BIOL 111: Central Nervous System PDF

BIOL 111: Central Nervous System Instructor: Dr. Pamela Paynter- (Shier, Butler & Lewis, 2009). 1  Objectives  Outline the development of the Central Nervous System (CNS)  List the functions of the brain  Discuss surface anatomy of the...

BIOL 111: Central Nervous System Instructor: Dr. Pamela Paynter- (Shier, Butler & Lewis, 2009). 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. (Shier, Butler & Lewis, 2009). 3  What do you know about the brain?  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. (Nebraska Department of Education, 2017). 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 (Marieb, 2003)  Brain Overview Functions of the brain: Makes decisions Interprets sensations Coordinates muscular Determines perception movements Regulates Stores memory visceral activities Determines Reasoning (Shier, Butler & Lewis, 2009). personality 7  Surface anatomy  Gyri (sing gyrus) Elevated ridges Entire surface  Grooves separate gyri Sulci are shallow grooves (sing sulcus) Deeper grooves are fissures (Los Angeles Valley College, n.d.). Surface anatomy (Los Angeles Valley College, n.d.).  Surface anatomy Cont’d Fissures Longitudinal: separates the cerebral Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Parietal lobe hemispheres Gyrus Sulcus Frontal lobe Transverse: separates Lateral sulcus Occipital lobe Temporal lobe Transverse cerebrum from (a) fissure Cerebellar hemisphere cerebellum Central sulcus Parietal lobe Corpus callosum Central sulcus Connects cerebral Longitudinal fissure Frontal lobe Occipital lobe Parietal lobe Insula hemispheres Occipital lobe Retracted temporal lobe (b) (c) 10 (Shier, Butler & Lewis, 2009). Regions of the Brain  Cerebral hemispheres  Diencephalon  Brain stem  Cerebellum (Marieb, 2003) Lobes of the Cerebrum Lobes: under bones of same name Five (5) lobes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus bilaterally: Parietal lobe Frontal lobe Parietal lobe Temporal lobe Occipital lobe Occipital lobe Frontal lobe Insula Plus: Insula Retracted temporal lobe (buried deep in (c) lateral sulcus) (Shier, Butler & Lewis, 2009). 12  Cerebral hemispheres  Divided by longitudinal fissure into right & left sides  Central sulcus divides frontal from parietal lobes (Los Angeles Valley College, n.d.).  Lateral sulcus separates temporal lobe from parietal lobe  Parieto-occipital sulcus divides occipital and parietal lobes (not seen from outside)  Transverse cerebral fissure separates cerebral hemispheres from cerebellum (Los Angeles Valley College, n.d.). 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) (Los Angeles Valley College, n.d.). 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 (Los Angeles Valley College, n.d.). Motor Areas (pre-central sulcus) Primary motor areas Frontal lobes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central sulcus Control voluntary muscles Motor areas involved with the control Sensory areas involved with of voluntary muscles cutaneous and other senses Concentration, planning, problem solving Broca’s area Frontal eye field Auditory area Parietal lobe Sensory speech area Anterior to primary motor Front lobe ( Wernicke’s area) Occipital lobe cortex Motor speech area (Broca’s area) Combining visual images, Usually in left hemisphere visual recognition Lateral sulcus of objects Visual area Interpretation of auditory patterns Controls muscles needed Cerebellum for speech Temporal lobe Brainstem Frontal eye field (Shier, Butler & Lewis, 2009). Above Broca’s area Controls voluntary movements of eyes and eyelids 17 Sensory Areas (post-central sulcus) Cutaneous sensory area Sensory area for taste Parietal lobe Near base of the central Interprets sensations on sulcus - Insula skin Sensory area for smell Arises from centers deep Visual area within the cerebrum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Occipital lobe Central sulcus Motor areas involved with the control Sensory areas involved with of voluntary muscles Interprets vision cutaneous and other senses Concentration, planning, problem solving Frontal eye field Parietal lobe Auditory area Auditory area Front lobe Sensory speech area ( Wernicke’s area) Temporal lobe Occipital lobe Motor speech area (Broca’s area) Combining Interprets hearing Lateral sulcus visual images, visual recognition of objects Visual area Interpretation of auditory patterns Cerebellum Temporal lobe Brainstem 18 (Shier, Butler & Lewis, 2009).  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 Sensory areas involved with of voluntary muscles cutaneous and other senses Concentration, planning, problem solving Frontal eye field Parietal lobe Auditory area Sensory speech area Front lobe ( Wernicke’s area) Occipital lobe Motor speech area (Broca’s area) Combining visual images, visual recognition Lateral sulcus of objects Visual area Interpretation of auditory patterns Cerebellum Temporal lobe Brainstem (Shier, Butler & Lewis, 2009). 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 areas Understanding speech Analyze and combine Choosing words to visual images with other express thought sensory experiences (Shier, Butler & Lewis, 2009). 