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About the size of a pearl, the hypothalamus directs a multitude of important functions in the body. Located in the diencephalon region of the forebrain, the hypothalamus is the control center for many autonomic functions of the peripheral nervous system. Connections with structures of the endocrine and nervous systems enable the hypothalamus to play a vital role in maintaining homeostasis. Homeostasis is the process of maintaining bodily equilibrium by monitoring and adjusting physiological processes.
Blood vessel connections between the hypothalamus and pituitary gland allow hypothalamic hormones to control pituitary hormone secretion. Some of the physiological processes regulated by the hypothalamus include blood pressure, body temperature, cardiovascular system functions, fluid balance, and electrolyte balance. As a limbic system structure, the hypothalamus also influences various emotional responses. The hypothalamus regulates emotional responses through its influence on the pituitary gland, skeletal muscular system, and autonomic nervous system.
The hypothalamus is involved in several functions of the body including:
- Autonomic Function Control
- Endocrine Function Control
- Motor Function Control
- Food and Water Intake Regulation
- Sleep-Wake Cycle Regulation
Directionally, the hypothalamus is found in the diencephalon. It is inferior to the thalamus, posterior to the optic chiasm, and bordered on the sides by the temporal lobes and optic tracts. The location of the hypothalamus, specifically its close proximity to and interactions with the thalamus and pituitary gland, enables it to act as a bridge between the nervous and endocrine systems.
Hormones produced by the hypothalamus include:
- Anti-Diuretic Hormone (Vasopressin) - regulates water levels and influence blood volume and blood pressure.
- Corticotropin-Releasing Hormone - acts on the pituitary gland causing the release of hormones in response to stress.
- Oxytocin - influences sexual and social behavior.
- Gonadotropin-Releasing Hormone - stimulates the pituitary to release hormones that influence the development of reproductive system structures.
- Somatostatin - inhibits the release of thyroid-stimulating hormone (TSH) and growth hormone (GH).
- Growth Hormone-Releasing Hormone - stimulates the release of growth hormone by the pituitary.
- Thyrotropin-Releasing Hormone - stimulates the pituitary to release thyroid-stimulating hormone (TSH). TSH regulates metabolism, growth, heart rate, and body temperature.
The hypothalamus consists of several nuclei (neuron clusters) that may be divided into three regions. These regions include an anterior, middle or tuberal, and posterior component. Each region can be further divided into areas that contain nuclei responsible for a variety of functions.
|Anterior||Thermoregulation; releases oxytocin, anti-diuretic hormone, and gonadotropin-releasing hormone; controls sleep-wake cycles.|
|Middle (Tuberal)||Controls blood pressure, heart rate, satiety, and neuroendocrine integration; releases growth hormone-releasing hormone.|
|Posterior||Involved in memory, learning, arousal, sleep, pupil dilation, shivering, and feeding; releases anti-diuretic hormone.|
The hypothalamus has connections with various parts of the central nervous system. It 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 brainstem includes the midbrain and portions of the hindbrain. The hypothalamus also connects to the peripheral nervous system. These connections enable the hypothalamus to influence many autonomic or involuntary functions (heart rate, pupil constriction and dilation, etc.). In addition, the hypothalamus has connections with other limbic system structures including the amygdala, hippocampus, thalamus, and olfactory cortex. These connections enable the hypothalamus to influence emotional responses to sensory input.
- The hypothalamus is located in the diencephalon region of the forebrain, directs a number of needed functions in the body and is the control center for several autonomic functions.
- These functional controls include: autonomic, endocrine, and motor function control. It is also involved in homeostasis and the regulation of both the sleep-wake cycle and in food and water intake.
- A number of important hormones are produced by the hypothalamus including: vasopressin (anti-diuretic hormone), corticotropin-releasing hormone, oxytocin, gonadotropin-releasing hormone, somatostatin, growth hormone-releasing hormone, and thyrotropin-releasing hormone. These hormones act on other organs or glands in the body.
Disorders of the hypothalamus prevent this important organ from functioning normally. The hypothalamus releases a number of hormones that control a variety of endocrine functions. As such, damage to the hypothalamus results in a lack of production of hypothalamic hormones needed to control important activities, such as maintaining water balance, temperature regulation, sleep cycle regulation, and weight control. Since hypothalamic hormones also influence the pituitary gland, damage to the hypothalamus impacts organs that are under pituitary control, such as the adrenal glands, gonads, and thyroid gland. Disorders of the hypothalamus include hypopituitarism (deficient pituitary hormone production), hypothyroidism (deficient thyroid hormone production), and sexual development disorders.
Hypothalamic disease is most commonly caused by brain injury, surgery, malnutrition related to eating disorders (anorexia and bulimia), inflammation, and tumors.
Divisions of the Brain
- Forebrain - encompasses the cerebral cortex and brain lobes.
- Midbrain - connects the forebrain to the hindbrain.
- Hindbrain - regulates autonomic functions and coordinates movement.