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Nervous System Roles • Monitors changes – What are the changes? • Processes and interprets sensory input • Effects a response Organization • CNS – Organs? • PNS – Organs? PNS • Sensory (afferent) - delivers messages from the sensory receptors toward the CNS • Motor (efferent) - delivers messages from the CNS to organs – Somatic nervous system - messages sent to muscles – Autonomic nervous system - messages sent to smooth muscle, cardiac muscles, and glands. – Which would be considered the involuntary nervous system? Why? Nervous Tissue • Neuroglial cells of CNS – Astrocytes - form a barrier between capillaries and neurons – Microglia - phagocytes – Ependymal - use cillia to circulate cerebrospinal fluid – Oligodendrocytes - form myelin sheath • Neuroglial cells of PNS – Schwann cells - form myelin sheath – Satellite cells • Neurons Neurons • Cell body – What is all here? • Dendrites - receive incoming electrical stimulus – Neurons have hundreds of dendrites • Axons - send out electrical stimulus – Neurons only possess one – mm to m in length. Where could an axon a meter in length be found? Axons • Possess hundreds or thousands of axon terminals • Terminals contain hundreds of vesicles – What are found in the vesicles (think about the axon innervating the muscle)? – Why are these chemical messengers needed? Axons • Most nerve fibers are covered with myelin – It is a fatty material. Function? • What cells make up the myelin sheath? • Gaps between cells are called nodes of Ranvier Neuron classification • Afferent (sensory neuron) – Examples? • Efferent (motor neuron) • Interneurons – What do you think these do? Neuron Physiology • Based on balance of what ions? • Threshold stimulus • All-or-none response Neuron Physiology • Resting membrane potenial (polarized) • Na+ is highly concentrated outside the cell • K+ is highly concentrated inside the cell Neuron Physiology • Stimulus initiates an action potential • Causes Na+ channels to open – What will this cause? – Depolarization • Once a small area is depolarized it stimulates adjacent areas – Creates an action potential Neuron Physiology • After depolarization, K+ channels open – What will this cause? – Repolarization • What has to happen in order to get back to resting potential? Neuron Physiology • Myelin sheath speeds up the propagation of the action potential • The impulse can travel at speeds up to 120 m/sec • How does the nerve impulse get from one neuron to the next? Reflex • Rapid, predictable, involuntary motions • What would a reflex be called that stimulates a skeletal muscle? Smooth muscles, heart, glands? • Reflex arcs – – – – – Sensory receptor Effector organ Sensory neurons Motor neurons Integration center (CNS) Central Nervous System Protection • Meninges - connective tissue membranes – Dura mater – Arachnoid mater – Pia mater • What do you think meningitis is? Central Nervous System Protection • Blood Brain Barrier – There are not spaces between cells in the brain capillaries – Significance? – What glial cells help form tight junctions between epithelial cells? – Lipid soluble molecules can easily pass. What types of molecules would not pass? Central Nervous System Protection • Blood Brain Barrier – Glucose is water soluble. How does it cross the BBB – The BBB is weaker in the emetic center of the brain. Why? Central Nervous System Cerebrospinal Fluid • Colorless liquid similar to blood plasma • Surrounds the brain and spinal cord • Role? Central Nervous System Brain • Cerebrum - most superior portion of the brain – Gyri - ridges – Sulci - grooves – Fissures - deeper grooves – These separate the lobes of the cerebrum Cerebrum • Motor areas, sensory areas, association areas • Each hemisphere is concerned with the functions of the opposite side of the body. • Hemispheres are not equal in function • No functional area works alone Cerebral lobes • Parietal - somatic sensory (primary and association) area – Impulses travel to and from sensory receptors (pain, cold, touch) – Sensory pathways are crossed • Occipital - visual (primary and association) area • Temporal - auditory association area – olfactory Cerebral Lobes • Frontal - primary motor area (patways are crossed) – Intellectual reasoning – Social acceptability – Complex memories (shared with temporal) – Language comprehension Cerebral Hemispheres • Gray matter - outermost (cerebral cortex) • White matter - inner – Consists of fiber tracts - bundles of nerve fibers that carry impulses to and from the cortex – Corpus callosum - connects the two hemispheres and allows for communication Central Nervous System Diencephalon • Thalamus - sensation is determined pleasant or unpleasant • Hypothalamus - regulation of body temperature, water balance, metabolism – Thirst, appetite, pain, pleasure, and sex centers – Regulates pituitary • Pituitary Gland - major hormone producer Central Nervous System Brain Stem • About the size of a large thumb • Midbrain - involved with vision and hearing • Pons - breathing center • Medulla Oblongata - controls vital visceral activities – Like what? Central Nervous System Cerebellum • Coordinates muscle movement • Monitors cerebrums intentions with actual performance • Contains the arbor vitae Spinal Cord • Extends from _________ to _________ • What are the layers of protection? Fluid? • Two way conduction • Major reflex center • Where would be a good location for CSF testing? • Cauda equina Peripheral Nervous System Nerves • Axon, fascicle, and nerve • endoneurium, perineurium, and epineurium • How would you describe the structure of a nerve?