Central Nervous System PDF

Central Nervous System By: Dr. Pamela Paynter-Armour 1 Objectives  Outline the development of the Central Nervous System (CNS)  List the functions of the brain  Discuss surface anatomy of the brain  Describe the regions of the Brain  Describe the protection of the CNS  Discuss the anatomy and...

Central Nervous System By: Dr. Pamela Paynter-Armour 1 Objectives  Outline the development of the Central Nervous System (CNS)  List the functions of the brain  Discuss surface anatomy of the brain  Describe the regions of the Brain  Describe the protection of the CNS  Discuss the anatomy and physiology of the Spinal Cord 2 Introduction The central nervous system (CNS) consists of the brain and spinal cord. The brainstem connects the brain to the spinal cord. 3. 3 What do you know about the brain? Central Nervous System (CNS) CNS develops from the ectoderm surface to produce the embryonic neural tube The neural tube becomes the brain and spinal cord The opening of the neural tube becomes the ventricles Four chambers within the brain Filled with cerebrospinal fluid 2 Brain Overview of the brain: Interprets sensations Determines perception Stores memory Reasoning 3. Functions Makes decisions Coordinates muscular movements Regulates visceral activities Determines personality 6 Surface anatomy  Gyri (sing gyrus)  Elevated ridges  Entire surface  Grooves separate gyri  Sulci are shallow grooves (sing sulcus)  Deeper grooves are fissures 1. Surface anatomy 1. Surface anatomy Cont’d Fissures Longitudinal: separates the cerebral hemispheres Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Parietal lobe Gyrus Sulcus Frontal lobe Transverse: separates cerebrum from cerebellum Lateral sulcus Occipital lobe Transverse fissure Cerebellar hemisphere Temporal lobe (a) Central sulcus Parietal lobe Corpus callosum Connects cerebral hemispheres Central sulcus Longitudinal fissure Parietal lobe Occipital lobe (b) Occipital lobe Frontal lobe Insula Retracted temporal lobe (c) 3. 9 Regions of the Brain Cerebral hemispheres Diencephalon Brain stem Cerebellum 2 Parts of the brain…the cerebrum Taking up 7/8ths of the brain’s weight, the cerebrum governs all sensory and motor activity. This includes sensory perception, emotions, consciousness, memory, and voluntary movements. It is divided into the left and right hemispheres. 4 Lobes of the Cerebrum Lobes: under bones of same name Five (5) lobes bilaterally: Frontal lobe Parietal lobe Temporal lobe Occipital lobe Plus: Insula (buried deep in lateral sulcus) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Parietal lobe Occipital lobe Frontal lobe Insula Retracted temporal lobe (c) 3. 12 Cerebral hemispheres Divided by longitudinal fissure into right & left sides  Central sulcus divides frontal from parietal lobes  1. Lateral sulcus separates temporal lobe from frontal and parietal lobe  Parieto-occipital sulcus divides occipital and parietal lobes (not seen from outside)  Transverse cerebral fissure separates cerebral hemispheres from cerebellum  1. Cerebral cortex  Executive functioning capability  Gray matter: neuron cell bodies, dendrites, associated glia, blood vessels and short unmyelinated axons  100 billion neurons with average of 10,000 contacts each  No fiber tracts (would be white)  2-4 mm thick (about 1/8 inch)  Brodmann areas (historical: 52 structurally different areas given) 1. Cerebral cortex  All the neurons are interneurons  By definition confined to the CNS  They have to synapse somewhere before the info passes to the peripheral nerves  Three kinds of functional areas  Motor areas: movement  Sensory areas: perception  Association areas: integrate diverse information to enable purposeful action 1. Motor Areas (pre-central sulcus) Primary motor areas Frontal lobes Control voluntary muscles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Motor areas involved with the control of voluntary muscles Sensory areas involved with cutaneous and other senses Concentration, planning, problem solving Broca’s area Anterior to primary motor cortex Usually in left hemisphere Controls muscles needed for speech Frontal eye field Above Broca’s area Controls voluntary movements of eyes and eyelids Frontal eye field Parietal lobe Auditory area Sensory speech area ( Wernicke’s area) Front lobe Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition of objects Lateral sulcus Visual area Interpretation of auditory patterns Cerebellum Temporal lobe Brainstem 3. 