2 A crucial part of the CNS that takes some part in regulating most organs 3 major functions (we will review 2 today).Regulating release of hormones from pituitary gland.Regulating the ANS; i.e., general visceral motor functions we reviewed last time.Regulating the “appetitive behaviours” (eating, drinking, mating).
3 A. Anterior-posterior sections of hypothalamus and review key nuclei. The 3 functional zones of the hypothalamus and the nuclei contained therein.Regulation of Pituitary: Parvocellular (anterior) ad magnocellular (posterior) neurosecretory systems.Overview of ANS functional anatomy (sympathetic, parasympathetic systems).Regulation of autonomic functions by descending projections from the hypothalamus.Regional anatomy.A. Anterior-posterior sections of hypothalamus and review key nuclei.B. Descending pathway and sc nuclei.C. Clinical Note: Horner’s Syndrome.
4 I. 3 Functional ZonesGeneral location of hypothalamus:- ventral to thalamus- just over optic chiasm and pituitary stalk (infundibulum).- divided in half by 3rd ventricle
8 - a thin nuclei bordering the 3rd ventricle. Periventricular zone- a thin nuclei bordering the 3rd ventricle.- regulates release of endocrine hormones from anterior pituitary gland (See Table 15-1).-uses neurosecretion as a portal vein system, rather than a neurotransmitter across a synapse.Middle zone- regulates hormone release from posterior pituitary.- regulates ANS.Lateral zone- integration and transmission of info from limbic system structures (important in emotional regulation – will view next lecture (limbic system).
9 3 Functional hypothalamic zones (Fig. 15-14) – Mediolateral zones
10 Hypothalamic peptides for anterior pituitary (Table 15-1)
11 II. Regulation of Pituitary: Parvocellular and Magnocellular Neurosecretory Systems Parvocellular system and the anterior pit.- Small-diameter neurons in several hypothalamic nuclei (of periventricular zone) – most medial – regulate anterior pituitary hormone release by neurovascular rather than synaptic transmission.
12 Parvocellular System (Fig. 15-4A) Note the various nuclei
13 Neurosecretion and Portal Vein System (Fig. 15-5): Note the path:Parvocellularneurosecretorycells anterior lobevia portal vein.Chemicals releasedare peptides, whicheither promote orinhibit the release ofhormones fromanterior lobesecretory cells(Table 15-1).
14 Magnocellular system and the posterior pituitary. - Here, peptide hormones are produced by large-diameter hypothalamic neurons from same nuclei of the middle zone.- Axons deliver these hormones down the infundibular stalk and terminate on fenestral capillaries (“leaky”) of the posterior pit - this is 1 place lacking a BBB.
15 Magnocellular System (Fig. 15-4B) Note the paraventricularand supraoptic nucleiHormones:Vasopressin (ADH) –peptide which incr bp by itseffects on vascularsmooth muscle as well as bypromoting H2O reabsorptionfrom DCTs of kidneys todecr urine vol.Oxytocin – incr uterinecontraction and milk ejectionfrom mammary glands.
16 III. Overview of Autonomic Nervous System Sympathetic and Parasympathetic systems – Fig Clearly distinct anatomical locations of preganglionic (central) neurons. Sympathetic: T1 L3 Parasympathetic: brainstem nuclei (reviewed last time): S2 S4 (sacral spinal cord). Also different locations of post-ganglionic neurons.
18 Sympathetic: peripheral ganglia located relatively close to the spinal cord (sympathetic trunk). Parasympathetic: peripheral ganglia located close to target organs (i.e., terminal ganglia of X).Note: organs distal to splenic flexure of colon served by sacral parasympathetic nuclei.For both systems, anatomical location of central neurons is analogous.
19 Sympathetic: intermediate zone of spinal cord (intermediolateral cell column) – Fig. 15-9. Parasympathetic: the 4 spinal cord nuclei reviewed last time (general visceral motor column): III, VII, IX, X and in sacral sc intermediate zone.
20 IV. Descending Projections from the Hypothalamus Regulate Autonomic Functions See Fig. 15-9
21 Descending pathwayscontrolling autonomicnervous system(Fig. 15-9):From middle functionalZone: parasympatheticn. (using ADH and oxytocin)+ several other areas bsparasym n. (dorsal motor n.of X) + preganglionic neurons(both sym and parasym) of sc.
22 FigNote: Mechanism of regulationIs very analogous to the way theCortex regulates descendingMotor pathways and motorNeurons.1 Difference: VisceromotorRegulation involves the 2-neuronCircuit (pre- and postganglionic)Some bs n. also contribute toautonomic system regulation:Solitary n intermediolateral n.(also known for chemosensorymechs) - a tie between viscero-sensory and visceromotor.
23 Ventral lateral medulla - adrenergic descending projections regulating bp. Postmedullary reticular formation - complex “reflex” response involving both visceral and somatic changes; e.g., startle incr bp.Raphe nuclei – projections from hypothalamus uses serotonin to spinal autonomous nuclei.
24 V. Regional AnatomySections through the hypothalamus – Schematic of major nuclei – FigAnterior hypothalamic section, showing preoptic region – Fig
32 C. Clinical Note: Horner’s Syndrome – damage to dorsaolateral pons/medulla or any part of descending autonomic control system disturbance of sympathetic functions: e.g., PICA occlusion.Pupillary constriction on same side.Partial drooping of eyelid.Decr secretory, incr warmth and redness on same side of face.Decr sympathetic function and unopposed parasympathetic function.