Neuroanat 1_Spinal cord to the diencephalon_2023_Student.html

Professor Andrew Dilley Organisation of the central nervous system: Spinal cord to the diencephalon Organisation of the central nervous system: Spinal cord, brainstem, cerebellum and the diencephalon Telencephalon and the meninges Ventricular system and cerebrospinal fluid Ascending and descendi...

Professor Andrew Dilley Organisation of the central nervous system: Spinal cord to the diencephalon Organisation of the central nervous system: Spinal cord, brainstem, cerebellum and the diencephalon Telencephalon and the meninges Ventricular system and cerebrospinal fluid Ascending and descending tracts of the spinal cord Autonomic pathways (central and peripheral components) Module 202 Neuroanatomy Sessions will mainly focus on the central nervous system Head and neck anatomy covered by Dominic O’Brien Development of the central nervous system Neurulation Central nervous system is formed from ectoderm Neuroectoderm cells receive inductive signals from notochord Cells thicken to form neural plate Lateral neural plate margins fold inwards to form neural tube Neural plate Neural folds Neuroectoderm (midline ectoderm) Notochord (within mesoderm) Neural groove Embryonic day 20 Cells at edges of neural plate are the neural crest cells Neural crest cells Ependymal layer - Lines ventricles Embryonic day 24 Ectoderm Lumen - Becomes ventricles + central canal Autonomic and sensory neurons and glia Cells of the adrenal gland Melanocytes Skeletal/connective tissue of the head Mantle layer - Becomes brain parenchyma Neural crest cells migrate into periphery and differentiate into: Neural tube thickens Clinical: Neural tube defects Failure of anterior neuropore to close = Anencephaly (fatal) Neural tube defects occur in ~1/1000 established pregnancies Spina bifida occulta (hidden, vertebral arch defect only) Spina bifida cystica (e.g., meningocele = meninges projects out) Failure of posterior neural tube to close = Spina bifida (divided by a cleft) - Leads to open vertebral canal - Leads to degeneration of forebrain + skull Expansion of cranial end to form main brain regions (primary vesicles) Primary brain vesicles Prosencephalon Mesencephalon Rhombencephalon = Forebrain = Midbrain = Hindbrain Prosencephalon Mesencephalon Rhombencephalon Cephalic flexure Cervical flexure Sagittal Development of the flexures: Spinal cord Secondary brain vesicles Embryonic day 36 Prosencephalon (Forebrain) Mesencephalon (Midbrain) Telencephalon (Cerebral hemispheres) Myelencephalon (Medulla) Metencephalon (Pons/Cerebellum) Rhombencephalon (Hindbrain) Diencephalon (Thalamus/hypothalamus) Optic vesicles (Eyes) Coronal Cranial end continues to expand to form secondary vesicles Pontine flexure Telencephalon Mesencephalon Metencephalon Myelencephalon Diencephalon Sagittal Development of the flexures: Spinal cord Adult central nervous system Dorsal Ventral Caudal Rostral Caudal Dorsal Ventral Midbrain (Mesencephalon) Cerebral hemispheres (Telencephalon) Medulla (Myelencephalon) Pons (Metencephalon) Thalamus/ hypothalamus (Diencephalon) BRAINSTEM FOREBRAIN: MIDBRAIN: HINDBRAIN: * * Cerebellum (Metencephalon) Midsagittal SPINAL CORD Grey and white matter Central nervous system is made up of grey and white matter Grey matter- mainly neuronal cell bodies (e.g., cerebral cortex, brain nuclei) White matter- mainly myelinated axons Coronal Cerebral cortex (grey matter) Corona radiata (White matter) Brain nuclei (gray matter) Grey and white matter appear different on MRI Spinal cord Spinal cord function Receives primary afferent fibres from somatic and visceral structures Sends motor axons to skeletal muscles Autonomic function Regulation of bodily functions at unconscious level (reflexes) Conveys ascending and descending tracts Spinal cord anatomy Atlas L1 vertebra Cauda equina (Lumbar and sacral dorsal and ventral roots) In lumbar cistern Length of spinal cord Spinal cord extends from atlas to L1 Spinal cord narrows at L1 to form the conus medullaris Pia continues as the terminal filum to attach to coccyx Spinal cord regions Lumbosacral enlargement - innervation to lower limb Cervical enlargement - innervation to upper limb Conus medullaris Internal part – pia External part – dura C1 C7 T1 T12 L1 L5 Sacrum Lumbar cistern - Contains the cauda equina Cervical region (C1-C8 spinal nerves) Thoracic region (T1-T12 spinal nerves) Lumbar region (L1-L5 spinal nerves) Sacral region (S1-S5 spinal nerves) Spinal cord is divided into four regions: - Corresponds to where spinal nerves from that region exit the vertebral column Terminal filum Spinal nerves Spinal nerves connect the periphery to the spinal cord