BMS 100 - Chapter 9 Outline, Part One: Neurons
    Neurons (p. 206)
  • Dendrites receive electrical signals from multiple sources and deliver them to the cell body
  • Cell body
  • Axon - conducts electrical signals away from cell body (if stimulated)
      Organs of the Nervous System (p. 203)
    1. Central Nervous System (CNS) = brain and spinal cord
    2. Peripheral Nervous System (PNS) = nerves (cordlike bundles of axons)
      • "cranial nerves" (12 pair) - connected to brain and reach to head, neck, etc.
      • "spinal nerves" (31 pair) - originate from the spinal cord
    3. Components of a reflex
      1. receptor = structure that detects a stimulus
      2. sensory neurons (in nerves) - conduct signals from receptors to the CNS
      3. interneurons (in CNS)
      4. motor neurons (in nerves) conduct signals to...
      5. effectors - muscles and glands that produce a response
      The Action Potential (AP) (p. 210)
  • an action potential (AP) is an electrical "wave" that travels along the membranes of neurons and muscle fibers
    1. nerve AP - travels along axon of neuron toward axon terminal
    2. muscle AP - spreads over muscle fiber membrane; APs cause muscle fibers to contract
  • when a neuron or a muscle fiber is not conducting an AP, its interior is electrically negative
  • APs are generated when the interior of the cell becomes electrically positive and they are terminated when the interior of the cell becomes electrically negative
  • ions and gates involved in APs
    1. sodium gates - when open, allow Na+ ions to diffuse inward, making the inside of the cell more positive (generates AP)
    2. calcium channels - in heart muscle; when open, allow Ca++ ions to diffuse inward, making the inside of the cell more positive (sustains AP)
    3. potassium gates - when open, allow K+ to diffuse outward, making the cell less positive (more negative) inside (terminates AP)
      Synapses (p. 214)
    1. synapse = a junction between two neurons (or between a neuron and a receptor or an effector)
    2. synaptic transmission
      1. presynaptic neuron - may have "synaptic knobs"; releases neurotransmitter molecules when AP arrives in axon terminal
      2. postsynaptic neuron - has receptors for neurotransmitters
        • binding of neurotransmitter to receptor may be "excitatory" or "inhibitory" to postsynaptic neuron
          • excitatory n.t. - makes postsyn. neuron more positive inside
          • inhibitory n.t. - makes postsyn. neuron more negative inside
        • excitatory signals, if adequate, trigger AP in postsynaptic neuron
    Chapter 9 Study Questions at OLC - 2, 3, 4, 5, 7, 8, 9, 12, 13, 18, 25, 31, 33, 34, 35, 36, 37, 41

    BMS 100 Chapter 9 Outline, Part Two - The Brain (p. 224)
    1. Gray Matter and White Matter
      1. gray matter contains cell bodies and synapses - capable of “processing” (thinking, learning, etc.)
      2. myelin and white matter
        1. glial cells may wrap around an axon, producing a myelin sheath (myelin is “fatty,” white, and nonconductive)
        2. “nodes” = gaps in the myelin sheath; APs jump from node to node - myelinated axons conduct impulses rapidly
        3. white matter contains many myelinated axons - for rapid conduction of large numbers of APs

    2. Cerebrum
      1. consists of two cerebral hemispheres connected by the corpus callosum
      2. lobes: frontal lobe, parietal lobe, occipital lobe, temporal lobe.
      3. cerebral cortex
        1. thin layer of gray matter near the surface
        2. all consciousness, intelligence, etc. occurs in the cerebral cortex
      4. Functional areas (three major types)
        1. Motor Areas – send commands to voluntary muscles
          1. primary motor cortex - in frontal lobe; axons from primary motor cortex project to opposite side of CNS
          2. motor speech area (Broca's area) - located in frontal lobe (of left hemisphere usually); activates muscles necessary for speech
        2. sensory areas – for detailed sensory perception
          1. primary visual cortex - in occipital lobes
          2. primary auditory cortex - in temporal lobes
          3. parietal lobes receive general sensory information (senses of touch, etc.)
        3. association areas – provide understanding, thought, decision-making, etc.

    3. Diencephalon
      1. thalamus
        1. sensory impulses from all senses except smell converge on thalamus
        2. axons from thalamus project to cerebral cortex
        3. thalamus "filters" input and controls sensory flow to cerebrum
      2. hypothalamus controls many glands, food and water intake, digestive activities, body temperature, some emotions, sleep-wake rhythms, etc.

    4. Brainstem - includes the medulla oblongata, which contains vital reflex centers:
      1. cardiac center - regulates heart rate and strength of contraction
      2. vasomotor center - controls blood pressure by regulating constriction of arteries
      3. respiratory center - sends APs to breathing muscles

    5. Cerebellum - required for balance and coordination of voluntary (skeletal) muscles
      1. cerebrum initiates “intent” (desired movement)
      2. actual movement is reported to cerebellum from spinal cord, eyes and ears; cerebellum sends "corrective feedback" (error-correcting signal) to refine pattern of motor activity
    Chapter 9 Study Questions at OLC - 2, 3, 4, 5, 7, 8, 9, 12, 13, 18, 25, 31, 33, 34, 35, 36, 37, 41
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    Fall 2010