Nervous System Anatomy Lecture Notes PDF

Any questions/remarks before we begin today’s lecture? 1 Nervous system anatomy Dr. Lavinia Carmen Uscătescu November 20th 2024 2 Outline 1. Centr...

Any questions/remarks before we begin today’s lecture? 1 Nervous system anatomy Dr. Lavinia Carmen Uscătescu November 20th 2024 2 Outline 1. Central nervous system (CNS) 2. Peripheral nervous system (PNS) Cortical and subcortical organisation Somatic vs. autonomic nervous The cerebellum system Commissures Sympathetic vs. parasympathetic The ventricular system nervous system Cerebral blood supply Cranial nerves The spinal cord 3 Cortical and subcortical organisation 4 A glimpse at subcortical organisation Bonus question cortex the grey matter layer on the brain surface from Latin (cortex): “bark of a tree” grey matter white matter composed largely of cell bodies composed largely of myelinated axons and unmyelinated interneurons 5 Nervous system subdivisions adapted from Pinel & Barnes, (2021), p. 74-75 6  The meninges meninges (plural of “meninx”) dura mater The three membranes that envelop the brain and spinal cord tough outer membrane surrounding from Latin and Greek (“meninx”): “membrane, covering” the brain and the spinal cord from Latin : “hard mother” arachnoid (mater) the middle membrane surrounding the brain and spinal cord from Latin (“arachnoides”) and from Greek (“arakhnoeides”): "cobweb-like" pia mater the innermost layer of the meninges from Latin : “tender mother” Pinel & Barnes, (2021), p. 76 7  See the Munich Brain Course at: https://www.intensivkurs-neuroanatomie.de/ Bear et al., (2015), p. 186 The subarachnoid space is filled with a clear liquid called “cerebrospinal fluid” (CSF). It also contains major blood vessels and cisterns (i.e., enlarged pockets of CSF created due to the separation of the arachnoid from the pia mater) 8 did you know…? ~ 20% of tumours found in the human brain are meningiomas (tumours that grow between the layers of the meninges). All meningiomas are encapsulated tumours (i.e., tumours that grow within their own membrane). They can influence the function of the brain only by the pressure they exert on surrounding tissue, and they are almost always benign tumours (i.e., are surgically removable, with little risk of further growth in the body). Pinel & Barnes, (2021), p. 260 9 did you know…? Meningitis is an inflammation of the meninges and subarachnoid space that can also involve the brain cortex and parenchyma owing to the close anatomical relationship between the cerebrospinal fluid (CSF) and the brain. Per definition, bacterial meningitis is an infection of the CSF-filled subarachnoid space. Inflammation of the meninges and subarachnoid space leads to the classic triad of meningitis symptoms — headache, fever, and neck stiffness. *brain parenchyma refers to the functional tissue in the brain that is made up of the two types of brain cell, neurons and glial cells https://www.nature.com/articles/nrdp201674 10 did you know…? Intracranial haemorrhage Subdural haemorrhage Epidural haemorrhage Epidural Subarachnoid haemorrhage haemorrhage Subdural haemorrhage Intracerebral Bleeding between Bleeding between haemorrhage the arachnoid mater the dura mater and and the dura mater the skull 11 The meninges in 3D https://www.youtube.com/watch?v=UkffBv4sh4U&list=PLp9HSlEm97VXyQ32Uwjfz3dpmQ8nl63zJ&index=6 12  Major landmarks and structures gyrus, (pl.) gyri convolution between grooves of the brain from Latin (gyrus): “circle” from Greek (gyros): “ring, circle” Bonus question sulcus, (pl.) sulci Purves et al., (2018), Appendix fissure between convolutions of the brain from Latin (sulcus): "furrow, trench, ditch" *The central sulcus is also known as the fissure of Rolando, or the Rolandic fissure 13 Brief overview of cortical localisation https://www.youtube.com/watch?v=akjdkBeFNLE 14 Neuroscientists use cortical and/or subcortical