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Nervous System

Nervous System. The Neuron. Also called the nerve cell It is the basic structural unit of the nervous system. The Neuron. Part of the Neuron Cell Body Nucleus (inside the cell body) Nerve Fibers. Nerve Fibers. Dendrites Carries impulses TOWARD the cell body Axon

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Nervous System

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  1. Nervous System

  2. The Neuron • Also called the nerve cell • It is the basic structural unit of the nervous system

  3. The Neuron • Part of the Neuron • Cell Body • Nucleus (inside the cell body) • Nerve Fibers

  4. Nerve Fibers • Dendrites • Carries impulses TOWARD the cell body • Axon • Single nerve fiber that carries impulses AWAY from the cell body

  5. Nerve Fibers • Myelin Sheath • Lipid (fat) cover over the axon • Increases the rate of transmission of an impulse • Insulates and protects the axon

  6. Nerve Impulses • Axon of a neuron lies close to the dendrites of many other neurons • Synapse • Space between dendrites of one neuron and axon of another neuron • Impulses “jump” the synapse

  7. Nerve Impulses • Neurotransmitters • Special chemicals located at the end of each axon • Allows the nerve impulse to pass from one neuron to another via the synapse or synaptic cleft • Synapse is the space between the axon of one neuron and the dendrites of the next

  8. Nerves • Bundle of nerve fibers (neuron, dendrites, axons, etc) enclosed by connective tissue • Nerve impulses travel to and from the brain at the rate of 170 mph

  9. Types of Nerves • AFFERENT/Sensory • Carries messages from all parts of the body (sensory organs) to the brain and spinal cord • EFFERENT/Motor • Carries messages from the brain and spinal cord to muscles and glands

  10. Division of the Nervous System • Two main divisions • Central Nervous System • Brain and Spinal Cord • Peripheral Nervous System • Made up of the nerves in the body • Broken down into Autonomic and Somatic divisions

  11. Central Nervous System • Brain • Mass of nerve tissue • Protected by membranes and the cranium (skull)

  12. Central Nervous System CEREBRUM • Largest and highest section of the brain • Has convolutions (folds) • Separated into lobes which are named from the skull bones that surround them • Frontal (1 lobe) • Parietal (2 lobes) • Temporal (2 lobes) • Occipital (2 lobes)

  13. Central Nervous System Cerebellum Diencephalon Located between the cerebrum and midbrain Contains two structures Thalamus – acts as relay center Hypothalamus – regulates Autonomic Nervous System • Section below the cerebrum • Responsible for coordination of muscles, balance and posture, and muscle tone

  14. Central Nervous System • Midbrain • Located below the cerebrum at the top of the brain stem • Responsible for conducting impulses between brain parts • Responsible for certain eye reflexes

  15. Central Nervous System • Pons • Located below the midbrain in the brain stem • Responsible for conducting messages to other parts of the brain • Responsible for certain reflex actions including chewing, tasting, production of saliva • Assists with respirations

  16. Central Nervous System • Medulla Oblongata • Lowest part of the brain stem • Connects with the spinal cord • Responsible for regulating the heart beat, respirations, swallowing, coughing, and blood pressure

  17. Central Nervous System • Spinal Cord • Continues down from the medulla oblongata • Ends at the 1st or 2nd lumbar vertebra • Surrounded and protected by the vertebrae • Carries AFFERENT (sensory) messages to the brain • Carries EFFERENT (motor) messages from the brain to the nerves that go to muscles and glands

  18. Central Nervous System • Meninges • Three membranes that cover and protect the brain and spinal cord • Dura mater • Thick, tough outer layer • Arachnoid • Middle, delicate web like layer • Pia mater • Innermost layer • Closely attached to the brain and spinal cord • Contains blood vessels that nourish the nerve tissues

  19. Central Nervous System

  20. Peripheral Nervous System • Consists of cranial nerves and spinal nerves • 12 Cranial Nerves • On Old Olympus Towering Tops A Finn Versus German Viewed All Hops • See worksheet • Spinal nerves • 31 pairs and their branches • Carries messages to and from the spinal cord

