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Chapter 11 Brain Anatomy & Functions 1 Meninges • Membranes surrounding CNS • Protect CNS • Three layers • Dura mater • Outer layer • Adheres to cranial bones • Tough 2 Meninges • Arachnoid mater • Thin, weblike • Pia mater • Inner layer • Adhere directly to brain • Very thin • Fibrous and vascular 3 Meninges • Spinal Cord • Same three layers • Provides protection 4 Ventricles • Interconnected cavities •Within cerebral hemispheres and brain stem •Continuous with central canal of spinal cord • Filled with cerebrospinal fluid (CSF) 5 Ventricles • Lateral ventricles • Third ventricle • Fourth ventricle • Cerebral aqueduct 6 Ventricles 7 Cerebrospinal Fluid • Secreted by choroid plexus • Circulates in ventricles, central canal of spinal cord, and subarachnoid space • Completely surrounds brain and spinal cord between the meninges 8 Cerebrospinal Fluid • Clear liquid • 80-150 ml in CNS • Contains proteins, glucose, and salts • Nutritive and protective • Shock absorber • Helps maintain stable ion concentrations in CNS 9 Spinal Cord • Slender column of nervous tissue continuous with brain • Extends downward through vertebral canal • Begins at level of foramen magnum & terminates near first & second lumbar 10 Cross Section of Spinal Cord 11 Functions of Spinal Cord • Center for spinal reflexes • Conduit for nerve impulses to and from the brain 12 Reflex Arcs Reflexes – automatic, subconscious responses to stimuli within or outside the body 13 Brain 14 Brain Functions Major Parts • Interprets sensations • Cerebrum • Determines perception • Two hemispheres • Stores memory • Basal nuclei • Reasoning • Diencephalon • Makes decisions • Brainstem • Coordinates muscular • Cerebellum movements • Regulates visceral activities • Determines personality 15 Brain 16 Brain Development Three Major Vesicles 1. Forebrain 2. Midbrain 3. Hindbrain 17 Brain Development 18 Cerebrum • Looks like cap of a mushroom • Spread over diencephalon • 7/8 total mass • Fills most of cranium 19 Clinical Application: Cerebrum • Result from displacement & distortion of neurons at the moment of impact • Concussion • Abrupt but temporary loss of consciousness following a blow to the head or the sudden stopping of a moving head • No visible bruising but post traumatic amnesia may occur 20 Clinical Application: Cerebrum • Contusion • Visible bruising of the brain due to trauma and blood leaking from microscopic vessels • Pia mater is torn • Results in unconsciousness for several minutes to many hours 21 Clinical Application: Cerebrum • Laceration • Tearing of the brain, usually from skull fractures or gunshot wound • Large blood vessels bleed into the brain and can cause cerebral hematoma, and increase cranial pressure 22 Lobes of Cerebral Hemispheres • Name of lobe corresponds with name of cranial bone • Frontal • Parietal • Temporal • Occipital • Insula 23 Functions of the Cerebrum • Interpreting impulses • Initiating voluntary movements • Storing information as memory • Retrieving stored information • Reasoning • Seat of intelligence and personality 24 Functional Regions of Cerebral Cortex Cerebral Cortex – thin layer of gray matter that constitutes the outermost portion of cerebrum; contains 75% of all neurons in nervous system 25 Structure of Cerebrum • Cerebral Cortex • Surface of cerebrum • Convolutions • Folds in cerebrum • Bumps or gyri • Sulci • Shallow grooves • Fissures • Deep grooves 26 Structure of Cerebrum • Corpus callosum • Connects cerebral hemispheres • Longitudinal fissure • Separates hemispheres • Transverse fissure • Separates cerebrum from cerebellum 27 Sensory Areas • Cutaneous Sensory Area • Parietal lobe • Interprets sensations on skin • Visual Area • Medial Occipital lobe • Interprets vision 28 Sensory Areas • Primary Gustatory • Taste • Near bases of the central sulci • Primary Olfactory • Smell • Arise from centers deep within the cerebrum 29 Sensory Areas • Auditory Area • Superior part of temporal lobe near lateral cerebral sulcus • Interprets hearing 30 Sensory Areas 31 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 32 Association Areas Frontal Lobe Association Areas • Concentrating • Planning • Complex problem solving Temporal Lobe Association Areas • Interpret complex sensory experiences • Store memories of visual scenes, music, and complex patterns Parietal Lobe Association Areas • Understanding speech • Choosing words to express thought Occipital Lobe Association Areas • Analyze and combine visual images with other sensory experiences 33 Hemisphere Dominance • The left hemisphere is dominant is 