 In this video, we will be discussing the nuclei of the hypothalamus. You are sure to get some questions about the functions of specific hypothalamic nuclei on step 1. We will be showing them on a diagram to help give you some context, but don't worry, you won't be responsible for visually identifying any of these nuclei on the test. What you will be responsible for is knowing the function of each nucleus of the hypothalamus that we are about to discuss. You often get questions that require you to know what kind of symptoms a patient is likely to experience if there is a lesion in the particular part of the hypothalamus. Or vice versa, identifying which nucleus is damaged based on what symptoms a patient has. Let's start with the lateral nucleus. The lateral nucleus is responsible for making you feel hungry. In a normal patient, activation of the lateral nucleus will stimulate a feeling of hunger. Lesions that affect this area of the hypothalamus will cause patients to experience hypophagia, a decreased desire to eat, as well as weight loss. Next up is the ventromedial nucleus. The ventromedial nucleus is responsible for making us feel full and satiated after eating. Any lesion that affects the ventromedial nucleus will interfere with the patient's ability to feel full after eating. These patients will often overeat and experience weight gain. The next area we'll talk about is the interior nucleus. The interior nucleus is responsible for decreasing body temperature when the body gets too hot. It controls our involuntary heat dissipation mechanisms like sweating. Thus, patients who have a damaged interior nucleus will experience heat intolerance and will often feel very hot, especially in warm environments where the body needs to cool itself down. That brings us to the posterior nucleus, which is responsible for increasing temperature of the body. It regulates involuntary heat conservation mechanisms like shivering. Thus, patients who sustain a lesion to their posterior nucleus will have trouble maintaining body temperature. They'll also experience cold intolerance. Next is the suprachiasmatic nucleus. This nucleus gets its name, suprachiasmatic, for being located above or superior to the optic chiasm. This nucleus is responsible for maintaining our circadian rhythm, or sleep wake cycle. Patients with lesions involving this nucleus will have difficulty regulating their sleep cycles. They may experience symptoms like insomnia or excessive sleepiness at inappropriate times during the day. You should remember that these are nonspecific symptoms that you'll probably have to rule out some more common abnormalities, for example, depression or hypothyroidism, before suspecting that a brain lesion is involved. Next, we have a pair of ventricular nucleus. The pair of ventricular nucleus is responsible for synthesizing oxytocin. Oxytocin has numerous functions, but it's best known for its role during childbirth and breast feeding. Oxytocin is synthesized and released during childbirth in response to a baby's head coming in contact with the cervix. Oxytocin causes the uterus to contract and help to birth the baby. In fact, we often administer exogenous oxytocin to patients in order to stimulate or augment labor. Therefore, demo patients with lesions in the pair of ventricular nucleus may experience issues during pregnancy. If you watched part one of our hypothalamus video, you'll remember that oxytocin is produced in the hypothalamus and released by the posterior pituitary, as opposed to being synthesized and produced by the hypothalamus itself. Next up, we have the supraoptic nucleus. The supraoptic nucleus synthesizes anti-diuretic hormone. Anti-diuretic hormone, also known as ADH or vasopressin, is a hormone that acts on the collecting duct of the kidney to increase the absorption of free water, thus increasing intravascular volume, making urine more concentrated and blood more dilute. It's released in response to increased serum osmolarity and decreased intravascular volume. ADH is another hormone that's produced in the hypothalamus and released by the posterior pituitary. Lesions to the supraoptic nucleus are important to identify because they can cause a condition called central diabetes insipidus. Diabetes insipidus is a condition that's caused by the inability to discrete ADH or by defective ADH receptors, and thus the inability to concentrate urine. Central diabetes insipidus is due to a lack of appropriate ADH secretion. It's usually due to a lesion affecting the posterior pituitary, but theoretically, a lesion to the supraoptic nucleus would cause the same presentation. Patients with this condition will experience polyuria and polydipsia, for excessive thirst. Urine studies will classically show a low urine osmolarity and a relatively increased serum osmolarity. Just don't get it confused with diabetes mellitus in which patients experience polyuria and polydipsia due to hyperglycemia. This video has been a review of the hypothalamic nuclei. The seven nuclei we discussed are the most commonly tested, and you should be familiar with the function of each one. Most of the questions you get about hypothalamic nuclei will be related to the symptoms that are present when one of these nuclei is damaged. So make sure you are able to correlate the function of each one of these hypothalamic areas to the disease states that arise when one of these areas is damaged. We hope you found this review helpful. Be sure to subscribe to our channel for more videos like this, and leave some suggestions in the comments for other topics you'd like to see.