20 Functions of the Cerebrum Interpreting impulses Initiating voluntary movements Storing information as memory Retrieving stored information Reasoning Seat of intelligence and personality (Shier, Butler & Lewis, 2009). 21 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. (Nebraska Department of Education, 2017). Functions of the Cerebral Lobes (Shier, Butler & Lewis, 2009). 23 Homunculus – “little man”  Body map: human body spatially represented Where on cortex; upside down (Los Angeles Valley College, n.d.). Hemisphere Dominance The left hemisphere is dominant in most individuals Dominant hemisphere Nondominant hemisphere controls: controls: Speech Nonverbal tasks Writing Motor tasks Reading Understanding and Verbal skills interpreting musical and Analytical skills visual patterns Computational skills Provides emotional and intuitive thought processes (Shier, Butler & Lewis, 2009). 25 Diencephalon  Made of three parts  Sits on top of the brain stem  Thalamus  Enclosed by the  Hypothalamus cerebral  Epithalamus hemispheres Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 7.34a (Marieb, 2003)  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 (Shier, Butler & Lewis, 2009). 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 (Shier, Butler & Lewis, 2009). 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 (Marieb, 2003) 29  Brainstem Three parts: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hypothalamus 1. Midbrain Diencephalon Thalamus Corpus Pons callosum 2. Medulla Corpora 3. quadrigemina Oblongata Midbrain Cerebral aqueduct Pons Reticular formation Medulla oblongata Spinal cord (Shier, Butler & Lewis, 2009). 30  Midbrain Between diencephalon and pons Contains bundles of Superior colliculus Corpora quadrigemina fibers that join lower parts Inferior Optic chiasma colliculus Optic nerve of brainstem and spinal Pituitary gland Thalamus Mammillary body Third cord with higher part of Optic tract ventricle brain Pons Cerebral peduncles Pineal gland Cerebral aqueduct Fourth Pyramidal tract ventricle Olive Cerebral peduncles Cerebellar peduncles (bundles of nerve fibers) Medulla oblongata Corpora quadrigemina Spinal cord (centers for visual and (a) (b) auditory reflexes) 31 (Shier, Butler & Lewis, 2009).  Pons Rounded bulge on underside of brainstem Between medulla oblongata and Corpora quadrigemina Superior colliculus midbrain Inferior Optic chiasma colliculus Optic nerve Pituitary gland Thalamus Mammillary body Optic tract Third ventricle Helpsregulate rate Pons Cerebral peduncles Pineal gland and depth of breathing Pyramidal tract Fourth ventricle Olive Cerebellar peduncles Relays nerve Medulla oblongata impulses – Spinal cord longitudinally & (a) (b) ventrally (Shier, Butler & Lewis, 2009). 32  Medulla Oblongata Enlarged continuation of spinal cord Conducts ascending and descending impulses between brain and spinal Superior colliculus Corpora quadrigemina Inferior cord Optic chiasma colliculus Optic nerve Pituitary gland Contains cardiac, Mammillary body Thalamus Third Optic tract ventricle vasomotor, and Pons Cerebral respiratory control peduncles Pineal gland Fourth centers Pyramidal tract ventricle Olive Cerebellar Contains various peduncles Medulla nonvital reflex control oblongata centers (coughing, Spinal cord sneezing, swallowing, (a) (b) and vomiting) (Shier, Butler & Lewis, 2009). 33  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. (Nebraska Department of Education, 2017).  Cerebellum Inferior to occipital lobes Posterior to pons and medulla oblongata Two hemispheres Longitudinal fissure Vermis connects Corpus callosum hemispheres Thalamus Cerebellar cortex (gray Superior peduncle matter) Pons Cerebellum Arbor vitae (white matter) Middle peduncle Inferior peduncle Cerebellar peduncles (nerve Medulla oblongata fiber tracts) Integrates sensory (Shier, Butler & Lewis, 2009). information concerning position of body parts Coordinates skeletal muscle activity 35 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 (Los Angeles Valley College, n.d.). Major Parts of the Brain (Shier, Butler & Lewis, 2009). 38  Functional Brain Systems Networks of distant neurons that function together Limbic system Reticular formation (Los Angeles Valley College, n.d.).  The Limbic System Consists of: Functions: Portions of frontal Controls emotional lobe experiences & Portions of produces feelings temporal lobe like rage, anger, Hypothalamus pleasure Thalamus survival behavior Basal nuclei Interprets sensory (motor control) impulses associated Other deep nuclei with smell (Shier, Butler & Lewis, 2009). 40  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… (Los Angeles Valley College, n.d.).  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 (Los Angeles Valley College, n.d.). 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 (Shier, Butler & Lewis, 2009). 