Measurements from the Muscle Receptor Organ (MRO) of the Crayfish, P. clarkiiOverviewMeasurements from the Muscle Receptor Organs of CrayfishIII. Receptor TypesMeasurements from the Muscle Receptor Organ (MRO) of the Crayfish, P. clarkii OverviewAnimal neurons involved in sensation are part of the afferent portion of a stimulus-response pathway. Most of these pathways begin with a specialized sensory organ, whichis typically composed of one or more sensory receptors and/or neurons. These receptors/neurons are designed to detect and transduce stimuli (ex. light or sound) into electrical impulses, the primary language of the animal nervous system. The muscle receptor organs (MROs) of crustaceans are one such type of specialized sensory organ. These organs function to report the position of a body part to the central nervous system (CNS) and help guide body movement. In crayfish (P. clarkii), each MRO is composed of a sensory neuron and an associated muscle. The dendrites of the sensory neuron are embedded in (or parallel to) their associated muscle such that they become stimulated when the muscle is stretched. There are two types of MROs in crustaceans — MRO1 and MRO2 — and they respond to different types of stimuli. Electrical impulses (also known as action potentials (APs)) can be recorded from an MRO1 as long as the stimulus (muscle stretch) is of sufficient intensity to depolarize the MRO1 neuron to threshold. Like most neurons, MRO1 sensory neurons encode the intensity of the stimulus (amount of stretch) by altering the frequency of APs fired. In contrast, MRO2 neurons respond to changes in the rate at which a stimulus is applied. In the first part of today’s laboratory, you will examine the superficial extensor nerve-muscle system of the crayfish by recording extracellularly from the nerve that carries sensory information from MROs to the CNS of the crayfish P. clarkii. Curling the tail of the crayfish stretches the superficial extensor muscle such that MRO1 becomes excited and fires action potentials. Once responses from MRO1 are observed, you will apply a prolonged stimulus of fixed intensity to elicit sensory adaptation in the MRO1. Sensory adaptation is the process by which a sensory system becomes less sensitive, or even non-responsive, to repeated or prolonged stimulation. In the last part of today’s exercise, you will attempt to elicit responses from MRO2 by varying the rate at which the stimulus (stretch) is applied. While the crayfish preparation has been completed for you, take the time to view the experimental set up, paying close attention to the flow of information from the stimulus to the computer monitor. Sketch/draw your interpretation of information flow in your laboratory notebook, noting all important instruments. As data are being recorded, youare responsible for recording your observations, values of importance (i.e. frequency, period, amplitude) and answers to the questions in your lab notebook. Also, be sure to note the software settings, paying close attention to values like the sampling rate. You will be required to turn in this information at the end of the laboratory period. SENSORY PHYSIOLOGY:Measurements from the Muscle Receptor Organs of CrayfishBE SURE TO WRITE THE QUESTIONS (Below) & ANSWERS TO THE QUESTIONS IN YOUR LABORATORY NOTEBOOK!I. Stimulus-Response Properties of MRO1In this exercise, you will record the stimulus-response properties of MRO1 while observing some of the basic features of a sensory system.1. What is the stimulus in this scenario? What is the response by MRO1?2. Does MRO1 respond to a stimulus of any intensity? Why or why not?3. What is the relationship between the stimulus and the response by MRO1 (i.e. does the response change with a change in stimulus intensity? How does it change?)4. Graph the relationship between stimulus intensity (small, medium & large stretch) and response by MRO1 using real data on your computer.II. Adaptation of MRO1In this exercise, you will apply a stimulus of fixed intensity over a prolonged period of time to elicit adaptation. 1. Define adaptation IN YOUR OWN WORDS. Draw what it looks like ON THE COMPUTER MONITOR and explain what you are seeing. Label the axes.2. Use the data to generate a graph that illustrates the relationship between stimulus duration and response frequency in MRO1. 3. What can you conclude about adaptation in MRO1 from the graph above (i.e. how does the duration of a stimulus effect the response in MRO1)? Be specific!4. Under what circumstances might an animal benefit from sensory adaptation? III. Receptor Types In this exercise, you will attempt to elicit a response from MRO2 by changing the wayin which you apply the stimulus.1. Were you successful in generating a response from MRO2?2. If yes, how was the response elicited?3. Did you observe any differences between the response from MRO1 and MRO2? If so, explain & draw the difference in your lab