Pituitary gland between

A disulfide bond between cysteine residues in different peptide chains links the otherwise separate chains together, while a disulfide bond between cysteine residues in the same chain forms a loop. Such is the case, for instance, with vasopressin, an antidiuretic hormone found in the pituitary gland. Note that the C-terminal end of vasopressin occurs as the primary amide, -CONHz, rather than as the free acid. 

The female menstrual cycle is divided into four functional phases follicular, ovulatory, luteal, and menstrual.6 The follicular phase starts the cycle, and ovulation generally occurs on day 14. The luteal phase then begins and continues until menstruation occurs.6 The menstrual cycle is regulated by a negative-feedback hormone loop between the hypothalamus, anterior pituitary gland, and ovaries6 (Fig. 45-1). 

Describe anatomical and functional relationships between the hypothalamus and the pituitary gland... 

The correlation of the hypothalamus and its hormones with the hormones of the anterior pituitary gland is summarized in figure 5.2. There is no direct vascular connection between the hypothalamus and the posterior lobe of the pituitary that would correspond to the portal vein system for the anterior lobe of the gland. Not all hypothalamo-pituitary hormones will be discussed in the subsequent sections. Only those that are well-defined chemical entities or have a direct connection with drug action are considered. 

The pituitary gland is situated in sella turcica or hypophyseal fossa of the sphenoid bone attached to the brain by a stalk which is continuous with the part of brain i.e. hypothalamus and there is a communication between the hypothalamus and the pituitary gland by means of nerve fibres and a complex of blood vessels. Pituitary gland consists of three parts - anterior lobe or adenohypophysis, posterior lobe or neurohypophysis and middle lobe or pars intermedia. 

There are relationships between the adrenal cortical hormones and the thyroid and pituitary glands. Depression or the function of the adrenals produces thyroid deficiency, w hereas administration of thyroxine stimulates the ACTH-adrenal conical mechanism. 

The pituitary gland is a small, pea-shaped structure located within the sella turcica at the base of the brain. The pituitary lies inferior to the hypothalamus and is attached to the hypothalamus by a thin stalk of tissue known as the infundibulum. The structural and functional relationships between the hypothalamus and pituitary gland are briefly discussed later in this section. A more detailed presentation of the anatomic and physiologic functions of the hypothalamus and pituitary gland can be found in several sources.8,14,32... 

Figure 7. Competition between [3H]-spiroperidol and dopamine for occupancy of binding sites in the NIL of the rat pituitary gland. The amount of [3H]-spiro-peridol bound to NIL tissue was determined in the presence of 2 fluphenazine (0), 2 (iM fluphenazine and 100 GTP (4) or dopamine (at the indicated concentrations) in the absence (O) or presence (9) of 100 GTP (33).

The above-described data show that CRF added to cells of the rat Intermediate lobe In culture causes a rapid stimulation of oe-MSH release and cyclic AMP accumulation, thus demonstrating a direct action of the peptide on pars intermedia cells (15). It is however difficult, using intact cells, to dissociate between increases in cyclic AMP levels due to stimulation of adenylate cyclase activity or to Inhibition of cyclic nucleotide phosphodiesterase or to a combination of both effects. Definitive proof of the role of adenylate cyclase In the action of CRF In the intermediate lobe of the pituitary gland is provided by the following findings of a CRF-lnduced stimulation of adenylate cyclase activity in homogenate of rat and bovine pars Intermedia cells. 

In humans the olfactory receptor cells lie in the mucous membrane at the top of the air passages on either side of the nasal septum. They occupy a total area of about 2 cm, which is small compared with most other mammals. Evidence from both anatomy and embryology shows that the development of the olfactory tissue is closely linked to that of the pituitary gland which lies at the base of the brain. Among other functions the pituitary plays a key role in the coordination of sexual activity and reproduction. This ancient association between the sense of smell and the reproductive process is one that has important implications for work of the perfumer. 

Other structures in this area make up the limbic system which is directly linked to the olfactory system. Areas called the septal nuclei and amygdala contain regions often called the pleasure centres, with the hippocampus concerned with motivational memory. Projections from the cerebral cortex connect with the thalamus, hypothalamus and posterior pituitary gland. The network of connections between all these different areas of the brain is highly complex. The role of the limbic system is significant in autonomic (involuntary or non-conscious) reactions that are implicated with emotional responses including fear, rage and motivation. 

Although earlier studies failed to find consistent effects of DA on cAMP levels or adenylate cyclase activity in anterior pituitary cells [13], intact pituitary gland [14,15] or homogenates [13,16], a functional connection between the two is now supported by many experimental approaches. DA and DA agonists inhibit cAMP levels in cultured rat pituitary cells at concentrations in the nanomolar range, comparable to those which inhibit PRL release [17-21], DA also inhibits cAMP accumulation stimulated by VIP or TRH [20]. Inhibition is also seen in human prolactinoma cells [22]. 

Growth hormone (somatotropin GH) is a protein hormone produced in specific cells (somatotrophs) of the pituitary gland. It comprises a single polypeptide chain of about 190 amino acids which folds, with formation of two disulphide bridges, to a compact tertiary structure (see also Addendum, p. 289). Amino acid sequences have been determined for GHs from several species [1,2] and these reveal a considerable amount of species variation in particular, human GH shows extensive differences from the GHs of non-primate mammals, and this has been interpreted as indicating a rapid rate of evolution for the GH gene in the primates [3,4], Differences in biological properties between human and non-primate GHs have also been observed, and will be considered later. 

Q1 What is the relationship between the thyroid gland, the pituitary gland and the hypothalamus ... 

Q4 Glucocorticoid secretion is controlled by the hypothalamus and anterior pituitary gland. Corticotrophin releasing factor (CRF) is produced in the hypothalamus and travels in the hypophyseal portal blood vessels to the anterior pituitary to release ACTH (adrenocorticotrophic hormone). There is a daily (circadian) rhythm in CRF and ACTH secretion, with a peak in the morning between 7 and 9 a.m. and a low point during the night. 

Although Brian is tired and weak, with a puffy face and significantly increased body weight, all of which may be observed in myxoedema (a severe form of adult hypothyroidism), his thyroid hormones and TSH concentration are normal. In hypothyroidism T3 and T4 concentrations are usually low, which leads to an increase in TSH because of reduced negative feedback between the thyroid hormones and the anterior pituitary gland. 

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