BIOL 201 Lecture Notes - Lecture 30: Nerve Growth Factor, Limb Bud, Spinal Cord
23 Jul 2018
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Document Summary
The body produces more cells than necessary during development. Polydactyly is caused by the cells making up the embryonic web between fingers not undergoing apoptosis. Apoptosis is also necessary during early brain development: axon and neuron pruning during nervous system connectivity. Spinal cord sends axons into limb bud: early in development, many axons innervate the same limb bud, there is a fight for neurotrophic factors (ex: such as nerve. Growth factor) which leads to selective innervation of the muscle fiber. Neurons that fail to synapse on the muscle fiber lack. Over time, motor neuron number in spinal cord decreases. Cutting off limb bud causes to less neurons finding a target and so more cell death on corresponding spinal cord side. Cells are inherently suicidal in the absence of trophic factors. Apoptosis is a tightly-regulated demolition program: prevents the dying cell from damaging its neighbours. Destroys internal components and broken into cell-confined fragments.
