The hypothalamus and pituitary gland work together to produce and release a number of hormones that are critically important for a long list of functions in the body. In this video, I will first introduce the hypothalamus and pituitary glands separately. Then I will describe the connections and communication between them that leads to hormone release. Finally, I will discuss the hormonal stress response of the HPA axis as an example of how the hypothalamus and pituitary gland work together. The hypothalamus is a small region located deep in the brain just below the phalamus. It sits above and is connected to the pituitary gland, a neuroendocrine gland whose function is regulated by the hypothalamus. The hypothalamus is a complex structure that contains more than a dozen nuclei with different functional specializations. It is involved in a long list of processes, many of which are critically important to maintaining homeostasis across various bodily systems. The hypothalamus receives information from the body and other parts of the nervous system about a range of physiological parameters and it can influence behavioral systems, the autonomic nervous system and neuroendocrine systems to initiate mechanisms to restore homeostasis when needed. Some of the major functions generally attributed to the hypothalamus include the regulation of thirst and drinking behavior, fluid and electrolyte balance, hunger and feeding, body temperature, stress responses, aggressive behaviors, reproductive behaviors, circadian rhythms, the sleep wake cycle, and more. One common method of anatomically subdividing the hypothalamus is from front to back into thirds. The frontmost region of the hypothalamus is called the preoptic area and it includes nuclei that play critical roles in the regulation of body temperature, fever, electrolyte balance, circadian rhythms, sexual behavior and more. The middle region is called the tubal hypothalamus. A structure called the infendibulum or pituitary stock emerges from the tubal hypothalamus and connects the hypothalamus to the pituitary gland. The nuclei in the tubal region play roles in hunger and feeding, sexual behavior, aggressiveness, and a number of autonomic and endocrine responses among other things. The posterior region contains nuclei involved in wakefulness, stress responses, memory, and other functions. The pituitary gland, also known as the hypothesis, is an endocrine gland that's often called the master gland because it not only secretes many important hormones, but also regulates the activity of a multitude of other hormone secretreting glands and target organs throughout the body. The pituitary gland is connected to and situated just below the hypothalamus. The hypothalamus controls hormone release from the pituitary gland. The pituitary gland is divided into anterior and posterior components. The posterior pituitary is also called the neurohypothesis. It is composed of the posterior lobe of the pituitary and a structure called the infendibular or pituitary stock which connects the hypothalamus to the pituitary gland. The anterior pituitary, also known as the adno hypothesis, consists of three parts. the anterior lobe, a smaller intermediate lobe that's typically only distinct in the fetal and newborn pituitary, and a section of tissue called the pars tuberis, which wraps around the infendibular stock. The anterior pituitary contains cells that produce several important hormones. Adreninocorticotropic hormone, thyroid stimulating hormone, luteinizing hormone, follical stimulating hormone, growth hormone, and prolactin. These hormones are produced in the anterior pituitary but their secretion into the bloodstream is controlled by signaling hormones made and secreted by the hypothalamus. Two hormones oxytocin and vasop prein are secreted into the bloodstream from the posterior pituitary. These hormones are not made in the pituitary gland but instead are synthesized in neurons in the hypothalamus. The axons of these neurons extend from the hypothalamus to the posterior pituitary and oxytocin and vasopressin are transported from their cytosynthesis in the cell body to axon terminals in the posterior pituitary. They are secreted into the bloodstream as a result of action potentials in the neurons they're found in. The hypothalamus controls hormone release from the pituitary gland in multiple ways. As noted earlier, the anterior pituitary produces and stores a variety of hormones and their release into the bloodstream is regulated by the hypothalamus. This regulation occurs through the use of hormones that are made in the hypothalamus called releasing and inhibiting hormones. As their names imply, releasing hormones stimulate hormone release while inhibiting hormones inhibit it. These hormones are delivered to the anterior pituitary via a specialized network of blood vessels called the hypothesial portal system which directly connects the hypothalamus and anterior pituitary to prompt hormone release from the anterior pituitary. The hypothalamus secretes a releasing hormone into the hypothesal portal system. The hypothesial portal system carries the releasing hormone to the anterior pituitary where it binds to receptors to cause hormone release. For example, growth hormone releasing hormone is secreted into the hypothesal portal system to trigger the release of growth hormone from the anterior pituitary. The hypothalamus also uses inhibiting hormones to regulate the release of certain pituitary hormones such as prolactin and growth hormone. As mentioned earlier, the posterior pituitary also releases two hormones into the bloodstream, but they are not synthesized in the pituitary gland. These two hormones oxytocin and vasop prein are produced in the cell bodies of neurons located in the hypothalamus. The axons of these neurons extend into the posterior pituitary and oxytocin and vasopressin are transported down those axons and stored in axon terminals in the posterior pituitary. Their release into the bloodstream is triggered by action potentials in the neurons they're found in. Thus, the hypothalamus regulates hormone release from both loes of the pituitary gland, but it does so using different mechanisms for each lobe. The hypothalamic pituitary adrenal or HPA axis is best known for its role in our body's reaction to stress. The HPA axis includes a group of hormone secretreting glands from the nervous and endocrine systems, the hypothalamus, pituitary gland, and adrenal glands. The hypothalamus is a small neuroendocrine structure situated just above the brain stem that controls the release of hormones from the pituitary gland, a hormone secretreting gland that sits just below the hypothalamus. The pituitary gland can release hormones into the bloodstream to reach a variety of targets. In the case of the HPA axis, hormones released from the pituitary gland travel down to the kidneys and influences secretion of hormones from endocrine glands called the adrenal glands, which sit on top of the kidneys. The primary function of the HPI axis is to regulate the stress response. When we experience something stressful, the hypothalamus releases a hormone called corticotropen releasing hormone or CR. CR signals the pituitary gland to secrete a hormone called adreninocorticotropic hormone or act into the bloodstream. ACT travels down to the adrenal glands where it prompts the release of a hormone called cortisol from the cortex or outer layer of the adrenal glands. The release of cortisol causes a number of changes that help the body to deal with stress. For example, it helps to mobilize energy like glucose so the body has enough energy to cope with a prolonged stressor. When cortisol levels in the blood get high, this is sensed by receptors in areas of the brain like the hypothalamus and hippocampus, which leads to the shutting off of the stress response through what is known as a negative feedback mechanism.