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Understanding the Nervous System: Neurons, Divisions, and Functions

Explore the intricate workings of the nervous system with a focus on neurons, CNS, PNS, and neural functions. Learn about neuron structures, classifications, functions, myelination, reflex arcs, and more. Delve into the brain and spinal cord coverings, spinal cord anatomy, spinal nerves, and their significance. Unravel the complexities of brain size and its variations. Enhance your knowledge of the nervous system for a better understanding of the body's control and integration mechanisms.

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Understanding the Nervous System: Neurons, Divisions, and Functions

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  1. Chapter 10Nervous System • Organs • Brain, Spinal Cord (CNS), and Nerves (PNS) • Function • Integration of all parts – organs - tissues - cells • Allows control of parts to enable unification: communication - control -integration - homeostasis - survival

  2. Chapter 10Nervous System • Cell Types of Neural Tissue • Neurons • Neuroglial cells

  3. Divisions of the Nervous System • Central Nervous System • brain • spinal cord • Peripheral Nervous System • nerves • cranial nerves • spinal nerves

  4. Neuron Structure Soma

  5. Neurons Structure: • Cellbody - Soma • Axon - sends messages away from soma • Dendrite - receives messages from axon to soma. Types of Neurons: • Afferent (sensory) - to spinal cord or brain • Efferent (motor) - away from spinal cord or brain • Interneurons (synapse between 1 and 2) - from afferent to efferent (from sensory to motor)

  6. Classification of Neurons – Functional Differences • Sensory Neurons • afferent • carry impulse to CNS • Interneurons • link neurons • Found in CNS • Motor Neurons • carry impulses away from CNS • carry impulses to effectors

  7. See hand out Divisions Nervous System

  8. Peripheral Nervous system • Spinal nerves and Cranial nerves Central Nervous System Brain and Spinal Cord Somatic Nervous System (Skeletal muscle) 2. Autonomic nervous system (internal environment – Smooth, Cardiac muscle, Glands) Sensory and Motor Neurons Outside environment Parasympathetic Division Salivation, Urination, Digestion, etc. Active under ordinary, restful conditions. Counterbalances effect of Sympathetic division Sympathetic Division Prepares body for emergency ‘Fight or Flight’

  9. Divisions of Peripheral Nervous System • Sensory Division • picks up sensory information and delivers it to the CNS • Motor Division • carries information to muscles and glands • Divisions of the Motor Division • Somatic – carries information to skeletal muscle • Autonomic – carries information to smooth muscle, cardiac muscle, and glands

  10. Functions of Nervous System • Sensory Function • sensory receptors gather information • information is carried to the CNS • Motor Function • decisions are acted upon • impulses are carried to effectors • Integrative Function • sensory information used to create • sensations • memory • thoughts • decisions

  11. Myelination of Axons • White Matter • contains myelinated axons • Gray Matter • contains unmyelinated structures • cell bodies, dendrites

  12. Myelination of Axons • Unmyelinated fibers conduct impulses slower. • Myelinated fibers conduct impulses faster • Nodes of Ranvier (short region of exposed axon between Schwann cells on neurons) • The more myelin the faster the impulse

  13. Multiple Sclerosis • Most common disease of the nervous system • Loss of myelin sheath • Hard plaque lesions replace myelin • Nerve conduction is impaired and weakened, loss of coordination, visual impairment and speech disturbances. • Most common in women between age 20-40 • No known Cure

  14. Reflex Arc

  15. Reflex Arc • Conduction of an impulse to and from the brain and spinal cord. • Types: • Two neuron arc - simplest form • Consists of afferent and efferent neurons • Three neuron arc - must common • Consists of afferent, interneurons, and efferent

  16. Two Neuron Arc

  17. Three Neuron Arc

  18. The Synapse Nerve impulses pass from neuron to neuron at synapses

  19. Synaptic Transmission Neurotransmitters are released when impulse reaches synaptic knob = Acetylcholine or AcH

  20. 20

  21. Brain and Cord Coverings • Bone is outer cover • Brain - Cranium • Spinal cord - Vertebrae • Meninges - inner cover • Dura Mater - outer, white fibrous tissue • Arachnoid Membrane - cobwebby, middle • Pia Mater - adheres to brain, transparent • Meningitis is inflammation of meninges

