Pituitary Gland And Hypothalamus Pdf


By Desotoure
In and pdf
03.12.2020 at 04:15
7 min read
pituitary gland and hypothalamus pdf

File Name: pituitary gland and hypothalamus .zip
Size: 1256Kb
Published: 03.12.2020

The Prostaglandins pp Cite as. Harris and coworkers Green and Harris, , Harris and Jacobsohn, conclusively demonstrated that the integrity of the whole endocrine system depends on a vascular linkage between the hypothalamus and the anterior pituitary.

Pituitary gland , also called hypophysis , ductless gland of the endocrine system that secretes hormones directly into the bloodstream. The pituitary gland lies at the middle of the base of the skull and is housed within a bony structure called the sella turcica, which is behind the nose and immediately beneath the hypothalamus. The pituitary gland is attached to the hypothalamus by a stalk composed of neuronal axons and the so-called hypophyseal-portal veins. Its weight in normal adult humans ranges from about to mg 0.

The Hypothalamus-Pituitary-Endocrine System

One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus is located below the thalamus and is part of the limbic system. All vertebrate brains contain a hypothalamus. In humans, it is the size of an almond. The hypothalamus is responsible for the regulation of certain metabolic processes and other activities of the autonomic nervous system.

It synthesizes and secretes certain neurohormones , called releasing hormones or hypothalamic hormones, and these in turn stimulate or inhibit the secretion of hormones from the pituitary gland. The hypothalamus controls body temperature , hunger , important aspects of parenting and attachment behaviours , thirst , [2] fatigue , sleep , and circadian rhythms. The hypothalamus is divided into 3 regions supraoptic, tuberal, mammillary in a parasagittal plane, indicating location anterior-posterior; and 3 areas periventricular, medial, lateral in the coronal plane, indicating location medial-lateral.

Hypothalamic nuclei are located within these specific regions and areas. In mammals, magnocellular neurosecretory cells in the paraventricular nucleus and the supraoptic nucleus of the hypothalamus produce neurohypophysial hormones , oxytocin and vasopressin. These hormones are released into the blood in the posterior pituitary. The hypothalamic nuclei include the following: [6] [7] [8].

Cross-section of the monkey hypothalamus displays two of the major hypothalamic nuclei on either side of the fluid-filled third ventricle. Hypothalamic nuclei on one side of the hypothalamus, shown in a 3-D computer reconstruction [12]. The hypothalamus is highly interconnected with other parts of the central nervous system , in particular the brainstem and its reticular formation.

As part of the limbic system , it has connections to other limbic structures including the amygdala and septum , and is also connected with areas of the autonomous nervous system. The hypothalamus receives many inputs from the brainstem , the most notable from the nucleus of the solitary tract , the locus coeruleus , and the ventrolateral medulla. Several hypothalamic nuclei are sexually dimorphic ; i.

The importance of these changes can be recognized by functional differences between males and females. For instance, males of most species prefer the odor and appearance of females over males, which is instrumental in stimulating male sexual behavior. If the sexually dimorphic nucleus is lesioned, this preference for females by males diminishes.

Also, the pattern of secretion of growth hormone is sexually dimorphic; [14] this is why in many species, adult males are visibly distinguishable from females. Other striking functional dimorphisms are in the behavioral responses to ovarian steroids of the adult. Males and females respond to ovarian steroids in different ways, partly because the expression of estrogen-sensitive neurons in the hypothalamus is sexually dimorphic; i.

Estrogen and progesterone can influence gene expression in particular neurons or induce changes in cell membrane potential and kinase activation, leading to diverse non-genomic cellular functions. Estrogen and progesterone bind to their cognate nuclear hormone receptors , which translocate to the cell nucleus and interact with regions of DNA known as hormone response elements HREs or get tethered to another transcription factor 's binding site.

Estrogen receptor ER has been shown to transactivate other transcription factors in this manner, despite the absence of an estrogen response element ERE in the proximal promoter region of the gene. In general, ERs and progesterone receptors PRs are gene activators, with increased mRNA and subsequent protein synthesis following hormone exposure. Male and female brains differ in the distribution of estrogen receptors, and this difference is an irreversible consequence of neonatal steroid exposure.

Estrogen receptors and progesterone receptors are found mainly in neurons in the anterior and mediobasal hypothalamus, notably:.

