NEUROSCIENCE MSP PROBLEM SET #11

  1. Circle all of the following that apply to Rapid Adapting Mechanoreceptors:
  1. All rapidly adapting mechanoreceptors respond to low frequencies.
  1. Meissner’s corpuscle is composed of an axon weaving throughout connective tissue cells that are anchored to the epidermis via collagen fibers.
  1. Mechanical deformation changes the ion permeability of the receptor membrane causing depolarization.
  1. Mechanoreceptors transmit their signals via action potentials along A and A axons.
  1. Meissner’s corpuscles and Pacinian corpuscles are located in the dermis.
  1. Mark T or F for the following statements, if false, please fill in correct statement:

___Merkel’s disks and Ruffini corpuscles, found in high density in the finger tips, are slow adapting sensory receptors with a low threshold of activation.

___Thermoreceptors are innervated by C fibers and A which are both slow conducting, unmyelinated axons.

___One Schwann cell can wrap itself around many axons to cause a myelin sheath.

  1. Explain the mechanisms of the sensory receptors involved in preventing hyperextension across a joint. Discuss three different proprioceptive functions:
  1. Being the thorough medical student that you are, you end your complete physical exam at your preceptor’s office with the neurologic exam. Your patient has mentioned that she occasionally feels tingling in her hands. With a tuning fork and a pin you test two sensory pathways. Describe the course of each stimuli from the Sensory Receptor to the Cortex. Specify the types of receptors stimulated, associated axons, their location, rate of adaptation and threshold of activation. Include the pathways involved and somatotopy maintained in the cortex.
  1. Circle all the choices that apply:

Hyperalgesia is the process through which there is enhanced response to painful stimuli. This is brought about by a LOWERED THRESHOLD TO PAIN / ENHANCED RESPONSE TO SUPRATHRESHOLD STIMULUS. Primary hyperalgesia is at the site of the injury and its underlying mechanism is CENTRAL SENSITIZATION / PERIPHERAL SENSITIZATION. In primary hyperalgesia, there is an enhanced response to HEAT / MECHANICAL STIMULATION. Secondary hyperalgesia is characterized by enhanced response in uninjured skin in close proximity to the site of injury. It’s mechanism is CENTRAL SENSITIZATION / PERIPHERAL SENSITIZATION. In secondary hyperalgesia, there is enhanced response to HEAT / MECHANICAL stimuli.

  1. Define Allodynia. What fibers seem responsible for conduction of sensation in this condition? What is another name for it?

Define Dysesthesia. Give an example of a pathological condition that can bring this about.

Define Referred Pain. Considering neuronal pathways, propose a mechanism that explains its occurrence.

  1. Mark T or F for the following statements, if false, please fill in correct statement:

___Direct brain stimulation of the periventricular gray, ventrobasal complex of the thalamus, rostroventral medulla, or the internal capsule can suppress nociception.

___Opiates and opioids exert their analgesic action by acting on GABA receptors which activate a cascade that decreases nerve cell excitability.

___Lowering of the sensory neuron action potential, decreasing the afferent evoked EPSP, and hyperpolarization of the dorsal horn neurons are all potential effects of opiates and/or opioids.

  1. Describe the concept of modulation of pain by other afferent inputs. Draw out a diagram and explain the gate theory of pain.