Brainstem by Dr. Rabia Inam Gandapore.pptx

Neuroanatomy Brainstem

1. Brainstem Dr. Rabia Inam Gandapore Assistant Professor Head of Department Anatomy (Dentistry-BKCD) B.D.S, M.Phil. Anatomy, Dip.Implant , CHPE, CHR, Dip . Arts

2. Teaching Methodology LGF (Long Group Format) SGF (Short Group Format) LGD (Long Group Discussion, Interactive discussion with the use of models or diagrams) SGD (Short Group) SDL (Self-Directed Learning) DSL (Directed-Self Learning) PBL (Problem- Based Learning) Online Teaching Method Role Play Demonstrations Laboratory Museum Library (Computed Assisted Learning or E-Learning) Assignments Video tutorial method

3. Goal/Aim (main objective) To help/facilitate/augment the students about the: Identify gross structures of the Medulla oblongata, Pons, and mid-brain on a model . Draw and label the cross sections of Medulla Oblongata, Pons, and midbrain at various levels. Enlist the clinical problems associated with Medulla Oblongata Pons, and mid-brain.

4. Specific Learning Objectives (cognitive) At the end of the lecture the student will able to: Identify gross structures of the Medulla oblongata, Pons, and mid-brain on a model. Draw and label the cross sections of Medulla Oblongata, Pons, and midbrain at various levels. Enlist the clinical problems associated with Medulla Oblongata Pons, and mid-brain.

5. Psychomotor Objective: (Guided response) A student to draw labelled diagram of the cross sections of Medulla Oblongata, Pons, and midbrain at various levels.

6. Affective domain To be able to display a good code of conduct and moral values in the class. To cooperate with the teacher and in groups with the colleagues. To demonstrate a responsible behavior in the class and be punctual, regular, attentive and on time in the class. To be able to perform well in the class under the guidance and supervision of the teacher. Study the topic before entering the class. Discuss among colleagues the topic under discussion in SGDs. Participate in group activities and museum classes and follow the rules. Volunteer to participate in psychomotor activities. Listen to the teacher's instructions carefully and follow the guidelines. Ask questions in the class by raising hand and avoid creating a disturbance. To be able to submit all assignments on time and get your sketch logbooks checked.

7. Lesson contents Clinical chair side question: Students will be asked if they know what is the function of Outline: Activity 1 Identify gross structures of the Medulla oblongata, Pons, and mid-brain on a model . Activity 2 Draw and label the cross sections of Medulla Oblongata, Pons, and midbrain at various levels. Activity 3 Enlist the clinical problems associated with Medulla Oblongata Pons, and mid-brain .

8. Recommendations Students assessment: MCQs, Flashcards, Diagrams labeling. Learning resources: Langman’s T.W. Sadler, Laiq Hussain Siddiqui, Snell Clinical Anatomy , Netter’s Atlas , BD Chaurasia’s Human anatomy, Internet sources links.

9. Brainstem Midbrain Pons Medulla

10. Brain Diencephalon Thalamus Hypothalamus Pineal gland Corpus callosum Lateral ventricle 3rd ventricle Cerebral aqueduct 4th ventricle

11. MidBrain

12. 1. Midbrain Nuclei in the mesencephalon, or midbrain, process visual and auditory information, coordinate and direct reflexive somatic motor responses to these stimuli Also contains centers involved with the maintenance of consciousness

13. Superior Colliculus Inferior Colliculus

14. Midbrain (mesencephalon) External anatomy Quadri-geminal plate-Auditory & Visual reflex Superior colliculus Inferior colliculus Crus Cerebri (Descending Pathway ) Cerebral peduncles CN III Nuclei ( Occulomotor ) CN IV (Trochlear)

15. Mesencephalon OR Midbrain The surface of the midbrain posterior to the aqueduct of the midbrain is called the roof, or tectum , of the mesencephalon. This region contains two pairs of sensory nuclei known collectively as the corpora quadrigemina or quadrigeminal plate (superior and inferior colliculus )

16. Midbrain conti .. These nuclei are relay stations concerned with the processing of visual and auditory sensations S uperior colliculus (small hill) receives visual input from the lateral geniculate of the thalamus on that side. I nferior colliculus receives auditory data from nuclei in the medulla oblongata; some of this information may be forwarded to the medial geniculate on the same side

