Chapter 2 Hypothalamic Hormones.docx

**[Chapter 2 Hypothalamic Hormones]** regulate **[anterior pituitary trophic hormones]** that in turn **[determine target gland secretion]** : **[Hypothalamic hormones]** **[Hypothalamus and pituitary gland:]** The **[hypothalamus]** lies at→ **[base of the brain]** in the **[diencephalon]** Hy...

**[Chapter 2 Hypothalamic Hormones]** regulate **[anterior pituitary trophic hormones]** that in turn **[determine target gland secretion]** : **[Hypothalamic hormones]** **[Hypothalamus and pituitary gland:]** The **[hypothalamus]** lies at→ **[base of the brain]** in the **[diencephalon]** Hypothalamus →contains a number of **[nuclei of neurons]** important in the regulation of hormone secretion from the pituitary. the **[vascular link]** is made between **[the hypothalamic neurosecretory]** neurons and ***the pituitary*** gland→the hypothalamic median eminence. is the **[functional link between]** the hypothalamus and the **[anterior pituitary gland]**: **[hypothalamic median eminence]** The master gland is: **[the pituitary]** the pituitary lies in: bony cavity, the **[sella turcica]** or pituitary fossa, in the sphenoid bone. **[Hypothalamic functions:]** 1)Regulates: blood pressure heartbeat rate & force digestive tract motility breathing depth & rate feelings of hunger and satiety sleep and sleep cycle 2)perception of pleasure, fear and rage 3\) body temp maintenance pituitary weighs: **[about 0.5 g]** pituitary weigh double during : **[puberty or pregnancy]** **[The pituitary (hypophysis ) consists of 2 parts:]** adenohypophysis→ The anterior pituitary... accounts for 3\\4 the gland weight. neurohypophysis→ posterior pituitary ***[vascular link]*** between the hypothalamus and the pituitary is called: **[portal system / The hypothalamic-- hypophysial portal system]** \***[\* vascular link function :]** **[chemicals]** are carried from **[hypothalamic cells]** to **[the anterior pituitary]** gland **[through i]**t. **[anterior pituitary :]** is **[the most richly vascularized of all mammalian tissues]** receiving 0.8 ml/g/min from a portal circulation portal circulation connecting the **[median eminence]** of the hypothalamus and the anterior pituitary. internal carotid arteries→ Arterial blood supply **[the posterior gland is]**: an outgrowth of the **[brain]**( neural origin).(neurohypophysis) it arises as a downward extrusion from the hypothalamus **[The anterior pituitary:]** grows **[upwards]** from the **[primitive oral cavity]**, which is termed **[Rathke's pouch]** is an evagination at the roof of the developing mouth in front of the buccopharyngeal membrane: Rathke\'s pouch. **[Hypothalamic hormones that control the anterior pituitary:]** TRH ( Thyrotropin releasing hormone): tripeptide (glutamic acid--histidine-- proline) , contains **[242 aa]** TRH-secreting neurons located : in the **[medial]** portions of the **[paraventricular]** nuclei TRH produced by: parvocellular neurons. TRH : Stimulates the release of thyroid stimulating **[hormone (TSH)]** in the **[anterior pituitary]** **[TRH half-life is = 6 min ]** **[GnRH ( Gonadotropin releasing hormone):]** linear decapeptide stimulates LH and FSH contains **** aa \*\***[Differences]** in the **[size]** and **[frequency]** of GnRH **[controls]** the secretion of **[LH and FSH]** low frequency→ FSH release↑ high frequency → LH release ↑ GnRH secreting neurons are located: in the **[preoptic]** area of the **[anterior hypothalamus]** half-life **[of 2-4 min]** **[ Dopamine:]** secreting neurons are located in: ***[the arcuate nuclei]*** It is the primary PRL-inhibitory hormone: **[Dopamine]** ***[The arcuate nucleus (ARC) is:]*** 1)located in the mediobasal hypothalamus 2)forms a morphological and functional entity with the median eminence (ME) 3)comprises several distinct types of neurons controlling: prolactin release food intake metabolism reproduction onset of puberty.\ **[half-life of 1-2 min]** **[CRH ( Corticotropin releasing hormone):]** It is a 41-aa peptide that is synthesized from a precursor of 196 aa ADH and angiotensin II: potentiate secretion of ACTH by CRH oxytocin: inhibits secretion of ACTH by CRH CRH-secreting neurons: anterior portion of the paraventricular nuclei. Neurons secrete: Oxytocin vasopressin (ADH) CRH TRH \*\*CRH **[increases]** significantly during **[late pregnancy]** and **[delivery]**. **[ GHRH ( Growth hormone releasing hormone):]** secreting neurons are located in : the arcuate nuclei **[GHRH:]** peptide hormone made in the hypothalamus stimulates the somatotrophs in the anterior pituitary (AP) to release **[GH]** contains 108 amino acids is a member of a homologous family of peptides that includes [**secretin**, glucagon,VIP] the major isoform of GHRH: 44 aa in length half-life : 3-7 min **[Secretin Family:]** a group of short brain-gut peptides named after the first hormone discovered among them. **[classified into five subgroups based on their structures:]** 1. Secretin; 2. Glucagon subfamily including : 3. (CRH) 4. Calcitonin (CCT) 5. Parathyroid hormone (PTH) **[Somatostatin]**: -is produced by neuroendocrine neurons of the ventromedial nucleus of the hypothalamus. -Tetradecapeptide( CONTAINS 14 aa) ***[\*\*Found]***: in the **[delta-cells]** of the **[pancreatic]** islets **[hypothalamus]** **[GIT mucosa]** **[C cells of the thyroid]** -Has 116 aa \- **[Iinhibits]**: GH TSH Insulin Glucagon Gastrin Pancreatic enzymes Secretin VIP a half-life of **[2-3 min]** **[Mechanism of action of the hypothalamic hormones:]** -bind to specific receptors on the plasma membrane of their target cells→ intracellular signaling (phosphatidylinositol metabolism and the adenylate cyclase system)→ ↑ intracellular calcium. -The stimulatory action of CRH and GHRH ??by the activation of **[adenylate cyclase.]** -the hypothalamic hormones is limited by ??a number of different **[negative-feedback systems.]**