NEUROENDOCRINOLOGY, KEY POSITION OF HYPOTHALAMUS

1. NEUROENDOCRINOLOGY, KEY POSITION OF HYPOTHALAMUS Olga Vajnerová, 2nd Faculty of Medicine, Charles University, Prague, 2011

2. Hypothalamus, a major control headquarters for the limbic system

3. Hypothalamus, a major control headquarters for the limbic system Hypothalamus Cortex Thalamus Temporal lobe Basal ganglia Septum Paraolfactory area

4. Hypothalamus, a major control headquarters for the limbic system Hypothalamus Cortex Thalamus Temporal lobe Basal ganglia Septum Paraolfactory area cingulate gyrus Parahippocampal gyrus Orbitofrontal cortex

5. Hypothalamus, a major control headquarters for the limbic system Hypothalamus Cortex Thalamus Temporal lobe Basal ganglia Septum Paraolfactory area cingulate gyrus Parahippocampal gyrus Orbitofrontal cortex Anterior nuclei

6. Hypothalamus, a major control headquarters for the limbic system Hypothalamus Cortex Thalamus Temporal lobe Basal ganglia Septum Paraolfactory area cingulate gyrus Parahippocampal gyrus Orbitofrontal cortex Anterior nuclei Hippocampus Amygdala

8. Functions of hypothalamus

9. Functions of hypothalamus

10. Relation to autonomic function Parasympathetic responses Urinary bladder contraction Sympathetic responses Increased adrenal medullary secretion Vasoconstriction Stress – fight or flight

11. Cardiovascular regulation Arterial pressure Heart rate Specific cardiovascular control centres are in…. Reticular regions of the pons and medulla Cardioexcitatory area Cardioinhibitory area Vasomotor area Via Sympathetic and Parasympathetic nerves

12. Influence on respiratory and gastointestinal reflexes Olfactory stimulus – from paleocortex Signals to visceromotor centres in medulla – nausea, vomiting

13. Transmission of emotions from limbic system Rage, anxiety and fear, joy, sadness Is connected with visceromotor and somatomotor reaction Hear rate, breathig rate, vasomotor reaction – pale or red skin, sweat glands, gastrointestinal motility and secretion, smooth muscle in skin, shivering

14. Biological rhythms Suprachiasmaticus nuclei – retinohypothalamic tract Pacemaker of circadian rhythms Sleep – wake cycle ACTH secretion Melatonin secretion Body temperature rhythm Activity patterns of animals

15. Regulation of body water • Thirst center • Lateral hypothalamus • Osmoreceptors – when the EF is too concetrated – develops intense desire to drink water • 2. Antidiuretic hormone

16. Gastrointestinal and feeding regulation Hunger center Lateral nuclei of the hypothalamus stimulation – extreme hunger, appetite, craving for food, hyperphagia Destruction of this area – lethal starvation, weight loss, muscle weakness, decreased metabolism Is permanently active Satiety center Ventromedial nuclei of the hypothalamus Stimulation – sense of complete satiety, refusal of food, aphagia Destruction – hunger centers overactive, continuing eating, obesity

17. Other important nuclei in feeding regulation Paraventricular, dorsomedial and arcuate nuclei of the hypothalamus ncl arcuatus = ncl infundibularis The site where multiple hormones converge to regulate food intake and energy expenditure Hypothalamus Receives hormonal signals (from GIT, adipose tissue) neural signals (from GIT) chemical signals (from blood about nutrients) signals from cerebral cortex (sight, smell and taste) Draw a picture

18. Orexigenic substances ?? Anorexigenic substances

19. Orexigenic substances stimulate feeding Ghrelin Anorexigenic substances ???

20. Orexigenic substances stimulate feeding Ghrelin Anorexigenic substances inhibit feeding CCK, insulin, leptin

21. Short-term regulation of food intake- gastrointestnal filling- GIT hormonal factors – CCK, insulin, ghrelin - oral receptors meter food intake Oral factors related to feeding such as chewing, salivation, swallowing, tasting

22. Intermediate and long-term regulation of food intake- concentration of glucose, amino acids, and lipids glucostatic theory of hunger and feeding regulation(rise in blood glucose level increases firing of neurons in the satiety center, decrease in hunger center - Temperature regulation and food intake Cold increased feeding Interaction between temperature-regulating systém and food intake-regulating systém - Feedback signals from adipose tissue - leptin

23. Regulation of body temperature Temperature regulating centers Temperature receptors

24. Regulation of body temperature Temperature regulating centers Temperature receptors 1. Peripheral Skin receptors (cold and warm) Deep body temperature receptors Spinal cord, abdominal viscera and great veins 2. Central Temperature detectors in hypothalamus Heat sensitive neurons, cold sensitiv neurons Praeoptic area

25. Posterior hypothalamus integrates the central and peripheral temperature sensory signals Control Heat-producing Heat- conserving reaction of the body Set point – crucial temperature level 37.1ºC Feedback gain for body temperature control

26. Temperature-decreasing mechanisms Vasodilation of skin blood vessels Inhibition of the sympathetic centers in the posterior hypothalamus Sweating Praeoptic area, via autonomic pathways to the spinal cord Sympathetic but cholinergic Decrease in heat production Inhibition of shivering and thermogenesis

27. Temperature-decreasing mechanisms Vasodilation of skin blood vessels Inhibition of the sympathetic centers in the posterior hypothalamus Sweating Praeoptic area, via autonomic pathways to the spinal cord Sympathetic but cholinergic Decrease in heat production Inhibition of shivering and thermogenesis

28. Temperature-decreasing mechanisms Vasodilation of skin blood vessels Inhibition of the sympathetic centers in the posterior hypothalamus Sweating Praeoptic area, via autonomic pathways to the spinal cord Sympathetic but cholinergic Decrease in heat production Inhibition of shivering and thermogenesis

29. What are temperature-increasing mechanisms ?? No Vasodilation of skin blood vessels NO Sweating Increase in heat production

30. Temperature-increasing mechanisms When the body is too cold 1. Vasoconstriction of skin blood vessels Stimulation of the sympathetic centers in the posterior hypothalamus 2. Piloerection via autonomic pathways to the spinal cord Sympathetic stimulation causes arrector pili muscles to contract 3. Increase in heat production, thermogenesis Shivering, sympathetic excitation of heat production, Thyroxin secretion

31. 3. Increase in heat production, thermogenesis Shivering Primary motor center for shivering in the dorsomedial portion of the posterior hypothalamus Excited by cold signals from the skin and spinal cord Tr hypothalamoreticularis, hypothalamospinalis to spinal motoneurons Non rhytmical signals, increase the tone of the skeletal muscles Probably feedback oscillation of the muscle spindle stretch reflex Sympathetic excitation of heat production Chemical thermogenesis, E and NE uncouple oxidative phosphorylation, energy in the form of heat but do not cause ATP to be formed Thyroxin secretion

32. Sympathetic excitation of heat production Chemical thermogenesis, E and NE uncouple oxidative phosphorylation, energy in the form of heat but do not cause ATP to be formed Thyroxin secretion