PS263 Chapter Notes - Chapter 4: Homeobox, Neural Development, Gastrulation
Document Summary
Muscles do not determine how many axons form. When a sympathetic nervous system neuron forms a synapse onto a muscle, the muscle delivers a protein called nerve growth factor ngf. Ngf promotes survival and growth of the axon. An axon that does not receive ngf degenerates and cell body dies. If axon does not make contact with appropriate postsynaptic cell by certain age it kills itself. Sns"s way of overproducing neurons and applying apoptosis enables cns to match number of axons to number of receiving cells. Each brain area has a period of massive cell death and often indicates maturation. Chemical that promotes the survival and activity of neurons. Essential to survival of motor neurons in periphery. However do not control survival of neurons in brain. One of the early stages of embryological development. Regulate expression of other genes and control start of anatomical development. All these genes share large sequence of dna bases.
