Hypothalamus_structure_nuclei_ functions.pptx

Nuclei of hypothalamus, medial fore brain bundle, fornix, stria terminalis, cortico hypothalamic fibers, pallido hypothalamic fibers, trticulo hypothalamic fibers, retino hypothalamic fibers, mammillo thalamic tract, para ventricular fibers, dorso medial nucleus of thalamus, frontal lobe of cerebral cortex, hypothalamo hypophyseal tract, pre optic nucleus, anterior nucleus, supra optic nucleus, dorso medial nucleus, ventro medial nucleus, lateral nucleus, arcuate nucleus, mammillary body, anti diuretic hormone, growth hormone- releasing hormone, growth hormone- releasing poly peptide, thyrotropin-releasing hormone, gonadotropin- releasing hormone, prolactin- inhibiting hormone, regulation of heart rate, regulation of blood pressure.

1. HYPOTHALAMUS Dr. E. Muralinath, Dr. C. Kalyan Chakravarthi, Dr. M. Guruprasad, Dr. K. Sravani Pragna, Dr. P. Manjari, Dr. D. Kusumalatha, Dr. K. Sridevi , Dr. Ch. Ramya Sudha and Dr. R. Gnana Lahari

2. I NTRODUCTION Hypothalamus is a diencephalic structure. It is located just below thalamus especially in the ventral part of diencephalon. NUCLEI OF HYPOTHALAMUS Nuclei of hypothalamus are categorized into three groups: Anterior or preoptic group 2. Middle or tuberal group 3. Posterior or mamillary group.

3. CONNECTIONS OF HYPOTHALAMUS AFFERENT CONNECTIONS TO HYPOTHALAMUS 1. Medial forebrain bundle: From rhinencephalon (limbic cortex) to preoptic nucleus, lateral nucleus and mamillary body 2. Fornix: From hippocampus to mamillary body 3. Stria terminalis: From amygdaloid to preoptic nucleus 4. Corticohypothalamic fibers: From prefrontal area (8) and precentral area (6) of cerebral cortex to the supraoptic and paraventricular nuclei of hypothalamus 5. Pallidohypothalamic fibers: From globus pallidus to diffused areas of hypothalamus 6. Thalamohypothalamic fibers: From dorsomedial and midline nuclei of thalamus to diffused areas of hypothalamus 7. Reticulohypothalamic fibers: From reticular formation of brainstem to diffused areas of hypothalamus 8. Retinohypothalamic fibers: Fibers from retina to supraoptic, suprachiasmatic and ventromedial nuclei of hypothalamus .

4. EFFERENT CONNECTIONS FROM HYPOTHALAMUS 1. Mamillothalamic tract: From mamillary body to anterior thalamic nuclei 2. Mamillotegmental tract: From mamillary body to the tegmental nuclei of midbrain 3. Periventricular fibers: Fibers from posterior, supraoptic and tuberal nuclei of hypothalamus pass through periventricular gray matter and reach the following: i. Reticular formation in brainstem and spinal cord ii. Dorsomedial nucleus of thalamus iii. Frontal lobe of cerebral cortex 4. Hypothalamohypophyseal tract: From supraoptic and paraventricular nuclei of hypothalamus to posterior pituitary.

5. TABLE 149.1: Nuclei of hypothalamus Posterior or Mamillary group 1. Preoptic nucleus 2. Paraventricular nucleus 3. Anterior nucleus 4. Supraoptic nucleus 5. Suprachiasmatic nucleus 1. Dorsomedial nucleus 2. Ventromedial nucleus 3. Lateral nucleus 4. Arcuate (tuberal) nucleus 1. Posterior nucleus 2. Mamillary body

6. FUNCTIONS OF HYPOTHALAMUS Hypothalamus is the important part of brain, associated with homeostasis of the body. It contro;s many vital functions of the body such as endocrine functions, visceral functions, metabolic activities, hunger, thirst, sleep, wakefulness, emotion, sexual functions, etc. . 1. SECRETION OF POSTERIOR PITUITARY HORMONES Hypothalamus is the site of secretion for the posterior pituitary hormones. Antidiuretic hormone (ADH) and oxytocin are secreted by supraoptic and paraventricular Nuclei respectively . The trnsport of these two hormones occurs with the help of of axonic or axoplasmic flow through the fibers of hypothalamohypophyseal tracts to posterior pituitary. .

7. 2. CONTROL OF ANTERIOR PITUITARY Hypothalamus regulates the secretions of anterior pituitary gland by secreting releasing hormones and inhibitory hormones. It secretes seven hormones. i. Growth hormone-releasing hormone (GHRH) ii. Growth hormone-releasing polypeptide (GHRP) iii. Growth hormone-inhibiting hormone (GHIH) or somatostatin iv. Thyrotropin-releasing hormone (TRH) v. Corticotropin-releasing hormone (CRH) vi. Gonadotropin-releasing hormone (GnRH) vii. Prolactin-inhibiting hormone (PIH). The secretion of these hormones happens by discrete areas of hypothalamus and transported to anterior pituitary by the hypothalamohypophyseal portal blood vessels. .

