Hypothalamus

-
Hypothalamus, part of the brain, important in regulating the internal activities of the body. Although the hypothalamus constitutes less than 1 percent of the total volume of the brain, it has an important influence on many of the body's functions, including sexual behavior, emotions, hormone production, and the autonomic nervous system.

ANATOMY

The human hypothalamus weighs about 4 g (0.14 oz) and is found behind the eyes, directly below the brain's thalamus and above the pituitary gland. The hypothalamus is divided into several distinct nuclei, that is, aggregates of nerve cell bodies. These nerves connect the brain with the hypothalamus and the hypothalamus to virtually all regions of the nervous system. The hypothalamus also receives nerve inputs from the erogenous zones (the genitalia and nipples), the viscera (internal organs), and the limbic system (concerned with motivation and drive).

FUNCTION

The hypothalamus controls a wide range of functions. It directs the “fight or flight” response of the autonomic nervous system. Fear or excitement causes signals to travel to the hypothalamus, which triggers a rapid heartbeat, faster breathing, widening of the pupils, and increased blood flow. The hypothalamus monitors blood glucose levels and the body's water content to regulate appetite for food or drink. It regulates sleep and sexual behavior.

ENDOCRINE FUNCTIONS OF THE HYPOTHALAMUS

The hypothalamus is responsible for controlling the hormones released from the pituitary gland. Two of these hormones are oxytocin and vasopressin (also called antidiuretic hormone or ADH).

Oxytocin plays a role in uterine contractions during childbirth. It also has a role in starting and maintaining the birth process. Breastfeeding also triggers the secretion of oxytocin via a nervous pathway that connects the nipple and the hypothalamus; oxytocin stimulates the flow of milk from the breast to the infant. Oxytocin secretion can also be caused by the sound of a baby crying—an example of the connections the hypothalamus has with the other parts of the brain.

See also HYPOTHALAMUS DISORDERS

Popular posts from this blog

Cellular Respiration

-
Cellular Respiration, process in which cells produce the energy they need to survive. In cellular respiration, cells use oxygen to break down the sugar glucose and store its energy in molecules of adenosine triphosphate (ATP). Cellular respiration is critical for the survival of most organisms because the energy in glucose cannot be used by cells until it is stored in ATP. Cells use ATP to power virtually all of their activities—to grow, divide, replace worn out cell parts, and execute many other tasks. Cellular respiration provides the energy required for an amoeba to glide toward food, the Venus fly trap to capture its prey, or the ballet dancer to execute stunning leaps. Cellular respiration occurs within a cell constantly, day and night, and if it ceases, the cell—and ultimately the organism—dies. Two critical ingredients required for cellular respiration are glucose and oxygen. The glucose used in cellular respiration enters cells in a variety of ways. Plants, algae, and cer
Read more

Respiratory System

-
. Respiratory System, in anatomy and physiology, organs that deliver oxygen to the circulatory system for transport to all body cells. Oxygen is essential for cells, which use this vital substance to liberate the energy needed for cellular activities. In addition to supplying oxygen, the respiratory system aids in removing of carbon dioxide, preventing the lethal buildup of this waste product in body tissues. Day-in and day-out, without the prompt of conscious thought, the respiratory system carries out its life-sustaining activities. If the respiratory system’s tasks are interrupted for more than a few minutes, serious, irreversible damage to tissues occurs, followed by the failure of all body systems, and ultimately, death. While the intake of oxygen and removal of carbon dioxide are the primary functions of the respiratory system, it plays other important roles in the body. The respiratory system helps regulate the balance of acid and base in tissues, a process crucial for the norma
Read more

Fertilization

-
Fertilization is the process in which gametes —a male's sperm and a female's egg or ovum—fuse together, producing a single cell that develops into an adult organism. Fertilization occurs in both plants and animals that reproduce sexually—that is, when a male and a female are needed to produce an offspring (see Reproduction ). Fertilization is a precise period in the reproductive process. It begins when the sperm contacts the outer surface of the egg and it ends when the sperm's nucleus fuses with the egg's nucleus. Fertilization is not instantaneous—it may take 30 minutes in sea urchins and up to several hours in mammals. After nuclear fusion, the fertilized egg is called a zygote. When the zygote divides to a two-cell stage, it is called an embryo. Fertilization is necessary to produce a single cell that contains a full complement of genes. When a cell undergoes meiosis , gametes are formed—a sperm cell or an egg cell. Each gamete contains only half the genetic materia
Read more