17. Anterior View Posterior View

18. 1. Superior colliculus Play critical role in generating eye & head movements to sudden visual & other stimuli Brachium of Superior colliculus receive visual information from ratina , visual cortex & Frontal eye field , these all converge on the Superior colliculus , descends fibers to nuclie in brainstem-control movement of eye OR descends to spinal cord to supply muscles of the head & neck. Tectospinal tract Structurally & functionally organized into superficial and deep layers 1. Superficial layers solely process visual information , with direct retinal inputs comprising a visuotopic map of the contralateral side 2. Deep layers of the colliculi receive multimodal inputs & help mediate saccadic eye movements through their efferent connections to the occular motor systems

19. 2. Inferior colliculus Principal midbrain nucleus of the auditory pathway receives input from several peripheral brainstem nuclei in the auditory pathway & auditory cortex. Auditory pathway- 3 subdivisions : the central nucleus , a dorsal cortex by which it is surrounded, and an external cortex which is located laterally Its bimodal neurons are implicated in auditory somatosensory interaction, receiving projections from somatosensory nuclei It is also responsive to specific amplitude modulation frequencies and this might be responsible for detection of pitch

20. Midbrain ( Rostral-Anterior) Internal anatomy Tectum : I nferior colliculus (auditory) Brachium of Inferior colliculus Tegmentum Crus Cerebri (Descending Pathway): 1. Corticospinal and Corticonuclear Fibers (middle) 2. Frontopontine fibers (medial) 3. Temporal/parietal/occipital pontine fibers (lateral Central gray matter Substantia nigra (dark Pars Compacta -DOPA, Pars reticularis -GABA) Ascending Tracts (Medial leminiscus , Trigeminal leminiscus , Spinoleminiscus , Lateral leminiscus -auditory)

21. Cerebral aqueduct- paraequiductal grey matter Medial longitudinal fasiculus Tectospinal fibers(SC and IC)- originate in SC Rubrospinal pathway-motor movement Deccusation of superior cerebellar peduncles Cerebral peduncles= Combination of tegmentum and crus cerebri Locus Coeruleus (Pain modulation-norepinephrine) Dorso raphe nucleus (Pain modulation) Mesenchephalic nucleus of trigeminal nerve (5)- proprioceptive Trochlear nerve-motor/eye superior oblique muscle

22. Internal anatomy Tectum : Superior colliculus (visual) Tegmentum Central gray matter Crus Cerebri (Descending Pathway): 1. Corticospinal and Corticonuclear (cranial nerve-brainstem)Fibers (middle) 2. Frontopontine fibers (medial) 3. Temporal/parietal/occipital pontine fibers (lateral Substantia nigra (dark Pars Compacta -DOPA, Pars reticularis -GABA) Ascending Tracts (Medial leminiscus , Trigeminal leminiscus , Spinoleminiscus )

23. Medial longitudinal fasiculus Dorsal tegmental deccusation Red nucleus Tectospinal fibers Oculomotor nucleus (III) – general somaticmotor Edinger-Westphal nucleus –PSNS-general visceral efferent fibers Cerebral peduncles= Combination of tegmentum and crus cerebri Trochlear nerve-motor/eye superior oblique muscle Pretectal nucleus-pupil light reflex, Lateral geniculate body Ventral tegmental Deccusation – Rubrospinal fibers Mesenchephalic nucleus of trigeminal nerve (5)-proprioceptive Cerebral aqueduct- paraequiductal grey matter

24. Midbrain (Caudal) Internal anatomy Trochlear nucleus

25. Nuclei of midbrain The mesencephalon also contains the major nuclei of the reticular formation Specific patterns of stimulation in this region can produce a variety of involuntary motor responses. Each side of the mesencephalon contains a pair of nuclei, the red nucleus and the substantia nigra

26. 3 . Red nucleus The red nucleus (at level of superior colliculus ) is provided with numerous blood vessels , giving it a rich red coloration. Integrates information from the cerebrum and cerebellum- Decussate at ventral part of tegmentum-Vental tegmentum decussation , Fibers decends down enter ventral gray horn to supply upper limb skeletal muscles-Flexors ( Rubrospinal tract ) Issues involuntary motor commands concerned with the maintenance of muscle tone and limb position Example: Crawling of babies, arm swinging during walking is controlled by the red nucleus Fine control of the fingers is not modified by the functioning of the red nucleus but relies on the corticospinal tract

27. 4 . Substantia nigra Substantia nigra (“black”) lies lateral to the red nucleus Nigrostriatal pathway- motor movement is well coordinated The gray matter in this region contains darkly pigmented cells, giving it a black color Plays an important role in regulating the motor output of the basal nuclei Involved in eye movement , motor planning-coordination of movement , reward-seeking , learning , and addiction Also serves as a major source of GABAergic inhibition to various brain targets

