Stress stimulates the hypothalamus, the part of the brain that regulates balance in the body, emotions, and needs such as hunger and thirst.
The hypothalamus sends signals to the adrenal glands through the spinal cord and the nervous system. The adrenal glands (medulla and cortex) produce large amounts of adrenaline, noradrenaline, and cortisol. Adrenaline makes the body alert and able to react quickly. Cortisol keeps your horse alert for a longer period of time. Like adrenaline, cortisol increases the heart rate, pumping oxygen through the body. Cortisol also increases blood sugar, resulting in more energy for a longer period.
Healthy tension ensures that your horse can continue to perform under pressure. After competition (or intensive training), tension is released and adrenaline and cortisol drop back to normal levels. When a horse experiences prolonged stress, the amount of cortisol in the body remains too high. Cortisol raises blood sugar levels – prolonged stress also leads to too much glucose in the body.
Long-term stress will cause your horse to have health issues over time.
