In times of stress, the hypothalamus activates the: sympathetic nervous system adrenal medulla posterior pituitary parasympathetic nervous system

In times of stress, the hypothalamus activates the **sympathetic nervous system**. Here's a brief explanation of the options: 1. **Sympathetic Nervous System**: This system is responsible for the body's 'fight or flight' response, which prepares the body to respond to stress or danger. It increases heart rate, dilates airways, and mobilizes energy. 2. **Adrenal Medulla**: While the adrenal medulla is activated by the sympathetic nervous system to release adrenaline (epinephrine) and norepinephrine, it is not directly activated by the hypothalamus. 3. **Posterior Pituitary**: This part of the pituitary gland releases hormones like oxytocin and vasopressin but is not primarily involved in the immediate stress response. 4. **Parasympathetic Nervous System**: This system is responsible for 'rest and digest' functions and is generally activated when the body is in a relaxed state, counteracting the effects of the sympathetic nervous system. Thus, the correct answer is the **sympathetic nervous system**.