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Central Nervous System 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 Spinal Figure 5.1 Brain system cord Page 136 (CNS) (Input to CNS (Output from CNS from periphery) to periphery) Peripheral Afferent nervous Efferent division system division (PNS) Sensory Visceral Somatic Autonomic stimuli stimuli nervous system nervous system Motor Sympathetic Parasympathetic neurons nervous system nervous system Skeletal Smooth muscle Cardiac muscle muscle Glands Effector organs (made up of muscle and gland tissue) 3 Classes of Neurons 1. Afferent neurons 2. Efferent neurons 3. Interneurons Central Peripheral nervous system nervous system (spinal cord) Cell Axon body terminals Afferent neuron Central Peripheral axon axon (afferent fiber) Receptor Interneuron Axon terminals Efferent neuron* Effector organ (muscle or gland) Cell Axon body (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 1. Bony structures –cranium 2. Cranial Meninges a. dura mater (outermost) b. arachnoid c. pia mater (innermost) 3. Cerebrospinal fluid & Ventricles • Cushioning, support, & nutrient transportation 4. Blood-brain barrier Cerebrospinal fluid Figure 5.6 (1) Page 141 Pia mater Arachnoid mater Cranial meninges Dura mater Pia mater Arachnoid mater Spinal meninges Dura mater 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 Transport mechanisms 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 1. Cerebral Cortex (Cerebrum) • 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 Somato- sensory cortex Major Functions 2. Basal nuclei (Cerebrum) • Inhibition of muscle tone • Suppress unwanted patterns of movement • Monitor and sustain slow contractions (i.e. posture) Basal nuclei (gray matter) Major Functions 3. Thalamus • Part of diencephalon • Relay station for synaptic (sensory) input 9 Screens out insignificant signals • Role in motor control Thalamus 8 Major Functions 4. Hypothalamus • 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 5. Limbic System • Region surrounding brain stem in forebrain • Emotion & behavior patterns Major Functions 6. Cerebellum (between brain stem & cerebrum) • 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 7. Brainstem (medulla, pons, midbrain) • 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 Cervical cord nerves Vertebrae Thoracic Thoracic nerves cord Lumbar Lumbar nerves cord Sacral Sacral nerves cord Coccygeal nerve 10 Spinal cord Figure 5.27 Page 172 Dorsal root ganglion Spinal nerve Meninges (protective Vertebra coverings) Intervertebral disk 1. Gray Matter • Shaped like the letter H 9 Neurons & glial cells 2. White Matter • Myelinated nerves (ascending & descending tracts) 3. Ventral roots • Motor nerves 4. Dorsal roots • Sensory nerves • Dorsal root ganglion (groups of cell bodies) Cell body of White matter Gray matter efferent neuron Interneuron Cell body of afferent neuron Dorsal root Afferent fiber Dorsal root ganglion From receptors To effectors Ventral root Spinal nerve Figure 5.29 Page 174 11 Reflexes & the Spinal Cord = Inhibitory interneuron Components of a Figure 5.33 = Excitatory interneuron reflex arc Page 178 = Synapse = Inhibits Receptor = Stimulates Afferent pathway Integrating center Efferent pathway Effector organs Thermal pain receptor in finger Ascending pathway to brain Afferent Pathway Stimulus Biceps Efferent pathway (flexor) Integrating center contracts Triceps (spinal cord) (extensor) Hand relaxes withdrawn Effector organs Response 12.
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