8. 3. CONTROL OF ADRENAL CORTEX A) Anterior pituitary controls adrenal cortex by secreting adrenocorticotropic hormone (ACTH). 4. CONTROL OF ADRENAL MEDULLA A) Dorsomedial and posterior hypothamic nuclei are excited by emotional stimuli. B) These hypothalamic nuclei, in turn, send impulses to adrenal medulla via sympathetic fibers and cause release of catecholamines, which are responsible to cope up with emotional stress 5. REGULATION OF AUTONOMIC NERVOUS SYSTEM A) Hypothalamus regulates autonomic nervous system (ANS). B) Sympathetic division of ANS is under the control of posterior and lateral nuclei of hypothalamus.  

9. 6. REGULATION OF HEART RATE A) Hypothalamus regulates heart rate through vasomotor center in the medulla oblongata. B)Activation of posterior and lateral nuclei of hypothalamus enhances the heart rate. . 7. REGULATION OF BLOOD PRESSURE A) Hypothalamus controls the blood pressure by acting on the vasomotor center. B)An activation of posterior and lateral hypothalamic nuclei enhances arterial blood pressure and activation of preoptic area decreases the blood pressure . 8. REGULATION OF BODY TEMPERATURE A) The regulation of b ody temperature happens by hypo othalamus, which sets the normal range of body temperature. B) The set point, under normal physiological conditions is 37°C. C) Hypothalamus has two centers which control the body temperature: i. Heat loss center that is observed in preoptic nucleus of anterior hypothalamus ii. Heat gain center that is located in posterior hypothalamic nucleus.

10. 9. REGULATION OF HUNGER AND FOOD INTAKE Food consumption is controlled by two centers present in hypothalamus: i . Feeding center ii. Satiety center

11. TABLE 1. : Functions of hypothalamus Functions Function: Control of anterior pituitary Action/ Center Releasing hormones and Inhibiting hormones Nuclei/ Parts involved: Discrete areas     Function: Secretion of posterior pituitary hormones Action/ Center Oxytocin Nuclei / Parts involved Para Ventricular Nucleus     Function: Secretion of posterior pituitary hormone Action / Center Antidiuretic hormone (ADH) Nuclei/ parts involved Supraoptic nucleus     Function: Control of adrenal cortex Action / Center Corticotropin-releasing hormone (CRH) Nuclei/ parts involved Paraventricular nucleus

12. Function Control of adrenal medulla Action / Center Catecholamines during emotion Nuclei / Parts involved Posterior and dorsomedial nuclei     Function: Regulation of autonomic nervous system (ANS) Action / Center: Sympathetic Nuclei / Parts involved Posterior and lateral nuclei     Function: Regulation of autonomic nervous system (ANS) Action/ center Para sympathetic Nuclei / Parts involved Anterior nuclei

13. Function” Regulation of heart rate Action / center: Acceleration Nuclei / parts involved Posterior and lateral nuclei     Function Regulation of heart rate Action / Center Inhibition Nuclei / Center Preoptic area  

14. Function; Regulation of blood pressure Action / Center Pressor effect Nuclei / Parts involved Posterior and lateral nuclei     Function Regulation of blood pressure Action / center Depressor effect Nuclei / Parts involved Preoptic area     Function: Regulation of body temperature Action / center Heat gain center Nuclei / parts involved Posterior hypothalamus

15. Function Regulation of body temperature Action / center Heat loss center Nuceli / Parts involced Pre optic nucleus     Function Regulation of hunger and food intake Action / Center Feeding center Nuclei / Parts involved Lateral nucleus     Function regulation of hunger and food int6ake Action / Center Satiety center Nuclei / parts involved Ventromedial nucleus

16. Function Regulation of water intake Action / Center Thirst center Nuclei / parts involved Lateral nucleus     Function Regulation of sleep and wakefulness Action / Center Sleep Nuclei / Parts involved Anterior hypothalamus     Function Regulation of sleep and wakefulness Action / Center Wakefulness Nuceli / Parts involved Mamillary body

17. Function Regulation of behavior and emotion Action / Center Reward center Nuclei / Parts involved Ventromedial nucleus     Function Regulation of behavior and emotion Action / Centre punishment center Nuclei / Parts involved Posterior and lateral nuclei     Function Regulation of sexual function Action / Centrer Sexual cycle Nuclei / Parts involved Tuberal and posterior nuclei

18. Function Regulation of response to smell Action / center Autonomic responses Nuclei / parts involved Posterior hypothalamus     Function: Role in circadian rhythm Action / Center Rhythmic changes Nuclei / Parts involved Suprachiasmatic nucleus

19. Feeding Center Feeding center is in the lateral hypothalamic nucleus. In experimental conditions, activation of this center in animals leads to uncontrolled hunger and enhanced food intake (hyperphagia), leading to obesity. Satiety Center Satiety center is in the ventromedial nucleus of the hypothalamus. An activation of this nucleus in animals leads to total loss of appetite and cessation of food intake.

