Thalamus and hypothalamus

Anatomy, physiology and Functions of thalamus and hypothalamus

1. Thalamus and Hypothalamus Presented by- Dr. Farhad U ddin Ahmed Dr. Hosney Jahan Dr. Md. Mahfuzul Alam Resident, Ophthalmology, NIO.

2. Thalamus Presented by- Dr. Farhad U ddin Ahmed Resident (Phase-A) Ophthalmology

3. Introduction Thalamus derives from a latin word that means “Inner Chamber” or “meeting Place” It is situated at the rostral end of brainstem Major part of diencephalon Paired, egg shaped mass of gray matter Important relay and integrative station for information

4. Relations of Thalamus Superior surface- Stratum zonale Body of Fornix Inferior surface- Subthalamus Tegmentum of midbrain

5. Relations of Thalamus Medial Surface- lateral wall of 3 rd ventricle Interthalamic adhesion Lateral Surface- External medullary lamina Reticular nucleus

6. Internal Structure of Thalamus The gray matter of the thalamus is divided by a “Y” shaped vertical sheet of white matter called the internal medullary lamina. It divides the thalamus into three part- Anterior part Medial part Lateral part

7. Classification of thalamic Nuclei Neuroanatomic classification -Anterior group of nuclei -Medial group of nuclei -Lateral group of nuclei

8. Connections of thalamus Every thalamic nucleus (except the reticular nucleus) sends axons to specific parts of the cerebral cortex and every part of the cerebral cortex sends reciprocal fibres back to the thalamic nuclei . Information received by the thalamus is always shared with the cerebral cortex and that the cortex and thalamus can modify each other's activities. Thalamus is an important relay station for two sensory motor axonal loops involving the cerebellum and basal nuclei Cerebellar- rubro - thalamic - cortical - ponto – cerebellar – loop Corticostriatal – pallidal – thalamic – cortical loop Both are necessary for normal voluntary movement.

9. Connections

10. A nterior group: Anterior thalamic nuclei Afferent- Mammillary body Cingulate gyrus Hypothalamus Efferent- Cingulate gyrus Function- Recent memory Emotional tone

11. Medial group: Dorsomedial Nucleus Afferent- Prefrontal cortex Other thalamic nuclei Hypothalamus Efferent- Prefrontal cortex (area 8, 9,10 ,11 and 12) Function- Integration of somatic, visceral and olfactory information Relation to emotional feelings and subjective states.

12. Lateral group: Ventral tier Ventral Anterior Nucleus Afferent- substantia nigra , corpus striatum, reticular formation, intralaminar thalamic nuclei, premotor and prefrontal cortices (areas 6 and 8 ). Efferent- Reticular formation, Premotor cortex , Substantia nigra , Corpus striatum, other thalamic nuclei Function- Influences motor activity of motor cortex

13. Ventral Lateral Nucleus Afferent- As in ventral anterior nucleus Major input from cerebellum Efferent- As in ventral anterior nucleus Major output from red nucleus Function- Influences motor activity of motor cortex

14. Ventral Posterior Nucleus subdivided in to 1. Posteromedial nucleus 2. P osterolateral nucleus Afferent- Ascending trigeminal and gustatory pathway Ascending sensory tracts Medial and lateral lamnisci Efferent- Primary somatic sensory (areas 3, 1, and 2 in post central gyrus) cortex via posterior limb of internal capsule. Function- Relay sensory impulse from face and taste ( VPM) Relay somatosensory impulse (touch pressure , pain, proprioception, temperature and kinesthetic) from trunk and limb(VPL)

15. Dorsal tier: Lateral dorsal, lateral posterior and Pulvinar Nucleus Afferent- Cerebral cortex Other thalamic nucleus Efferent- Cerebral cortex Other thalamic nucleus Function- Correlates visual & auditory information with other sensations

16. Others nucleus Intra laminar Nuclei Within the internal medullary lamina Afferent- Reticular formation Spinothalamic and trigeminothalamic tracts Efferent- Cerebral cortex Corpus striatum Function- Influences levels of consciousness and alertness

17. Midline nuclei Adjacent to the 3 rd ventricle & in the interthalamic connection Afferent Reticular formation Hypothalamous Midbrain Efferent Hyppocampal formation Amygdala Cingulate gyrus Function Part of limbic system, memory and arousal

18. Reticular Nucleus Between external medullary lamina and posterior limb of internal capsule Afferent- Cerebral cortex, reticular formation Efferent- Other thalamic Nuclei Function- R egulations of inter- thalamic activity

