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Unit IV: Coordination Central Nervous System Chapter 12 and 13 Central Nervous System • Consists of the brain and the spinal cord • Functions of the CSF: 1. Buoyancy 2. Protection 3. Interstitial fluid in thalamus Chemical stability Nutrients, O2 Capillaries Waste products, CO2 Astrocyte Removal of waste Production of CSF Neuron Ependymal cells Cerebrospinal fluid in third ventricle Blood - Brain Barrier • Composed of tightly joined blood capillaries in the brain • Highly permeable to: – H2O, glucose, O2, CO2, alcohol, caffeine, nicotine, anesthetics • Circumventricular Organs • Blood – CSF barrier Functions of the Spinal Cord • Conduction • Locomotion – central pattern generators (walking) • Reflexes Anatomy of the Spinal Cord • Cylinder of nerve tissue within the vertebral canal – 1.8 cm x 45 cm • Spinal cord extends to L1 in adults • 31 pairs of spinal nerves • Cervical, thoracic, lumbar, and sacral regions Meninges of the CNS • Fibrous membranes surrounding brain and spinal cord • Dura mater – epidural space • Arachnoid mater – layer of simple squamous epithelium adhering dura mater – loose mesh of fibers joining to the pia mater – creates subarachnoid space • Pia mater – denticulate ligaments anchor the cord Meninges of the Spinal Cord Structure of Spinal Cord Dorsal root White matter Gray matter • Central area of gray matter shaped like a butterfly and surrounded by white matter in three columns Dorsal root ganglion Spinal nerve Segment C3 Ventral root White matter • Gray matter = neuron somas with little myelin Gray matter Segment T3 • White matter = myelinated axons Segment L1 Segment S Central canal Gray Matter • Dorsal/posterior horns – Sensory neuron fibers enter here and may synapse with interneuron • Ventral/anterior horns – Contain somas of somatic motor fibers • Lateral horns – thoracic and lumbar regions, contain neurons of sympathetic nervous system • Gray commissure – connects right and left sides • Central canal – lined with ependymal cells and filled with CSF Gray matter: Central canal Posterior horn Gray commissure Lateral horn Anterior horn Dorsal root of spinal nerve Dorsal root ganglion Spinal nerve Ventral root of spinal nerve White Matter • • • • • • Bundles of myelinated axons 3 pairs of columns or funiculi Ascending and descending tract Contralateral Ipsilateral Decussation Ascending tracts Descending tracts White matter: Posterior column Lateral column Anterior column Spinal nerve The Brain - General • Directions: Rostral and Caudal Cerebrum Diencephalon (covered by cerebrum) • Major parts: − Cerebrum − Cerebellum − Brainstem • Cerebrum is largest area • Cerebellum contains 50% of the neurons Pons Medulla oblongata Cerebellum Spinal cord Mesencephalon (covered by cerebrum) White Matter of Cerebrum • Most of cerebrum is white matter • Types of tracts: – projection tracts – association tracts Projection fibers Longitudinal fissure – commissural tracts Corpus callosum Anterior commissure Anterior view Gray Matter of Cerebrum • Involved in neural integration • Three places: 1. Cerebral Cortex • Motor cortex, sensory cortex, auditory, visual Gray Matter of Cerebrum • Three places: 2. Basal Nuclei • Subconscious motor control 3. Limbic System • Emotional states • Memory storage • Thinking – linking conscious intellectual functions of cerebral cortex with unconscious autonomic functions of brainstem Brain Scans Rostral Caudal Visual cortex 1 The word cad is seen in the visual cortex. Location of Hindbrain Cerebellum Pons Medulla Oblongata Spinal Cord Hindbrain Medulla Oblongata • 3 cm extension of spinal cord • Ascending and descending nerve tracts • Sensory and motor nuclei receive input from: – controls: – cardiac center – vasomotor center – two respiratory centers • Cranial nerves IX – XII begin or end here − Salivation, swallowing, gastric secretions and motility, auditory Hindbrain Pons • • • • Relays signals from cerebellum to cerebrum Cranial nerve V