section 14

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section 14
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  1. the master controlling and communicating system of the body
    nervous system
  2. functions of the nervous system?
    • sensory input
    • Integration
    • Motor output
  3. What is sensory input?
    monitoring stimuli occurring inside and outside the body
  4. What is integration?
    The interpretation of sensory input
  5. What is motor output?
    The response to stimuli by activating effector organs
  6. What are the two major sections in the nervous system?
    • The central nervous system 
    • Peripheral nervous  system
  7. Peripheral System?
    • paired spinal and cranial nerves
    • carries messages to and from the spinal cord and brain
    • everything else that is not the central nervous system
  8. Central Nervous system?
    • Brain and spinal cord
    • integration and commander center
    • the middle
  9. The Peripheral System can be divided into what 2 sections?
    Sensory division and Motor division
  10. Sensory division?
    • AFFERENT
    • sensory afferent fibers- carry impulses from skin, skeletal muscles, and joints to the brain
    • Visceral afferent fibers- transmit impulses from visceral organs to the brain
  11. Motor division?
    • EFFERENT 
    • transmit impulses from CNS to effector organs
  12. The motor division can be divided into what?
    • Somatic nervous system
    • Autonomic nervous system
  13. Somatic nervous system?
    conscious control of skeletal muscles
  14. Autonomic nervous system?
    • Regulates smooth muscles, cardiac muscle, and glands
    • divisions- sympathetic and parasympathetic
  15. What are the two principal cell types of the nervous system?
    • Neurons 
    • Supporting cells
  16. Neurons?
    • excitable cells that transmit electrical signals
    • most communication is done by them
  17. what are neuroglia or glial cells?
    • They are the supporting cells in the nervous system
    • cells that surround and wrap neurons
  18. What are the functions of Neuroglia?
    • provide support scaffolding for neurons
    • segregate and insulate neurons
    • guide developing neurons to the proper connections
    • promote health and growth
  19. What are dendrites?
    • short, tapering, and diffusely branched processes
    • they are the receptive, or input, regions of the neuron
    • electrical signals are conveyed as graded potentials
    • they get signals from other neurons
  20. What is an axon hillock?
    • cone-shaped area from which axons arise
    • That is where the action potential comes from
  21. Schwann cell?
    the insolation sheet made of myelin that insulates the axon in the PNS
  22. What is axon?
    Where the cell sends a signal
  23. What is the Soma?
    • The nerve cell body
    • It cannot divide
    • Biosynthetic (making things for life)
    • Focal point for the outgrowth of neuronal processes(dendrites/axons)
    • Axon hillock
  24. What is the difference between a graded potential and an action potential?
    • Graded- vague electrical signal
    • Potential- direct and strong enough to be sent to another neuron
  25. Nerve fibers?
    Long axons
  26. What are the main two functions of an axon?
    • generate and transmit action potentials
    • they secrete neurotransmitters from axonal terminals
  27. axonal terminal?
    • branches terminus of an axon
    • signals will exit through it
  28. What is the function of the myelin sheath?
    • protect the axon in the Peripheral Nervous System
    • electrically insulate fibers from one another
    • increase the speed of the nerve impulse transmission
  29. What are the Nodes of Ranvier?
    gaps in the myelin sheath between adjacent Schwann cells
  30. What is Neurilemma?
    the nucleus and cytoplasm in a Schwann cells
  31. Schwann cells are in which nervous system?
    The Peropheral Nervous Sytem
  32. Oligodedrocytes
    • makes the myelin sheaths in axons in the CNS
    • There is no neurilemma
    • and the Nodes of Ranvier are widely spread
    • there is no neurilemma
  33. Regions of the Brain and Spinal Cord?
    • White matter- dense collections of myelinated fibers
    • Gray matter- mostly soma and unmyelinated fibers (not as dense)