28. 5 . Cerebral peduncles The nerve fiber bundles on the ventrolateral surfaces of the mesencephalon are the cerebral peduncles (peduncles, little feet) Contain : Ascending fibers that synapse in the thalamic nuclei Descending fibers of the corticospinal pathway that carry voluntary motor commands from the primary motor cortex of each cerebral hemisphere

29. Cerebro-rubro & Cerebrothalamic Fibers Cerebellum (posture, tone , coordination ) fibers go to contralateral red nucleus , called cerebello-rubro fibers, some move to thalamus, some directly from cerebellum-cross over and go directly to cerebral cortex . Decussation made via cerebro-rubro or cerebrothalamic fibers and goes to cerebral cortex or may decends to the cerebellum in the medulla region via inferior olives –climbing fibers

30. Oculomotor Nerve General Somatic efferent fibers of oculomotor nerve-supply the skeletal muscle of eye LR6 SO4 ATR3- Eye Muscles Mnemonics Extra-Ocular Skeletal Muscles of Eye Superior Rectus Inferior Rectus Medial Rectus Inferior Oblique Levator palpebrae superioris General Visceral efferent supply by edinger westphal nucleus- Parasympathetic fibers Sphincter Pupil-constriction Cilliary muscle-suspensory ligaments ( accomation of Near vision)

31. Medial Longitudinal Fasiculus Stimuli enters vestibular nuclei- stimulate the 6 th cranial nerve ( abducens ) , it will cross over and ascends and stimulate the 3 rd cranial nerve ( oculomotor ) (contralateral) and can also supply the trochlear nerve. So move the head to right the eye will move eye to the left, so the lateral rectus of one eye will move in that direction while the medial rectus will move in the opposite direction

32. Functional significance of midbrain Visual and auditory reflexes Coordinates eye movements Pupillary reflex Consciousness and arousal

33. Arterial supply of Midbrain Branches of Posterior cerebral artery Basilar artery

34. Clinical Relevance Midbrain

35. Midbrain lesions: Benedikt Syndrome CN 3-Oculomotor, medial lemniscus, red nucleus Occulomotor palsy (CN3) Contralateral loss of proprioception (ML) Involuntary movements- tremor, ataxia (Red Nucleus )

36. Weber’s Syndrome CN3 , corticospinal tract, corticobulbar tract Occulomotor nerve palsy Contralateral hemiparesis Pseudobulbar palsy UMN CN motor weakness Exagerrated gag reflex Tongue spastic (no wasting) Spastic dysarthria

37. Parinaud’s Syndrome Posterior midbrain : Superior colliculus & pretectal area V ertical gaze palsy Pseudo Argyll Robertson pupil Often from pinealoma/ germinoma of pineal region Cerebral aqueduct obstruction- non-communicating hydrocephalus, compression from a pineal tumor

38. PONS

39. 2. Pons Extends superiorly from the medulla oblongata to the mesencephalon Forms a prominent bulge on the anterior surface of the brain stem The term pons refers to a bridge ,& the pons connects the cerebellum to the brain stem The cerebellar hemispheres lie posterior to the pons Two are partially separated by the fourth ventricle On either side, the pons is attached to the cerebellum by three cerebellar peduncles Lies immediately superior to the medulla It contains nuclei involved with both somatic and visceral motor control

40. Pons contains Sensory and motor nuclei for four cranial nerves . (V , VI , VII & VIII ). These cranial nerves innervate: J aw muscles Anterior surface of the face One of the extra-ocular muscles (the lateral rectus) Organs of hearing and equilibrium in the inner ear Nuclei concerned with the involuntary control of respiration

41. Pons contains On each side of the brain, the reticular formation in this region contains two respiratory centers A pneustic center : controls intensity of breathing and is inhibited by the stretch receptors, or by signals from the pnuemotaxic center . It increases tidal volume. P neumotaxic center : upper pons, terminating inspiration , and regulating inspiratory volume and respiratory rate. involved in the fine-tuning of breathing. These centres modify activity of respiratory rhythmicity center in medulla oblongata

42. Pons External anatomy: Basilar pons (pons proper) Middle cerebellar peduncle (MC) Basilar artery 4th ventricle CNN V, VI, VII, VIII

43. Tegmentum Basilar

44. Basilar Part of Pons Pontine nuclei -Descending motor fibers from cerebral cortex synapse on pontine nuclie , some cross over and go to contralateral cerebellum (cross over, left one go to right side cerebellum) via the pontocerebellar fibers into the middle cerebellar peduncles which enters the cerebellum

