I'm rushing and have to leave, and I cannot say off the top of my head what are the conditions under which each does what it does, but my recollection is that they are two distinct types of bipolars. I think the bipolars representing on-center connections are depolarizing (invaginating) bipolars and off-center connections are made with hyperpolarizing (basal junction) bipolars. Whether glutamate causes the cell to hyper- or depolarize is a function of the kind of cell.
Try here <http://webvision.med.utah.edu/OPL2.html#horizontal> for an explanation. It's at the bottom of the page, and seems pretty sound, to me. m ------ "There is no power for change greater than a community discovering what it cares about." -- Margaret Wheatley -----Original Message----- From: DeVolder Carol L [mailto:[EMAIL PROTECTED] Sent: Tuesday, October 09, 2007 3:05 PM To: Teaching in the Psychological Sciences (TIPS) Subject: [tips] Sensation and Perception people--help please OK, hopefully someone can help me out. I'm trying to work through in my head the logic of phototransduction. I know what happens within the rods and cones, what I'm confused about is what happens at the bipolar level. I'm a little rusty on it and I seem to be getting different things from different texts. For example. Blake and Secular say that there are two types of bipolar cells--one type depolarizes in response to an increase in glutamate (i.e. in the dark) and one kind depolarizes to a decrease in glutamate (i.e. in the light). So the response of bipolars is to depolarize--the same result from different cells under different conditions. But Kandel, Schwartz, and Jessel indicate that in one condition glutamate will depolarize bipolars and in another it will hyperpolarize them, so different responses are evoked by different conditions. I've read so darned many texts on the subject that I am getting really confused, and if I'm confused, I can only imagine how my students will feel. What is it that I'm missing here? Ultimately the message has to become an action potential in the RG cell, I'm just not sure exactly when. I feel like telling them that it's just magic. Thanks, Carol Carol DeVolder, Ph.D. Professor of Psychology Chair, Department of Psychology St. Ambrose University Davenport, Iowa 52803 phone: 563-333-6482 e-mail: [EMAIL PROTECTED] --- To make changes to your subscription contact: Bill Southerly ([EMAIL PROTECTED]) ---
