032008 - March 20, 2008 Slide 1: Divergent: same message in...

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March 20, 2008 Slide 1: Divergent: same message in different ways, same sensory fiber branches or innervates two different poles of neurons (interneuron for inhib to cause message to two different muscles- ext/flex); Sensory fibers convey state of muscle by sending AP of same size/duration but control their rate of output in proportion to some property of muscle. - More stretched the muscle, the higher the rate. Weak stretch, low rate. - Duration by change in rate Motor neurons use temporal (make neuron sensitive of rate of input) and spatial summation (motor neuron pulls input from large no of neurons thru convergent cxns, ensures that whenit send command to muscle to contract, command is appropriate command)- use of these summations improves quality of command to muscle Inhibition used to override excitation (brain controls reflexes like this); inhibit motor neuron to turn off stretch reflex. - Override reflexes - Takes signals and reverse their sign (purple interneuron in diagram) 2: Vert nervous system made of: sensory, motor, central processing components Mammals, primates, and humans: command center dwarfs other components; most machinery devoted to making sense of sensory info and deciding what to do next. 3: Major subdivisions of brain using embryo Fore (telencephalon and di), mid, hindbrain (metence and myelenc): 5 major - Telencephalon (occupies hemispheres, most of brain): ganglia (motor control), hypocampus (memory) - Diencephalon: thalamus (info goes here before cortex), hypothal (hormonal systems) Midbrain - contain many nuclei for sensory and motor control Mentenc - cerebellum: motor control, improving and learning - pons: pathway thru which fibers enter cerebellum Myel - medulla: breathing, heartrate 4: Brain stem: midbrain, pons, medulla together Today’s lecture is over pathway from sensory to processing then from brain to peripheral system 5: Schmoo Brain Schmoo- character in mid-20 th century, used to teach neuroanatomy: represents typical mammalian brain
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Pathway into CNS , 3 major pathways from periphery to brain 1) Reflex Pathway: Automatic circuit designed to protect us, operates autonomically, no consciousness req’d a. Touching something hot/sharp, hand withdraws, awareness of event afterwards; fairly direct b. Useful clinical tools for neurologists, as unconscious patients may still respond c. Two major neurons: i. Primary sensory neuron (cell body in dorsal root ganglia, synapses on motor neurons that will cause muscles to contract) 2) Cerebellar Channels a. Cerebellum good for fine-tuning motor learning: all sensory modalities sending copies of signals into cerebellum, branch goes into medulla and synapse at particular nucleus which has secondary sensory neurons which send to cerebellum b. Signals sent to cerebellum c. Damage to cerebellum; probs with tremor and motor skills these two are for ones we’re not really aware of; we don’t use it to make conscious axns 3) Lemniscal Channel:
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This note was uploaded on 04/10/2008 for the course BIO 365R taught by Professor Draper during the Spring '08 term at University of Texas.

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032008 - March 20, 2008 Slide 1: Divergent: same message in...

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