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The Hypothalamus. A crucial part of the CNS that takes some part in regulating most organs 3 major functions (we will review 2 today). 1.Regulating release.

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Presentation on theme: "The Hypothalamus. A crucial part of the CNS that takes some part in regulating most organs 3 major functions (we will review 2 today). 1.Regulating release."— Presentation transcript:

1 The Hypothalamus

2 A crucial part of the CNS that takes some part in regulating most organs 3 major functions (we will review 2 today). 1.Regulating release of hormones from pituitary gland. 2.Regulating the ANS; i.e., general visceral motor functions we reviewed last time. 3.Regulating the “appetitive behaviours” (eating, drinking, mating).

3 I.The 3 functional zones of the hypothalamus and the nuclei contained therein. II.Regulation of Pituitary: Parvocellular (anterior) ad magnocellular (posterior) neurosecretory systems. III.Overview of ANS functional anatomy (sympathetic, parasympathetic systems). IV.Regulation of autonomic functions by descending projections from the hypothalamus. V.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 Zones General location of hypothalamus: - ventral to thalamus - just over optic chiasm and pituitary stalk (infundibulum). - divided in half by 3 rd ventricle

5

6 Hypothalamic Nuclei

7 Hypothalamus (Fig. 15-1, 2)

8 A.Periventricular zone - a thin nuclei bordering the 3 rd 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. B.Middle zone - regulates hormone release from posterior pituitary. - regulates ANS. C.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 ) – Mediolateral zones

10 Hypothalamic peptides for anterior pituitary (Table 15-1)

11 II. Regulation of Pituitary: Parvocellular and Magnocellular Neurosecretory Systems A.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: Parvocellular neurosecretory cells  anterior lobe via portal vein. Chemicals released are peptides, which either promote or inhibit the release of hormones from anterior lobe secretory cells (Table 15-1).

14 B.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 paraventricular and supraoptic nuclei Hormones: Vasopressin (ADH) – peptide which incr bp by its effects on vascular smooth muscle as well as by promoting H 2 O reabsorption from DCTs of kidneys to decr urine vol. Oxytocin – incr uterine contraction and milk ejection from 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.

17 Fig – The ANS

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 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 pathways controlling autonomic nervous system (Fig. 15-9): From middle functional Zone: parasympathetic n. (using ADH and oxytocin) + several other areas  bs parasym n. (dorsal motor n. of X) + preganglionic neurons (both sym and parasym) of sc.

22 Fig Note: Mechanism of regulation Is very analogous to the way the Cortex regulates descending Motor pathways and motor Neurons. 1 Difference: Visceromotor Regulation involves the 2-neuron Circuit (pre- and postganglionic) Some bs n. also contribute to autonomic system regulation: -Solitary n  intermediolateral n. (also known for chemosensory mechs) - 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 Anatomy A.Sections through the hypothalamus – Schematic of major nuclei – Fig Anterior hypothalamic section, showing preoptic region – Fig

25 Fig – Major nuclei

26 Anterior hypothalamus – Fig Note the preoptic region

27 Paraventricular Nucleus – Fig This nucleus contributes to all 3 functions we have discussed: 1. Parvocellular division  anterior pituitary 2. Magnocellular division  posterior pituitary 3. Autonomic division  descending paths

28 Posterior Hypothalamus Fig Section reveals mammillary bodies. These, along with Lateral zone noted earlier, play important role in behavioural Regulation and the limbic system.

29 Mid-medullary Section B. Descending Pathways and Spinal Cord Nuclei Descending fibres In dorsolateral tegmentum. DLF also contains ascending and descending fibres to hypothalamus. Adrenergic cell group in VL medulla – analogous to intermedio- lateral location in sc.

30 1.Intermediolateral sympathetic (preganglionic) nucleus in thoracic sc. 2.Parasympathetic preganglionic nucleus in intermediate zone of sacral sc.

31 Spinal cord nuclei and paths: 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.


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