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Neurophys 17- (Neuroplasticity and memory (Memory mechanism (Theoretical…

- - - - networks of interconnected neuron like elements, connections via synapses, can be trained/can learn, neurons process info in parallel (make decisions faster)
      - firing rule determines when they generate APs, train network to undertake task by applying rule, training rule is what will happen to synapse when you activate it
    - - memory stored as connection strength in neural network, one neuron for several memories, distributed so memory doesnt depend on single neurons
      - usually located close to region that responds to specific modality, network allows for slow decay of memory, parts of brain that sense particular functions become active when you recall them
      - stimulating system causes it to get stronger over time - interconnections activate all other neurons in system -output is effected by larger part of system
    - - in neurons, changes in synaptic strength from prior activity
      - Hebb's theory: memory resides in strength of synapse, associative memory formed if strength of specific synaptic connection is increased when pre synaptic element and post synaptic cell are active at same time (LTP) -produces memory
      - synaptic strength weakened if pre synaptic terminal is active when post synaptic is inactive (LTD) - speeds up memory formation
- - - - contractions only if nutrient in lumen, abolished by tetrodotoxin (blocks neural AP), contraction blocked by nicotinic or muscarinic ach receptor
      - contraction of smooth muscle dont depend on CNS, confined to local region or cover long segments (propagate)
  - - - simultaneous inhibition on both oral and anal side of contraction, contraction confined,
      - requires rhythmic pattern generator, band of active excitatory motoneurons at site of contractions, two bands of active inhibitory on either side
      - blocking nhibitory converts segmentation to propulsion (contraction on one side, relaxation on anal side)
    - - relaxation on anal and contraction on oral side-doesnt explain segmentation, there are some descending interneurons taht make contact w ascendng interneurons
    - - Dogiel identified shapes of enteric neurons -2nd type, have axons going to mucosa and processes supplying other myenteric ganglia
      - Hirst identified mynteric neruons w after hyperpolarising potentials (AHPs) following APs
      - neurons w/out synaptic input are sensory neurons
      - AH neurons have synaptic input, chemcial stimuli applied to mucosa evoke bursts of AP - response even when synaptic transmission blocked-they must be sensory
      - neurons with synaptic input can be sensoy - if neuron responds to sensory stimulus wout synatpic transmission it must have sensory functions in addition to any other function