17 Sensory Areas (post-central sulcus) Cutaneous sensory area Sensory area for taste Parietal lobe Interprets sensations on skin Visual area Occipital lobe Interprets vision Near base of the central sulcus Sensory area for smell Arises from centers deep within the cerebrum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Motor areas involved with the control of voluntary muscles Sensory areas involved with cutaneous and other senses Concentration, planning, problem solving Frontal eye field Parietal lobe Auditory area Auditory area Temporal lobe Interprets hearing Sensory speech area ( Wernicke’s area) Front lobe Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition of objects Lateral sulcus Visual area Interpretation of auditory patterns Cerebellum Temporal lobe Brainstem 3. 18 Association Areas Regions that are not primary motor or primary sensory areas Widespread throughout the cerebral cortex Analyze and interpret sensory experiences Provide memory, reasoning, verbalization, judgment, emotions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Motor areas involved with the control of voluntary muscles Sensory areas involved with cutaneous and other senses Concentration, planning, problem solving Frontal eye field Parietal lobe Auditory area Sensory speech area ( Wernicke’s area) Front lobe Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition of objects Lateral sulcus Visual area Interpretation of auditory patterns Cerebellum Temporal lobe Brainstem 3. 19 Association Areas Frontal lobe association areas Temporal lobe association Concentrating areas Planning Interpret complex sensory Complex problem solving experiences Store memories of visual scenes, music, and complex patterns Parietal lobe association Occipital lobe association areas Understanding speech Choosing words to express thought areas Analyze and combine visual images with other sensory experiences 3. 20 Functions of the Cerebrum Interpreting impulses Initiating voluntary movements Storing information as memory Retrieving stored information Reasoning Seat of intelligence and personality 3. 21 The Cerebrum The cortex is also divided into 4 lobes that correspond to the overlying bones of the skull: the frontal lobe specializes in motor activity, personality, and speech; the parietal lobe is where language, temperature, pressure, touch are interpreted; the temporal lobe contains centers for hearing, smell, and language input; the occipital lobe specializes in vision. 4 Functions of the Cerebral Lobes 3. 23 Homunculus – “little man”  Body map: human body spatially represented  Where on cortex; upside down 1. Hemisphere Dominance The left hemisphere is dominant in most individuals Dominant hemisphere controls: Speech Writing Reading Verbal skills Analytical skills Computational skills Nondominant hemisphere controls: Nonverbal tasks Motor tasks Understanding and interpreting musical and visual patterns Provides emotional and intuitive thought processes 3. 25 Diencephalon Sits on top of the brain stem Made of three parts Thalamus Enclosed by the cerebral hemispheres Hypothalamus Epithalamus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 2 Slide Diencephalon Cont’d Thalamus Gateway for sensory impulses heading to cerebral cortex Sensory relay station Receives all sensory impulses (except smell) Channels impulses to appropriate part of cerebral cortex for interpretation 3. 27 Diencephalon Cont’d Hypothalamus Maintains homeostasis by regulating visceral activities (such as HR, BP, temperature, H2O & electrolyte balance, hunger, thirst, sleep & wakefulness) Links nervous and endocrine systems (hence some say the neuroendocrine system 3. 