45. Basilar Tegmentum

46. Tagmentum Part of Pons Trapezoid body -auditory-cochlear fibers called Acoustic striafrom cochlear nuclei they cross and ascend into lateral laminiscus Medial to lateral Medio leminiscus Trigeminal Leminiscus Spino Leminiscus Lateral Leminisus -sensory information from inner ear Ventral- spinocerebellar tract- ascending tract Rubrospinal tract- decending tract

47. Tectospinal tract- decending motor information Medial longitudinal faciculus -ascending tract connects 3,4, 6 CN Trigeminal motor nucleus Trigeminal sensory nucleus-central or principal pontine nucleus of trigeminal nerve 4 th Ventricle Superior medullary velum Superior cerebellar peduncle (small piece)

48. Cranial nerve nuclei of Pons Rostral Pons •Trigeminal nucleus (V) Caudal Pons • Abducens nucleus (VI) • Facial nucleus (VII) • Sup salivatory nucleus (VIII)

49. Level of Facial and Abducens Nerve Basilar Part Pontine nuclei- Descending motor fibers from cerebral cortex synapse on pontine nuclie , some cross over and go to contralateral cerebellum (cross over, left one go to right side cerebellum) via the pontocerebellar fibers into the middle cerebellar peduncles which enters the cerebellum Tegmentum Part Trapezoid body-auditory-cochlear fibers called Acuastic striafrom cochlear nuclei they cross and ascend into lateral laminiscus Medial to lateral Medio leminiscus Spino Leminiscus Ventral- spinocerebellar tract- ascending tract

50. Spinal nucleus of trigeminal nerve Trigeminal leminiscus Facial nerve-Sensory & motor fiber= motor nucleus (Special visceral efferent fibers), Superior salvatory nucleus (parasympathetic fibers, General visceral efferent), Nucleus of tractus solitaries (special visceral afferent fibers), General somatic afferent fibers-ear SENSORY FIBERS- spinal nucleus of CN5) Abducens nerve-motor/general somatic efferent fibers Vestibular nuclear complex (Superior, Medial & Lateral-Pons but Inferior-Medulla) 4 th Ventricle Superior medullary velum

51. Superior cerebellar peduncle (small piece) Dorsal Cochlear nuclei Ventral Cochlear nuclei Inferior cerebellar peduncle Superior olivary nucleus Rubrospinal tract Medial longitudinal fasiculus Facial colliculus Tectospinal tract

52. Pons (Rostral/Mid) Internal anatomy Trigeminal motor nucleus

53. Pons (caudal) Facial nucleus (Innervate muscles of the face) Superior salivatory nucleus (Origin of preganglionic parasympathetic neurons) Abducens nucleus

54. Tracts at Pons level Nuclei that process and relay cerebellar commands arriving over the middle cerebellar peduncles via ascending, descending, and transverse tracts . The longitudinal tracts interconnect other portions of the CNS Middle cerebellar peduncles are connected to the transverse fibers of the pons that cross its anterior surface Anterior cerebellar peduncles contain efferent tracts arising at cerebellar nuclei. These fibers permit communication between the cerebellar hemispheres of opposite sides Inferior cerebellar peduncles contain both afferent and efferent tracts that connect the cerebellum with the medulla oblongata

55. Pontine reticular formation Transmits excitatory signals downward into the spinal cord through the reticulospinal tract in the anterior column of the cord Performs automatic processing of incoming sensations and outgoing motor commands

56. Clinical Relevance PONS

57. Medial Pontine Syndrome Corticospinal tract, CN6, CN7 Contraleral hemiperisis CN6 palsy Lateral gaze syndrome: MLF, CN6 nucleus Gaze palsies- cant look to affected side Facial weakness/droop affected side

58. Lateral Pontine Syndrome Vestibular nuclei: nystagmus, vertigo, N/V Spinothalamic tract: contralateralpain / temp Spinal V nucleus: ipsilateral face pain/temp Sympathetic tract: Horner’s Syndrome Facial nucleus: ipsilateral facial droop, loss of corneal reflex Cochlear nucleus- deafness AICA stroke

59. Medulla Oblongata

60. 3. Medulla Oblongata The spinal cord connects to the brain stem at the medulla oblongata. Superior portion of the medulla oblongata has a thin, membranous roof Inferior portion resembles the spinal cord. Relays sensory information to the thalamus & to other brain stem centers . Contains major centres concerned with the regulation of autonomic function , such as heart rate, blood pressure, and digestive activities

61. Medulla oblongata Nuclei in the medulla oblongata may be relay stations along sensory or motor pathways Constituents : Relay stations Cranial nerve nuclei Autonomic nuclei Reflex centers Cardiovascular centers Respiratory rhythmicity centres

