Brainstem II Lecture Notes PDF

Brainstem II Dr Jittima Muensoongnoen [email protected]  Learning Outcomes By the end of the session (and recommended reading) you should be able to: Describe the function of the brainstem Identify the specific region/...

Brainstem II Dr Jittima Muensoongnoen [email protected]  Learning Outcomes By the end of the session (and recommended reading) you should be able to: Describe the function of the brainstem Identify the specific region/level of the brainstem when examining a brainstem section. Identify and describe the major gross morphological features of the brainstem and relate these with underlying/associated internal structures. Identify and describe internal structures of different levels of the brainstem. including major descending & ascending tracts, main nuclei & cranial nerve nuclei and relate these to their pathway and function. Describe the reticular formation in terms of its location, major nuclei and function. What are the functions of the brainstem?  Functions of the brainstem Serves as a conduit for the ascending tracts and descending tra Contains important reflex centres (e.g. respiration, cardiovascular system & consciousness) Contains the nuclei of cranial nerves III – XII.  Quiz 4 1 2 Ventral 5 3 6 7  Quiz 4 1 = midbrain 1 2 = pons 3 = medulla oblongata 2 4 = mamillary body Ventral 5 = basilar part of pons 5 3 6 = cerebellum 6 7 = spinal cord 7 ainstem is made up of: midbrain, pons & medulla Mammilla ry body midbrain pons Mid P Cerebellum M Ventral Spinal cord Basillar part medulla Cerebellum Spinal cord Which level? 2 C B A ventral 1 3 ventral ventral Which level? 2 medulla midbrain pons medulla olive pyramid ventral 1 3 pons midbrain interpeduncular cerebral peduncle fossa ventral basilar part ventral  Medulla Mid-medulla pyramid olive pyr am i trac dal t inferior olivary nucleus Anterior median fissure  Dorsal Vestibul motor ar nucleus of nuclei the vagus 4th ventricle Hypoglossal inferior nucleus cerebellar peduncle midbrain pons NTS & tract 4th medial lemn Spinal trigeminal spinothalamic medulla tract & tract nucleus iscus py r a l am i d Dorsal aspect: tra ct inferior olivary Hypoglossal Cerebellum removed nucleus nerve (CN XII) Mid-medulla  Medulla Rostral medulla pyramid olive py r inferior olivary a l am nucleus tra id ct  Spinal NTS & trigeminal tract tract vestibular nuclei and nucleus 4th ventricle inferior cerebella midbrain r peduncle NA pons Vestibulocochl 4th medial le ear nerve (CN VIII) medulla inferior mniscus spinothalamic tract olivary nucleus py r am id al t ra ct Dorsal aspect: Cerebellum removed NA = nucleus ambiguus Rostral medulla yramidal tract/corticospinal tract pyramidal cell bodies cortex Neurones (in layer V) of the cortex - pyramidal cells (their cell body has pyramidal shape). At the junction between the medulla & spinal cord, most of these fibres cross midline – at the pyramidal decussation (the decussation of the pyramids). In the spinal cord - synapse with internuncial neurone medulla (interneurones), which in turn synapse with motor neurones in the ventral horn. Pyramidal The remaining fibres cross the midline at the spinal cord decussatio level n  Corticobulbar (corticonuclear) tract The tract originates from the cortex and terminates in the LMNs (lower motor neurones) in the cranial nerve nuclei -innervate the skeletal muscles of the head & neck (e.g. muscles of facial expression and muscles of mastication). e.g. CN VII innervates the muscles of facial expression  Spinothalamic pathway Dorsal column pathway Pain, temperature, light (crude) touchDiscriminative touch, vibration, conscious proprioception Cortex Cortex Thalamus Thalamus Brainstem Brainstem Spinal cord Spinal cord Sensory pathways https://www.pinterest.com Second-order neurones – in the spinal cord Second-order neurons – in the medulla Brown-Sequard syndrome: hemisection of the spinal cord Spinothalamic tract Dorsal