In neonatal life, gonadal steroids influence the development of the neuroendocrine hypothalamus. For instance, they determine the ability of females to exhibit a normal reproductive cycle, and of males and females to display appropriate reproductive behaviors in adult life.

In primates, the developmental influence of androgens is less clear, and the consequences are less understood. Within the brain, testosterone is aromatized to estradiol , which is the principal active hormone for developmental influences.

The human testis secretes high levels of testosterone from about week 8 of fetal life until 5—6 months after birth a similar perinatal surge in testosterone is observed in many species , a process that appears to underlie the male phenotype.

Estrogen from the maternal circulation is relatively ineffective, partly because of the high circulating levels of steroid-binding proteins in pregnancy. Sex steroids are not the only important influences upon hypothalamic development; in particular, pre-pubertal stress in early life of rats determines the capacity of the adult hypothalamus to respond to an acute stressor. The hypothalamus has a central neuroendocrine function, most notably by its control of the anterior pituitary , which in turn regulates various endocrine glands and organs.

Releasing hormones also called releasing factors are produced in hypothalamic nuclei then transported along axons to either the median eminence or the posterior pituitary , where they are stored and released as needed.

In the hypothalamic—adenohypophyseal axis, releasing hormones, also known as hypophysiotropic or hypothalamic hormones, are released from the median eminence, a prolongation of the hypothalamus, into the hypophyseal portal system , which carries them to the anterior pituitary where they exert their regulatory functions on the secretion of adenohypophyseal hormones.

After their release into the capillaries of the third ventricle, the hypophysiotropic hormones travel through what is known as the hypothalamo-pituitary portal circulation. Once they reach their destination in the anterior pituitary, these hormones bind to specific receptors located on the surface of pituitary cells.

Depending on which cells are activated through this binding, the pituitary will either begin secreting or stop secreting hormones into the rest of the bloodstream. Other hormones secreted from the median eminence include vasopressin , oxytocin , and neurotensin. In the hypothalamic-neurohypophyseal axis, neurohypophysial hormones are released from the posterior pituitary, which is actually a prolongation of the hypothalamus, into the circulation.

It is also known that hypothalamic-pituitary-adrenal axis HPA hormones are related to certain skin diseases and skin homeostasis. There is evidence linking hyperactivity of HPA hormones to stress-related skin diseases and skin tumors. The hypothalamus coordinates many hormonal and behavioural circadian rhythms, complex patterns of neuroendocrine outputs, complex homeostatic mechanisms, and important behaviours. The hypothalamus must, therefore, respond to many different signals, some of which are generated externally and some internally.

Delta wave signalling arising either in the thalamus or in the cortex influences the secretion of releasing hormones; GHRH and prolactin are stimulated whilst TRH is inhibited. Olfactory stimuli are important for sexual reproduction and neuroendocrine function in many species. For instance if a pregnant mouse is exposed to the urine of a 'strange' male during a critical period after coitus then the pregnancy fails the Bruce effect.

Thus, during coitus, a female mouse forms a precise 'olfactory memory' of her partner that persists for several days. Pheromonal cues aid synchronization of oestrus in many species; in women, synchronized menstruation may also arise from pheromonal cues, although the role of pheromones in humans is disputed. Peptide hormones have important influences upon the hypothalamus, and to do so they must pass through the blood—brain barrier.

The hypothalamus is bounded in part by specialized brain regions that lack an effective blood—brain barrier; the capillary endothelium at these sites is fenestrated to allow free passage of even large proteins and other molecules. Some of these sites are the sites of neurosecretion - the neurohypophysis and the median eminence. However, others are sites at which the brain samples the composition of the blood. Two of these sites, the SFO subfornical organ and the OVLT organum vasculosum of the lamina terminalis are so-called circumventricular organs , where neurons are in intimate contact with both blood and CSF.

These structures are densely vascularized, and contain osmoreceptive and sodium-receptive neurons that control drinking , vasopressin release, sodium excretion, and sodium appetite. They also contain neurons with receptors for angiotensin , atrial natriuretic factor , endothelin and relaxin , each of which important in the regulation of fluid and electrolyte balance.

The circumventricular organs may also be the site of action of interleukins to elicit both fever and ACTH secretion, via effects on paraventricular neurons. It is not clear how all peptides that influence hypothalamic activity gain the necessary access.