  34. Neuron structural Classification?
    • Multipolar- three or more processes (most common
    • bipolar- two processes
    • unipolar- single, short process
  35. Neuron Functional classification?
    • Sensory (afferent)- transmit impulses toward the CNS
    • Motor (efferent)- carry impulses away from CNS
    • Interneurons (associations neurons)- shuttle signals through CNS pathways
  36. Action potentials or nerve impulses are what?
    always the same regardless of stimulus
  37. Voltage?
    measure of potential energy generated by separate charge (how much electrical energy there is)
  38. Potential Difference?
    voltage measured between 2 points (the difference of energy in 2 places)
  39. Current?
    the flow of electrical charge between 2 points
  40. Resistance?
    hindrance to charge flow (how much it will take to stop a current)
  41. Insulator?
    Substance with high electrical resistance
  42. Conductor?
    • substance with low electrical resistance (they transmit energy)
    • ex. wires
  43. Electrical Current in the body?
    • Flow of ions rather than electrons
    • Na+, K+, Cl-
  44. Membrane potential?
    • When there number of ionic charges is difference across the membrane.
    • K+ leaks out (diffusion) Inside becomes negative and outside becomes positive
    • The membrane provides a resistance to ion flow
  45. High permeability= ?
    Low permeability= ?
    Low resistance, high resistance
  46. Most cells have a resting potential of what?
    -70mV
  47. A membrane potential is measured....
    relative to the intercellular charge (negative in a resting cell(
  48. The resting potential difference (-70mV) is generated by what?
    the concentration gradients of Na+, K+, Cl- and protein (A-)
  49. Ionic differences (resting potential) are consequences of what?
    • Differential permeability Na+ and K+ (whether there is resistance)
    • Operation of the sodium- potassium pump (letting things through)
  50. Chemical gradient: sodium-potassium pump?
    results in an unequal distribution of ions across the plasma membrane. K+ in   Na+ out
  51. How does the Sodium- potassium pump work?
    • While K+ is being leaked out Na+ us being pumped in
    • But then there is a pump that pushes K+ in and Na+ out to not reach equilibrium and keep a resting membrane (-70mV)
  52. What are the 3 main things to consider during the initiation and propagation of nerve impulses?
    • ion channels
    • membrane potential
    • the effects of each on one another
  53. What is the different kinds of ion channels?
    • passive, or leakage, channels- always open
    • chemically gated channels- open with binding neurotransmitter
    • voltage gated channels- open and close in response to membrane potential (electrical charge)
    • mechanically gated channels- open and close in response to physical perturbations of receptors
  54. How do neurons communicated with one another?
    • through chemically gated channels.
    • When neurotransmitter binds to the receptor it changes the shape of the protein channel and things can come in and out
  55. confrontational change?
    When the protein channels change cause of something touched it or bumped into it
  56. How are voltage changes created?
    When gated channels are opened, ions diffuse across the membrane through the channel, movement is along their chemical gradients, an electrical current of ions is created and the voltage changes across the memebrane
  57. membrane potentials are produced by?
    • Changes in the membrane permeability to ions via Voltage gated channels
    • Result in alterations of ion concentrations across the membrane
  58. types of signals
    • graded potentials
    • action potential
  59. depolarization?
    the inside of the membrane becomes less negative
  60. hyperpolarization?
    the inside of the membrane becomes more negative than the resting potential (-70mV)
  61. repolarization?
    the return of the membrane to its normal resting membrane potential (-70mV)
  62. Graded potentials?
    • Can only travel short distances
    • decrease in intensity with distance
    • their magnitude varies with the strength of stimulus
    • sufficiently strong graded potentials can initiate action potentials
  63. Action Potentials?
    • only generated by muscle cells and neurons
    • they do not decreases in strength over sistance (cause of myolin sheath)
    • they are the principal means of neural transmission
  64. An action potential of a neuron is what?
    a nerve impulse
  65. resting state?
