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Central Nervous System Overview ¾ Nervous and endocrine systems major regulators of the body • Rapid response to external & internal stimuli Nervous System = 2 systems • Central Nervous System (CNS) • Peripheral Nervous System (PNS) ¾ CNS consists of: 1. Brain 2. Spinal cord ¾ PNS consists of: 1. Afferent (sensory) division 2. Efferent (motor) division 9 Efferent system divided into Somatic Nervous System (SNS) 9 Autonomic nervous system (ANS) 1 Central nervous system (CNS) Brain (Input to CNS from periphery) Sensory stimuli (Output from CNS to periphery) Peripheral nervous system (PNS) Afferent division Figure 5.1 Page 136 Spinal cord Visceral stimuli Efferent division Somatic nervous system Motor neurons Autonomic nervous system Sympathetic nervous system Parasympathetic nervous system Smooth muscle Cardiac muscle Glands Effector organs (made up of muscle and gland tissue) Skeletal muscle 3 Classes of Neurons 1. Afferent neurons 2. Efferent neurons 3. Interneurons Central nervous system (spinal cord) Axon terminals Peripheral nervous system Cell body Central axon Afferent neuron Peripheral axon (afferent fiber) Receptor Interneuron Axon terminals Efferent neuron* Effector organ (muscle or gland) Cell body Axon (efferent fiber) 2 Central Nervous System Cells of the CNS ¾ Nervous tissue in CNS comprised of glial cells or neuroglia: 1. Astrocytes: scaffolding, blood-brain barrier, injury & scar tissue, remove excess K+, enhance chemical signaling 2. Oligodendrocytes: form myelin sheaths in CNS 3. Microglia: immune defense cells of CNS 4. Ependymal cells: support cerbrospinal fluid, possibly aid in formation of new neurons & glial cells Space containing cerebrospinal fluid Ependymal cell Astrocyte Microglial cell Oligodendrocyte Figure 5.3 Page 138 3 Protection for the Brain Bony structures – cranium 1. Cranial Meninges 2. a. dura mater (outermost) b. arachnoid c. pia mater (innermost) Cerebrospinal fluid & Ventricles 3. • 4. Cushioning, support, & nutrient transportation Blood-brain barrier Cerebrospinal fluid Figure 5.6 (1) Page 141 Pia mater Arachnoid mater Dura mater Pia mater Arachnoid mater Dura mater Cranial meninges Spinal meninges Figure 5.6 (2) Page 141 Scalp Skull bone Dura mater Arachnoid mater Pia mater Brain (cerebrum) 4 CSF and Ventricles ¾ Fluid filled cavities within the brain • Cerebrospinal fluid 9Shock absorption 9Higher in Na+ than K+ Right lateral ventricle Left lateral ventricle Third ventricle Central canal of spinal cord Figure 5.5 Page 139 Fourth ventricle 5 Blood-brain Barrier ¾ Highly selective • Tight junctions 9H20 soluble compounds need active transport Pore passage Carrier-mediated transport Lipid-soluble substances Transport mechanisms Transport mechanisms Lipid-soluble substances Tight junction (no pores) Water-lined pore Anatomical Organization of the Brain Table 5.3 (1) Page 144 Cerebral cortex Basal nuclei Thalamus Hypothalamus Cerebellum Midbrain Brain stem Pons Medulla 6 Major Functions Cerebral Cortex (Cerebrum) 1. • • • • Sensory perception Personality & language Conscious thought & memory Complex motor patterns (voluntary movement) Cerebral Cortex Lobes 1. Frontal lobe – voluntary motor activity (primary motor cortex), speaking, thought 2. Parietal lobes – proprioception & body feelings (somatosensory cortex) 3. Temporal lobe – auditory/olfactory areas 4. Occipital lobe – visual areas Frontal lobe Parietal lobe Occipital lobe Temporal lobe 7 Primary motor cortex Somatosensory cortex Major Functions Basal nuclei (Cerebrum) 2. • • • Inhibition of muscle tone Suppress unwanted patterns of movement Monitor and sustain slow contractions (i.e. posture) Basal nuclei (gray matter) Major Functions Thalamus 3. • • Part of diencephalon Relay station for synaptic (sensory) input 9 Screens out insignificant signals • Role in motor control Thalamus 8 Major Functions Hypothalamus 4. • • • Homeostatic function Temperature, thirst regulation (urine output), food intake Link between nervous & endocrine systems 9 ANS coordinating center • Emotional & behavioral patterns Mamillary bodies (part of hypothalamus) Major Functions Limbic System 5. • • Region surrounding brain stem in forebrain Emotion & behavior patterns Major Functions Cerebellum (between brain stem & cerebrum) 6. • Vestibulocerebellum 9 Balance & eye movement • Spinocerebellum 9 Coordinated skill & voluntary movements • Cerbrocerebellum 9 Planning & initiation of voluntary movement Vestibulocerebellum Spinocerebellum Cerebrocerebellum Cerebellum 9 Major Functions Brainstem (medulla, pons, midbrain) 7. • • • • Houses majority of cranial nerves CV, Respiratory, & digestive control centers Regulation of muscles involved in reflexes (equilibrium & posture) Reception of synaptic input from spinal cord Brainstem Spinal Cord Figure 5.28 Page 173 Cervical cord Cervical nerves Thoracic cord Thoracic nerves Lumbar cord Sacral cord Vertebrae Lumbar nerves Sacral nerves Coccygeal nerve 10 Spinal cord Figure 5.27 Page 172 Dorsal root ganglion Spinal nerve Meninges (protective coverings) Vertebra Intervertebral disk Gray Matter 1. • Shaped like the letter H 9 Neurons & glial cells White Matter 2. • Myelinated nerves (ascending & descending tracts) Ventral roots 3. • Motor nerves Dorsal roots 4. • • Sensory nerves Dorsal root ganglion (groups of cell bodies) Cell body of efferent neuron Cell body of afferent neuron Afferent fiber White matter Gray matter Interneuron Dorsal root Dorsal root ganglion From receptors To effectors Ventral root Spinal nerve Figure 5.29 Page 174 11 Reflexes & the Spinal Cord = Inhibitory interneuron = Excitatory interneuron = Synapse = Inhibits = Stimulates Figure 5.33 Page 178 Thermal pain receptor in finger Components of a reflex arc Receptor Afferent pathway Integrating center Efferent pathway Effector organs Ascending pathway to brain Afferent Pathway Stimulus Biceps (flexor) contracts Hand withdrawn Efferent pathway Triceps (extensor) relaxes Integrating center (spinal cord) Effector organs Response 12