Neuroendocrine system and Neurosecretion

Neuroendocrine system,HPA axis,HPT axis ,HPG-axis ,neurosecretory cells, Neurosecretion

1. CONTENT Neuroendocrine System Introduction Hypothalamic controle of pituitary gland& Hypothalamus Hypophyseal portal system. Major Neuroendocrine systems Neurosecreation 1.Introduction 2.Relationship between posterior pituitary and the hypothalamus 3.Functions of posterior pituitary hormones

2. Neuroendocrine System Endocrine System interacts and cooperates with the nervous system to regulate the activities of the organ systems of the body. The neuroendocrine system is the mechanism by which the hypothalamus maintains homeostasis, regulati ng reproduction, me tabolism, eating and drinking behaviour, energy utilization, osmolarity a nd blood pressure etc. T he secretory activity of many endocrine glands( Pituitary , Thyroid , Adrenal a nd Gonads ) is controlled by the nervous system. H ypothalamus regulates Pituitary Functions. N eurons in the h ypothalamus secrete releasing hormones and inhibiting hormones in anterior pituitary gland.

3. Fig.Showing , The secretory activity of many endocrine glands is controlled by the nervous system.

4. Hypothalamic control of Anterior pituitary gland secretion Hypothalamus controls the hormonal secretions of the anterior pituitary, which in turn r egulates other endocrine glands. Neurons in the hypothalamus secrete releasing hormones and inhibiting hormones into blood capillaries at the base of the hypothalamus. Reasing & inhibiting hormones released by Paravocellular Neurosecretory cells of the hypothalamus.

5. Hypothalamic -Releasing hormones : CRH (Corticotropn releasing Hormone) Stimulates the release of ACTH TRH (Th yrotropin- Releasing Hormone) Stimulates the release of TSH GnRH (G onadotropin -Releasing Hormone ) stimulates the release of FSH& LH GHRH(Growth Hormone Releasing Hormone) Stimulates the release of GH Hypothalamic Inhibiting Hormones : MIH ( melanotropin-inhibiting hormone) inhibits the secretion of MSH. Dopamine Inhibits the secretion of PRL SRIF (Somatostatin Release Inhibiting Factor) Inhibits the secretion of STH Releasing and Inhibiting hormones

6. Hypophyseal Portal System Hypothalamus is connected to Anterior Pituitary via Hypothalamic-Hypophysial Portal System (HHPS). HHPS are capillaries that carries blood from Hypothalamus to Anterior Pituitary and back to Hypothalamus; Releasing Hormones produced in the Ventral Hypothalamic Neurons are carried via the Hypothalamic Portal System into the Anterior Pituitary. where they stimulate or inhibit the production of Anterior Pituitary hormones.

7. HPT-Axis HPT-Axis is part of the neuroendocrine system responsible for the regulation of metabolism. The hypothalamus senses low circulating levels of thyroid hormone (Triiodothyronine (T3) and Thyrox ine (T4)) and responds by releasing thyrotropin ­releasing hormone (TRH). The TRH stimulates t he pituitar y to produce thyroid­stimulating hormone (TSH). The TSH, in turn, stimulates the thyroid to p roduce thyroid hormone until levels in the blood return to normal. Thyroid hormone exerts negative f eedback c ontrol over the hypothalamus as well as anterior pituitary, thus controlling the release of b oth TRH from hypothalamus and TSH from anterior pituitary gland

8. HPT-Axis

9. HPA-Axis HPA axis is a complex set of direct influencesand feedback interactions among three endocrine glands: the hypothalamus, the pituitary gland and the adrenal gland. The HPA axis has a central role in regulating many homeostatic systems in the body, including the metabolic system, cardiovascular system, immune system, reproductive system and central nervous system.

10. Fig.HPG-Axis

11. Neurosecreation Neurosecretion is the storage, synthesis and release of hormones from neurons. Such neurons are called neurosecretory cells, and their products are often called neurohormones. These neurohormones, produced by neurosecretory cells, are normally secreted from nerve cells in the brain (Hypothalamus) that then circulate into the blood. N eurons that originat e in hypothalamus terminate in posterior pituitary P osterior pituitary gland Stores and Secrets (but does not synthesize ) tw o important hormones Vassopressin (ADH) and Oxytocin T hese two hormones secreted by neurosecr etory cells (Magnocellular neurons) of Hypothalamus . H ypothalamus two nuclei 1) Paraventricular nucleus (oxytocin) and 2) Supraoptic nucleus (ADH)