19. Medial geniculate nucleus Afferent- Inferior colliculus, lateral lemniscus from both ears but predominantly the contralateral ear Efferent- The auditory radiation of the internal capsule to the primary auditory cortex in temporal lobe (areas 41 and 42 ) Function- Hearing

20. Lateral geniculate nucleus Afferent- O ptic tract Efferent- Optic radiation to visual cortex of occipital lobe (area-17) Function- V ision

21. Blood Supply of Thalamus Blood supply of the thalamus is derived from four parent vessels: basilar root of the posterior cerebral, posterior cerebral, posterior communicating, and internal carotid. The basilar root of the posterior cerebral artery , via paramedian branches, supplies the medial thalamic territory. The posterior cerebral artery , via its geniculothalamic branch, supplies the posterolateral thalamic territory. The posterior communicating artery , via the tuberothalamic branch, supplies the anterolateral thalamic territory. The internal carotid artery , via its anterior choroidal branch, supplies the lateral thalamic territory.

22. Reference- S nell C linical Neuroanatomy 8 th ed.

23. Anatomy and connection of hypothalamus Presented by Dr. Hosney Jahan Phase- A, Ophthalmology

24. Introduction Part of Diencephalone which lies below the thalamus. Forms the floor and lower parts of the lateral walls of the 3 rd ventricle. Small in size weighing only 4 gm, forms only 0.3% of total brain mass. Mainly acts through 3 systems – autonomic nervous system, endocrine system and limbic system.

25. Boundaries Anteriorly – Lamina terminalis, extends from the optic chiasma to the anterior commissure. Posteriorly – Subthalamus. Inferiorly – Structures in the floor of the 3 rd ventricle (i.e. tuber cinereum, infundibulum and mamillary bodies). Superiorly – Thalamus. Laterally - Internal capsule. Medially – Bounded by the cavity of 3 rd ventricle.

26. Antero-Posteriorly Divided Into Preoptic region – area adjoining the lamina terminalis. Supra optic region – above the optic chiasma. Tuberal region – includes the tuber cinereum, infundibulum and area around it. Mammillary region – includes the mammillary bodies and area around it.

27. Hypothalamic Nuclei Hypothalamus is made up of numerous small nuclear masses called hypothalamic nucleus. They are divided into medial and lateral zones by an imaginary parasagittal plane between fornix and mammillothalamic tract.

28. Nuclei

29. Region Nucleus Functions Preoptic region Preoptic nucleus GnRH release Supraoptic region Supraoptic nucleus Vasopressin release Anterior nucleus Thermo regulation, sweating Paraventricular nucleus TRH, CRH and oxytocin release Tuberal region Arcuate nucleus GnRH, feeding and Dopamine release Ventromedial nucleus Satiety centre Dorsomedial nucleus Controls BP, HR& GI stimulation

30. Connections of the Hypothalamus The hypothalamus has afferent and efferent connections with the rest of the body through : Neural connections Bloodstream Cerebrospinal fluid

31. Afferent Nervous Connections of the Hypothalamus Somatic and visceral afferents. General somatic sensation and gustatory and visceral sensations reach the hypothalamus through collateral branches of the lemniscal afferent fibers and the tractus solitarius and through the reticular formation Visual afferents leave the optic chiasma and pass to the suprachiasmatic nucleus Olfaction travels through the medial forebrain bundle Auditory afferents have not been identified, but since auditory stimuli can influence the activities of the hypothalamus, they must exist.

32. Corticohypothalamic fibers arise from the frontal lobe of the cerebral cortex and pass directly to the hypothalamus Hippocampohypothalamic fibers pass from the hippocampus through the fornix to the mammillary body. Many neurophysiologists regard the hypothalamus as the main output pathway of the limbic system Amygdalohypothalamic fibers pass from the amygdaloid complex to the hypothalamus through the stria terminalis and by a route that passes inferior to the lentiform nucleus Thalamohypothalamic fibers arise from the dorsomedial and midline thalamic nuclei Tegmental fibers arise from the midbrain.

33. Efferent Nervous Connections of the Hypothalamus Descending fibers to the brainstem and spinal cord I nfluence the peripheral neurons of the autonomic nervous system They descend through a series of neurons in the reticular formation Connected to the parasympathetic nuclei of the oculomotor, facial, glossopharyngeal, and vagus nerves in the brainstem

34. Reticulospinal fibers connect the hypothalamus with sympathetic cells of origin in the lateral gray horns of the first thoracic segment to the second lumbar segment of the spinal cord and the sacral parasympathetic outflow at the level of the second, third, and fourth sacral segments of the spinal cord.

