Endocrinology 3 - Hypothalamus and Pituitary Brain Higher centres include: Basal ganglia Cerebellum Cerebrum (including cortex of the brain & limbic system) Voluntary control, planning, imitation Lower centres include: Brain stem (medulla oblongata, pons and mid brain) Thalamus Hypothalamus Simple reflexes, autonomic control Hypothalamus Sits below the thalamus in brain - organised of discrete groups of neurons (nuclei) Each area has its function The way its organised i? integral to its Specific areas regulate the body temp or food intake e.g. arcuate nucleus, paraventricular nucleus - has a crucial role in the endocrine system: 1. It's an endocrine organ a. Releases hormones b. That travel through the circulatory system c. And bind to receptors in the anterior pituitary 2. Produces hormones that travel down nerve fibres and then released in posterior pituary a. Not a lot of hormones released in this way 3. Via nerve fibres that innervate (supply with nerves) posterior pituitary (PP) 4. Via autonomic innervations of more distant glands Adrenal medulla Pineal Kidney parathyroid Pancreatic islets Cerebrum (the right hemisphere, at the longitudinal fissure between it and the left hemisphere) Hypothalamus Thalamus Pineal gland Corpus callosum Optic chiasm Front of brain Brain stem Midbrain Pons Medulla Cerebellum (b) Brain, sagittal view
Hypothalamic Nuclei: Paraventricular Nucleus Dorsomedial Nucleus Anterior Nucleus Posterior Nucleus Preoptic Area Ventromedial Nucleus Suprachiasmatic Nucleus Supraoptic Nucleus Anterior Pituitary Mamillary Body Arcuate Nucleus Infundibulum Posterior Pituitary Main function of the hypothallus is to maintain the status quo of the body It does that sometime by using hormones Hypothalamus maintains levels of: - Blood pressure - Temp - Fluid and electrolyte - Body weight - Sleep These factors are regulated around the 'hypothalamic set point' (a range) This set point can change over time (age) but is generally fixed Pituitary Gland (hypophysis) - Not part of the brain - But is close to the hypothalamus o Anatomically and physiologically - Acts as a secondary control of the endocrine system - Receives signals of the hypothalamus and then releases tropic hormones that have an effect on the target tissue - Two regions; o Anterior (most used) - indirect connection (portal blood vessels) o Posterior - direct connection (neurons) During embryogenesis: - Part of the hypothalamus grows down (posterior) o Mainly neuronal tissue - And part of the pharynx grows up (anterior) Mostly endocrine cells Blood Supply - The anterior pituitary receives blood after it has been through the hypothalamus - Goes through the pituitary gland through the hypothalamic-hypophysial portal system o Rapid - The blood vessels that make up these systems are fenestrated
o particularly leaky - huge gaps - releasing hormones from the hypothalamus therefore means it will inevitably go through the pituitary gland - hormones secreted by the pituitary are taken away into the venous return MB Hypophyseal nerve trace Hypophyseal portal circulation AL PL Pituitary gland Posterior pituitary hormones oxytocin and vasopressin - the posterior has its own blood supply o hormones aren't delivered by this blood supply but can be taken away and