oxygenated blood to the muscles. - **Increased breathing rate:** Breathing becomes faster and deeper, increasing oxygen intake into the lungs. - **Glycogen to glucose conversion:** Adrenaline stimulates the liver to break down its store of glycogen into glucose, which is released into the bloodstream. This increases the blood glucose concentration, providing more fuel for cellular respiration in the muscles. - **Redirection of blood flow:** Blood vessels supplying non-essential areas (like the digestive system) constrict, while vessels supplying the muscles and brain dilate. This diverts more blood to where it is most needed.