35. The mammillothalamic tract Arises in the mammillary body and terminates in the anterior nucleus of the thalamus The pathway is relayed to the cingulate gyrus The mammillotegmental tract arises from the mammillary body and terminates in the cells of the reticular formation in the tegmentum of the midbrain Multiple pathways to the limbic system

36. Hypothalamo -Hypophyseal tract Connects hypothalamus to posterior pituitary. Vasopressin and oxytocin are transported to posterior pituitary along the fibers of the tract by axoplasmic flow.

37. Tubero -Infundibular Tract The releasing hormones and release inhibiting hormones are produced in the cells of tuberal and infundibular nuclei and are transported upto the median eminence along the tubero infundibular tract. Releasing hormone – TRH, CRH, GnRH & LHRH . Release inhibitory hormone – Dopamine & GHIH .

38. References Snell Clinical Neuro Anatomy 8 th ed.

39. Functions and Applied Aspect B y Dr. Md. Mahfuzul Alam Resident, Phase A Ophthalmology

40. Sensory integration: Serves as an important sensory relay station and integrative center for most inputs to cerebral cortex. Capable of recognition of pain, thermal & tactile sensations Influences voluntary movement s. Through ascending activating system – maintains state of wakefulness and alertness Impulses received from hypothalamus projected to prefrontal & cingulate gyrus – Determination of mood 6. Recent memory and emotions Functions of Thalamus

41. The thalamus may be invaded by neoplasm undergo degeneration following disease of its arterial supply damaged by hemorrhage Thalamus applied aspect

42. Bilateral thalamic infarction

43. Thalamic Haemorrhage

44. Sensory Loss Due to Thrombosis or hemorrhage of one of the arteries supplying the thalamus Damage to the VPM and VPL nucleus result in the loss of all forms of sensation in the opposite side of the body Usually, a thalamic lesion results in dysfunction of neighboring structures Lateral extension of thalamic disease may involve the internal capsule and produce extensive motor and sensory deficits Effect of lesion of the Thalamus

45. Thalamus ia an important relay station for two sensory – motor axonal loop involving the cerebellum and basal nuclei Cerebellar-rubro-thalamic-cortical-ponto-cerebellar loop. Corticalstriatal-pallidal-thalamic-cortical loop. Both loop necessary for normal voluntary movement. So impairment in any portion of this loop may impaired voluntary movement. Effect in lesion in the thalamus

46. Effect of lesion of the Thalamus Thalamic syndrome Caused due to infarct in thalamo -geniculate artery, a branch of the posterior cerebral artery. The clinical hallmark is a pansensory loss which is contralateral to the lesion, paresthesia , and thalamic pain. Transient hemiparesis, hemiataxia , tremor, choreiform movements, and spatial neglect, all contralateral to the lesion in the thalamus

47. Effect of lesion of the Thalamus Thalamic hand The contralateral hand is in an abnormal posture in some pateints with thalamic lesions. Pronation and flexion of hand, flexion of MCP joint and extension of interphalangeal joints. The condition is due to altered muscle tone in the different groups of muscle .

48. Abnormal Involuntary Movements Choreoathetosis with ataxia may follow vascular lesions of the thalamus It is not certain whether these signs in all cases are due to the loss of function of the thalamus or to involvement of the neighboring caudate and lentiform nuclei The ataxia may arise as the result of the loss of appreciation of muscle and joint movement caused by a thalamic lesion Effect of lesion of the Thalamus

49. Bilatteral thalamic lesion: Uncommon Causes: Metabolic and toxic process . Wernicke’s encephalopathy . Osmotic myelinolysis . Wilsons dise ase . Hypoxic Ischemic Encephalopathy. 2 . Viral infectious. . Japanes B encephalitis . West neil encephalitis 3. Vascular occlution

50. Surgical Relief of Pain by Thalamic Cauterization The intralaminar nuclei of the thalamus are known to take part in the relay of pain to the cerebral cortex. Cauterization of these nuclei has been shown to relieve severe and intractable pain associated with terminal cancer.

51. Functions of Hypothalamus

52. ADH Oxytocin GH TSH ACTH FSH LH Prolactin Hypothalamus GHRH TRH CRH GnRH ADH Oxytocin Adenohypophysis Neurohypophysis Pituitary Gland Portal Axoplasmic flow ENDOCRINE CONTROL

53. HPT AXIS The hypothalamic–pituitary–thyroid axis is part of the endocrine system responsible for the regulation of metabolism. HYPOTHALAMUS 63

54. HPA AXIS The  hypothalamic-pituitary-adrenal axis  ( HPA  or  HTPA axis ). The interactions among these organs constitute a major part of the neuroendocrine system that controls reactions to stress and regulates many body processes, including digestion ,the immune system, mood and emotions, sexuality and energy storage and expenditure. HYPOTHALAMUS 64

55. HPG AXIS The hypothalamic–pituitary–gonadal axis is a critical part in the development and regulation of a number of the body's systems, such as the reproductive and immune systems. This axis controls development, reproduction, and aging in animals. HYPOTHALAMUS 65

56. Autonomic control of Body Hypothalamus has a controlling influence on the autonomic nervous system. Stimulation of anterior hypothalamic area influence parasympathetic respose . Stimulation of posterior hypothalamic area influence sympathetic respose .

