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Figure 5.6 Optomotor neurons in the lobula plate of a blowfly. (a) On the left is one of the three HS neurons that would respond to anticlockwise movements around the yaw axis; and on the right is one of the VS neurons that responds to downward motion over its eye. (b) Neuron H1, which is excited by movements in the back-to-front direction over its own eye, the right eye for the H1 drawn here. Its axon carries information from one lobula plate to the other. (a modified from Dvorak, Bishop & Eckert, 1975; copyright © 1975 Springer-Verlag; b modified from Franceschini etal., 1989; copyright © 1989 Springer-Verlag.)

Figure 5.6 Optomotor neurons in the lobula plate of a blowfly. (a) On the left is one of the three HS neurons that would respond to anticlockwise movements around the yaw axis; and on the right is one of the VS neurons that responds to downward motion over its eye. (b) Neuron H1, which is excited by movements in the back-to-front direction over its own eye, the right eye for the H1 drawn here. Its axon carries information from one lobula plate to the other. (a modified from Dvorak, Bishop & Eckert, 1975; copyright © 1975 Springer-Verlag; b modified from Franceschini etal., 1989; copyright © 1989 Springer-Verlag.)

moving forwards. During rotation, movement flows forwards over one eye and backwards over the other, whereas when the fly moves forwards, both eyes see backwards movement.

The ways that the HS and VS neurons respond to moving stimuli suggest that they could be important in controlling optomotor responses and there is strong, indirect evidence that they play such a role (Hausen & Egelhaaf,

1989). The output processes of the HS and VS neurons intermingle with dendrites of a small group of neurons that carry information from the brain to motor neurons that control flight and neck muscles. Optomotor responses are impaired in flies after minute cuts are made into the brain to sever the axons of these neurons, or if the HS neurons are killed by irradiating them with a laser. Also, in Drosophila, some mutants that lack the HS neurons do not produce normal optomotor responses. Therefore, it is likely that these neurons are an important part of the cockpit of the fly, helping it to maintain a particular flight course.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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