Unit 4 exam

• Components of the central nervous system

  • Spinal cord
  • Brain
• Components of the peripheral nervous system

  • Nerves
  • Ganglia
• Divisions of the peripheral nervous system

  • Sensory (afferent) division
  • Motor (efferent) division
• Subdivisions of the motor (efferent) division

  • Somatic nervous system
  • Autonomic nervous system
• Neuroglia


  Glial cells that support neurons
• Types of neuroglia


  • Astrocytes
  • Microglia
  • Oligodendrocytes
  • Schwann cells
• Neurons


  Specialized cells that conduct messages in the form of electrical impulses
• Neuron traits


  • Longevity
  • Amitotic
  • High metabolic rate
• Neuron parts


  • Dendrites
  • Soma (cell body)
  • Axon
• Functional classes of neurons

  • Sensory afferents
  • CNS interneurons
  • Motor efferents
• Structural classes of neurons

  • Multipolar
  • Bipolar
  • Unipolar
• Voltage


  Separation of charges, potential energy
• Current


  Voltage divided by resistance (I=V/R)
• Types of membrane ion channels

  • Leakage channels
  • Chemically gated channels
  • Voltage gated channels
  • Mechanically gated channels
• Resting membrane potential


  Typically -70 mV
• Depolarization


  Change in membrane potential towards 0 mV, cell becomes less negative
• Hyperpolarization


  Change in membrane potential away from 0 mV, cell becomes more negative
• Graded potentials


  Changes in membrane voltage that vary with stimulus strength, decremental (fade with distance)
• Action potentials


  Long distance signals on axons, all-or-none, non-decremental
• Phases of an action potential

  • Rest
  • Depolarization
  • Repolarization
  • After-hyperpolarization
• Refractory periods


  Times when the cell is less responsive to stimuli
• Myelinated axons


  Faster conduction velocity than unmyelinated axons
• Fatter axons


  Faster conduction velocity than skinnier axons
• Synapse


  Junction between two neurons where information is transferred
• Types of synapses


  • Electrical synapses
  • Chemical synapses
• Parts of a chemical synapse


  • Presynaptic terminal
  • Synaptic cleft
  • Postsynaptic dendrite or soma
• Neurotransmitter clearance


  Enzyme degradation, diffusion away, reuptake by presynaptic cell
• Excitatory postsynaptic potential (EPSP)

  Depolarization that makes the cell more likely to fire an action potential
• Inhibitory postsynaptic potential (IPSP)


  Hyperpolarization that makes the cell less likely to fire an action potential
• Spatial summation


  Simultaneous inputs from multiple presynaptic cells are added
• Temporal summation


  Successive inputs from the same presynaptic cell, inputs close together in time
• Presynaptic inhibition


  Another neuron inhibits the release of excitatory neurotransmitter from a presynaptic cell
• Classes of neurotransmitters


  • Acetylcholine
  • Amino acids (glutamate, GABA)
  • Biogenic amines (norepinephrine, dopamine)
  • Neuropeptides (endorphins)
  • Lipids (endocannabinoids)
  • Purines (adenosine)
• Types of neurotransmitter receptors

  • Ionotropic (direct, chemically gated channels)
  • Metabotropic (indirect, G-protein coupled)
• Diverging circuits


  Few presynaptic cells communicate with several postsynaptic cells
• Converging circuits


  Many presynaptic cells communicate with few postsynaptic cells
• Serial processing


  Processing in sequence, e.g. retina -> thalamus -> cortex
• Parallel processing


  Simultaneous processing in different parts of the nervous system
• Developments of the nervous system

  • Neural plate
  • Neural tube
  • Neural crest
• Primary vesicles of the neural tube

  • Forebrain
  • Midbrain
  • Hindbrain