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[[Image:Canine Brain CS showing Hypothalamus1.jpg|thumb|right|450px|'''Canine Brain Cross Section''' ''Courtesy of BioMed Image Archive'']]

[[Image:Canine Brain CS showing Hypothalamus1.jpg|thumb|right|450px|'''Canine Brain Cross Section''' ''Courtesy of BioMed Image Archive'']]

== Hypothalamus ==

== Hypothalamus ==

The hypothalamus is a small area in the ventral diencephalon of the [[Forebrain - Anatomy & Physiology|forebrain]], in the floor of the third ventricle, and is a functional link between the [[Nervous and Special Senses - Anatomy & Physiology#Nervous System|nervous]] and [[Endocrine System - Anatomy & Physiology|endocrine]] systems.

The hypothalamus is a small area in the ventral diencephalon of the [[Forebrain - Anatomy & Physiology|forebrain]], in the floor of the third ventricle, and is a functional link between the [[Nervous and Special Senses - Anatomy & Physiology#Nervous System|nervous]] and [[Endocrine System Overview - Anatomy & Physiology|endocrine]] systems.

The hypothalamus controls most of the [[Endocrine System - Endocrine Glands - Anatomy & Physiology|endocrine glands]] within the body, largely through stimulation of the [[Endocrine System - Pituitary Gland - Anatomy & Physiology|Pituitary Gland]] by secretion of [[Endocrine System - Hormones - Anatomy & Physiology#Classifications of Hormones|neurohormones]]. It is a vital regulator of homeostasis, including [[Thermoregulation - Anatomy & Physiology| Thermoregulation]].

The hypothalamus controls most of the [[Endocrine System Overview - Anatomy & Physiology|endocrine glands]] within the body, largely through stimulation of the [[Pituitary Gland - Anatomy & Physiology|Pituitary Gland]] by secretion of [[Hormones - Anatomy & Physiology#Classifications of Hormones|neurohormones]]. It is a vital regulator of homeostasis, including [[Thermoregulation - Anatomy & Physiology| Thermoregulation]].

==Nuclei==

==Nuclei==

*'''Thermoreceptors''': Neurons in the anterior hypothalamus respond to heat by initiating peripheral vasodilation and sweating. Neurons in the posterior hypothalamus respond to cold by initiating shivering, piloerection and peripheral vasoconstriction. These mechanisms are part of the [[Thermoregulation - Anatomy & Physiology|Thermoregulation]] system.

*'''Thermoreceptors''': Neurons in the anterior hypothalamus respond to heat by initiating peripheral vasodilation and sweating. Neurons in the posterior hypothalamus respond to cold by initiating shivering, piloerection and peripheral vasoconstriction. These mechanisms are part of the [[Thermoregulation - Anatomy & Physiology|Thermoregulation]] system.

*'''Osmoreceptors''': respond to an increase in blood osmolarity by releasing Antidiuretic Hormone (ADH) from the Supraoptic Nucleus which is then secreted by the posterior pituitary and acts to retain water at the kidneys. It also stimulates neurons in the thirst centre in the lateral hypothalamus in an attempt to increase water intake.

*'''Osmoreceptors''': respond to an increase in blood osmolarity by releasing Antidiuretic Hormone (ADH) from the Supraoptic Nucleus which is then secreted by the posterior pituitary and acts to retain water at the kidneys. It also stimulates neurons in the thirst centre in the lateral hypothalamus in an attempt to increase water intake.

*'''Energy Balance''': Neurons in the arcuate nucleus sense blood glucose and [[Endocrine System - Hormones - Anatomy & Physiology|hormones]]. Leptin causes satiety, ghrelin stimulates appetite.

*'''Energy Balance''': Neurons in the arcuate nucleus sense blood glucose and [[Hormones - Anatomy & Physiology|hormones]]. Leptin causes satiety, ghrelin stimulates appetite.

'''''Indirect Inputs''''' from bloodstream include information about:

'''''Indirect Inputs''''' from bloodstream include information about:

*Temperature

*Temperature

*Osmotic Pressure

*Osmotic Pressure

*[[Endocrine System - Hormones - Anatomy & Physiology|Hormone]] concentrations - including Leptin, Cortisol, Oestrogens, Progesterone, Androgens, T3.

*[[Hormones - Anatomy & Physiology|Hormone]] concentrations - including Leptin, Cortisol, Oestrogens, Progesterone, Androgens, T3.

'''''Indirect Neural Inputs''''':

'''''Indirect Neural Inputs''''':

*Uses Visceral and [[Macroscopic Anatomy of the CNS#The Somatosensory Nervous System|Somatic Sensory]] neurons, the Limbic System and the [[Macroscopic Anatomy of the CNS#Other Important Features|Reticular Activating System]].

*Uses Visceral and somatic sensory neurons, the Limbic System and the Reticular Activating System.

==Outputs==

==Outputs==

#'''''Biological Clock''''' - Light sensed by [[Macroscopic Anatomy of the CNS#The Wall|retina]] causes stimulation of neurons leading the the suprachiasmatic nucleus which stimulates the [[Endocrine System - Pineal Gland - Anatomy & Physiology|Pineal Gland]] as a result.

#'''''Biological Clock''''' - Light sensed by [[Eye - Anatomy & Physiology|retina]] causes stimulation of neurons leading the the suprachiasmatic nucleus which stimulates the [[Pineal Gland - Anatomy & Physiology|Pineal Gland]] as a result.

#'''''Secretory''''' Neurons - ADH and Oxytocin are released by the Supraoptic and Paraventricular nuclei cell bodies. The axons descend into the [[Endocrine System - Pituitary Gland - Anatomy & Physiology#Posterior Pituitary Gland|Posterior Pituitary gland]], where they terminate in blood vessels releasing the [[Endocrine System - Hormones - Anatomy & Physiology|hormone]] directly into circulation. Thus the posterior pituitary acts as a storage site and is not a true [[Endocrine System - Endocrine Glands - Anatomy & Physiology|endocrine gland]].

#'''''Secretory''''' Neurons - ADH and Oxytocin are released by the Supraoptic and Paraventricular nuclei cell bodies. The axons descend into the [[Pituitary Gland - Anatomy & Physiology#Posterior Pituitary Gland|Posterior Pituitary gland]], where they terminate in blood vessels releasing the [[Hormones - Anatomy & Physiology|hormone]] directly into circulation. Thus the posterior pituitary acts as a storage site and is not a true [[Endocrine System Overview - Anatomy & Physiology|endocrine gland]].

#'''''Hypothalamic Hormones''''' - the hypothalamus releases [[Endocrine System - Hormones - Anatomy & Physiology|hormones]] which have an activating or inhibitory effect on their target organ, hence they are named Releasing or Inhibitory Hormones respectively.  

#'''''Hypothalamic Hormones''''' - the hypothalamus releases [[Hormones - Anatomy & Physiology|hormones]] which have an activating or inhibitory effect on their target organ, hence they are named Releasing or Inhibitory Hormones respectively.  

'''Releasing Hormones''':

'''Releasing Hormones''':

*Thyrotropin Releasing Hormone (TRH)

*Thyrotropin Releasing Hormone (TRH)

==Negative Feedback==

==Negative Feedback==

The Hypothalamus works along with the Pituitary and it's target glands by [[Endocrine System - Negative Feedback - Anatomy & Physiology|negative feedback.]]

[[Image:HypothalamicPituitaryAxis.jpg|right|thumb|205px|<small><center>'''Schematic Diagram of the Hypothalamic Pituitary Axis</center></small>]]

[[Category:Endocrine System - Anatomy & Physiology]]