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Nervous Tissue

Nervous Tissue. Organization of the Nervous System. Divisions of the Nervous System. Central Nervous System brain spinal cord Peripheral Nervous System peripheral nerves cranial nerves spinal nerves. 10-1. CNS. PNS. Divisions of Peripheral Nervous System. Sensory Division

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Nervous Tissue

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  1. Nervous Tissue

  2. Organization of the Nervous System

  3. Divisions of the Nervous System • Central Nervous System • brain • spinal cord • Peripheral Nervous System • peripheral nerves • cranial nerves • spinal nerves 10-1

  4. CNS PNS

  5. 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 10-4

  6. Divisions Nervous System 10-5

  7. 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 10-6

  8. Function of the Nervous System sensory input motor input sensory receptor effector integration

  9. Neuroglia

  10. Types of Neuroglial Cells • Schwann Cells • peripheral nervous system • myelinating cell • Astrocytes • CNS • scar tissue • mop up excess ions, etc • induce synapse formation • connect neurons to blood vessels • Oligodendrocytes • CNS • myelinating cell • Ependyma • CNS • ciliated • line central canal of spinal cord • line ventricles of brain • Microglia • CNS • phagocytic cell 10-11

  11. Types of Neuroglial Cells 10-12

  12. Neuron Structure 10-7

  13. Regeneration of A Nerve Axon 10-13

  14. Typical Neuron dendrite cell body Myelin sheath Synapse axon

  15. Neuron Membrane Outside cell Na+ -70mV K+ Inside cell

  16. Myelination of Axons • White Matter • contains myelinated axons • Gray Matter • contains unmyelinated structures • cell bodies, dendrites 10-8

  17. Nodes of Ranvier Schwann Cells Axon Myelin Sheath

  18. Classification of Neurons • Bipolar • two processes • eyes, ears, nose • Unipolar • one process • ganglia • Multipolar • many processes • most neurons of CNS

  19. Classification of Neurons • Sensory Neurons • afferent • carry impulse to CNS • most are unipolar • some are bipolar • Interneurons • link neurons • multipolar • in CNS • Motor Neurons • multipolar • carry impulses away from CNS • carry impulses to effectors 10-10

  20. Resting Membrane Potential • inside is negative relative to the outside • polarized membrane • due to distribution of ions • Na+/K+ pump 10-14

  21. Potential Changes • at rest membrane is polarized • threshold stimulus reached • sodium channels open and membrane depolarizes • potassium leaves cytoplasm and membrane repolarizes 10-15

  22. Local Potential Changes • occur on membranes of dendrites and cell bodies • caused by various stimuli • chemicals • temperature changes • mechanical forces • if membrane potential becomes more negative, it has hyperpolarized • if membrane potential becomes more positive, it has depolarized • graded • summation can lead to threshold stimulus that starts an action potential 10-16

  23. Action Potentials • nerve impulse • occur on axons • all-or-none • refractory period • absolute - time when threshold stimulus does not start another action potential • relative – time when stronger threshold stimulus can start another action potential 10-17

  24. Action Potentials 10-18

  25. Impulse Conduction 10-19

  26. Saltatory Conduction

  27. Resting Potential of an Axon

  28. Propagation of an Action Potential

  29. Propagation of an Action Potential

  30. Synapses Ca2+ Presynaptic neuron Postsynaptic membrane Synaptic vesicles containing neurotransmitters

  31. Synapses

  32. The Synapse Nerve impulses pass from neuron to neuron at synapses 10-21

  33. Synaptic Transmission Neurotransmitters are released when impulse reaches synaptic knob 10-22

  34. Synaptic Potentials • EPSP • excitatory postsynaptic potential • graded • depolarizes membrane of postsynaptic neuron • action potential of postsynaptic neuron becomes more likely • IPSP • inhibitory postsynaptic potential • graded • hyperpolarizes membrane of postsynaptic neuron • action potential of postsynaptic neuron becomes less likely 10-23

  35. Summation of EPSPs and IPSPs • EPSPs and IPSPs are added together in a process called summation • More EPSPs lead to greater probability of action potential 10-24

  36. Impulse Processing • Neuronal Pools • groups of interneurons that make synaptic connections with each other • interneurons work together to perform a common function • each pool receives input from other neurons • each pool generates output to other neurons 10-26

  37. Convergence • neuron receives input from several neurons • incoming impulses represent information from different types of sensory receptors • allows nervous system to collect, process, and respond to information • makes it possible for a neuron to sum impulses from different sources 10-27

  38. Divergence • one neuron sends impulses to several neurons • can amplify an impulse • impulse from a single neuron in CNS may be amplified to activate enough motor units needed for muscle contraction 10-28

  39. Neurotransmitters • Acetylcholine- slows heart rate; PNS • Glutamate- most prevalent neurotransmitter in the brain • Aspartate- in CNS • GABA- inhibitory neurotransmitter • Glycine- inhibitory neurotransmitter • Norepinephrine- awakening from deep sleep • Epinephrine- increase heart rate • Dopamine- movement of skeletal muscles • Seratonin- sensory perception, temp regulation, mood, sleep • Nitric oxide- may play a role in memory and learning • Enkephalin- inhibit pain impulses by suppressing release of substance P • Substance P- enhances perception of pain tyrosine

  40. brain

  41. skin skull dura mater arachnoid layer pia mater cerebral cortex Coverings of the Brain-Meninges

  42. Menenges: • Covers and protects CNS • Protects blood vessels and encloses venus sinuses • Contains CSF • Forms partition within the skull

  43. Cerebruspinal Fluid Brain Ventricles CSF Spinal Cord Lf. Ventricle Rt. Ventricle Saggital View Anterior View

  44. CSF • 150 ml in adult • contains: glucose, proteins,lactic acid, urea, cations, anions, WBC • Functions: • Reduces wt. of brain by 97% • Prevents head injury • Supplies brain with nutrition • Transports hormones along ventricular channels

  45. Cerebrum • Involved with higher brain functions. • Processes sensory information. • Initiates motor functions. • Integrates information.

  46. Corpus Callosum Right Hemisphere Left Hemisphere Brain has 2 Hemispheres • Left & Right sides are separate • Corpus Callosum : major pathway between hemispheres • Some functions are ‘lateralized’ • language on left • math, music on right • Lateralization is never 100%

  47. Right-Left Specialization of the Cerebrum left side • language development • mathematical & learning capabilities • sequential thought processes right side • visual spatial skills • musical and artistic activities • intuitive abilities

  48. Medial surface of right hemisphere Corpus Callosum Corpus Callosum • Major ( but not only) pathway between sides • Connects comparable structures on each side • Permits data received on one side to be processed in both hemispheres • Aids motor coordination of left and right side

  49. cerebral cortex white matter corpus callosum basal ganglia ventricles Cerebrum Cross-Section

  50. Corpus Callosum • What happens when the corpus callosum is cut? • Sensory inputs are still crossed • Motor outputs are still crossed • Hemispheres can’t exchange data

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