  21. Peripheral Nervous System • Spinal nerves • 31 pairs and their branches • Carries messages to and from the spinal cord • Plexus • Each nerve goes directly to a particular part of the body or network with other spinal nerves • Supplies sensation to large segments (Dermatomes) of the body

  22. Plexus Cervical Brachial Lumbar Sacral

  23. Dermatomes

  24. Autonomic Nervous System • Important part of the Peripheral Nervous System • Helps maintain a balance in the involuntary functions • Heart rate, respirations, temperature, digestion, etc. • Allows the body to react in times of emergency

  25. Autonomic Nervous System • Two divisions • Sympathetic Nervous System • Parasympathetic Nervous System • Two systems work together to • Maintain HOMEOSTASIS (balanced state) • Control involuntary body functions at proper rates

  26. Autonomic Nervous System • Sympathetic Nervous System • “Fight or Flight” • Acts in times of emergencies • Prepares the body to act • Increases heart rate, respirations, and blood pressure • Slows down the digestive tract

  27. Autonomic Nervous System • Parasympathetic Nervous System • Counteracts the actions of the Sympathetic system after an emergency • Lowers heart rate, respirations, and blood pressure • Increases activity of the digestive tract

  28. Graphic Organizer CNS and PNS

  29. Pathophysiology - CVA • Cerebrovascular Accident (CVA) • Also called Stroke • Blood flow to the brain has been interrupted resulting in lack of oxygen to the brain and therefore destruction of brain tissue • Causes • Cerebral hemorrhage from hypertension, aneurysm (weak blood vessel), trauma • Occlusion (blockage) caused by atherosclerosis (fat build up) or thrombus (blood clot)

  30. Pathophysiology - CVA • Symptoms • Varies depending on the area of the brain affected and the amount of brain tissue damaged • Loss of consciousness • Dizziness • Weakness • Paralysis on one side of the body (hemiplegia) • Mental confusion • Visual disturbances • Aphasia (speech and language impairment) • Incontinence

  31. Treatment - CVA • Like a heart attack, the quicker treatment is administered the less the damage occurs • Within first three hours give thrombolytic (clot bursting) drugs such as TPA • CT scan done first because if caused by hemorrhage cannot give thrombolytic • Angioplasty – opens cerebral artery, dissolves clot and restores blood flow

  32. Treatment - CVA • Long term treatment depends on the damage that has occurred • Often need therapies such as physical, occupational, and speech therapies • May need assistive devices such as canes, walkers, and braces • Prevention of blood clots – thin blood • Take ASA, Coumadin, etc for the rest of your life • Treat underlying conditions such as high blood pressure, atherosclerosis, diabetes, etc

  33. Pathophysiology – Parkinson’s Disease • Chronic, progressive condition involving degeneration of brain cells • Usually occurs in persons over 50 years of age but not always • Caused by lack of or imbalance of a neurotransmitter, dopamine, in the brain • Cells that produce dopamine stop producing and die • When dopamine levels drop neurons start firing abnormally causing the classic tremors

  34. Pathophysiology – Parkinson’s Disease • Symptoms • Tremors, stiffness, and muscular rigidity • Cog Wheeling • Pill rolling • Forward leaning position and a shuffling gait • Difficulty in stopping while walking • Loss of facial expression and drooling • Parkinson’s Mask • Mood swings, behavioral changes, and frequent depression

  35. Treatment – Parkinson’s Disease • No known cure • Medication to lessen symptoms and possibly slow progression • Levodopa – synthetic dopamine • Physical therapy and assistive devices to limit the muscular rigidity

  36. Other Diseases of the Nervous System • Paraplegia = paralysis of the lower extremities • Encephalitis = inflammation of the brain caused by virus, bacteria, or chemical agent • Hydrocephalus = excessive accumulation of cerebrospinal fluid in the ventricles

  37. Other Diseases of the Nervous System • Neuralgia = nerve pain • Epilepsy = condition involving abnormal electrical impulses in the brain resulting in convulsions or seizure • Cerebral palsy = disturbance in voluntary muscle action caused by brain damage • Multiple sclerosis = A chronic, progressive, disabling condition resulting from a degeneration of the myelin sheath

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