pairs, each formed by a dorsal and ventral root Ventral roots – Efferent fibres Dorsal roots – Afferent fibres Peripheral nervous system Spinal cord anatomy and blood supply Vertebral canal Sits protected within vertebral column (in vertebral canal) Surrounded by the dura Receives a blood supply from: Anterior and posterior spinal arteries (from the vertebral arteries) Segmental spinal arteries (at each level) Ventral Dorsal Basilar artery Vertebral arteries Anterior spinal artery Posterior spinal arteries Epidural fat Rhombencephalon / mesencephalon [Brainstem] Brainstem function (see cranial nerve lectures) Spinal cord is continuous with the brainstem Brainstem is functionally important Contains cranial nerve nuclei Autonomic role Vital respiratory and cardiovascular centres Vomiting centre Nuclei involved with motor control, sleep White matter tracts Clinical: Damage to brainstem is often devastating and life-threatening Three main regions are: Midbrain Pons Medulla oblongata Main brainstem regions Ventral Dorsolateral Midbrain Pons Medulla Pineal gland Mesencephalon Rhombencephalon Medulla oblongata Pyramid Corticospinal tract – main voluntary motor pathway Nuclei form part of ascending tract (see spinal cord lecture) Ventral Dorsolateral Olive Formed by olivary nuclei Motor relay to cerebellum (climbing fibres) Cuneate tubercle Gracile tubercle Contains nuclei that are important in controlling respiration and the cardiovascular system MRI showing the brainstem Pons Middle cerebellar peduncle White matter tracts linking brainstem with cerebellum Contains reticular formation Nuclei concerned with sleep, motor control Transverse fibres forming cerebellar peduncles Ventral Dorsolateral Relays information to the cerebellum Pons means bridge (latin) MRI showing the brainstem Midbrain Cerebral peduncles (crus cerebri) (Feet of the brain) Corticospinal tract – main voluntary motor pathway Superior colliculus - Vision - Eye movements Inferior colliculus - Auditory Ventral Dorsolateral - Relay nuclei MRI showing the brainstem Continuous with the forebrain Midbrain internal anatomy Superior colliculus (vision) Cerebral peduncles (crus cerebri) Substantial nigra Red nucleus Motor coordination – relay between cortex and cerebellum Dopaminergic neurons Part of basal ganglia Red nucleus Substantial nigra MRI showing the midbrain Ventral Dorsal Substantia nigra lies within the midbrain Cerebellum Cerebellum function Cerebellum is posterior to brainstem Primarily involved with motor control: Control of posture Coordinating and planning limb movements Control of eye movements Clinical: Cerebellar lesions cause gait disturbances, upper limb ataxia and eye movement disorders Cerebellum anatomy Structure similar to the cerebral hemispheres: Outer gray matter Underlying white matter Two cerebellar hemispheres Three lobes, divided into lobules Contains nuclei Vermis Anterior lobe Posterior lobe Flocculonodular lobe Right hemisphere Left hemisphere Connected to brainstem by cerebellar peduncles Primary fissure Superior Inferior Middle Internal structure Cerebellar cortex Arbor vitae (‘tree of life’) MRI showing the cerebellum Highly folded Receives inputs from periphery, spinal cord, brainstem and cerebral cortex via: Mossy fibres (from pons and spinal cord) Climbing fibres (from medulla) Motor outputs are to thalamus (to cortex) and brainstem Lobule Vermis Horizontal Dentate nucleus (tooth like/serrated) Diencephalon Diencephalon is continuous with the midbrain Comprises the thalamus and hypothalamus Diencephalon Thalamus Hypothalamus Central location important Main functions: Relays sensory information to the cortex Involved with consciousness, sleep, memory and motor functions Paired structure Divided into nuclear groups Thalamus Thalamus Coronal MRI showing the thalamus Interthalamic adhesion Hypothalamus Hypothalamus Inferior to thalamus Main function: Homeostasis Coordinates the autonomic nervous system and neuroendocrine system Involved in thermoregulation, feeding, drinking, circadian rhythms Receives inputs from limbic system Pituitary gland (endocrine gland) Pineal gland (Produces melatonin) Thalamus MRI showing the diencephalon Clinical: Hypothalamic lesions linked to endocrine syndromes Ventral surface Hypothalamus sits between the optic chiasm and mammillary bodies Hypothalamus Mammillary bodies - Part of limbic system Optic chiasm (CN2) Optic nerves converge/decussate to form optic tracts Frontal lobe Temporal lobe Olfactory bulbs (CN1) Development of the central nervous system Anatomy of the spinal cord Anatomy of the brainstem Anatomy of the cerebellum Anatomy of the diencephalon Summary Next Lecture: Telencephalon and meninges