Identification and connection of motor neurons. Ort, C.A., Kristan, W.B., Jr., Stent, G.S.: Neuronal control of the swimming in the medicinal leech. Light and dark adaptation of vertebrate rods and cones. Norman, R.A., Werblin, F.S.: Control of retinal sensitivity. Nicholls, J.G., Purves, D.: Monosynaptic chemical and electrical connections between sensory and motor cells in the central nervous system of the leech. Mystick, Diane: Rohde's fiber a septate axon in the leech. Their structure, physiology, ecology, and embryology. Das Nervensystem des vorderen Körperendes und seine Metamerie. Livanow, N.: Untersuchungen zur Morphologie der Hirudineen. Lasansky, A., Fuortes, M.G.F.: The site of origin of electrical responses in visual cells of the leech, Hirudo medicinalis. Laverack, M.S.: Mechanoreceptors, photoreceptors, and rapid conduction pathways in the leech, Hirudo medicinalis. Kaiser, F.: Beiträge zur Bewegungsphysiologie der Hirudineen. Hesse, R.: Untersuchungen über die Organe der Lichtempfindung bei niederen Tieren. In: Bronn, H.G., Klassen und Ordnungen des Tierreichs 4, III, 4, 321–496 (1936) Herter, K.: Die Physiologie der Hirudineen. Hansen, K.: Elektronenmikroskopische Untersuchungen der Hirudineen-Augen. Hanke, Ruth F.: The nervous system and the segmentation of the head in the Hirudinea. Graham, C.H., Hartline, H.K.: The response of single visual sense cells to light of different wave lengths. Gee, W.: The behavior of leeches with especial reference to its modifiability. Gardner-Medwin, A.R., Jansen, J.K.S., Taxt, T.: The “giant” axon of the leech. 159, 1–14 (1975)įuortes, M.G.F., Poggio, G.F.: Transient responses to sudden illumination in cells of the eye of Limulus. 48, 1081–1093 (1965)įioravanti, R., Fuortes, M.G.F.: Analysis of responses in visual cells of the leech. One of these neurons has the sensillum in the ipsilateral dorso-medial body wall of the same segment as its receptive field and another neuron the bilateral set of ventral sensilla in the body wall of the next posterior segment.īehrens, M.E., Wulff, V.J.: Light-initiated responses of retinula and eccentric cells in the Limulus lateral eye. ![]() ![]() Several higher order sensory neurons were identified in the segmental ganglion that receive photosensory input from the sensilla. The photosensory response of a single eye is directionally selective, whereas that of a single sensillum has much less directional selectivity. They are almost insensitive to red and violet light at both extremes of the visible spectrum. Ocular and sensillar photoreceptors make their maximal response to green light at a wavelength of about 540 nm. Both ocular and sensillar photoreceptors adapt to the intensity of interpulse background illumination the ocular receptors adapt so completely that their level of background activity is nearly independent of the background light intensity, whereas the ventral sensillar photoreceptors adapt incompletely, so that their background activity rises with the background light intensity. The amplitude of the early peak response and the level of the steady state plateau rise linearly with the log of the light pulse intensity, but the dynamic range of the early peak response is much narrower than that of the plateau. In response to a pulse of light the photoreceptors produce a train of impulses whose frequency first rises to an early peak and then declines to a steady state plateau at which it remains until the end of the pulse. The photoreceptor cells of each eye or sensillum project their axons centrally via a characteristic cephalic or segmental nerve which carries the photosensory input to the brain or to the segmental ganglion. The medicinal leech, Hirudo medicinalis possesses two types of photosensory organs: five bilateral pairs of eyes embedded in two longitudinal rows in the dorsal surface of the head, and seven bilateral pairs of sensilla situated in both the dorsal and the ventral surface of each of the 21 body segments.
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