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

3. 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

4. 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,regulating reproduction, metabolism, eating
and drinking behaviour, energy utilization, osmolarity and
blood pressure etc.
• The secretory activity of many endocrine
glands(Pituitary,Thyroid,Adrenal and Gonads) is
controlled by the nervous system.
• Hypothalamus regulates Pituitary Functions.
• Neurons in the hypothalamus secrete releasing

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

7. Hypothalamic control of Anterior
pituitary gland secretion
• Hypothalamus controls the hormonal
secretions of the anterior pituitary, which in
turn regulates 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.

8. Hypothalamic -Releasing hormones :
•CRH (Corticotropn releasing Hormone) Stimulates the release of
ACTH
•TRH (Thyrotropin-Releasing Hormone) Stimulates the release of
TSH
•GnRH (Gonadotropin-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.
Releasing and Inhibiting hormones

9. 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.

14. 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 Thyroxine
(T4)) and responds by releasing thyrotropin releasing
hormone (TRH). The TRH stimulates the pituitary to
produce thyroidstimulating hormone (TSH). The TSH,
in turn, stimulates the thyroid to produce thyroid
hormone until levels in the blood return to normal.
Thyroid hormone exerts negative feedback control over
the hypothalamus as well as anterior pituitary, thus
controlling the release of both TRH from hypothalamus
and TSH from anterior pituitary gland

15. HPT-Axis

16. 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

18. Fig.HPG-Axis

19. 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.
• Neurons that originate in hypothalamus terminate in posterior
pituitary
• Posterior pituitary gland Stores and Secrets (but does not
synthesize) two important hormones Vassopressin (ADH) and
Oxytocin
• These two hormones secreted by neurosecretory cells
(Magnocellular neurons) of Hypothalamus.
• Hypothalamus two nuclei 1) Paraventricular nucleus (oxytocin)