Brainstem & Cranial Nerves 2020 PDF

BRAINSTEM & CRANIAL NERVES BDS2 John Pizzey Nov 2020 1 1 AIMS 1. To know the position of the brainstem in the central nervous system 2. To learn the general morphology and organisation of the brainstem 3. To learn the names and locations of the 12 cranial nerves 4. To review the general function of...

BRAINSTEM & CRANIAL NERVES BDS2 John Pizzey Nov 2020 1 1 AIMS 1. To know the position of the brainstem in the central nervous system 2. To learn the general morphology and organisation of the brainstem 3. To learn the names and locations of the 12 cranial nerves 4. To review the general function of the brainstem and cranial nerves 2 2 Part 1: BRAINSTEM 3 3 Sagittal section of the brain Pons Cerebellum Hindbrain Medulla 4 4 Sagittal section of the brain Midbrain Hindbrain 5 5 Sagittal section of the brain Thalamus Brainstem 6 6 Lateral view of brainstem 7 7 Brainstem Functions Conduit for ascending and descending pathways Conduit for cerebellar connections Houses most cranial nerve nuclei Chemoreception, salivation, mastication, swallowing Reticular formation – arousal; cardiovascular and respiratory centres – vital life-supporting role Raphe, locus coeruleus nuclei - mood,sleep Substantia nigra – movement control 8 8 Transverse section through the closed medulla 9 9 Transverse section through the pons 10 10 Transverse section through the midbrain 11 11 Part 2: CRANIAL NERVES 12 12 C.I C.II C.III C.IV C.V C.VI C.VII C.VIII C.IX C.X C.XI C.XII Cranial Nerves Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Spinal Accessory Hypoglossal On Old Olympus’ Towering Top A Finn And German Viewed A Hop http://www.medicalmnemonics.com/ 13 13 The 12 Pairs of Cranial Nerves The 12 Pairs of Cranial Nerves 14 14 Cranial nerve columns 15 15 Olfactory nerve (C.I) Carries special sensory information responsible for the sense of smell Synapse within the olfactory bulb 16 16 The Olfactory Nerve (C.I) 17 17 Optic Nerve (C.II) Special sensory nerve of vision 18 18 Oculomotor, Trochlear, Abducens (C.III, IV, VI) Oculomotor nerve (C.III) – Somatomotor: Primary source of innervation for 4 of the extraocular muscles – Parasympathetic: pupillary muscles (light reflex); ciliary muscles (accommodation reflex) Trochlear nerve (C.IV) – Innervates superior oblique Abducens nerve (C.VI) – Innervates lateral rectus 19 19 Cranial nerves controlling the extraocular muscles (C.III, IV, VI) PLAY 20 20 Trigeminal (C.V) Motor nucleus (muscles of mastication) Spinal nucleus (sensory) – thermal/nociception from head and neck Principal nucleus (sensory) –touch, proprioception Mesencephalic nucleus –jaw reflexes 21 21 Trigeminothalamic Tract A. Trigeminal ganglion B. Trigeminal principal nucleus C. Thalamus (VPM) D. Cerebral cortex (S I) E. Trigeminal spinal nucleus F. Trigeminal mesencephalic nucleus G. Trigeminal motor nucleus 1. Spinal tract of trigeminal F nerve 2. Ventral trigeminothalamic G E tract 3. Dorsal trigeminothalamic tract 4. Corona radiata V. Trigeminal nerve 22 22 Peripheral branches of C.V 23 23 Facial (C.VII) Motor – muscles of facial expression (mimetic muscles) Sensory – skin of ext auditory meatus, eardrum Special sensory – taste (ant 2/3 of tongue); palate Parasympathetic – innervation of salivary glands (but NOT parotid; lacrimal glands 24 24 UMN vs LMN Lesions of nerves supplying facial muscles UMN Lesion (A) With an upper motor neuron (UMN) lesion of facial muscles, the upper face is spared because both Hemispheres contribute to movement of the upper face & the unaffected hemisphere can compensate. Such lesions involve face area of primary motor cortex or descending corticobulbar fibers Called CENTRAL FACIAL PALSY or CORTICOBULBAR PALSY LMN Lesion (B) With a lower motor neuron (LMN) lesion to C. VII, the entire face is affected on one side. Such lesions involve the motor facial nucleus or facial nerve in pons, cranial cavity, middle cavity or on its course of peripheral distribution Called PERIPHERAL FACIAL PALSY or BELL’S PALSY 25 25 Vestibulocochlear (C.VIII) Vestibular branch monitors balance, position and movement Cochlear branch monitors hearing 26 26 Vestibulocochlear (C.VIII) 27 27 Glossopharyngeal (C.IX) Special sensory – taste (post 1/3 of tongue) Visceral sensory – blood pCO2/[H+] monitoring (carotid body) Sensory – post 1/3 of tongue; oropharynx Motor – upper pharynx Parasympathetic – parotid gland 28 28 Glossopharyngeal nerve 29 29 Vagus (C.X) Sensory i) somatosensory Motor - mucous membranes of laryngopharynx, larynx and upper trachea ii) visceral - trachea, lungs, carotid sinus, abdominal veins, gut (to splenic flexure) i) somatic - lower pharynx, upper oesophagus (swallowing and vomiting) ii) parasympathetic - cardiac muscle (control of heart beat), smooth muscle in GIT (GI motility), trachea and bronchi (airway diameter) 30 30 Vagus (C.X) A mixed sensory and motor nerve Main parasympathetic nerve – “Wanders” into thorax and abdomen 31 31 Spinal accessory (C.XI) Innervation of muscles associated with shoulder and head movement (eg sternocleidomastoid and trapezius) Note that there is probably only a spinal root of C.XI. Earlier texts additionally refer to a cranial root but these are now thought to be aberrant fibres of C.X 32 32 Spinal accessory (C.XI) The Spinal accessory (or just Adapted from Wendy Rappazzo Harford Community College Spinal accessory (C.XI) 33 33 Hypoglossal (C.XII) Motor - Intrinsic muscles of the tongue - Most extrinsic tongue muscles 34 34 Hypoglossal (C.XII) 35 35 Special Nuclear Groups Nucleus Ambiguus IX, X Motor: larynx, pharynx, upper oesophagus -Vomiting, swallowing, modulation of phonation Nucleus Tractus Solitarius VII, IX, X (Solitary Nucleus) Visceral Sensory: tongue, carotid body, carotid sinus, GIT, trachea, bronchi - Chemoreception (inc taste, pCO2/[H+] monitoring, gut distension, blood pressure monitoring 36 36 Brainstem & Cranial Nerves: Summary 1. The brainstem contains vital life-supporting functions, housing the cardiovascular and respiratory centres. 2. All major monoaminergic pathways arise from the brainstem. 3. The brainstem contains ascending and descending tracts, multiple nuclear groupings. 4. 12 pairs of nerves - mixed nerves from motor, sensory, (visceral or somatic), special sensory or parasympathetic classes. 5. All cranial nerves (except the Trochlear nerve, C.IV) exit/enter from the ventral surface of the CNS. 6. All (except the Olfactory nerve, C.I) exit/enter brainstem nuclei. 7. Cranial nerve testing is important and frequently performed to test CNS integrity, particularly the integrity of the brainstem. 37 37