HBS202 Case Study 1 - HBS202 Advanced Systems Physiology A SP3 2020 HBS202 Case study 1 – excitable tissues and toxins This module concentrates on the electrical excitability of nerves and muscles,...

hello i need you to complete a graph and answer the questions please . excel graph is needed as per instructions .


HBS202 Case Study 1 - HBS202 Advanced Systems Physiology A SP3 2020 HBS202 Case study 1 – excitable tissues and toxins This module concentrates on the electrical excitability of nerves and muscles, which is due to channels in the plasma membrane opening and closing and producing changes in ion permeability. There are many different types of ion channels within nerve and skeletal muscle cells. This case study is going to look at the effects of targeting some of these ion channels, using venom from several species of Australian animals. Due to millions of years of evolutionary pressure (i.e. the quicker you can immobilise your prey the more likely you are to catch it, and the less likely it is to fight back!), animal venoms often contain neurotoxins with very specific and potent effects on particular ion channels. In the laboratory we can examine neuromuscular activity using the chick biventer cervicis nerve-muscle preparation. The biventer cervicis muscle is located in the back of the neck and helps a chick holds its head up. In this preparation the biventer muscle and the nerve that stimulates it are isolated and placed into an organ bath. Using electrodes, we are able to electrically stimulate the nerve to produce an action potential and then measure the contraction of the muscle using a force transducer. In this particular experiment the nerve has been stimulated and in addition to measuring the muscle contractions, the amount of ACh released has been measured. The following venoms have been used. 1. Redback spider (Latrodectus hasseltii) – contains a toxin which forms pores in the cell membrane of neurons, allowing the influx of Ca2+ into the nerve terminal 2. Blue-ringed octopus (Hapalochlaena lunulata) – contains a toxin which blocks voltage- gated Na+ channels 3. Tiger snake (Notechis scutatus) – contains a toxin which prevents ACh binding to nAChRs on muscle fibres The amount of ACh released during a single stimulation (i.e. one action potential) was measured in the presence of each venom, as well as in the absence of any venom (i.e. the control measurement). To provide more accurate results, the experiment was conducted 6 times. HBS202 Advanced Systems Physiology A SP3 2020 The following data were collected (units are mM of ACh per action potential: Control Redback spider Blue-ringed octopus Tiger snake 302 506 5 296 310 514 15 315 289 473 23 275 267 524 12 301 287 457 16 306 306 578 4 298 Your task is to draw a graph of these data (using Microsoft Excel) including appropriate axis labels and a figure legend. Instructions on how to do this can be found on the LMS (5 marks). In addition, please answer the following questions: 1. In addition to measuring muscle contraction and neurotransmitter release, it is also possible to use electrodes to measure the conduction of action potentials along a motor neuron. Given the mechanism of action of these venoms, predict what effect each of them would have had on the conduction of action potentials along the motor neuron in this experiment. Remember to justify your answer. (1.5 marks) 2. What effect do you predict each of these toxins will have on muscle contractions of the biventer muscle in response to motor nerve stimulation? You must justify your answer including the necessary physiological mechanisms. (1.5 marks) 3. Every venomous creature produces a slightly different venom which targets different receptors and ion channels. Would you expect a venom that targets muscarinic ACh receptors to have an effect in a chick biventer preparation? Justify your answer including a thorough explanation of why you think this is the case. (2 marks)