How do the brain and the body communicate with each other?
Why do you feel hungry when you haven’t eaten? Why does your heart start beating faster when you feel scared? Our thoughts and emotions often feel in sync with physical sensations in our bodies because the brain and the body communicate information to each other that is important for keeping us healthy and safe. One way that the brain and body communicate with each other is by using chemical messengers called hormones. The parts of the body that produce hormones are called endocrine glands, and together the endocrine glands make up the endocrine system. Endocrine glands release hormones into the bloodstream, and hormones then travel to different organs in the body to convey information [1].
For example, your body uses hormones to communicate to your brain about energy balance and food intake. When you haven’t eaten in a while and your stomach is empty, your stomach will release a hormone called ghrelin into the bloodstream. Ghrelin travels to a brain region called the hypothalamus, where it signals that you need to eat. In response to this message, your brain will prepare to eat by making you feel hungry and making you crave and seek out food. After you have eaten, your stomach will stop releasing ghrelin. When the hypothalamus doesn’t receive as much ghrelin signaling, it knows that the stomach is full, and you will stop feeling hungry [2]. Without this communication between the stomach and the brain, we wouldn’t know when we need more energy and food, and we wouldn’t know when to stop eating!
Your brain can also send signals to your body based on sensory information, thoughts, or emotions. If you see a bear, you’ll probably feel scared, and your brain will prepare your body to run away from the bear using hormone signals. First, neurons in the hypothalamus (the same brain region that receives ghrelin signals!) will release a hormone called corticotropin releasing hormone (CRH). CRH will then signal to neurons in the pituitary gland (an endocrine gland that sits below the hypothalamus), causing it to release another hormone called adrenocorticotropic hormone (ACTH). ACTH enters the bloodstream and signals to the adrenal glands, which release a hormone called cortisol. Finally, cortisol signals to many organs in the body to prepare you to run away from the bear. For example, it signals to the heart to increase your heart rate and blood pressure, and to your liver to release stored glucose (sugar) so you have energy [3]. You’re probably unlikely to run into a bear in your everyday life, but the same hormone signaling pathway can be initiated by more common stressors too, such as needing to take a test in school.
It is crucial that our brain and body communicate with each other, and several medical conditions are associated with the endocrine system not functioning correctly. Too much ghrelin release can lead to obesity, and dysfunction of the hormones involved in the stress response can occur in conditions like post-traumatic stress disorder (PTSD) [2,3]. Ghrelin and cortisol are just two examples of over 50 types of hormones that send signals throughout the brain and the body [1]. Thanks to hormones, our bodily processes can be in harmony with our thoughts and emotions.
Citations:
1. (2024). Overview of the Endocrine System. Environmental Protection Agency. [Online]. [Accessed 13-Feb-2025].
2. Klok et al. (2007). The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review. Obes Rev.8(1): 21-34.
3. Herman et al. (2016). Regulation of the hypothalamic-pituitary-adrenocortical stress response. Compr Physiol. 6(2):603–621.
Image citation:
1. (2024). Overview of the Endocrine System. Environmental Protection Agency. [Online]. [Accessed 13-Feb-2025].
Edited by Emma Hays