VI, VII, VIII arise at junction with medulla Contains nuclei concerned with swallowing, sleep, hearing, eye movements, taste, facial expressions and sensations, and posture Tracts Ascending tracts Descending tracts Respiratory Centers Pneumotaxic center Apneustic center Transverse fibers Cerebellum Midbrain Fourth ventricle Pons Medulla oblongata Spinal cord Olivary nucleus Reticular formation Hindbrain Cerebellum • 10% mass but 60% more surface area = ½ of all brain neurons • Functions − Adjust postural muscles (balance & equilibrium) − Fine-tune movements • General role in evaluation of sensory inputs – Tactile sensors in fingertips (ex. Textures without looking) – Timekeeping center (elapsed time between stimuli) – Some hearing (pitch, distinguish between similar sounding words) – AD/HD (small cerebellums) Structures of the Midbrain • Cerebral Peduncles − Nerve fiber bundles – Contain corticospinal tracts (fine motor control) • Tegmentum – Collaborates with cerebullum (fine motor control) • Substantia nigra – sends inhibitory signals to basal nuclei and thalamus Pineal gland – Parkinson disease Thalamus Superior colliculus Posterior view of brain stem and diencephalon Red nucleus Substantia nigra Inferior colliculus Cerebral peduncles Reticular activating system (RAS) Structures of the Midbrain • Central gray matter (pain awareness) • Tectum (two of each) – superior colliculi (visual reflexes) – inferior colliculi (auditory reflexes) • Reticular formation – Somatic motor control – cardiovascular control – Pain modulation – Habituation – Sleep and consciousness • Irreversible coma Cranial Nerves of the Brainstem Midbrain Cerebral peduncle Superior colliculus Inferior colliculus Oculomotor III Trochlear IV Trigeminal V Pons Abducens VI Facial VII Vestibulocochlear VIII Glossopharyngeal IX Vagus X Accessory Nerve XI Hypoglossal XII Medulla oblongata Spinal nerve C1 Spinal nerve C2 Spinal cord Lateral view Midbrain and Forebrain leaves Corpus callosum Thalamus Habenula Anterior commissure Pineal gland Hypothalamus Optic chiasm Pituitary gland Midbrain (a) Epithalamus Forebrain (Diencephalon) Thalamus • Relays nearly all sensory input going to cerebrum Key role in motor control output arousal, eye movements, taste, smell, hearing, equilibrium and somesthetic senses Emotional and memory functions of limbic system Thalamus Optic chiasm Optic tract Cerebral peduncle (midbrain) Lateral view of the left thalamus and midbrain Forebrain (Diencephalon) Hypothalamus • Generally controls ANS and endocrine system • Functions: 1. hormone secretion Hypothalamic Nuclei 2. autonomic effects Autonomic centers 3. thermoregulation Preoptic area 4. food and water intake Suprachiasmatic nucleus Hormonal centers 5. Sleep/wake cycles 6. Memory-mammillary 7. emotional behavior Thalamus Hypothalamus Pons Infundibulum Anterior pituitary gland Posterior pituitary gland Mamillary body Forebrain (Diencephalon) Epithalamus Consists of : • Pineal gland secretes melatonin (Circadian rhythms) • Habenula connects limbic system to cerebrum Forebrain (Telencephalon) Cerebrum Right Cerebral Hemisphere Left Cerebral Hemisphere Sensory information Interpretive centers Analyzing the emotional context of a conversation General interpretive and speech centers Reading, writing, and speaking premotor cortex analytical tasks RIGHT HAND LEFT HAND Prefrontal cortex Prefrontal cortex Speech center Writing Auditory cortex (right ear) General interpretive center (language and mathematical calculation) Visual cortex (right visual field) C O R P U S C A L L O S U M Anterior commissure Analysis by touch Auditory cortex (left ear) Spatial visualization and analysis Visual cortex (left visual field) Forebrain (Telencephalon) Cerebrum • Gyri and Sulci – increase surface area for more neurons! Cerebral Cortex Functions • Brain waves • Sleep • Cognition • Memory • Emotion • Sensation • Special Senses • Motor Control • Language • Lateralization of Cerebrum Alpha waves Beta waves Theta waves Delta waves