Human nervous system

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Human nervous system

  1. 1. Essential Understandings Describe the basic structure of a neuron, and compare the functions of the three classes of neurons. Explain how a nerve impulse is transmitted across a chemical synapse List the major regions of the brain and the main functions of each region. Describe the overall anatomy of the peripheral nervous system, including the cranial nerves and spinal nerves. Explain how the somatic system differs from the autonomic system. Contrast the overall functions of the sympathetic and para-sympathetic divisions of the autonomic nervous system. List all tissues that light passes through from when it enters the eye until it is converted into a nerve impulse. Discuss the role of rods and cones in transducing a light stimulus into a nerve impulse Distinguish the parts of the ear that make up the outer ear, middle ear, and inner ear. Describe the mechanism by which sound waves in the outer ear are converted into nerve impulses in the inner ear.
  2. 2. Regulation Processes by which a stable internal environment is kept.Regulation is brought about by the Nervous and Endocrine system.Neuron Cell specialized in transmitting impulses – a nerve cellDendrites part of nerve cell that receives impulses, towards the cell bodyAxon carries impulses away from the cell body of a neuronTerminal Branches The axons end that is in contact with another cell.Synapse The GAP between the terminal branch and another cell.Neurotransmitters Chemicals released from the tip of an axon into the synapse when a nerve impulse arrives; may stimulate or inhibit the next neuron
  3. 3. Nerves A bundle of axons or fibers, bound together.Sensory neurons carry signals from receptors & transmit information to brain and spinal cordMotor neurons carry signals from central nervous system to the muscles and glands.Inter neurons process signals from one sensory neurons and relay signals to motor neurons.Receptors receive stimuli from the environment. The sense organsEffectors A muscle or a gland that responds to a stimuli.Reflex arc Pathway of sensory receptors ,neurons, effector(s) that participate in a reflex
  4. 4. Central Nervous system (CNS)Cerebrum part of the forebrain, associated with higher functions, including language and abstract thoughtCerebellum concerned with fine motor coordination and body movement, posture, and balance;Medulla The region of the brain that, controls heart rate, constriction and dilation of blood vessels, respiration, and digestion.Spinal Cord receives sensory information and sends output motor signals; with the brain, forms the central nervous system.Peripheral nervous systemSomatic Nervous system -neurons that connect the CNS to skeletal muscles (voluntary), the skin & sense organsAutonomic nervous system Serves the internal organs of the body, Usually no voluntary control. Ex. breathingMalfunctions: Alzheimer’s, Parkinson’s, Multiple Sclerosis, stroke…
  5. 5. BrainSpinal Cord Peripheral nerves
  6. 6. CerebrumCerebellum Medulla Spinal Cord
  7. 7. Nucleus More information Dendrites axon Synapse Myelin Sheath Terminal Branch
  8. 8. How many neurons (nerve cells) are in the brain? How big are they?It is estimated that there are 100 billion (100,000,000,000) neuronsin the human brain. To get an idea of how many 100 billion is, thinkof this:Assume that you were going to count all 100 billion cells at a rate of1 cell per second. How long would it take you to count all 100 billioncells? Calculations say it would take about 3,171 years!!!.
  9. 9. Central Nervous System brain spinal cord Peripheral Nervous System cranial nerves spinal nerves sensory fibers motor fibers somatic nervous autonomic nervoussystem (to skeletal system (to smooth muscles) muscle, cardiac muscle, and glands) sympathetic parasympathetic division division
  10. 10. Peripheral Nervous System Any neurons outside of the CNS. Sensory Division –  bringsin stimuli from external environment  monitors status of internal environment Motor Division –  Somatic – carries signals to skeletal muscles  Autonomic – coordinates functions of organs and helps maintain homeostasis. Sympathetic and Parasympathetic  Oftenhave opposite effects on the body.  One system stimulates, the other inhibits
  11. 11. TheSenseOrgans
  12. 12. TheEYE
  13. 13. Main Parts of the Eye Cornea – light enters, transparent layer of cells Aqueous Humor – in anterior chamber, light passes through Iris – colored part; regulates size of pupil Pupil – black dot; opening; light enters inner eye Lens – behind pupil; focuses light onto retina Vitreous Humor – fluid behind lens Retina – has photoreceptors  Rods – black and white; extremely sensitive to light  Cones – color, less sensitive to light. Concentrated in the FOVEA. Optic Nerve – Carries impulses to the brain. Sclera and Choroid – outer layers of the eye
  14. 14. The EAR
  15. 15. Outer Ear Auricle (Pinna) – visible part of the ear. Collects sound Auditory Canal – sound enters, ear canal Tympanum(eardrum) - membrane. Vibrates
  16. 16. Middle Ear Hammer(malleus) – bone…attached to eardrum…accepts vibrations and passes them to Anvil(incus) – bone – accepts vibrations and passes them to Stirrup(stapes) = bone – accepts vibrations and passes them to the Oval Window
  17. 17. Inner Ear Oval Window – attached to stirrup… creates pressure waves in the cochlea Cochlea - snail like. Fluid filled. Lined with tiny sensory cilia that produce nerve impulse…….taken to the… Auditory Nerve(cochlear nerve) – takes impulse to the brain
  18. 18. Eustachian TubeConnectthe EAR, NOSE, AND THROAT
  19. 19. BALANCE Semicircular Canals – helps CNS maintain balance and your sense of equilibrium. Filled with fluid…lined with ciliary sensory nerves. When your head changes position, the hairs sense and send impulses to the brain.
  20. 20. TASTE AND SMELL Smell – chemoreceptor in the lining of the nasal passages. Taste – taste buds on the tongue. Sensitivity to taste varies on the area of the tongue. Sweet, sour, bitter, salty.
  21. 21. Touch Not found in one particular place. All skin regions are sensitive to touch. Temperature (Hot and Cold), Pain, Pressure, light touch. Greatest concentration of touch receptors: face, hand, toes

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