20. Mechanism of Regulation of Food Intake Under normal physiological conditions, appetite and food intake are well balanced and continues in a cyclic manner. Feeding center and satiety center of hypothalamus play an important role regarding the regulation of appetite and food intake. These centers are controlled by the following mechanisms: i. Glucostatic mechanism ii. Lipostatic mechanism iii. Peptide mechanism iv. Hormonal mechanism v. Thermostatic mechanism.

21. i. Glucostatic Mechanism A) Cells of satiety center act as glucostats or glucose receptors, which are activated by enhganced blood glucose level. B) While taking food, blood glucose level enhances . s lowly the glucostats are activated and satiety center is activated. C) At one stage, it develops the feeling of ‘fullness’. Now, the satiety center inhibits the feeding center and stops the food intake also. D) After few hours of food intake, the blood glucose level reduces and satiety center shows inactivity .

22. ii. Lipostatic Mechanism A) Leptin is a peptide secreted by adipocytes (cells of adipose tissue). B) It plays an important role in regulating the food intake and adipose tissue volume. C) If the volume of adipose tissues enhances , adipocytes secrete and release a large quantity of leptin into the blood. D) While circulating through brain, leptin crosses the blood-brain barrier and gains an emtry into hypothalamus.

23. Mode of action of leptin Leptin acts through some specific neuropeptides in hypothalamus, such as: a. Neuropeptide Y: It is secreted in small intestine, medulla and hypothalamus. Generally , this peptide activates the food consumption . But, leptin inhibits neuropeptide Y, resulting in stoppage of food intake..   b. Pro-opiomelanocortin (POMC): The secretion of POMC occurs from anterior pituitary. It is also secreted from hypothalamus, lungs, GI tract and placenta. Normally, it inhibits food intake. Leptin activates the secretion of POMC.   Leptin receptor Many leptin receptors are recognized . Whatever it may be , leptin shows its action via ‘LepRb’, which is the only active receptor present in many nuclei of hypothalamus.

24. iii. Peptide Mechanism A) Some peptides control the food intake either by activating or inhibiting the feeding center, directly or indirectly. B) The important one among the peptides is ghrelin. C) The secretion of Ghrelin takes place from stomach during fasting. D) It directly acrtivates the feeding center and enhances the appetite and food intake. a. Ghrelin b. Neuropeptide Y.   Peptides, which decrease the food intake: a. Leptin b. Peptide YY.

25. iv. Hormonal Mechanism Some endocrine hormones and GI hormones stopo t the food consumption by acting through hypothalamus. Hormones which inhibit the food consumption : a. Somatostatin b. Oxytocin c. Glucagon d. Pancreatic polypeptide e. Cholecystokinin. v. Thermostatic Mechanism A) Food consumption is inversely proportional to body temperature. B) So in fever, the food intake is reduced . Exact mechanism of this fact is not known.

26. 10. REGULATION OF WATER BALANCE Hypothalamus controls water content of the body by two mechanisms: i. Thirst mechanism ii. Antidiuretic hormone (ADH) mechanism.   i. Thirst Mechanism A) Thirst center is in the lateral nucleus of hypothalamus. B) There are some osmoreceptors in the areas adjacent to thirst center. C) If the ECF volume reduces , the osmolality of ECF is enhances . D) If the osmolarity enhances by 1% to 2%, the osmoreceptors are activated . ii. ADH Mechanism A) Simultaneously, if the volume of ECF decreases along w ith enhanced osmolality, the supraoptic nucleus is activated and ADH is released. B) ADH is responsible for retention of water by facultative reabsorption in the renal tubules. C) It enhances the ECF volume and brings the osmolality back to the normal level.

27. 11. REGULATION OF SLEEP AND WAKEFULNESS A) Mamillary body in the posterior hypothalamus is treated as the wakefulness center. B) An activation of mamillary body causes wakefulness and its lesion results in sleep. C) An activation of anterior hypothalamus also results in sleep.

28. 12. ROLE IN BEHAVIOR AND EMOTIONAL CHANGES A) The behavior of animals and human beings is mostly influenced by two responding systems in hypothalamus and other structures of limbic system. B) These two systems act opposite to one another. C) The responding systems are associated with the affective nature of sensations, i.e. whether the sensations are pleasant or painful. D) Hypothalamus consists of two centers for behaviorial and emotional changes. They are: i. Reward center ii. Punishment center. Reward Center Reward center is located in medial forebrain bundle and ventromedial nucleus of hypothalamus. An e lectrical stimulation of these areas in animals pleases or satisfies the animals. Punishment Center Punishment center is located in posterior and lateral nuclei of hypothalamus. An e lectrical stimulation of these nuclei in animals results in pain, fear, defense, escape reactions and other elements of punishment.

