Published: Sat, January 07, 2017
World | By Tasha Manning

Kedokteran dan Kesehatan

Kedokteran dan Kesehatan

The mammillary part of the hypothalamus consists of the posterior hypothalamic nucleus and the prominent mammillary nuclei. The posterior nucleus is a large, ill-defined group of cells that may play a role in thermoregulation (see below). The mammillary nuclei are considered to be part of the hypothalamus on anatomical grounds, but, unlike the other hypothalamic nuclei, they do not appear to be closely related to autonomic and endocrine functions. Instead, the mammillary nuclei is believed to play a role in memory, and will be discussed during the limbic system lecture. For now, just associate the mammillary nuclei with memory.

Functions of the Hypothalamus: Many of the functions of the hypothalamus are of a homeostasis and nature (maintenance of constant body states). Several of these have already been described in conjunction with the description of the nuclei involved. Such functions require the integration of
activity in many different body systems. A good example is temperature regulation (see Fig. 7, but do not learn this figure). When body temperature increases, neurons in the anterior part of the hypothalamus turn on mechanisms for heat dissipation that include sweating and dilation of blood vessels in the skin. When body temperature decreases, neurons in the posterior part of the hypothalamus are responsible for heat production through shivering, vasoconstriction in the skin, and blockage of perspiration. Lesions in the anterior part can result in hyperthermia (increase in body temperature) and lesions in the caudal part can result in hypothermia when the environmental temperature is low.

A recent, very significant Finding a direct projection from the hypothalamus to the preganglionic sympathetic neurons in the lateral horn of the spinal cord and to the preganglionic parasympathetic neurons in the dorsal motor nucleus of the vagus. (Recall from Dr. Harting's lecture that Horner's syndrome can result from interruption of the pathway from the hypothalamus to the lateral horn as it passes through the brain stem.) The cells of origin for these projections are located in many Different parts of the hypothalamus. The
hypothalamus has long been known as the "head ganglion" of the autonomic nervous system, but has been assumed to mediate its effects through multisynaptic pathways.

It is important to bear in mind, however, that many other areas of the brain, especially those collectively termed the limbic system (following lecture), are involved in the control of emotions.

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Another aspect of hypothalamic function that is interesting to consider is that it may be the site where, in many cases, emotional factors influence body functions. It is well known that many functions that are under autonomic or hormonal control are influenced to a large degree by
emotions. For example, emotional factors can influence or block menstruation, lactation, or sexual function. Since the hypothalamus is concerned with control of emotions, and regulation of both hormone release and autonomic nervous system, it is thought to be involved in the mediation of such effects.

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