In the case of prolactin and leptin , there is evidence of active uptake at the choroid plexus from the blood into the cerebrospinal fluid CSF. Some pituitary hormones have a negative feedback influence upon hypothalamic secretion; for example, growth hormone feeds back on the hypothalamus, but how it enters the brain is not clear.

There is also evidence for central actions of prolactin. Subsequent to this, T3 is transported into the thyrotropin-releasing hormone TRH -producing neurons in the paraventricular nucleus.

Thyroid hormone receptors have been found in these neurons , indicating that they are indeed sensitive to T3 stimuli. In addition, these neurons expressed MCT8 , a thyroid hormone transporter, supporting the theory that T3 is transported into them.

T3 could then bind to the thyroid hormone receptor in these neurons and affect the production of thyrotropin-releasing hormone, thereby regulating thyroid hormone production. The hypothalamus functions as a type of thermostat for the body. All fevers result from a raised setting in the hypothalamus; elevated body temperatures due to any other cause are classified as hyperthermia. However, it is more common for such damage to cause abnormally low body temperatures.

The hypothalamus contains neurons that react strongly to steroids and glucocorticoids — the steroid hormones of the adrenal gland , released in response to ACTH.

It also contains specialized glucose-sensitive neurons in the arcuate nucleus and ventromedial hypothalamus , which are important for appetite. The preoptic area contains thermosensitive neurons; these are important for TRH secretion. Oxytocin secretion in response to suckling or vagino-cervical stimulation is mediated by some of these pathways; vasopressin secretion in response to cardiovascular stimuli arising from chemoreceptors in the carotid body and aortic arch , and from low-pressure atrial volume receptors , is mediated by others.

In the rat, stimulation of the vagina also causes prolactin secretion, and this results in pseudo-pregnancy following an infertile mating. In the rabbit, coitus elicits reflex ovulation. In the sheep, cervical stimulation in the presence of high levels of estrogen can induce maternal behavior in a virgin ewe. These effects are all mediated by the hypothalamus, and the information is carried mainly by spinal pathways that relay in the brainstem.

Stimulation of the nipples stimulates release of oxytocin and prolactin and suppresses the release of LH and FSH. Cardiovascular stimuli are carried by the vagus nerve. The vagus also conveys a variety of visceral information, including for instance signals arising from gastric distension or emptying, to suppress or promote feeding, by signalling the release of leptin or gastrin , respectively.

Again this information reaches the hypothalamus via relays in the brainstem. In addition hypothalamic function is responsive to—and regulated by—levels of all three classical monoamine neurotransmitters , noradrenaline , dopamine , and serotonin 5-hydroxytryptamine , in those tracts from which it receives innervation. For example, noradrenergic inputs arising from the locus coeruleus have important regulatory effects upon corticotropin-releasing hormone CRH levels.

The extreme lateral part of the ventromedial nucleus of the hypothalamus is responsible for the control of food intake. Stimulation of this area causes increased food intake. Bilateral lesion of this area causes complete cessation of food intake.

Medial parts of the nucleus have a controlling effect on the lateral part. Bilateral lesion of the medial part of the ventromedial nucleus causes hyperphagia and obesity of the animal. Further lesion of the lateral part of the ventromedial nucleus in the same animal produces complete cessation of food intake. There are different hypotheses related to this regulation: [32]. The medial zone of hypothalamus is part of a circuitry that controls motivated behaviors, like defensive behaviors.

Exposure to a predator such as a cat elicits defensive behaviors in laboratory rodents, even when the animal has never been exposed to a cat. Fos-labeled cell analysis showed that the PMDvl is the most activated structure in the hypothalamus, and inactivation with muscimol prior to exposure to the context abolishes the defensive behavior. Likewise, the hypothalamus has a role in social defeat : Nuclei in medial zone are also mobilized during an encounter with an aggressive conspecific.

The defeated animal has an increase in Fos levels in sexually dimorphic structures, such as the medial pre-optic nucleus, the ventrolateral part of ventromedial nucleus, and the ventral premammilary nucleus.

Overview of the Pituitary Gland

Are you hot right now? Maybe you're like Goldilocks and are just right. What about your height? Are you tall? Maybe your metabolism is lightning fast and you're always hungry, or maybe it's a bit slow and you stay full longer. All of these—regardless of which one you identify with—are regulated by the endocrine system.