column/medial lemniscus pathway Corticospinal tract **Function **Contralateral or Ipsilateral  Pons superior cerebellum cerebellar Middle peduncle cerebell main 4th ventricle middle cerebellar ar sensory & peduncle peduncl motor e nucleus of CN Vtrigeminal nerve (CN V) Middle cerebell ar pons peduncl e pyramidal tract ascending sensory tracts (medial lemniscus & transverse spinothalamic The pathway forms the connection linking pontine fibres tract) cerebellum the cortex and cerebellum (this will be covered in the cerebellum lecture. Corticopontine fibres - Pontine nuclei - Transverse pontine fibres. These fibres cross midline to the opposite side and Cerebellar peduncles: 3 pairs Contains nerve fibres/tracts which travel to or from the cerebellum. superior Dorsal view - cerebellum pons removed S middle cerebellum I M inferior Peduncle = stalk  Cerebral aqueduct (only present in the Midbrain tectum (roof) midbrain) tegmentum a gr ni ia nt Crus cerebri ta bs Su midbrain Crus cerebri + Tegmentum = Cerebral pedunc Superior colliculi Inferior colliculi ventral dorsal Midbrain Cerebral aqueduct tectum (roof) tegmentum a gr ni ia nt Crus cerebri ta bs Su midbrain Crus cerebri + Tegmentum = Cerebral pedunc Visual reflexes (superior colliculi) & auditory pathway (inferior Ascending colliculi) & descending tracts Cranial nerve nuclei Dopaminergic neurones (motor & reward system)  Hydrocephalus https://www.mayoclinic.org/diseases-conditions/ craniosynostosis/multimedia/cranial-sutures-and- fontanels/img-20006785 The cerebral aqueduct is a common site of blockage (e.g. tumor) – quite small. A condition known as the hydrocephalus. Hydro = water. Cepahlus = head. Standford Children Health https://link.springer.com/article/10.1007/s00381- 024-06495-5 idbrain: Level of the superior colliculus ventral PAG = Periaqueductal grey superior colliculus oculomoto cerebral r nerve aqueduc (CN III) t oculomoto r nucleus superio dorsal r PAG collicul us ascending sensory tracts su (medial red nucleus bs lemniscus & t an spinothalamic ti a t al tract) ac d ni tr mi gr ra a py oculomotor nerve Red nuclei are only found at the level of the  Dopaminergic neurones Substantia nigra In addition to motor function - play an important role in motivation & reward. Can you see a difference? normal Parkinson’s a gr ni ia nt ta bs Su In Parkinson’s disease - substantia nigra appears very pale  Reticular formation reticular = resembles a net made up of nerves cells and nerve fibres scattered Reticular formation throughout the centre of the brainstem. direct & indirect connections with all levels of CNS medulla  Reticular formation Major nuclei Raphe nuclei: serotonin Cholinergic reticular nuclei Noradrenergic neurones: locus coeruleus  medulla Raphe nuclei Groups of neurones either in or adjacent the midline (raphe) of the brainstem. Synthesise and secret serotonin (5-HT). Active in deep sleep. Serotonin pathways to the forebrain from the Raphe Nuclei Cholinergic reticular nuclei Acetylcholine Active in the awake state Cholinergic pathways  Noradrenergic neurones locus coeruleus: noradrenaline active in awake regulates arousal, attention  Reticular formation Function Control of skeletal muscles Control of somatic and visceral sensations Control of ANS Control of endocrine nervous system Sleep, arousal, consciousness Pain modulation  Consciousness Consciousness = ‘awareness of oneself & one’s surrounding’ (Kiernan et al., 2014).  Cortex The reticular activating system Thalamus (RAS) Basal forebrain hypothalamus RAS Brainstem compression & coma extra or subdural haemorrhage temporal lobe uncus tentorium cerebelli  Stroke What level of the brainstem we are looking at and how do you know i basilar part of pons basilar part of pons  Learning Central (extra resources) Questions? Brainstem Quiz oundational features of the brainstem (By the Noted anatomist) s://www.youtube.com/watch?v=BAfrD6pf22k www.pinterest.com