ZOO 3603C - Exam 3 Questions And Answers (Verified And Updated)

ZOO 3603C - Exam 3 Questions And Answers (Verified And Updated) Axonal Guidance: where are motor neurons produced? - answerventral spinal cord Axonal Guidance: what is the optic vesicle? - answeran outgrowth of the forebrain neuroepithelium, the developing eye Axonal Guidance: how is he lens induced? - answerWhen the optic vesicle meets the surface ectoderm, the lens is induced in the ectoderm Axonal Guidance: what are the layers of the developing eye? - answerneural retina - inner layer of optic vesicle pigmented retina - outer layer of optic vesicle Sclera - formed from neural crest, surrounding the optic vesicle Axonal Guidance: what is the business end of the neuronal cell called? - answerthe growth cone Axonal Guidance: where is the primary visual cortex? - answerthe back of the brain Axonal Guidance: why do we have 3D vision? - answerbecause half of neurons from the eye go to the opposite side primary visual cortex and the other goes straight back Axonal Guidance: Name the retinotectal connections. - answerEye --- tectum: temporal --- rostral nasal --- caudal dorsal --- lateral ventral --- medial Axonal Guidance: what hypothesis did Roger Sperry propose about axonal growth cones and connection to tectum? - answerChemoaffinity hypothesis Axonal Guidance: what is the chemoaffinity hypothesis and how was it proven? - answer1:1 connections between retinal ganglion cells and tectal cells Evidence: rotate frog eye, axons reconnect to their original places, frog jumps the wrong way Axonal Guidance: what are the problems with the chemoaffinity hypothesis? - answer1) too molecularly demanding - need more genes than are in the genome 2) growth during development - eye grows in concentric rings, where tectum grows mostly posteriorly and laterally 3) spreading/compression Axonal Guidance: what happens if you ablate half of the eye or half of the tectum in a frog? - answerIt becomes half blind. However, after four weeks, axons reconnect in the remaining tectum and full vision is restored Proves not 1:1 because the eye is more plastic and can change Axonal Guidance: what was George Stratton's experiment? - answerhe wore goggles that made him see upside down and after four days his vision corrected. Axonal Guidance: what behavior specifies where the eye ganglion connects to the tectum? - answerAvoidance behavior. A positive dislike for a particular stripe/type of tectum. Axons respond in a gradient. Axonal Guidance: what is the molecule that specifies ganglion specificity for tectum? - answerRAGS = repulsive axon guidance signal Expressed in caudal to rostral gradient in tectum Axonal Guidance: what kind of gradient is there in the chick tectum? - answerEphrin-A gradients Axonal Guidance: How are eph and ephrins involved in axonal guidance? - answer-high levels of eph (temporal) in the retina bind to low levels of ephrin in the tectum (rostral) -low levels of eph (nasal) in the retina bind to high levels of ephrin in the tectum (caudal) Axonal Guidance: what do we know about the DV axis of retina? - answernot much, but we have enough about medial and lateral to make a 2D map Evolution: what time period did tetrapods begin coming onto land? - answerDevonian Period Evolution: what were the triggers for limb development? - answerdecreasing food decreasing reproductive opportunities more competition Evolution: did tetrapods come from actinopyerygii? - answerair breathing fish fins have no homologous structures