29. Role of Reward and Punishment Centers The importance of the reward and punishment centers lies in the behavioral pattern of the individuals. Almost all the activities of day-to-day life depend upon reward and punishment. Rage Rage refers to violent and aggressive emotional expression with extreme anger. It can be developed in animals by activating the punishment centers in posterior and lateral hypothalamus. The reactions of rage are expressed by developing a defense posture, which includes: i. Extension of limbs ii. Lifting of tail iii. Hissing and spitting iv. Piloerection v. Wide opening of eyeballs vi. Dilatation of pupil vii. Severe savage attack even by mild provocation. Sham Rage Sham rage means false rage. It is an extreme emotional condition that resembles rage and happens in some pathological conditions in humans. In physiological conditions, the animals and human beings regulate a balance between the rage and its opposite state. This balanced condition is otherwise known as the calm emotional state.

30. 13. REGULATION OF SEXUAL FUNCTION A) In animals, hypothalamus plays an important role regarding the maintenance of the sexual functions, particularly in females. B) A decorticate female animal will echibit regular estrous cycle, provided the hypothalamus is intact.   14. ROLE IN RESPONSE TO SMELL A) Posterior hypothalamus along with other structures such as hippocampus and brainstem nuclei are responsible for the autonomic responses of body to olfactory stimuli. B) The responses include feeding activities and emotional responses namely fear, excitement and pleasure. 15. ROLE IN CIRCADIAN RHYTHM A) Circadian rhythm is the regular recurrence of physiological processes or activities, which happen in cycles of 24 hours. B) It is also termed as diurnal rhythm. C) The term circadian is a Latin word, meaning ‘around the day’. Circadian rhythm develops in response to recurring daylight and darkness.

31. APPLIED PHYSIOLOGY – DISORDERS OF HYPOTHALAMUS The lesion of hypothalamus happens because of tumors, encephalitis and ischemia. Following features develop in hypothalamic lesion:   1. Disturbances in carbohydrate and fat metabolisms, when lateral, arcuate and ventromedial nuclei are participated in lesion   2. Disturbance in sleep because of the lesion in mamillary body and anterior hypothalamus   3. Disturbance in sympathetic or parasympathetic function happens because of lesion in posterior, lateral and anterior nuclei   4. Emotional manifestations, resulting in sham rage due to lesion in ventromedial and posterolateral parts

32. 5. Disturbance in sexual functions because of the lesion in midhypothalamus. One or more of the above features can become prominent, leading to some clinical manifestations such as: 1. Diabetes insipidus 2. Dystrophia adiposogenitalis 3. Kallmann syndrome 4. Laurence-Moon-Biedl syndrome 5. Narcolepsy 6. Cataplexy.

33. DIABETES INSIPIDUS Diabetes insipidus is the condition manifested by excretion of large quantity of water through urine. .   DYSTROPHIA ADIPOSOGENITALIS This condition is manifestred by obesity and sexual infantilism, associated with dwarfism (if the condition occurs during growing period). It is also termed as Fröhlich syndrome. .

34. KALLMANN SYNDROME Kallmann syndrome is a genetic disorder manifested by hypogonadism, associated with anosmia (loss of olfactory sensation) or hyposmia (decreased olfactory sensation).     LAURENCE-MOON-BIEDL SYNDROME This disorder of hypothalamus is manifested by moon face (facial contours become round by hiding the bony structures), obesity, polydactylism (having one or more extra fingers or toes), mental retardation and hypogenitalism. NARCOLEPSY Narcolepsy is a hypothalamic disorder along with abnormal sleep pattern. There is a sudden attack of uncontrollable desire for sleep and the person suddenly falls asleep. CATAPLEXY Cataplexy is the sudden uncontrolled outbursts of emotion associated with narcolepsy. Due to emotional outburst like anger, fear or excitement, the person becomes completely exhausted along with muscular weakness.  

35. REVIEW QUESTIONS   Long Questions   Explain about afferent connections and Efferent connections regarding Hypothalamus Describe in detail about the functions of hypothalamus Write in detail about the functions of hypothalamus   Short Question   Names of nuclei of Hypothalamus

36. Fig 1. Hypothalamus - definition

37. Fig 2. Hypothalamus - An overview

38. Fig 3. Hypothalamus Structure

39. Fig 4. Diagram of Hypothalamus

40. Fig 5. Hypothalamus - Gross structure

41. Fig 6. Hypothalamus - Gross Anatomy

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