If your institution subscribes to this resource, and you don't have a MyAccess Profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus. Please consult the latest official manual style if you have any questions regarding the format accuracy. Describe the physiologic and anatomic relationships between the hypothalamus and the anterior and the posterior pituitary. Understand the integration of hypothalamic and pituitary function and identify the 2 different pathways used for hypothalamic-pituitary interactions. Identify the appropriate hypothalamic releasing and inhibitory factors controlling the secretion of each of the anterior pituitary hormones.

Numerous glands throughout the body produce hormones. The hypothalamus produces several releasing and inhibiting hormones that act on the pituitary gland, stimulating the release of pituitary hormones. Of the pituitary hormones, several act on other glands located in various regions of the body, whereas other pituitary hormones directly affect their target organs. Other hormone-producing glands throughout the body include the adrenal glands, which primarily produce cortisol; the gonads i. Many of these hormones are part of regulatory hormonal cascades involving a hypothalamic hormone, one or more pituitary hormones, and one or more target gland hormones.

The Endocrine System

The pituitary is a pea-sized gland that is housed within a bony structure sella turcica at the base of the brain. The sella turcica protects the pituitary but allows very little room for expansion. The pituitary controls the function of most other endocrine glands and is therefore sometimes called the master gland. In turn, the pituitary is controlled in large part by the hypothalamus, a region of the brain that lies just above the pituitary.

One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus is located below the thalamus and is part of the limbic system. All vertebrate brains contain a hypothalamus. In humans, it is the size of an almond. The hypothalamus is responsible for the regulation of certain metabolic processes and other activities of the autonomic nervous system.

This complex secretes several hormones that directly produce responses in target tissues, as well as hormones that regulate the synthesis and secretion of hormones of other glands. In addition, the hypothalamus—pituitary complex coordinates the messages of the endocrine and nervous systems. In many cases, a stimulus received by the nervous system must pass through the hypothalamus—pituitary complex to be translated into hormones that can initiate a response. The hypothalamus is a structure of the diencephalon of the brain located anterior and inferior to the thalamus Figure

Hypothalamus

Hypothalamus

 Да. Есть ли в Севилье такое место, где тусуются панки. - No lo se, senor. He знаю. Но уж определенно не здесь! - Он улыбнулся.  - Может, все-таки чего-нибудь выпьете.

В ее обязанности в качестве главного криптографа входило поддерживать в шифровалке мирную атмосферу - воспитывать. Особенно таких, как Хейл, - зеленых и наивных. Сьюзан посмотрела на него и подумала о том, как жаль, что этот человек, талантливый и очень ценный для АНБ, не понимает важности дела, которым занимается агентство. - Грег, - сказала она, и голос ее зазвучал мягче, хотя далось ей это нелегко.  - Сегодня я не в духе. Меня огорчают твои разговоры о нашем агентстве как каком-то соглядатае, оснащенном современной техникой.

Задача дешифровщиков состояла в том, чтобы, изучив его, получить оригинальный, или так называемый открытый, текст. АНБ пригласило Беккера, потому что имелось подозрение, что оригинал был написан на мандаринском диалекте китайского языка, и ему предстояло переводить иероглифы по мере их дешифровки. В течение двух часов Беккер переводил бесконечный поток китайских иероглифов. Но каждый раз, когда он предлагал перевод, дешифровщики в отчаянии качали головами. Очевидно, получалась бессмыслица.

Но этого было достаточно. СЛЕДОПЫТ ИЩЕТ… - Следопыт? - произнес.  - Что он ищет? - Мгновение он испытывал неловкость, всматриваясь в экран, а потом принял решение.

 - Мне нужен совет. Джабба встряхнул бутылочку с острой приправой Доктор Пеппер. - Выкладывай. - Может быть, все это чепуха, - сказала Мидж, - но в статистических данных по шифровалке вдруг вылезло что-то несуразное. Я надеюсь, что ты мне все объяснишь.

The Endocrine System: Hypothalamus and Pituitary

1 Comments

Catherine E.
12.12.2020 at 13:39 - Reply

is composed of two morphologically and functionally distinct glands connected to the hypothalamus - the adenohypophysis and the neurohypophysis. The adenohypophysis consists of the pars tuberalis, which forms the outer covering of the pituitary stalk, and the pars distalis or anterior lobe.

Leave a Reply