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Nervous System: Functions and Structures

Explore the functions and structures of the nervous system, including its role in monitoring changes, processing sensory input, and eliciting motor responses. Learn about the structural and functional classifications, as well as the anatomy of neurons and glial cells. Understand how nerve impulses work in the central nervous system and the physiology of the brain. Dive into the regions of the brain, lobes, and their specific functions to gain a comprehensive understanding of this vital system.

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Nervous System: Functions and Structures

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  1. Nervous System

  2. 3 Functions of the Nervous System • 1. Monitor changes inside and outside the body. • Changes are stimuli and the gathered information is the sensory input. • 2. Processes and interprets the sensory input and makes decisions about what should be done at each moment this is integration. • 3. It then effects a response by activation muscles or glands this is called motor output.

  3. Structural Classification • Central Nervous System-(CNS)- brain and spinal cord • Interpret incoming sensory information and issue instructions based on past experience and current conditions. • Peripheral Nervous System-(PNS)- nerves that extend from the brain and spinal cord. • Carry impulse to and from the brain.

  4. Functional Classification • Functional Classification has to only with the PNS structures. • Sensory division-(afferent)- convey impulses to the CNS • Somatic sensory fibers- transmit impulses from the skin, skeletal muscles and joints. • Visceral sensory fibers- transmit impulses from the visceral organs. • Motor division-(efferent)- carries impulse from the CNS to effector organs, muscles and glands. Bring about motor response.

  5. Functional Classification • Motor division has two subdivisions • Somatic nervous system- allows us to consciously, or voluntarily, control our skeletal muscles. • Voluntary Nervous System • Autonomic Nervous System- regulates events that are automatic or involuntary. • Involuntary Nervous System

  6. Structure and Function • Neuroglia- supporting cells in the CNS are lumped together. Literally meaning “nerve glue” • Astrocytes-star-shaped cells that account for nearly half of the neural tissue. These cells protect by picking up excess ions and recapturing released neurotransmitters. • Microglia- spiderlike phagocytes that dispose of debris, including dead cells and bacteria

  7. Cont. • Ependymal- line the cavities of the brain and the spinal cord. Helps circulate cerebrospinal fluid that fills those cavities that cushion the brain. • Oligodendrocytes- glia that wrap their flat extensions tightly around the nerve fibers, producing fatty insulating coverings called myelin sheaths. • Glia cannot transmit nerve impulses • This is what most tumors are formed from in the brain. • In the PNS support cells are: • Schwann cells – form myelin sheath • Satellite cells- act as protective cushioning cells

  8. Neurons Anatomy • Neuron- nerve cell that transmit messages from one part of the body to another. • All have: • Cell bodythat contains a nucleus • One or more slender processes extending from the cell body. • Cell body- metabolic center of the neuron. • Have all organelles except centrioles • Nissl substance- rough ER • Neurofibrils- intermediate filaments that are important in maintaining cell shape

  9. Neuron Anatomy • Fibers- vary in length from microscopic to 3-4 feet long • Dendrites- convey incoming messages toward the cell body. • Branch like projections off of the cell body but not long arms. • Axons- generate nerve impulses and typically conduct them away from the cell body. • Long arm like projection from the cell body.

  10. Neuron Anatomy • Axonal Terminal- contain little sacs that have neurotransmitters in them that send and receive nerve impulses. • Synaptic cleft- tiny gas • Neurons never actually touch each other. • Myelin- covers axons and is a white fatty material. Increases nerve impulse speed. • CNS nerves are called tracts • PNS nerves are called nerves • White matter is mylinated and Grey matter has no myelin.

  11. Classification • MultipolarNeuron-Many processes coming off of the cell body • Bipolar Neuron- two processes coming off of the cell body • UnipolarNeuron- one processes coming off of the cell body

  12. PhysiologyNerve Impulse

  13. Central Nervous System • In the embryonic development the CNS first appears as a tube (Neural Tube). • Then it expands to four regions of the brain to form chambers called ventricles.

  14. Functional Anatomy of the Brain • Weighs a little over 3 lbs. • Four Regions- • Cerebral hemisphere • Diencephalon • Brain stem • cerebellum

  15. Cerebral Hemisphere • Most superior part of the brain • Largest region of the brain • Gyri- covers the entire surface of the cerebral hemispheres exhibits elevated ridges of tissue. • Sulci- shallow grooves • Fissures- deeper grooves

  16. Lobes • Parietal lobe- recognize pain, coldness, or a light touch. • Most sensitive areas are the lips and the fingertips. • Occipital lobe- visual area • Temperal lobe- auditory area • Deep inside the temporal lobe is the olfactory area

  17. Lobes • Frontal lobe- primary motor area • Allows us to move and have motor control • Broca’s area- ability to speak • Speech area- located on the temporal, parietal, and occipital • Corpus Callosum-connects the cerebral hemispheres. Allows the hemispheres to communicate.

  18. Diencephalon • Sits atop the brain stem and is enclosed by the cerebral hemispheres. • Major structures- • Thalamus-sensory impulses • Hypothalamus- regulation of body temp., water balance, and metabolism. Thirst, appetite, sex, and pain. Regulates the pituitary gland. • Pituitary gland- anterior floor by a slender stalk. • Epithalamus- roof of 3rd ventricle. Pineal body and the choroid plexus.

  19. Brain Stem • Size of your thumb in diameter. • Structures are the midbrain, pons, and medulla oblongata. • Controls breating and blood pressure. • Midbrain- reflex centers involved with vision and hearing. • Pons- control of breathing. • Medulla Oblongata- vital visceral activities. Heart rate, breathing, swallowing, and vomiting. • Reticular Formation- motor control of visceral organs. • RAS- plays a role in consciousness and the awake/sleep cycles. Damage to this area can result in coma.

  20. Cerebellum • Large cauliflowerlike • Skeletal muscle activity • Equilibrium apparatus of the inner ear, eye • Compared to the auto pilot. • If damaged movement becomes clumsy like a drunk person

  21. Brain Injuries • Concussion- slight brain injury • Dizzy, loss of consciousness briefly, no permanent damage • Contusion- marked tissue destruction. • Cerebral edema- swelling of the brain due to injury.

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