What is the hypothalamus?
The hypothalamus is a part of the midbrain. An important function of the hypothalamus is to link the nervous system to the endocrine (hormonal) system through the pituitary gland. The hypothalamus is considered the regulator of all hormonal functions in the body.
The hypothalamus is a part of the midbrain. It is named that because of its proximity to the “thalamus,” the part of the brain responsible for all sensations the body receives. An important function of the hypothalamus is to link the nervous system to the endocrine (hormonal) system through the pituitary gland. The hypothalamus is considered the regulator of all hormonal functions in the body. It produces various hormones (substances) that control other glands of the body. Hormones produced by the hypothalamus include
- Anti-diuretic hormone (vasopressin): It regulates water levels and influences blood pressure.
- Corticotropin-releasing hormone (CRH): It acts on the pituitary gland releasing hormones in response to stress.
- Oxytocin: It influences sexual and social behavior.
- Gonadotropin-releasing hormone (GnRH): It stimulates the pituitary to release hormones that influence the development of reproductive system structures.
- Somatostatin: It inhibits the release of thyroid-stimulating hormone (TSH) and growth hormone (GH).
- GH-releasing hormone: It stimulates the release of GH by the pituitary.
- Thyrotropin-releasing hormone: It stimulates the pituitary to release TSH. TSH regulates metabolism, growth, heart rate and body temperature.
The hypothalamus may be divided into three regions. Each region is responsible for various functions.
Other functions of the anterior region of the hypothalamus include
- Temperature regulation
- Release of hormones such as oxytocin, anti-diuretic hormone and gonadotropin-releasing hormone
- Control of sleep–wake cycles
Functions of the middle or tubular region of the hypothalamus include
- Control of blood pressure, heart rate and food uptake habits
- Release of GH-releasing hormone
Functions of the posterior region of the hypothalamus include
- It is involved in memory, learning, arousal, sleep, pupil dilation, shivering and feeding
- It helps release anti-diuretic hormone
Other functions
- The hypothalamus connects with the brainstem, the part of the brain that relays information from the peripheral nerves and spinal cord to the upper parts of the brain.
- The hypothalamus also connects to the peripheral nervous system. These connections enable the hypothalamus to influence many involuntary functions (heart rate, pupil constriction and dilation, etc.).
- In addition, the hypothalamus has connections with other limbic system emotion controlling part of the brain, including the amygdala, hippocampus, thalamus and olfactory cortex. These connections enable the hypothalamus to influence emotional responses to sensory input.
Summary
The key function of the hypothalamus is to produce hormones that keep the body in a stable condition called homeostasis. It does this by coordinating messages and signals (hormones) received from other glands with those from the brain (nerve impulses). Together, the hormones made by the hypothalamus directly or indirectly regulate
- Body temperature
- Sleep and alertness
- Appetite and body weight
- Thirst
- Circadian (daily) rhythms
- Blood pressure and heart rate
- Sex drive
- Learning and memory
- Mood
- Sickness behaviors (fatigue, fever and loss of appetite)
Besides these, the hypothalamus secretes hormones that are involved in many other functions such as appetite and thirst control. Optimum levels of hormones in the bloodstream are necessary for the body to function properly. Low or high levels of a particular hormone could lead to hypothalamus disorders. These include
- Insomnia (problem with sleep cycles)
- Frequent urination
- Infertility
- Fluctuations in appetite and thirst
- Unusually high or low blood pressure
- Diabetes insipidus (an uncommon disorder that causes an imbalance of fluids in the body, which makes you very thirsty)
Disorders of the hypothalamus include
- Hypopituitarism (deficient pituitary hormone production)
- Hypothyroidism (deficient thyroid hormone production)
- Sexual development disorders
Hypothalamic disease is most commonly caused by brain injury, surgery, malnutrition-related to eating disorders (anorexia and bulimia), inflammation and tumors.