28 Diencephalon Cont’d Epithalamus Forms the roof of the third ventricle Houses the pineal body (an endocrine gland) produces melatonin signaling nighttime sleep Includes the choroid plexus – forms cerebrospinal fluid 2 29 Brainstem Three parts: 1. Midbrain Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hypothalamus Diencephalon Thalamus Corpus callosum 2. Pons 3. Medulla Oblongata Corpora quadrigemina Midbrain Cerebral aqueduct Pons Reticular formation Medulla oblongata Spinal cord 3. 30 Midbrain Between diencephalon and pons Contains bundles of fibers that join lower parts of brainstem and spinal cord with higher part of brain Cerebral aqueduct Cerebral peduncles (bundles of nerve fibers) Corpora quadrigemina (centers for visual and auditory reflexes) Superior colliculus Corpora quadrigemina Optic nerve Inferior colliculus Optic chiasma Pituitary gland Thalamus Mammillary body Third ventricle Optic tract Pons Cerebral peduncles Pineal gland Fourth ventricle Pyramidal tract Olive Cerebellar peduncles Medulla oblongata Spinal cord (a) (b) 3. 31 Pons Rounded bulge on underside of brainstem Between medulla oblongata and midbrain Superior colliculus Corpora quadrigemina Optic nerve Inferior colliculus Optic chiasma Pituitary gland Thalamus Mammillary body Third ventricle Optic tract Helps regulate rate and depth of breathing Pons Cerebral peduncles Pineal gland Fourth ventricle Pyramidal tract Olive Cerebellar peduncles Relays nerve impulses – longitudinally & ventrally Medulla oblongata Spinal cord (a) (b) 3. 32 Medulla Oblongata Enlarged continuation of spinal cord Conducts ascending and descending impulses between brain and spinal cord Contains cardiac, vasomotor, and respiratory control centers Contains various nonvital reflex control centers (coughing, sneezing, swallowing, and vomiting) Superior colliculus Corpora quadrigemina Optic nerve Inferior colliculus Optic chiasma Pituitary gland Thalamus Mammillary body Third ventricle Optic tract Pons Cerebral peduncles Pineal gland Fourth ventricle Pyramidal tract Olive Cerebellar peduncles Medulla oblongata Spinal cord (a) (b) 3. 33 The Cerebellum The cerebellum is the second largest part of the brain. It contains nerve fibers that connect it to every part of the central nervous system. It coordinates voluntary and involuntary patterns of movements. It also adjusts muscles to automatically maintain posture. 4 The Cerebellum Cerebellum Inferior to occipital lobes Posterior to pons and medulla oblongata Two hemispheres Vermis connects hemispheres Cerebellar cortex (gray matter) Arbor vitae (white matter) Cerebellar peduncles (nerve fiber tracts) Integrates sensory information concerning position of body parts Coordinates skeletal muscle activity Longitudinal fissure Corpus callosum Thalamus Superior peduncle Cerebellum Pons Middle peduncle Inferior peduncle Medulla oblongata 3. 36 Functions of cerebellum       Smooths, coordinates & fine tunes bodily movements Helps maintain body posture Helps maintain equilibrium How?  Gets info from cerebrum re: movements being planned  Gets info from inner ear re: equilibrium  Gets info from proprioceptors (sensory receptors informing where the parts of the body actually are)  Using feedback, adjustments are made Also some role in cognition Damage: ataxia, incoordination, wide-based gait, overshooting, proprioception problems 1. Major Parts of the Brain 3. 38 Internal Brain Structure This MRI of a normal brain reveals the different regions of the brain, each of which has specific functions. Such detailed images allow physicians to visualize diseases, effects of injuries and abnormalities in the brain. Functional Brain Systems Networks of distant neurons that function together Limbic system Reticular formation 1. The Limbic System Functions: Consists of: Portions of frontal lobe Portions of temporal lobe Hypothalamus Thalamus Basal nuclei (motor control) Other deep nuclei Controls emotional experiences & produces feelings like rage, anger, pleasure Survival behavior Interprets sensory impulses associated with smell 3. 