22. Intro CNS and PNS 2023 AP Dr CNMT.pdf

Introduction to Central and Peripheral Nervous System AP. Dr. Che Norma Mat Taib [email protected] Department of Human Anatomy Faculty of Medicine and Health Sciences, UPM Organization of Nervous System Two Regional Div...

Introduction to Central and Peripheral Nervous System AP. Dr. Che Norma Mat Taib [email protected] Department of Human Anatomy Faculty of Medicine and Health Sciences, UPM Organization of Nervous System Two Regional Divisions: o Central nervous system (CNS) Brain and spinal cord Integration and command centre o Peripheral nervous system (PNS) Paired spinal nerves and cranial nerves Carries messages to and from spinal cord and brain 2 Two Functional Divisions: o Sensory/Afferent division – Sensory afferent fibres – carry impulses from skin, skeletal muscles and joints to brain – Visceral afferent fibres – transmit impulses from visceral organs to brain SAME o Motor/Efferent division – Transmits impulses from the CNS to effector organs (such as muscles + glands) Motor division: oSomatic nervous system Conscious control of skeletal muscles oAutonomic nervous system (ANS) Regulates smooth + cardiac muscles and glands 2 divisions: sympathetic and parasympathetic Spinal Cord o Cylindrical, 45 cm in length o Occupies the upper 2/3 of vertebral canal o Begins superiorly at the foramen magnum o Terminates inferiorly at level of o Adult: lower border of L1 vertebra or intervertebral disc between L1 & L2 o Young child – ends at upper border of L3 vertebra o Tapers to form a cone called CONUS MEDULLARIS o From tip of conus medullaris - FILUM TERMINALE extends caudally, and it attached to the 1st COCCYX 4 o 2 enlargements: External features at lower end of spinal cord 5 Three membranes surround/cover all of CNS 1) Dura mater/DM – thick outermost fibrous layer. - continuous above with meningeal layer 3) Pia mater of DM of brain. Inferiorly it extends to level of lower border of S2 vertebra 2) Arachnoid mater 2) Arachnoid mater/AM 1) Dura mater – delicate fibrous strands connect the arachnoid with pia mater 3) Pia mater/PM – vascular membrane that closely invests the spinal cord 6 Internal Structure of Spinal Cord o Grey mater (collection of cell bodies of neurons) - Anterior horn --- cell bodies of motor neurons - Posterior horn --- cell bodies of sensory neurons - Lateral horn --- cell bodies of sympathetic neurons found in the 1st thoracic to L2 or L3 segment of spinal cord o White mater (collection of nerve fibres/tracts/columns) - posterior/dorsal white column - anterior/ventral white column - lateral white column - anterior white commissure functions ascending tracts - sensory toward brain 7 descending tracts - motor from brain BLOOD SUPPLY OF SPINAL CORD o 2 Posterior spinal arteries (from vertebral artery or posterior inferior cerebellar artery/PICA) o 1 Anterior spinal artery (from vertebral artery). o Segmental/Radicular arteries – variable in number (from deep cervical, posterior intercostal, lumbar arteries). It anastomose with anterior & posterior spinal arteries. Arteria radicular magna (Adamkiewicz)? 8 Ventricles of Brain o Arise from expansion of lumen of neural tube o Ventricles are: Paired C-shaped lateral ventricles Third ventricle found in diencephalon Fourth ventricle found in hindbrain, dorsal to pons 9 Cerebro-Spinal Fluid (CSF) oFormation in ventricles by specialised ependymal cells of choroid plexuses (~500 mL/day) oFunctions transport medium shock absorption buoyancy (floats the brain) 10 CSF Circulation Lateral ventricles foramen of Monro Third ventricle Sylvius aqueduct Fourth ventricle median aperture (of Magendie) & lateral apertures (of Luschka) Subarachnoid space over brain & spinal cord Reabsorption into venous sinus blood via arachnoid granulations/villi into superior sagittal sinus. 11 Cerebral Hemispheres o Form superior part of brain and make up 83% of its mass o Contain ridges/gyri and shallow grooves/sulci o Contain deep grooves called fissures o Are separated by longitudinal fissure o Have three basic regions: cortex, white mater and basal nuclei Grey mater White mater 12 Major Lobes, Gyri and Sulci of Cerebral Hemisphere cerebral o Deep sulci divide hemispheres into five lobes: hemisphere – Frontal, parietal, temporal, occipital and insula o Central sulcus – separates frontal and parietal lobes cerebellum o Parietal-occipital sulcus brainstem – separates parietal and occipital lobes o Lateral sulcus – separates parietal and temporal lobes o Precentral and postcentral gyri border the central sulcus 13 Cerebral Cortex o Cortex – superficial grey mater; accounts for roughly 40% of mass of brain o It enables sensation, communication, memory, understanding and voluntary movements o Each hemisphere acts contralaterally (controls the opposite side of body) o Hemispheres are not equal in function o No functional area acts alone; conscious behaviour involves the entire cortex 14  Brain Hemisphere and their functions See if you can tell what hemisphere is being used in each task! 1) Drawing a picture of an imaginary castle. 2) Doing your math homework. 