43  Protection of the Central Nervous System  Scalp and skin  Skull and vertebral column  Meninges (Marieb, 2003) Protection of the Central Nervous System  Cerebrospinal fluid  Blood brain barrier (Marieb, 2003) Meninges Functions Cover and Protect CNS Protect blood vessels Contains CSF Forms partitions in the skull (Shier, Butler & Lewis, 2009). 46  Meninges 1. Dura mater: 2 layers of fibrous connective tissue, fused except for dural sinuses  Periosteal layer attached to bone  Meningeal layer - proper brain covering 2. Arachnoid mater 3. Pia mater (Los Angeles Valley College, n.d.). 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 (Los Angeles Valley College, n.d.).  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 (Los Angeles Valley College, n.d.). Ventricles  Central cavities expanded  Filled 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 (Los Angeles Valley College, n.d.). Lateral ventricles Paired, horseshoe shape In cerebral hemispheres Anterior are close, separated only by thin Septum pellucidum (Los Angeles Valley College, n.d.). Third ventricle In diencephalon Connections ○ Interventricular foramen ○ Cerebral aqueduct (Los Angeles Valley College, n.d.). Fourth ventricle In the brainstem Dorsal to pons and top of medulla Holes (aperture) connect it with subarachnoid space (Los Angeles Valley College, n.d.). Ventricles and Location of the Cerebrospinal Fluid (Marieb, 2003)  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. Cerebrospinal Fluid  Secreted by the  Completely surrounds the choroid plexuses (roofs brain and spinal cord of ventricles)  Excess or wasted CSF is Filtration of plasma absorbed by the arachnoid from capillaries villi through ependymal  Clear fluid similar to blood cells (electrolytes, plasma glucose)  100-160 ml  Nutritive and protective Circulates in (Cushions) ventricles, central canal  Helps maintain stable ion of spinal cord, and the concentrations in the CNS subarachnoid space 56 (Shier, Butler & Lewis, 2009). (Shier, Butler & Lewis, 2009). 57  Hydrocephalus (Los Angeles Valley College, n.d.).  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 mechanisms- Excludes 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 (Los Angeles Valley College, n.d.). 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 pressure and respiratory (Shier, Butler & Lewis, 2009). rate Ranges from light to heavy 60  Memory Short term memory Long term memory Working memory Changes Closed neuronal circuit structure or function of Circuit is stimulated neurons over and over Enhances When impulse flow synaptic ceases, memory does transmission(Shier, also unless it enters Butler & Lewis, 2009). long-term memory via memory consolidation 61  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 (Marieb, 2003)  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 (Marieb, 2003) 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 (Marieb, 2003) Spinal Cord 65  Spinal Cord Extends downward through vertebral canal Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Begins at the foramen magnum and terminates at Foramen magnum Brainstem the first and second lumbar Cervical enlargement Cervical enlargement vertebrae (L1/L2) Spinal cord interspace Below is the cauda equina Vertebral canal (a collection of spinal Lumbar enlargement Lumbar enlargement nerves) Conus medullaris Cauda Conus medullaris Enlargements occur in the equina Filum cervical and lumbar regions terminale (a) (b) 66 (Shier, Butler & Lewis, 2009). Spinal Cord Anatomy  Exterior white mater – conduction tracts (Marieb, 2003) Spinal Cord Anatomy  Internal gray matter - mostly cell bodies  Dorsal (posterior) horns  Anterior (ventral) horns (Marieb, 2003) Spinal Cord Anatomy  Central canal filled with cerebrospinal fluid (Marieb, 2003) 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 (Marieb, 2003) Functions of Spinal Cord Conduit for nerve impulses to and from the brain and brainstem Center for spinal reflexes (Shier, Butler & Lewis, 2009). 71  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. Fasciculus gracilis Dorsal column Fasciculus cuneatus Posterior spinocerebellar tract Lateral corticospinal tract Lateral reticulospinal tract Rubrospinal tract Anterior spinocerebellar tract Lateral spinothalamic tract Anterolateral system Anterior spinothalamic tract Anterior reticulospinal tract Medial reticulospinal tract Anterior corticospinal tract (Shier, Butler & Lewis, 2009). 72 References  Los Angeles Valley College. (n.d.). Central Nervous System: “CNS”. Retrieved from http://www.lavc.edu/instructor/watson_k/ docs/Lecture%2013%20-%20Central %20Nervous%20System.ppt 73 References Cont’d  Marieb, E. (2003). The Nervous System. Retrieved from http://www.haspi.org/curriculum-library/A -P-Core-Labs/12%20Nervous %20System/Powerpoint %20Presentations/Nervous%20System %201.ppt 74 References Cont’d  Shier, D., Butler, J. & Lewis, R. (2009). Nervous System II. Retrieved from http://nhscience.lonestar.edu/biol/durha m/docs/biol2401/chapt11_holes_lecture. ppt  4. Nebraska Department of Education. (2017). Retrieved from: https://www.education.ne.gov/wp- content/uploads/2017/07/179-Anatomy- Nervous-System.ppt (Shier, Butler & Lewis, 2009). 75