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Nervous System

Nervous System. Nervous System. Cell types of Neural tissue Neurons Neuroglial cells. Divisions of the Nervous System. Central Nervous System Brain Spinal cord Peripheral Nervous System Peripheral nerves Cranial nerves Spinal nerves. Divisions of Peripheral Nervous System.

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Nervous System

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  1. Nervous System

  2. Nervous System • Cell types of Neural tissue • Neurons • Neuroglial cells

  3. Divisions of the Nervous System • Central Nervous System • Brain • Spinal cord • Peripheral Nervous System • Peripheral nerves • Cranial nerves • Spinal nerves

  4. 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.

  5. Divisions Nervous System

  6. Sensory Function Sensory receptors gather information Information is carried to the CNS Integrative Function Sensory information used to create Sensations Memory Thoughts Decisions Motor Function Decisions are acted upon Impulses are carried to effectors Functions of Nervous system

  7. Neuron Structure

  8. Myelination of Axons • White Matter • Contains myelinated axons • Gray Matter • Contains unmyelinated structures • Cell bodies, dendrites

  9. Classification of Neurons • Bipolar • Two processes • Eyes, ears, nose • Unipolar • One process • Ganglia • Multipolar • Many processes • Most neurons of CNS

  10. 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 Classification of Neurons

  11. Schwann Cells Peripheral nervous system Myelinating cell Oligodendrocytes CNS Myelinating cell Microglia CNS Phagocytic cell Astrocytes CNS Scar tissue Mop up excess ions, etc Induce synapse formation Connect neurons to blood vessels Ependyma CNS Ciliated Line central canal of spinal cord Line ventricles of brain Types of Neuroglial Cells

  12. Types of Neuroglial Cells

  13. Regeneration of A Nerve Axon

  14. Resting Membrane Potential • Inside is negative relative to the outside • Polarized membrane • Due to distribution of ions • Na+/K+ pump

  15. Potential Changes • At rest membrane is polarized • Threshold stimulus reached • Sodium channels open and membrane depolarizes • Potassium leaves cytoplasm and membrane repolarizes

  16. 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 (see paragraph under potential changes) • Summation can lead to threshold stimulus that starts an action potential

  17. 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

  18. Action Potentials

  19. Impulse Conduction

  20. Saltatory Conduction

  21. The Synapse • Nerve impulses pass from neuron to neuron at synapses

  22. Synaptic Transmission • Neurotransmitters are released when impulse reaches synaptic knob.

  23. 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

  24. 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

  25. Neurotransmitters

  26. Impulse Processing • Neuronal Pools • Groups of interneurons that make synaptic connections with each other • Interneurons work together to peform a common function • Each pool receives input from other neurons • Each pool generates output to other neurons

  27. 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

  28. Divergence • One neuron sends impulses to several neurons • Can amplify an impulse • Impulse from a single neuron is CNS may be amplified to activate enough motor units needed for muscle contraction

  29. Symptoms Blurred vision Numb legs or arms Can lead to paralysis Treatments No cure Bone marrow transplant Interferon (anti-viral drug) hormones Causes Myelin destroyed in various parts of CNS Hard scars (scleroses) form Nerve impulses blocked Muscles do not receive innervation May be related to a virus Clinical ApplicationMultiple Sclerosis

  30. Meninges of the Spinal Cord • Meninges • Membranes surrounding CNS • Protect CNS • Three layers • Dura mater – outer, tough • Arachnoid mater – weblike • Pia mater – inner, delicate

  31. Meninges of the Spinal Cord

  32. Spinal Cord Structure • Extends foramen magnum to 2nd lumbar vertebra.

  33. Cross Section of Spinal Cord

  34. Spinal Cord Functions • Center for spinal reflexes • Conduit for nerve impulses to and from the brain

  35. Reflex Arcs • Reflexes – automatic, subconscious responses to stimuli

  36. Knee-jerk Reflex • Helps maintain posture

  37. Withdrawal Reflex • Protective

  38. Crossed-Extensor Reflex • Flexor muscles contract • Flexor muscles on opposite side inhibited • Extensor muscles on opposite side contract for balance

  39. Tracts of the Spinal Cord • Ascending tracts conduct sensory impulses to the brain • Descending tracts conduct motor impulses from the brain to motor neurons reaching muscles and glands.

  40. Ascending Tracts • Fasciculus cuneatus • Lateral spinothalamic

  41. Functions interprets sensations determines perception stores memory reasoning makes decisions coordinates muscular movements regulates visceral activities determines personality Major Parts cerebrum two cerebellar hemispheres diencephalon brain stem cerebellum Brain

  42. Structure of Cerebrum • corpus callosum • connects hemispheres • convolutions • bumps or gyri • sulci • grooves • longitudinal fissure • separates hemispheres • transverse fissure • separates cerebrum from cerebellum

  43. Lobes of Cerebrum • Frontal • Parietal • Temporal • Occipital • Insula

  44. Functions of Cerebrum • interpretation • initiating voluntary movements • storing memory • retrieving memory • reasoning • center for intelligence and personality

  45. Functional Regions of Cerebral Cortex • Cerebral Cortex – thin layer of gray matter that constitutes the outermost portion of cerebrum; contains 75% of all neurons in nervous system

  46. Motor Areas • Primary Motor Areas • frontal lobes • control voluntary muscles • Broca’s Area • anterior to primary motor cortex • usually in one hemisphere • controls muscles needed for speech • Frontal Eye Field • above Broca’s area • controls voluntary movements of eyes and eyelids

  47. Motor Areas

  48. Sensory Areas • Cutaneous Sensory Area • parietal lobe • interprets sensations on skin • Visual Area • occipital lobe • interprets vision • Auditory Area • temporal lobe • interprets hearing

  49. Sensory Areas

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