41 Limbic System Cont’d Called the “emotional” brain Is essential for flexible, stable, adaptive functioning  Links different areas so integration can occur    Integration: separate things are brought together as a whole  Processes emotions and allocates attentional resources  Necessary for emotional balance, adaptation to environmental demands (including fearful situations, etc.), for creating meaningful connections with others (e.g. ability to interpret facial expressions and respond appropriately), and more… 1. Reticular formation Runs through central core of medulla, pons and midbrain Reticular activating system (RAS): keeps the cerebral cortex alert and conscious  Some motor control  1. Lifespan Changes Brain cells begin to die before birth Over average lifetime, brain shrinks 10% Most cell death occurs in temporal lobes By age 90, frontal cortex has lost half its neurons Number of dendritic branches decreases Decreased levels of neurotransmitters Fading memory Slowed responses and reflexes Increased risk of falling Changes in sleep patterns that result in fewer sleeping hours 3. 44 Protection of the Central Nervous System Scalp and skin Skull and vertebral column Meninges 2 Protection of the Central Nervous System Cerebrospinal fluid Blood brain barrier 2 Meninges Functions  Cover and Protect CNS  Protect blood vessels  Contains CSF  Forms partitions in the skull 3. 47 Meninges Dura mater: 2 layers of fibrous connective tissue, fused except for dural sinuses 1.   2. 3. Periosteal layer attached to bone Meningeal layer - proper brain covering Arachnoid mater Pia mater 1. Dura mater - dural partitions Subdivide cranial cavity & limit movement of brain  Falx cerebri  In longitudinal fissure  Falx cerebelli  Runs vertically along vermis of cerebellum  Tentorium cerebelli  Sheet in transverse fissure between cerebrum & cerebellum 1.  Arachnoid mater  Between dura and arachnoid: subdural space  Dura and arachnoid cover brain loosely  Deep to arachnoid is subarachnoid space ○ Filled with CSF ○ Lots of vessels run through (susceptible to tearing)  Superiorly, forms arachnoid villi: CSF valves  Pia mater  Delicate, clings to brain following convolutions 1. Ventricles  Central  Filled cavities expanded with CSF (cerebrospinal fluid)  Lined by ependymal cells (these cells lining the choroid plexus make the CSF)  Continuous with each other and central canal of spinal cord 1. Lateral ventricles  Paired, horseshoe shape  In cerebral hemispheres  Anterior are close, separated only by thin Septum pellucidum 1. Third ventricle  In diencephalon  Connections ○ Interventricular foramen ○ Cerebral aqueduct 1. Fourth ventricle  In the brainstem  Dorsal to pons and top of medulla  Holes (aperture) connect it with subarachnoid space 1. Ventricles and Location of the Cerebrospinal Fluid 2 Cerebrospinal Fluid A colorless fluid is produced in the ventricles of the brain; it surrounds the brain and spinal cord. It is called cerebrospinal fluid, and it cushions the brain and cord from shocks that could cause injury. It is maintained at a level around 1/2 - 2/3 cup. 4 Cerebrospinal Fluid  Secreted by the choroid plexuses (roofs of ventricles)  Filtration of plasma from capillaries through ependymal cells (electrolytes, glucose) Circulates in ventricles, central canal of spinal cord, and the subarachnoid space Completely surrounds the brain and spinal cord  Excess or wasted CSF is absorbed by the arachnoid villi  Clear fluid similar to blood plasma  100-160 ml  Nutritive and protective (Cushions)  Helps maintain stable ion concentrations in the CNS  3. 57 3. 58 Hydrocephalus 1. Blood-Brain Barrier Tight junctions between endothelial cells of brain capillaries, instead of the usual permeability  Includes the least permeable capillaries of the body  Highly selective transport mechanismsExcludes many potentially harmful substances  Allows nutrients, O2, CO2  Not a barrier against uncharged and lipid soluble molecules; allows alcohol, nicotine, and some drugs including anesthetics 1.  