atlases for parcellation. There is considerable inter-individual neuroanatomical variability! cytoarchitectonic atlas an atlas based on the cellular composition of the central nervous system's tissues under the microscope Lawrence et al., (2021), https://www.nature.com/articles/s41597-021-00849-3 … and many more! 15 Apart from cytoarchitectonic atlases, we can also use functional parcellations (i.e., anatomically unconstrained). https://www.youtube.com/watch?v=BiCOWD6iSdo https://pubmed.ncbi.nlm.nih.gov/31740342/ 16 The Brodmann cytoarchitectonic atlas Korbinian Brodmann (1868 – 1918) He distinguished 52 anatomically and functionally distinct areas in the human cerebral cortex, based on the shapes of cells and variations in their layered arrangement (cytoarchitectonics). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6202576/ 17  The hemispheres Right Left hemisphere hemisphere Motor (descending) Sensory (ascending) fibres fibres Decussation (crossing) of fibres https://pubmed.ncbi.nlm.nih.gov/15664541/ contralateral vs. ipsilateral https://tinyurl.com/c7u5s5v4 18  The lobes of the brain (Prosencephalon) (Mesencephalon) ascending sensory and descending motor pathways (Rhombencephalon) superior (vision) and inferior (auditory) colliculi pons and cerebellum medulla Mtui et al., (2021), p. 8 Pinel & Barnes, (2021), p. 87 19 Purves et al. (2018), Appendix The banks of the lateral (Sylvian) fissure have been pulled apart to expose the insula https://sites.uclouvain.be/braininteratlas/en/chapter/external-configuration 20 https://sites.uclouvain.be/braininteratlas/en/chapter/external-configuration 21 3D visualization tools https://neuroanatomy.ca/3D/wholebrainPG.html https://tinyurl.com/bdeuk3r8 22 Annotated surface neuroanatomical images https://webpath.med.utah.edu/HISTHTML/NEURANAT/NEURANCA.html#1 23 Frontal lobe sulci and gyri: lateral and mid-sagittal view https://radiopaedia.org/articles/frontal-lobe 24  Parietal lobe sulci and gyri: lateral, dorsal, and mid-sagittal view https://radiopaedia.org/articles/parietal-lobe 25 Temporal lobe sulci and gyri: lateral and mid-sagittal view https://radiopaedia.org/articles/temporal-lobe 26 Occipital lobe sulci and gyri: lateral and mid-sagittal view https://radiopaedia.org/articles/occipital-lobe 27 Limbic lobe/system: primary components hippocampus https://www.britannica.com/science/limbic-system The limbic system => regulation of motivated behaviours (i.e., fighting, fleeing, feeding, and mating). 28  Limbic lobe/system: primary functions collection of nuclei involved in cingulate gyrus emotion and pain regulation refining motor output basal ganglia a sensory relay in visual, auditory, somatosensory, and gustatory thalamus systems; also, significant roles in motor activity, emotion, memory, arousal, and other sensorimotor association functions contains a control centre for many functions of the autonomic nervous system, and it has effects on the hypothalamus endocrine system memory formation hippocampus amygdala emotion (primarily fear learning) 29 The basal ganglia The caudate and putamen are collectively known as the striatum. Pinel & Barnes, (2021), p. 93 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3543080/ 30 The basal ganglia in 3D https://www.youtube.com/watch?v=JBuAFWKWxDQ 31 The cerebellum 32  The cerebellum accounts for only 10% of total brain volume but contains more than one-half of its neurons. Different regions of the cerebellum receive projections from distinct brain and spinal structures and then project back to the brain. The cerebellum is composed a series of highly regular, repeating units, each containing the same basic microcircuit. The similarity of the architecture and physiology in all regions of the cerebellum implies that different regions of the cerebellum perform similar computational operations on different inputs. 