57. Temperature regulation The anterior portion of the hypothalamus controls those mechanisms that dissipate heat loss. The posterior portion results in vasoconstriction of the skin and blood vessels and inhibition of sweating, there may also be shivering, in which skeletal muscles produce heat.

58. Regulation of Food and Water Intake Hunger center : lateral region of hypothalamus. Satiety center : Medial region Thirst center : lateral region In addition, supraoptic n. of hypothalamus exert a careful control on the osmolarity of blood through secretion of ADH. Emotion and Behavior Emotion and behavior are a function of the hypothalamus, the limbic system, and the prefrontal cortex.

59. Control of Circadian Rhythms The hypothalamus controls many circadian rhythm . Body temperature Adrenocortical activity Eosinophil count Renal secretion Sleeping and wakefulness.

60. Sexual dimorphism Several hypothalamic nuclei are sexually dimorphic i.e. there are clear differences in both structure and function between males and females. . The importance of these changes can be recognised by differences in sexual behaviour between males and females .

61. Clinical Disorders Associated With Hypothalamic Lesions The hypothalamus may be the site of inflammation, neoplasm, or vascular disorder. Its widespread influence on many homeostatic and behavioral functions means that a lesion of the hypothalamus will produce a large number of different syndromes

62. Obesity and Wasting Severe obesity can occur as the result of hypothalamic lesions Associated with genital hypoplasia or atrophy Severe cachexia is suggestive of damage to the hypophysis (pituitary gland) Sexual Disorders In children, there may be sexual retardation and, rarely, sexual precocity with hypothalamic lesions After puberty, the patient with hypothalamic disease may have impotence or amenorrhea Clinical Disorders Associated With Hypothalamic Lesions

63. Hyperthermia and Hypothermia Hyperthermia - Head injury or following surgical operations in the region of the hypothalamus Hypothermia also can follow a lesion of the hypothalamus Cranial Diabetes Insipidus Diabetes insipidus results from a lesion of the supraoptic nucleus. Large volumes of urine of low specific gravity Extremely thirst and drinks large quantities of fluids Clinical Disorders Associated With Hypothalamic Lesions

64. Disturbances of Sleep The occurrence of either frequent short periods of sleep during the waking hours or insomnia has been observed in patients with hypothalamic lesions Emotional Disorders Attacks of unexplained weeping or laughter, uncontrollable anger, depressive reactions all have been observed in patients with hypothalamic lesions. Clinical Disorders Associated With Hypothalamic Lesions

65. Horner’syndrome . It is a syndrome due to lesion in the sympathetic pathway. Clinical Disorders Associated With Hypothalamic Lesions

66. Is observed frequently with a variety of cerebral lesion (infract, haemorrhage , meningitis , encephalitis) that do not involve hypothalamus And with many type of local hypothalamic diseases (trauma, surgery , vascular lesion ) Clinical Disorders Associated With Hypothalamic Lesions SIADH

67. A moderate reduction in serum sodium concentration is a common finding in patient with acute intracranial disease and post operatively in neurosurgical patient. Mechanism of hyponatremia in these case , AN P That is found mainly in the wall of cardiac atria but also in neuron surrounding the third ventricle in the anteroventral hypothalamic region. Clinical Disorders Associated With Hypothalamic Lesions Cerebral salt wasting syndrome

68. Kallmann syndrome This syndrome characterised by failure to start puberty, primary amenorrhoea and anosmia. The GnRH releasing neurones originate in an area of the developing brain called the olfactory placode . T hen it passes through the cribriform plate into   the olfactory bulb where the sense of smell is generated. From there it migrates t o the hypothalamus . HYPOTHALAMUS 78

69. Kallmann Syndrome Any problems with the development of the olfactory bulb will prevent the progression of the GnRH releasing neurones through it. If the releasing neurones are prevented from reaching the hypothalamus, no GnRH will be released . So in turn , no FSH or LH will be released which results in the failure of puberty and deficient production of testosterone in men , oestrogen and progesterone production in women . HYPOTHALAMUS 79

70. Reference Snell Clinical Neuroanatomy 8 th ed.