Where is the hypothalamus located?
The hypothalamus is a small, almond-sized, cone-shaped structure that projects downwards, ending in the infundibular stalk of the brain. This is a tubular connection to the pituitary gland, with which it has a direct relationship. The two are connected by nervous and chemical pathways.
If you want to imagine where it’s placed, the hypothalamus is around your eye level, nearly exactly at the center of the brain. It’s as small as a pea and weighs less than one percent of the weight of the brain. But despite its size, its functions are extremely complex and highly specialized.
It is a region in the brain and is part of the limbic system. This system is made up of various brain structures on both sides of the thalamus, located beneath the cerebrum. The limbic system as a whole is integral to the regulation of emotion and formation of memory. As such, it is involved in a person’s motivational processes and behaviors. It also supports olfaction, the sense of smell.
The limbic system also includes the olfactory bulbs, hippocampus, amygdala, fornix and its columns, anterior thalamic nuclei, mammillary body, septum pellucidum, limbic cortex, habenular commissure, cingulate gyrus, parahippocampal gyrus, and the limbic midbrain areas.
The hypothalamus also forms the ventral or bottom part of the diencephalon, lateral to the third ventricle. Aside from the hypothalamus, neighboring brain sections that are part of the diencephalon are the thalamus, epithalamus, and the subthalamus.
What is the function of the hypothalamus?
The hypothalamus is made up of interconnecting neurons, nourished by a rich supply of blood. It has a control center for many functions of the autonomic nervous system, which involves the involuntary and unconscious functions of the body.
Homeostasis. One of the major functions of the hypothalamus is to keep the body working in a stable, constant condition. It is responsible for keeping the system running normally. It responds to the internal and the external environment and adjusts body processes to allow us to adapt.
The hypothalamus is in charge of regulating the body temperature, blood pressure, fluid and electrolyte balance, body weight, as well as our everyday bodily rhythms. An example of which is the secretion of melatonin every night, that heralds sleep. It also allows us to recognize thirst and hunger, and feel full after a meal.
Aside from keeping things in order, the hypothalamus also collects the information over time and creates adjustments to correct any imbalances.
Hormones. The hypothalamus is also responsible for the regulation and even production of some hormones. It has a complex interaction with the pituitary gland, which in turn affects the endocrine system.
They hypothalamus has two sets of nerve cells for hormone production. The first set sends hormones directly into the blood stream through the posterior lobe of the pituitary gland. Hormones involved in this process are the oxytocin and the anti-diuretic hormones. Oxytocin is involved particularly in childbirth, by stimulating contractions in the uterus. It is also important for breastfeeding.
The second produces inhibiting and stimulating hormones that control the gonads, adrenal cortex and thyroid glands. These hormones travel to the anterior lobe of the pituitary gland through a network of blood vessels in the pituitary stalk. It also produces hormones that stimulate the production of growth hormones and of prolactin, which is key to milk production.
Aside from the two previously mentioned, the hypothalamus also produces the following hormones:
- Dopamine. This is a neurotransmitter that affects the reward and pleasure centers. It allows people to see rewards and the actions necessary to be taken to achieve those rewards. It also aids in the regulation of movement and emotional response.
Corticotrophin-releasing hormone. The primary function of this hormone is related to the stress hormone system. It causes the release of the adrenocorticotropic hormone from the pituitary gland, which travels through the blood stream to the adrenal glands to stimulate the secretion of the stress hormone, cortisol.
Aside from this, it also acts on the brain, causing several effects: suppressing the appetite, increasing anxiety, and improving memory and selective attention. Together, these make up the body’s different responses to stressful situations.
- Somatostatin. This particular hormone inhibits the secretion of growth and thyroid-stimulating hormones in the pituitary gland. It slows down the rapid reproduction of normal and tumor cells.
- Gonadotrophin-releasing hormone. This hormone is involved in the maintenance of the body’s reproductive functions. It travels to the pituitary glands to stimulate two hormones. These are the follicle and the luteinising hormones. These work on the testes and the ovaries by controlling the levels of the hormones produced by these two organs, namely testosterone, progesterone, and oestradiol. In men, these hormones control the sperm production. Whereas in women, these control the maturation and release of an egg, or the menstrual cycle.