3) Daydreaming when you should be studying! 15 Functional Areas of Cerebral Cortex o Three types of functional areas are: Motor areas – control voluntary movement Sensory areas – conscious awareness of sensation Association areas – integrate diverse information 16 17 It may be difficult to differentiate Broca's area from Wernicke's area as they both have to do with speech, but there are a few differences which you can focus on remembering in order to help you better understand the two. Broca's area, is located in frontal lobe. It is the motor speech area. It helps in movements required to produce speech. When there is an issue in this area, a patient can understand the speech of others, but can't produce any speech him or herself → Broca's aphasia. Wernicke's area, is located in parietal and temporal lobes, is the sensory area. It helps in understanding speech & using correct words to express our thoughts. When there is an issue in this area, a patient may be able to produce speech, but cannot understand the speech of others → Wernicke's aphasia. 18 Cerebral White Mater o Consists of deep myelinated fibres and their tracts o It is responsible for communication between: cerebral cortex and lower CNS centre, and areas of the cerebrum o Types include: Frontal plane/section Commissural fibres – connect corresponding grey areas of the two hemispheres Association fibres – connect different parts of the same hemisphere Projection fibres – enter the hemispheres from lower brain or cord centres 19 Commissural Fibres Habenular nuclei - located anterior to pineal gland, 20 emotional response to odor Basal Ganglia (BG)/Basal Nuclei o Masses of grey mater found deep within cortical white mater o Corpus striatum is composed of three parts: Caudate nucleus Lentiform nucleus – composed of putamen & globus pallidus * Fibres of internal capsule running between and through caudate & lentiform nuclei 21 o Functions of Basal ganglia Influence muscular activity Regulate attention and cognition Regulate intensity of slow or stereotyped movements Inhibit antagonistic and unnecessary movement Frontal plane/section Transverse plane/section Diencephalon oCentral core of forebrain oConsists of three paired structures – thalamus, hypothalamus and epithalamus oEncloses the third ventricle 23 Thalamus oPaired, egg-shaped masses that form the superolateral walls of third ventricle oConnected at the midline by the intermediate mass oContains many nuclei: oNuclei project and receive fibres from the cerebral cortex 24 Thalamic Function oAfferent impulses from all senses converge and synapse in the thalamus oImpulses of similar function are sorted out, edited and relayed as a group oAll inputs ascending to the cerebral cortex pass through the thalamus oPlays a key role in mediating sensation, motor activities, cortical arousal, learning and memory 25 Hypothalamus o Is located below thalamus, it caps brainstem and forms the inferolateral walls of third ventricle o Mammillary bodies Small, paired nuclei bulging anteriorly from the hypothalamus Relay station for olfactory pathways o Infundibulum – stalk of the hypothalamus; connects to the pituitary gland o Main visceral control centre of the body 26 Hypothalamic Function oRegulates blood pressure, rate and force of heartbeat, digestive tract motility, rate and depth of breathing and many other visceral activities oIs involved with perception of pleasure, fear and rage oControls body temperature oRegulates feelings of hunger and satiety oRegulates sleep and the sleep cycle oEndocrine functions 27 Epithalamus oMost dorsal portion of diencephalon; forms roof of third ventricle oPineal gland – extends from the posterior border and secretes melatonin ❖ Melatonin – a hormone involved with sleep regulation, sleep-wake cycles and mood 28 Brainstem contains nuclei from which cranial nerves arises. Vital centres also lie in the brainstem (you will learn in detail in physiology). IV Cerebellum o Is located dorsal to pons and medulla o Protrudes under occipital lobes of cerebrum o Makes up 11% of brain’s mass o Provides precise timing and appropriate patterns of skeletal muscle contraction o Cerebellar activity occurs subconsciously oTwo bilaterally symmetrical hemispheres connected medially by vermis oFolia = transversely oriented gyri oEach hemisphere has three lobes: anterior, posterior and flocculonodular 32 o Neural arrangement – grey mater cortex, internal white mater, scattered nuclei * Arbor vitae – distinctive treelike pattern of the cerebellar white mater oThree paired fibre tracts that connect the cerebellum to the brain stem oAll fibres in the cerebellum are ipsilateral oSuperior peduncles connect midbrain to cerebellum oMiddle peduncles connect pons to cerebellum oInferior peduncles connect medulla to cerebellum 33  CIRCLE OF WILLIS (Circulous Arteriosus) o Arteries in the base of brain are interconnected to form an arterial circle – Circle of Willis o This anastomosis helps in equalising the pressure in blood vessels of the two sides before supplying the brain. o Location: present in the interpeduncular fossa, within interpeduncular cistern. 