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Lecture 28.docx

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York University
BIOL 3060
Colin Steel

Lecture 28: Nervous System ->Looking inside the organisms, and observing how they function and how the structures work together to perform flight mechanisms ->A locust thorax can fly by itself; didn’t require a head or an abdomen= so the pattern of movement is generated by electrical activity in the thorax ->Invertebrates: good, because they have really noticeable nerve cells, and can easily identify distinguish the same nerve cell from one animal to another - something that cannot do with vertebrates ->Locust: can assign numbers to all the nerve cells in the ganglia, so that if a nerve cell is needed to be observed and recorded from, the numbered cell is easy to identify = consistency ->The core of the whole generation for pattern in flight comes from 3 nerve cells: They are all numbered, for easy identification -They are all pacemakers, and are all interconnected with nervous connections Nerve cell 301: pacemakers – will keep discharging AP unless it is inhibited by an input  synapses with the premotor interneurons and causes an activation (+)  they will start discharging AP once its resting potential goes beyond the threshold  i) Premotor neurons: 301 discharges activation signals to these neurons = these neurons will then cause the depressor muscles to contract causing a downstroke of the wings  ii) When they release AP, they will discharge a signal towards 511, inhibiting its function (which is to inhibit the depressor muscles) this allows the premotor neurons to do their job  511: it provides an inhibitory input to 501 (which functions as inhibition for 301) – but when inhibited by 301, it allows 501 to regulate the discharge of inhibitory signals to 301, stopping it from contracting the depressor muscles (301 causes its own inhibition)  -When this happens: when 301 is silenced, it removes inhibition of 511 = 511 can cut in and start firing AP to inhibit the contraction of depressor muscles  -Also it allows 511 to inhibit the function of 501, causing 501 NOT to inhibit the elevator muscles= preparing them for contraction BUT NOT inducing contraction themselves -> the inhibition of 501, then stops the inhibition of 301, allowing them to discharge AP and the whole cycle starts again to generate depressor muscles to contract a downstroke of the wings  Elevator muscles: receive inhibitory supply from 501  - when 501 starts to discharge considering its stop of inhibition, it actively discharges the elevator muscles  = All these function to regulate and inhibit the antagonist muscles, which are the elevator muscles -> So that these muscles don’t contract simultaneously THIS PRODUCES THE RHYTHMICAL PATTERNS OF INDUCING THE DEPRESSOR MUSCLES TO CONTRACT, AS WELL AS P
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