33 Functional organisation https://www.researchgate.net/publication/230554485_Cerebellar_Ataxia 34  Nonmotor Functions of the Cerebellum Ulmer et al. (2016), https://www.ajnr.org/content/37/6/1005 35 The cerebellum in 3D https://www.youtube.com/watch?v=mpO4lTDr1to&t=379s 36 Commissures 37 Corpus callosum medial view of the corpus callosum 3D rendering of the corpus callosum https://neuroanatomy.ca/interactive/CortexMedial.html Purves et al., (2018), Appendix https://neuroanatomy.ca/3D/3-4brainPG.html commissure corpus callosum a connecting band of nerve tissue in the CNS (callosal commissure) from Latin (“commissura”): "joint, juncture" a broad band of nerve fibres that connects the left and right hemispheres of the brain from Latin: "tough body" 38 Commissurotomy and “split-brain” https://www.nobelprize.org/prizes/medicine/1981/sperry/facts/ https://app.jove.com/v/10162/ testing-cognitive-abilities-split-brain-patients-using-visual 39 The ventricular system 40  There are four ventricles within the brain, all of which developed from the original hollow space (lumen) within the neural tube. The ventricles are lined by ependymal cells. In some places the ependymal cells form specialized clusters with blood vessels called choroid plexuses, which secrete cerebrospinal fluid (CSF) into the ventricles. Mtui et al., (2021), p. 3 41 The lateral ventricles are the largest Lateral ventricles (one within each cerebral hemisphere). Interventricular foramen CSF flows from the lateral ventricles through small openings (the interventricular Third ventricle foramina/ the foramina of Monro) into Cerebral aqueduct the third ventricle (a narrow midline space between the right and left diencephalon). Fourth ventricle Central aqueduct https://www.stepwards.com/?page_id=11243 The third ventricle is continuous caudally with the cerebral aqueduct (or aqueduct of Sylvius), which runs through the midbrain. At its caudal end, the aqueduct opens into the fourth ventricle, a larger space dorsal to the pons and medulla. The fourth ventricle, covered on its dorsal aspect by the cerebellum, narrows caudally to form the central canal of the spinal cord. 42 Localisation of ventricles https://www.youtube.com/watch?v=zqQ6iKw5DjY 43  Everything Everywhere All at Once … in 3D https://www.brainfacts.org/3D-Brain#intro=false&focus=Brain 44 Cerebral blood supply 45  The major artery carrying oxygenated blood away from the heart is the aorta  common carotid arteries  internal and external carotid arteries. The external carotid arteries supply blood to the tissues on the surface of the cranium. The internal carotid arteries enter the cranium through the carotid canal in the temporal bone. The bases of the common carotids contain baroreceptors (stretch receptors) Welch et al., (2019) https://onlinelibrary.wiley.com/doi/full/10.1002/ccd.28126 that immediately respond to the drop in blood pressure upon standing. 46  The Circle of Willis A second set of vessels that supply the CNS are the vertebral arteries. After they enter the cranium, they merge into the https://anatomytool.org/content/rcsi-drawing-circle-willis-english-labels anterior spinal artery supplying the anterior aspect of the spinal cord. 47 A 3D view of the Circle of Willis https://www.youtube.com/watch?v=9hhfM7rQHiM 48 3D rendering of the Circle of Willis 3D rendering of the brainstem plus the Circle of Willis https://tinyurl.com/53fwsfj4 https://tinyurl.com/dsxzajwr 49 Venous return After passing through the CNS, blood returns to the circulation through a series of dural sinuses and veins. The superior sagittal sinus absorbs CSF from the meninges. The superior sagittal sinus drains to the confluence of sinuses, along with the occipital sinuses and straight sinus, to then drain into the transverse sinuses. The transverse sinuses connect to the sigmoid sinuses, which then connect to the jugular veins. https://teachmeanatomy.info/neuroanatomy/vessels/dural-venous-sinuses/ From there, the blood continues toward the heart to be pumped to the lungs for reoxygenation. 