Thyrotrophin-releasing hormone. One of the smallest hormones in the human body, thyrotrophin-releasing hormones regulate the release of thyroid-stimulating hormones, which then regulate the production of thyroid hormones in the thyroid gland.
It also acts as a neurotransmitter and affects arousal and the brain’s feeding center. A surplus of this hormone would lead to loss of appetite.
Hypothalamic dysfunction can be caused by many different factors, among which are inflammation or infection (like tuberculosis); injury due to trauma, radiation or surgery; or genetic defect. Hypothalamic disease can also be caused by malnutrition, including that which results from eating disorders like anorexia and bulimia.
Symptoms of hypothalamic disorders include: increased appetite, rapid weight gain, extreme thirst, and frequent urination. They can also cause impaired vision, dizziness, headaches, and sleeping problems. Depending on which part of the hypothalamus was damaged, symptoms can vary widely. Other signs to watch out for are delayed or premature puberty, enlarged breasts, menstrual problems, emotional problems, loss of male body hair, and hair and skin changes.
Hypoadrenalism and hypothyroidism can also just be symptoms of a hypothalamic disorder, which could be more difficult to diagnose. These symptoms may present themselves as diseases where in fact there are deeper underlying causes.
Other symptoms include: fatigue and cold intolerance.
Damage to the hypothalamus can manifest as different diseases, according to which side of it was damaged. Considering that it is such a small part of the brain, it is difficult to grasp how it still has different parts that when damaged, can disrupt very different areas of everyday life.
Hyperphagia. Damage to the ventromedial hypothalamus causes a disease called hyperphagia. The ventromedial hypothalamus is in charge of food satiety. This means that it creates the sensation of fullness to signal that one should stop eating. People with hyperphagia overeat and gain a lot of weight. They become helpless as their bodies become obese. It can become frustrating if they do not realize that this is caused by damage to their hypothalamus, that it is not a lack of self-discipline and that it is not their fault.
Aphagia and Adipsia. On the flip side of that coin, another disease causes a complete lack of eating. This disease is known as aphagia. It is caused by damage in the lateral hypothalamus. Similarly, adipsia causes a total lack of drinking.
Loss of Sexual Appetite. Sexual motivation or desire is another area of life that is affected or controlled by the hypothalamus. Research in animals shows that damage in the front or anterior part of the hypothalamus can disrupt, diminish or completely eliminate sexual desires.
Neurogenic Diabetes Insipidus. Another disease that damage to the hypothalamus can result in is diabetes insipidus or water diabetes. One of the hormones produced in the hypothalamus and secreted by the pituitary gland is the anti-diuretic hormone called vasopressin. This regulates the amount of urine the kidney produces. People who are afflicted with diabetes insipidus have a decreased level of vasopressin. This makes the kidney unable to retain water and produce too much urine which is pale and dilute. This is harmful to the body because anti-diuretics allow the body to detain fluid when one is hydrated. This causes concentrated dark urine. However, for people with diabetes insipidus, even if they do become dehydrated, the kidneys will still produce dilute urine, worsening the situation.
Its symptoms include: excessive urine production, three to 18 liters a day; excessive thirst; and urinating frequently at night, affecting sleep. These symptoms are similar to that of diabetes mellitus, except the patient’s blood sugar levels will be normal and there will be no sugar present in their urine.
If you suspect that you have this condition, it is of utmost importance that you keep yourself hydrated and to consult a doctor as soon as possible.
Development Disorders. The hypothalamus is also in charge of producing growth hormone-release hormones (GHRH). Damage to the hypothalamus may cause disruption in a person’s growth. A child can enter puberty late or early. Different scenarios may develop, among which are gonadotropin deficiency which could lead to infertility, poor somatic growth, precocious puberty, and failure to initiate or complete puberty. Disorders of this nature are typically associated with unexplained weight gain and low levels of sex hormones.
Tertiary Hypothyroidism. The thyroid is one of the main organs that the hypothalamus has an auxiliary effect on. Through a complex chain, the hypothalamus helps regulate the production of thyroid hormones. These hormones are used in metabolic activity. When there is an insufficient level of thyroid hormones in the body, metabolic activity becomes suppressed, leading to weight gain. This has serious repercussions on issues of obesity.