    Both Na+ and K+ channels are closed
  66. Depolarization?
    • Na+ channels open
    • K+ channels close
    • The membrane potential becomes less negative
  67. Repolarization?
    • Na+ closes
    • K+ open to make the inside less positive
  68. Hyperpolarization?
    Sometimes Na+ comes in but K+ rushes out fast to try to get to -70 mV
  69. What is the purpose of of the Sodium-Potassium Pump?
    to restore resting condition by kicking out Na+ and bringing back in K+
  70. Threshhold potential?
    When graded potentials sum to approximately -55mV
  71. What happens when a grade potentials reach a threshold potential?
    It triggers action potentials
  72. What is a refractory period?
    • It ensure that each action potential is separate
    • It enforces one-way transmission of nerve impulses
    • Prevents muscle lock ups
  73. Why is tetrodoxin bad?
    • it blocks sodium V-gated sodium channels and inhibits nerve impulse generation
    • One becomes paralized
  74. Threshold
    membrane is depolorized by 15 to 20mV
  75. Strong stimuli can generate what more often than a weak stimuli?
    action potentials
  76. Stimuli intensity is determined by what?
    the frequency of impulse transmittion
  77. The rate of impulse propagation is determined by what?
    • axon diameter 
    • presence of a myelin shealth
  78. axon diameter?
    the larger the diameter, the faster the impulse
  79. presence of myelin sheath?
    myelination dramatically increases impulse speed
  80. The current passes through a myelinated axon only where?
    the Nodes of Ranvier
  81. action potentials are triggered where?
    Nodes of Ranvier and jump from one node to the next
  82. Conduction of current is faster in what?
    myelinated axons than numyelinated axons
  83. Synapse?
    • a junction that mediates information transfer from one neuron:
    • to another neuron
    • to an effector
  84. presynaptic neuron?
    conducts impulses toward the synapse
  85. Postsynaptic neuron?
    transmits impulses away from the synapse
  86. Chemichal synapses?
    release and reception of neutransmitters
  87. what are chemical synapses composed of?
    • axonal terminal of the presynaptic neuron which contain synaptic vesicles 
    • receptor region on the dendrite or soma of the postsynaptic neuron
  88. synaptic cleft?
    fluid filled space that prevents direct transmission of nerve impulses
  89. What is a transmission across the synaptic cleft?
    • is a chemical event (not electrical)
    • ensures unidirectional communications between neurons
  90. How does the synaptic cleft transfer information?
    • Graded potential signals the soma
    • The soma fires an action potential
    • Action Potential goes down the axon to axonal terminal and signals Ca release 
    • That causes release of neurotransmitters into the synaptic cleft and bind to receptors on postsynaptic neuron
    • Then postsynaptic membrane permeability changes causing an excitatory or inhibitory effect
  91. reuptake?
    When some neurotransmitters get stuck in the presynaptic neuron instead of going to the postsynaptic neuron
  92. How are neurotransmitters removed?
    • enzymes degrade them
    • they are reabsorbed by astrocytes or presynaptic terminals
    • they diffuse from synaptic cleft
  93. Channel- linked receptors?
    • composed of integral membrane proteins
    • control neurotransmitter action
    • chemically gated channels
    • causes graded potentials
  94. excitatory receptors?
    • depolarize  membranes
    • only in chemically gated channels
    • can initiate Action Potentials
    • diffusion of Na+ into cells causes local depolarization
  95. inhibitory receptors?
  96. hyperpolarize membranes
    • causes membrane to become more permeable to potassium and chloride
    • makes inside more negative
    • reduces the chance of an action potential
  97. Where are voltage gates?
    in the hillock (the starting point of Action Potential)
  98. Summation?
    graded potentials are summed to either depolarize or hyperpolarize a postsynaptic neuron
  99. temporal summation?
    presynaptic neuron transmit impulses in rapid fire order (many have to add up until an action potential happens)
  100. spatial summation?
    postsynaptic neuron is stimulated by a large number of terminals at the same time  ( a bunch of them fire at once and make an action potential)
  101. neurotransmitters?
    chemicals used for neuronal communication with the body and the brain
  102. acetylcholine?
    neurotransmitters releases during muscle contractions

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