62. Olfactory & Optic-Not included

63. Posterior View

64. Medulla Oblongata Decussation Pons Vestibular Nuclei Complex Cochlear Nuclei Complex Pontobulbar body Striae-medullaris Corticospinal tract Spinal Lemniscus Rubrospinal Tract Inferior Salvatory Nucleus Sympathetic tract

65. Decussation Olives

66. Medulla Oblongata Decussation Lemnisci Spinoolivary tract Olivospinal Tract Spinotectal tract Vestibulospinal tract Anterior Spinothalamic tract

67. Medulla Oblongata Decussation Pyramidal Corticospinal tract

68. Relay stations: Ascending tracts may synapse in sensory or motor nuclei that act as relay stations and processing centers . For example: T he nucleus gracilis and the nucleus cuneatus pass somatic sensory information to the thalamus (DCML pathway) The olivary nuclei relay information from the spinal cord , the cerebral cortex, diencephalon, and brain stem to the cerebellar cortex . The bulk of the olivary nuclei create the olives , prominent bulges along the ventrolateral s urface of the medulla oblongata

69. Nuclei: Nuclei of cranial nerves: Contains sensory and motor nuclei associated with five of the cranial nerves (VIII, IX, X, XI, and XII). These cranial nerves innervate muscles of the pharynx, neck, and back, as well as visceral organs of the thoracic and peritoneal cavities. Autonomic nuclei: The reticular formation in the medulla oblongata contains nuclei and centers responsible for the regulation of vital autonomic functions.

70. Major Medullary centers These reflex centers receive input from cranial nerves , the cerebral cortex, the diencephalon , and the brain stem , their output controls or adjusts the activities of one or more peripheral systems . Major centers include the following: Cardiovascular centers , which adjust heart rate, the strength of cardiac contractions, and the flow of blood through peripheral tissues. On functional grounds, the cardiovascular centers may be subdivided into cardiac and vasomotor centers , but their anatomical boundaries are difficult to determine. Respiratory rhythmicity centers , which set the basic pace for respiratory movement, their activity is regulated by inputs from the apneustic and pneumotaxic centers of the pons.

71. Medullary reticular formation Medullary reticular system : transmits inhibitory signals to same antigravity anterior motor neurons via medullary reticulospinal tract , located in lateral column of the cord

72. Reticular Formation Set of interconnected nuclei located through the length of brainstem Includes ascending pathways to cortex in the ascending reticular activating system (ARAS) & descending pathways to spinal cord via reticulospinal tracts . Reticular formation is divided into 3: Raphe nuclei- synthesis of serotonin,play role in mood regulation & analgesic pathway Gigantocellular nuclei- involved in motor coordination Parvocellular nuclei- regulate exhalation

73. General functions of reticular formation Somatic motor control –function in maintaining tone, balance, and posture—especially during body movements. The reticular formation also relays eye and ear signals to the cerebellum so that cerebellum can integrate visual, auditory & vestibular stimuli in motor coordination. Cardiovascular control – R eticular formation includes cardiac & vasomotor centers of medulla oblongata. Pain modulation – Reticular formation is one means by which pain signals from the lower body reaches cerebral cortex. Its the origin of descending analgesic pathways. Sleep and consciousness – Habituation – This is a process in which the brain learns to ignore repetitive, meaningless stimuli while remaining sensitive to others.

74. Clinical Relevance MEDULLA OBLONGATA

75. Medial Medullary Syndrome Corticospinal , medial leminiscus , CN 12 Contralateral hemiperasis Contralateral loss of propioception /vibration Flaccid paralysis tongue deviation to side of lesion Anterior spinal artery stroke

76. Lateral medullary syndrome (Wallenberg’s Syndrome) Vestibular nuclei: nystagmus, vertigo, N/V Sympathetic tract: Horner’s Syndrome Spinothalamic tract: contraleralpain /temp Spinal V nucleus: ipsilateral face pain/temp Nucleus ambiguus (IX, X)- hoarseness, dysphagia PICA stroke

77. Decerebrate Rigidity Results from damage to rostral brainstem (Midbrain and pons) Causes blockage of normal strong input to the medullary reticular nuclei from the cerebral cortex, the red nuclei & the basal ganglia. Medullary reticular inhibition system becomes non functional and the pontine excitatory system becomes overactive.

78. Internal Anatomy of Brainstem Spinal nerve anatomy Dorsal root • Somatic sensory neurons • Visceral sensory neurons Ventral root • Visceral motor neurons • Somatic motor neurons That’s why sensory nuclei are lateral to motor nuclei in brainstem

79. Thank You Any Questions?