Types of Sleep Slow wave Rapid Eye Movement Non-REM sleep (REM) Person is tired Paradoxical sleep Decreasing activity of Some areas of brain reticular system active Restful Heart and respiratory Dreamless rates irregular Reduced blood Dreaming occurs 3. pressure and respiratory rate Ranges from light to heavy 61 Memory Short term memory Working memory Closed neuronal circuit Circuit is stimulated over and over When impulse flow ceases, memory does also unless it enters long-term memory via memory consolidation Long term memory Changes structure or function of neurons Enhances synaptic transmission3. 62 Traumatic Brain Injuries (TBI) Concussion Slight or mild brain injury Bleeding & tearing of nerve fibers happened Recovery likely with some memory loss Contusion A more severe TBI Nervous tissue destruction occurs Nervous tissue does not regenerate Cerebral edema Swelling from the inflammatory response May compress and kill brain tissue 2 Cerebrovascular Accident (CVA) Commonly called a stroke The result of a ruptured blood vessel supplying a region of the brain Brain tissue supplied with oxygen from that blood source dies Loss of some functions or death may result 2 Alzheimer’s Disease Progressive degenerative brain disease Mostly seen in the elderly, but may begin in middle age Structural changes in the brain include abnormal protein deposits and twisted fibers within neurons Victims experience memory loss, irritability, confusion and ultimately, hallucinations and death 2 Spinal Cord 66 Spinal Cord Extends downward through vertebral canal Begins at the foramen magnum and terminates at the first and second lumbar vertebrae (L1/L2) interspace Below is the cauda equina (a collection of spinal nerves) Enlargements occur in the cervical and lumbar regions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Brainstem Foramen magnum Cervical enlargement Cervical enlargement Spinal cord Vertebral canal Lumbar enlargement Lumbar enlargement Conus medullaris Cauda equina Conus medullaris Filum terminale (a) 3. (b) 67 Spinal Cord Anatomy Exterior white mater – conduction tracts 2 Spinal Cord Anatomy Internal gray matter - mostly cell bodies Dorsal (posterior) horns Anterior (ventral) horns 2 Spinal Cord Anatomy Central canal filled with cerebrospinal fluid 2 Spinal Cord Anatomy Meninges cover the spinal cord Nerves leave at the level of each vertebrae Dorsal root Associated with the dorsal root ganglia – collections of cell bodies outside the central nervous system Ventral root 2 Functions of Spinal Cord Conduit for nerve impulses to and from the brain and brainstem Center for spinal reflexes 3. 72 Tracts of the Spinal Cord Ascending tracts conduct sensory impulses to the brain Descending tracts conduct motor impulses from the brain to motor neurons reaching muscles and glands Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dorsal column Fasciculus gracilis Fasciculus cuneatus Posterior spinocerebellar tract Lateral corticospinal tract Lateral reticulospinal tract Rubrospinal tract Anterior spinocerebellar tract Anterolateral system Lateral spinothalamic tract Anterior spinothalamic tract Anterior reticulospinal tract Medial reticulospinal tract 3. Anterior corticospinal tract 73 References 1. Los Angeles Valley College. (n.d.). Central Nervous System: “CNS”. Retrieved from http://www.lavc.edu/instructor/watson_k/do cs/Lecture%2013%20%20Central%20Nervous%20System.ppt 74 References Cont’d 2. Marieb, E. (2003). The Nervous System. Retrieved from http://www.haspi.org/curriculum-library/AP-CoreLabs/12%20Nervous%20System/Powerpo int%20Presentations/Nervous%20System %201.ppt 75 References Cont’d 3. Shier, D., Butler, J. & Lewis, R. (2009). Nervous System II. Retrieved from http://nhscience.lonestar.edu/biol/durham/ docs/biol2401/chapt11_holes_lecture.ppt 4. Nebraska Department of Education. (2017). Retrieved from: https://www.education.ne.gov/wpcontent/uploads/2017/07/179-AnatomyNervous-System.ppt 3. 76