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 34 Hemisphere Differences • Anatomical • Frontal lobe of left hemisphere is smaller • Left handed people • Right parietal and occipital lobes are narrower 35 Hemisphere Differences • Right Hemisphere • Left handed • Music and artistic awareness • Space and patter perception • imagination • Left Hemisphere • Right handed • Numerical and scientific skills • Sign language and reasoning 36 Memory Short Term • Working memory • Closed neuronal circuit • Circuit is stimulated over and over • When impulse flow ceases, memory does also • Unless it enters longterm memory via memory consolidation Long Term • Changes structure or function of neurons • Enhances synaptic transmission 37 Motor Areas • Primary Motor Areas • frontal lobes • control voluntary muscles • 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 38 Motor Areas 39 Functions of the Cerebral Lobes 40 Diencephalon • Between cerebral hemispheres and above the brainstem • Surrounds third ventricle • Thalamus • Hypothalamus • Optic tracts • Optic chiasma • Infundibulum • Posterior pituitary • Mammillary bodies • Pineal gland 41 Diencephalon Thalamus •Oval structure above midbrain •Gateway for sensory impulses heading to cerebral cortex • Receives all sensory impulses (except smell) • Channels impulses to appropriate part of cerebral cortex for interpretation •Interpretation of pain, temperature, and pressure 42 Diencephalon Hypothalamus • Small portion inferior to thalamus • Protected by sella turcica • Maintains homeostasis by regulating visceral activities • Water concentrations • Hormone concentrations • Blood temperature • Links nervous and endocrine systems 43 Diencephalon • Homeostatic functions • Regulates autonomic nervous system • Reception & integration of sensory impulses from viscera • Mind over body (stress--heart rate increases) • Rage & aggression • Regulates body temperature • Regulates food intake (hunger & full feelings) • Thirst • Sleep patterns 44 Diencephalon Limbic System Consists of • portions of frontal lobe • portions of temporal lobe • hypothalamus • thalamus • basal nuclei • other deep nuclei Functions • controls emotions • produces feelings • interprets sensory impulses 45 Brain Stem Three Parts 1. Midbrain 2. Pons 3. Medulla Oblongata 46 Midbrain •“Mesencephalon” •Between diencephalon and pons • Contains bundles of fibers that join lower parts of brainstem and spinal cord with higher part of brain 47 Midbrain • Cerebral aqueduct – Connects 3rd & 4th ventricles of brain • Cerebral peduncles – bundles of nerve fibers – Motor pathway between cerebrum & lower parts of nervous system • Corpora quadrigemina – centers for visual and auditory reflexes 48 Pons • Rounded bulge on underside of brainstem • Between medulla oblongata and midbrain • Helps regulate rate and depth of breathing • Relays nerve impulses to and from medulla oblongata and cerebellum 49 Medulla Oblongata • Enlarged continuation of spinal cord • Conducts ascending and descending impulses between brain and spinal cord • Contains 3 reflex centers • Cardiac •Heart rate & force of contraction • Vasomotor •Controls diameter of blood vessels • Respiratory •Controls breathing patterns 50 Medulla Oblongata • Contains various nonvital reflex control centers – – – – Coughing Sneezing Swallowing Vomiting 51 Medulla Oblongata • Reticular Formation • Complex network of nerve fibers scattered throughout the brain stem • Extends into the diencephalon • Connects to centers of hypothalamus, basal nuclei, cerebellum, and cerebrum • Filters incoming sensory information • Arouses cerebral cortex into state of wakefulness 52 Cerebellum • Inferior to occipital lobes • Posterior to pons and medulla oblongata • Two hemispheres • Vermis connects hemispheres • Cerebellar cortex • Gray matter on surface • Arbor vitae • White matter inside •Tree-like pattern • Cerebellar peduncles • nerve fiber tracts 53 Cerebellum • Dentate nucleus • Largest nucleus in cerebellum • Integrates sensory information concerning position of body parts • Coordinates skeletal muscle activity • Maintains posture 54 Cerebellum • Damage results in • Lack of muscle control • Change of speech pattern • Severe dizziness • Disturbances of gait (walking) 55 Life-Span 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 56 Clinical Application Cerebral Injuries and Abnormalities Cerebrovascular Accident • Stroke • Sudden interruption in blood flow • Brain tissues die Cerebral Palsy • Motor impairment at birth • Caused by blocked cerebral blood vessels during development • Seizures • Learning disabilities 57