50 The aftermath of a haemorrhagic stroke 51 The spinal cord 52 The vertebral column (and the spinal cord within it) is divided into cervical, thoracic, lumbar, sacral, and coccygeal regions. The peripheral nerves (spinal or segmental nerves) that innervate much of the body arise from the spinal cord’s 31 pairs of spinal nerves. On each side of the midline, the cervical region of the cord gives rise to 8 cervical nerves (C1–C8), the thoracic region to 12 thoracic nerves (T1–T12), the lumbar region to 5 lumbar nerves (L1–L5), the sacral region to 5 sacral nerves (S1–S5), and the coccygeal region to one coccygeal nerve. Purves et al. (2018), Appendix 53 Two regions of the spinal cord are enlarged to accommodate the greater number of nerve cells and connections needed to process information related to the upper and lower limbs. The spinal cord expansion that corresponds to the arms is called the cervical enlargement (segments C3–T1). The spinal cord expansion that corresponds to the legs is called the lumbosacral enlargement (segments L1–S2). Because the spinal cord is considerably shorter than the vertebral column in adults, lumbar and sacral nerves run for some distance in the vertebral canal before emerging, => collection of nerve roots known as the cauda equina (from Latin: “horse’s tail”). 54 The spinal cord in 3D https://www.youtube.com/watch?v=GlSGd3C5qZc&list=PLp9HSlEm97VXyQ32Uwjfz3dpmQ8nl63zJ&index=9 55 Peripheral nervous system 56 Peripheral nervous system (PNS) *afferent conducting signal inwards **efferent conducting signal outwards *arrive **exit interacts with the external environment; regulates the body’s internal environment; composed of afferent nerves that carry composed of afferent nerves that carry sensory signals from the skin, skeletal muscles, sensory signals from internal organs to the CNS, joints, eyes, ears, etc., to the CNS, and and efferent nerves that carry motor signals efferent nerves that carry motor signals from the CNS to internal organs. from the CNS to the skeletal muscles. 57 https://tinyurl.com/y49526vk 58  Cranial nerves The 12 cranial nerves are generally considered to be components of the PNS. However, the first and second cranial nerves (olfactory and optic, respectively) are considered to be extensions of the CNS, because they are myelinated by oligodendrocytes, whereas the 10 other cranial nerves are myelinated by Schwann cells. sense of smell Bonus question visual input innervation of four extrinsic eye muscles innervates the muscles of facial expression innervation one extrinsic eye muscles hearing and equilibrium sensory innervation to the face and motor innervation to the innervates the tongue and chewing muscles pharynx innervates organs in the innervates the muscle that abducts thorax and abdomen the eyeball (turns the eye laterally) head rotation innervates tongue muscles 59 Useful mnemonic: “On occasion, our trusty truck acts funny. Very good vehicle any how” On Funny CN I Olfactory CN VII Facial Occasion Very CN II Optic CN VIII Vestibulocochlear Our Good CN III Oculomotor CN IX Glossopharyngeal Trusty Vehicle CN IV Trochlear CN X Vagus Truck Any CN V Trigeminal CN XI Accessory Acts How CN VI Abducens CN XII Hypoglossal 60 Cranial nerves: overview Purves et al. (2018), Appendix 61 https://www.youtube.com/watch?v=i8OHZ8t6vg0&list=PLp9HSlEm97VXyQ32Uwjfz3dpmQ8nl63zJ&index=9 62 Additional resources curiouser and curiouser … 64 https://www.youtube.com/@EHSLDigitalPublishing/featured 65 A free Coursera course given by Duke university professor Leonard White https://www.coursera.org/learn/medical-neuroscience 66 A wonderful collection of resources and visualization tools for neuroscience and neuroanatomy, associated with the Coursera course (see previous slide) https://www.learnmedicalneuroscience.nl/ 67