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Unformatted text preview: BMD ENG 301 FINAL HOMEWORK (3% of total course points; due: 12/9/09) 1. Where would one find mossy fibers, to what do they connect, and where are their cell bodies located? [3 points]
Mossy fibers are found in the cerebellum, connect to granule cells and deep cerebellar nuclei. Their cell bodies are located in the pontine nuclei. 2. For each of the following cell types indicate to where it sends its axon and which small molecular weight neurotransmitter it releases: a. The Purkinje cell [2 points] b. A Striatopallidal neuron [2 points] c. A Pallidal projection neuron [2 points] d. A projection neuron of the substantia nigra pars compacta [2 points] e. A projection neuron of the substantia nigra pars reticulata [2 points] f. A spinal alpha motor neuron [2 points]
Alpha spinal neurons sends axons to extrafusal muscle fibers and uses acetylcholine exclusively. g. A Pacinian corpuscle [2 points] h. A Ia afferent [2 points] 3. What is a projection neuron? [1 point] 4. Where might one find a mirror motor neuron? [1 point]
In the premotor cortex 5. Which axon type is responsible for second pain and how did its name come about? [3 points]
The C fiber axon is responsible for second pain 6. Where in the spinal cord are the motor neurons that innervate distal muscles located? [2 points]
They are located in the lateral ventral horn. 7. Contrast the properties of alpha and gamma motor neurons, describing their different roles. [4 points] 8. Provide three pieces of evidence to support the assertion that the perception of pain is not only a result of the action of a peripheral noxious insult. [3 points] 9. Some neurons have co-transmitters. What does this mean and what advantage might it have? [3 points]
This means that the neuron can release more than one type of neurotransmitter which means that it has can produce more combinations of neurotransmitters and can convey more signals to the next neuron. 10. Explain the difference between sensory-discriminative and affectivemotivational pain perception and sketch out schematically the neural pathways that subserve each. [7 points] Sensory-discriminative pain perception corresponds to the more precise qualities of pain such as the location, intensity, and the quality of the noxious stimulation. Affective-motivational pain perception relates more to the emotions and unease experienced by the individual exposed to the noxious stimulation. 11. What is two-point discrimination and what does it tell us about sensory innervation of the skin? Which tactile receptor do you think is most likely probed with this test? How could the test be modified to investigate innervation by other tactile sensors? [10 points]
Two-point discrimination is the distance required for the brain to recognize to different points of contact. This tells us how receptors in the skin respond at different parts of the skin. The tactile receptors most likely probed with this test are the Cerkel cell afferents because they provide the most accurate spacial data of the various mechanoreceptors. This test could be modified by making some kind of dynamic testing since other mechanoreceptors are better at interpreting vibrations or other types of movements. 12. What are the two adenosine receptors that are most prominent in the brain? Explain how they work to influence synaptic transmission and intracellular biochemistry. [8 points]
The adrenosine receptors most prominent in the brain are A1 and A2A ("1" and "2A" should be in subscripts). 13. Sketch the time course of an action potential (include scales for voltage and time) and underneath on the same time scale sketch the time courses of the ionic conductances that give rise to the action potential. Indicate through arrows and accompanying text what accounts for the conductance changes you have sketched. Finally, as lines underneath the conductance plots, indicate the absolute and relative refractory periods and explain why you have separated them as you have. [19 points] 14. Contrast the myotatic and flexor reflexes, indicating key differences and similarities in the underlying circuitry. [8 points] 15. Explain the effect of Parkinson’s disease on the indirect pathway of the basal ganglia and suggest why the disease is called hypokinetic. [8 points] 16. Provide a brief description for how long term depression operates in the cerebellum. [8 points] 17. Provide three pieces of evidence that neurotransmitter is released from vesicles at a neural synapse. [3 points] 18. What switches off the post-synaptic effect of synaptic transmission at the neuromuscular junction? [2 points] 19. How could you explain GABA producing an excitatory post synaptic potential as it can during neural development? [3 points] 20. List four types of CNS glial cell and briefy describe the function of each. [8 points] 21. Contrast the benefits and costs of transmitting signals within neurons via electrotonic potentials and via trains of action potentials. [6 points] 22. Basing your answer on your knowledge of the motor system, explain why vigorous exercise leads to muscle fatigue. [5 points] 23. A patient presents in the ER with spasticity (hyperactive deep reflexes, increased muscle tone) and can’t seem to grip the pencil he’s been given to fill out his paperwork. The attending physician has had a rough night (no sleep, an abusive superior, etc.) and is having trouble thinking straight at 3 a.m. While you’re waiting for attention, give her a hand with the diagnosis (what you think the problem is) and then suggest a simple test that she might try to triage this patient and quickly reach you, being next in line. [4 points] 24. What is the size principle and what is its effect on motor responses? [3 points]
The size principle is the relationship of which motor units are recruited into the motor pool. Low threshold motor units are first recruited, then larger and larger motor units are recruited. 25. Provide a brief description for how a generic metabotropic receptor works, discussing the multitude of potential end points. [8 points] 26. Provide evidence that there is plasticity in the adult somatosensory cortex of mammals. [4 points] ...
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