Many of the responses to stress are attributed to activation of the sympathetic nervous system and are mediated by

Responses to stress are attributed to activation of the sympathetic nervous system and are mediated by adrenal medulla which is the central portion of the adrenal gland.

Explanation:

Stress is a physical, mental, and emotional response to a threat, and causes bodily and mental tension. There are different causes of stress, for example, an exam, a divorce, moving from a house, being fired, somebody's death.

The body's stress response is mediated by the sympathetic nervous system (SNS), and the hypothalamic-pituitary-adrenal (HPA) system. The SNS is responsible for the neural fight-or-flight response to stress.

In a stressful situation the hypothalamus, which is in charge of the stress response, sends signals to the pituitary gland and the adrenal medulla. The adrenal medulla secretes the neurotransmitters and hormones adrenaline and noradrenalin to the bloodstream. These hormones get the body ready for a response to stress, by increasing heart biting frequency and strength, increasing blood pressure, stimulating respiration, and dilating respiratory tracts.

Once the threat factor is over, the body gets back into a balanced state.