Topic 3 Lectorial PDF

Lectorial 3 – Neurotransmitters, Receptors & Integration of Electrical Signals (3 activities & 2 cases) Activity 1 - Autonomic Receptors & Neurotransmitters One of the clinical uses of drugs which act on the autonomic system is to control blood flow and blood pressure. Which division of the autono...

Lectorial 3 – Neurotransmitters, Receptors & Integration of Electrical Signals (3 activities & 2 cases) Activity 1 - Autonomic Receptors & Neurotransmitters One of the clinical uses of drugs which act on the autonomic system is to control blood flow and blood pressure. Which division of the autonomic nervous system has a direct effect on both blood vessel constriction and heart rate? During activation of this division, should the tissues and organs be receiving more blood flow or less? How does one division with one neurotransmitter control both constriction and dilation of blood vessels? Which adrenergic receptor subtype would you expect to find on the following tissues' blood vessels? Coronary Skeletal GI tract (J[P]P[`;OLYHWL\[PJTHUPW\SH[PVUVM[OLULY]V\ZZ`Z[LT A number of drugs that act on autonomic function are used clinically for various purposes. Below are some drug therapeutic actions at autonomic receptors. Use your knowledge of autonomic function to predict which receptor subtype the drug will be acting at in each example and whether it will OH]L[VHJ[SPRL[OL UL\YV[YHUZTP[[LYVYHJ[[VISVJR[OLYLJLW[VY[VHJOPL]L[OLKLZPYLKM\UJ[PVU  A drug, acting at adrenergic receptors, used to relieve bronchoconstriction during an asthma attack  A drug, acting at cholinergic receptors, used to relieve bronchoconstriction during an asthma attack  A drug, acting at adrenergic receptors, used to reduce blood pressure and cardiac arrhythmias by dropping heart rate  A drug, acting at adrenergic receptors, used to relieve nasal congestion 5. A drug, acting at adrenergic receptors, used in anaphylaxis, to reverse the vasodilation and bronchoconstriction produced by the IgE-triggered release of histamine Case 1 - Misuse of autonomic receptor knowledge The poison gas used in the terrorist attack on the Japanese subway system in 1995 was sarin gas. This substance belongs to a group of compounds known as organophosphates, which are highly toxic to humans and other animals. These compounds are used very widely as pesticides, which means that accidental poisoning occurs regularly, along with the deliberate poisoning of warfare or terrorism. These nerve agents are acetylcholinesterase inhibitors. The signs and symptoms of organophophate poisoning are very characteristic and predictable by anyone who knows the function of the neurotransmitter which will be in excess as a result of the poison. From the description above, which neurotransmitter will be in excess? Based on this what effects on physiological function are these poisons are likely to produce? Which of the effects is most likely to be the one that causes death of a person who has been exposed to these poisons? Case 2 - Trouble at the gym Arnold has been a body builder for some time, and takes great pride in his ability to lift heavy weights down at the gym. One day, while working on the free weights, Arnie suddenly complains of severe back pain and collapses on the floor, apparently unable to walk. While waiting for the paramedics to arrive and pick Arnie up, you do some investigations of your own (without moving Arnie). Arnie’s back is very sore in the lumbar region, and he doesn’t want it to be touched. The muscles at the lumbar level feel very hard and tense. You get your reflex hammer out and try out Arnie’s stretch reflexes. The reflexes seem very weak in the ankles and knees. Arnie complains of pins and needles sensation down the back of both calves. Arnie is taken off to hospital where an MRI is performed. The results are shown on the next page, together with normal vertebral columns for reference. What abnormalities can you see on Arnie's MRI ? (be as specific as you can) How would the abnormality you identified have produced Arnie’s symptoms? Based on the results of your reflex testing on Arnie, which type(s) of neurons have been affected? Explain how you know. Activity 3 – Integrating information Body control requires both excitatory and inhibitory nervous system signals. An individual neuron can only release 1 specific neurotransmitter, the effect of the neurotransmitter is then determined by the combination of the neurotransmitter and the receptor present on the post-synaptic cell. Draw a diagram showing a synapse between 2 neurons, label the parts of the neuron and describe the mechanism to cause neurotransmitter release and what effect it will have on the post-synaptic neuron if it is inhibitory or excitatory. In many instances a single neuron will receive pre-synaptic input from multiple neurons which could be either inhibitory or excitatory. Draw a diagram showing this structure and consider what will happen in the post-synaptic cell when the excitatory pre-synaptic cell is active compared with the inhibitory pre-synaptic cell. What would happen if both pre-synaptic cells were active at the same time? What would happen if the inhibitory pre-synaptic cell was activated longer than the excitatory one?