34  CIRCLE OF WILLIS o Formation: Five arteries join in the base of brain to form the Circle of Willis:- 1. Anterior communicating artery (single) 2. Anterior cerebral arteries (paired) 3. Internal carotid arteries (paired) 4. Posterior communicating arteries (paired) 5. Posterior cerebral arteries (paired) o Branches : Two sets of branches arise from the circle – Cortical and Central branches. They supply the brain substance. 35 Peripheral nervous system (PNS) o is located outside the CNS and consist of nerves and receptors. Cranial nerves, spinal nerves and their associated ganglion PNS carries impulses from receptors such as pain and sound to CNS and it carries impulses from CNS to effectors, glands and muscles that carry out actions directed by the CNS PNS is subdivided into - sensory-somatic nervous system and - autonomic nervous system Sensory-Somatic Nervous System consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves.  Distribution of Spinal Nerves Cervical plexus Cervical nerves Brachial plexus C1– C8 Cervical enlargement Intercostal Thoracic nerves nerves T1– T12 Lumbar enlargement Lumbar plexus Lumbar nerves L1– L5 Sacral plexus Sacral nerves S1– S5 Cauda equina Coccygeal nerve C0 Human Anatomy and Physiology, 7e Copyright © 2007 Pearson Education, Inc., by Elaine Marieb & Katja Hoehn publishing as Benjamin Cummings. Thoracic spinal segment & spinal nerve Spinal nerves - 31 pairs come from spinal cord: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral& 1 coccygeal. A pair of spinal nerve come from a spinal segment. Each spinal nerve contains dorsal root (sensory) fibres and ventral root (motor) fibres. Dorsal root has a dorsal root ganglion (DTG) which convey impulses to CNS. Ventral root send motor fibres to the skeletal muscles. Dorsal and ventral roots unites at vertebral foramen to form the spinal nerve. Dorsal root Dorsal root contains sensory fibres and Ventral root contains motor fibres. Ventral root o Each spinal nerve divide into posterior and anterior rami. o Anterior and posterior rami contain both sensory and motor fibres. o Anterior rami are larger than posterior rami. o They form cervical, brachial, lumbar and sacral plexuses. o In thoracic region they remain segmental, as intercostal nerves dividing into * lateral cutaneous branches (sensory) and * mixed anterior branches. o Posterior rami consist of * medial branches (sensory) and * lateral branches (motor). Cervical plexus Key: = Ventral rami Segmental branches Hypoglossal nerve (XII) Lesser occipital nerve Ventral rami: C1 Greater auricular nerve C2 Transverse cutaneous nerve C3 Ansa cervicalis C4 Accessory nerve (XI) Phrenic nerve C5 Supraclavicular nerves  Brachial plexus Human Anatomy and Physiology, 7e Copyright © 2007 Pearson Education, Inc., by Elaine Marieb & Katja Hoehn publishing as Benjamin Cummings.  Lumbar plexus Ventral rami: L1 Iliohypogastric Ilioinguinal L2 Iliohypogastric (L1) Femoral Ilioinguinal (L1) Lateral femoral L3 cutaneous Genitofemoral (L1,2) Obturator Lateral femoral cutaneous Anterior L4 femoral of thigh (L2,3) cutaneous Saphenous Obturator (L2,3,4) L5 Femoral (L2,3,4) Lumbosacral trunk (L4,5) (a) Key: = Ventral rami (b) Human Anatomy and Physiology, 7e Copyright © 2007 Pearson Education, Inc., by Elaine Marieb & Katja Hoehn publishing as Benjamin Cummings.  Sacral plexus Ventral rami: L4 Superior Superior gluteal gluteal L5 Inferior Lumbosacral gluteal trunk Pudendal S1 Inferior Sciatic gluteal Posterior Common S2 femoral fibular cutaneous Tibial Common S3 fibular Posterior femoral Tibial cutaneous S4 Sural Pudendal Deep S5 fibular Sciatic C0 Superficial fibular (a) Key: Plantar branches = Ventral rami (b) Human Anatomy and Physiology, 7e Copyright © 2007 Pearson Education, Inc., by Elaine Marieb & Katja Hoehn publishing as Benjamin Cummings. Rami communicantes join the spinal nerve to the sympathetic trunk.  Spinal Reflexes o Reflexes are automatic responses to stimuli o Spinal reflexes result from the stimulation of a spinal reflex arc. o Basic elements of a reflex arc o Receptor o Afferent pathway (sensory) o Synapse in spinal cord (integrating center) o Efferent pathway (motor) o Response (effector) Human Anatomy, 3rd edition Prentice Hall, © 2001 CRANIAL NERVES Olfactory N (CN I) Oculomotor N (CN III) Optic N (CN II) Trochlear N (CN IV) Trigeminal N (CN V) Abducens N (CN VI) Facial N (CN VII) Vestibulocochlear N (CN VIII) Glossopharyngeal N (CN IX) Hypoglossal N (CN XII) Vagus N (CN X) Accessory N (CN XI) 48 N = Nerve  Pure sensory (S) = 1, 2, 8 Pure motor (M) = 3, 4, 6, 11, 12 Both (S + M) = 5, 7, 9, 10 Parasymp. = 3, 7, 9, 10 * Has parasympathetic fibers Dermatomes is area of skin supplied by a spinal nerve. There are eight cervical nerves (C1 being an exception with no dermatome), twelve thoracic nerves, five lumbar nerves and five sacral nerves. Dermatomes are used: To test skin sensation + to localise the level of a lesion of spinal nerves. Also used to localise the level of a nerve lesion within the spinal cord. Local anaesthesia can be used to numb/anaesthetise a specific dermatome.