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).
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 Zones
General location of hypothalamus:
- ventral to thalamus
- just over optic chiasm and pituitary stalk (infundibulum).
- divided in half by 3rd ventricle

6. Hypothalamic Nuclei

7. Hypothalamus (Fig. 15-1, 2)

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:
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. 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 H2O 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. 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 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
Sections through the hypothalamus – Schematic of major nuclei – Fig
Anterior hypothalamic section, showing preoptic region – Fig

25. Fig – Major nuclei

26. Anterior hypothalamus – Fig. 15-10 Note the preoptic region

27. Paraventricular Nucleus – Fig. 15-11
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
Mid-medullary Section
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. Intermediolateral sympathetic (preganglionic) nucleus in thoracic sc.
Parasympathetic preganglionic nucleus in intermediate zone of sacral sc.

31. Spinal cord nuclei and paths: Fig. 15-21

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.