  22. Meninges

  23. Meninges White matter Grey matter

  24. Spinal Cord

  25. Spinal Cord • 17 - 18 in. in length • Two bulges • Cervical region - sends nerves to upper limbs • Lumbar region - sends nerves to lower limbs • Grey Matter • Inner core, looks like an H in cross section, made of interneurons and motor neuron somas • White Matter • Surrounds gray matter, consists of nerve fibers in bundles (axons and dendrites)

  26. Spinal Nerves • 31 pairs - they are numbered according to where they are located. • Emerge from cord through foramen of vertebrae. • Each nerve level attaches to a body section • Dermatone - patches of skin that correspond to each nerve. • Herpes Zoster - (causes chicken pox and shingles) lies dormant at the ends of nerves. • Causes eruptions of red swollen patches which are very painful

  27. Spinal nerves

  28. Dermatomes

  29. Spinal nerves Spinal Nerves • Broken neck at 3, 4, or 5 vertebrae = damage to phrenic nerve • This nerve controls the diaphragm • Without artificial respiration, patient will die.

  30. Brain • Size • 3 pounds • Larger in men than women • Larger in young than old • Full size by age 18 • Contains 100 billion neurons http://www.cbsnews.com/2100-500165_162-6890474.html

  31. Brain

  32. oblongata Brain stem

  33. Brainstem Midbrain Pons Medulla oblongata Cerebellum Diencephalon Cerebrum Divisions of the Brain

  34. Divisions of the Brainstem • Medulla Oblongata • Most vital part of the brain • Injury or disease proves fatal • Lowest part of brainstem • Function • Vital centers - cardiac, dilates blood vessels (drops and increases blood pressure), respiratory • Nonvital centers - vomiting, coughing, sneezing, hiccupping, swallowing.

  35. Divisions of the Brainstem • Pons • Above the medulla oblongata • Function • Helps regulate respiration gases, chewing, saliva secretion, hearing

  36. Divisions of the Brainstem • Midbrain • Located above the pons and below the cerebrum • Function • Reflex center: eye movements, hearing

  37. Cerebellum • Second largest part of the brain • Function • Maintains equilibrium • Helps control posture • Smoothes movements instead of being jerky, trembling or uncoordinated • Diseases (hemorrhage, tumor) • Cause ataxia - muscle incoordination • Diagnose with a finger to nose test • Tremors • Disturbances of walk and balance

  38. Diencephalon • Located between the midbrain and cerebrum • Consists of the hypothalamus and thalamus • Hypothalamus: regulator of autonomic activities; mind-body link (tears); maintains water balance, waking state, appetite, and body temperature • Thalamus: recognizes sensations of pain, temp., and touch; relays sensory impulses to cerebrum; associates sensory impulses to emotions, arousal or alerting mechanism

  39. Cerebrum Gyrus/ fold Cerebellum

  40. Cerebrum • Largest part of the brain • Consists of two halves and 5 lobes • Right hemisphere • Spatial abilities - see whole picture • Left hemisphere • Analytical skills

  41. Cerebrum • Five Lobes • Frontal - forehead • Parietal - posterior top • Temporal - temples • Occipital - posterior base • Insula - hidden from view

  42. Cerebrum • Function • Sensory: visual and auditory • Motor ability: movement of muscles • Integrative ability: • Ability to receive sensory impulses and send motor impulses. • Consciousness: state of awareness • Memory: major mental activity • Use of language: ability to speak and write words and understand words • Emotions

  43. Cerebrum 43

  44. http://www.pbs.org/wgbh/nova/assets/swf/1/mapping-the-brain/mapping-the-brain.htmlhttp://www.pbs.org/wgbh/nova/assets/swf/1/mapping-the-brain/mapping-the-brain.html http://www.pbs.org/wgbh/nova/body/brain-trauma.html http://www.pbs.org/wgbh/nova/body/psychology-magic.html http://www.pbs.org/wgbh/nova/body/mirror-neurons.html http://www.pbs.org/wgbh/nova/body/how-memory-works.html

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