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Unformatted text preview: PSYC 401 LAB MANUAL LAB 4 - ROACH GIANTS PAGE 1 Core Questions What activity pattern does wind cause the CNS? How many interneurons carry wind information in the connectives? What is the neural code for wind strength? How quickly can wind information get to the thorax? What is a sensory threshold and how do you measure it? What is the layout of an invertebrate nervous system? What are the basic techniques of microsurgery? How do you use hook electrodes? CNS Sensory Systems I Giant interneurons play a central role in escape systems WHAT ARE WE GOING TO DO? After using basic microsurgical techniques to expose the CNS, you will use a hook electrode to monitor neuron activity (APs) in the connectives. You will determine the threshold for response to wind stimuli and the effects of increasing wind strength on the latency to respond, the number of neurons active, and their pattern of Fring. Web resources: Basic cockroach info with lots of links Cockroach FAQ Cockroach-inspired technology For fun - be sure to explore INPUT - PROCESSING - OUTPUT This is the most basic way to look at the functioning of the nervous system. Afferent neurons provide the input, interneurons do the processing within the CNS, and efferent neurons carrying commands to muscles are the output. Effective escape from predators requires maximally fast responses. High-speed signals and minimal processing time are two ways to achieve that speed. Insects have no myelin, so high conduction velocities for the action potentials require the very large axons of giant interneurons (GIs). We will study the extremely sensitive and fast sensory system that cockroaches use to detect wind like that generated by an oncoming predator. PSYC 401 LAB MANUAL LAB 4 - ROACH GIANTS PAGE 2 THE BASIC IDEA When wind strikes the back of the cockroach, it bends very thin (Fliform) hairs on the cerci. A single afferent neuron produces APs when each hair is bent. Along with its brethren from other hairs, the axon travels to the 6th abdominal ganglion where it synapses with one or more GIs. In the image, an afferent is green, GI1 is brown, and GI3 is blue. There are 7 GIs on each side of the ganglion in Periplaneta americana , 4 in the ventral group (GI1-4; vGIs) and 3 in the dorsal group (GI5-7; dGIs). The vGIs are the neurons most involved in the wind-based escape response. The structure of each GI is known in great detail thanks to the injection of dye into the individual cells using an intracellular electrode. Each GI has a unique shape, but they all have a similar overall design. The cell body is near the edge of the ganglion and the neurites are mostly on the opposite side. The axon ascends toward the thorax....
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- Spring '11