Cheryl is removing an Angel\'s Trumpet plant loaded with flowers from her backya
ID: 165612 • Letter: C
Question
Cheryl is removing an Angel's Trumpet plant loaded with flowers from her backyard. Some pollen lodges in her right eye, and she stops to remove it, but about 20 minutes later, her vision is "off", Upon looking in the mirror she sees that the pupil of her right eye is very dilated(left is normal). Thinking she might be having a stroke, she sits down and takes her pulse, which is very fast(105 bpm), even though she hasn't been active for at least 30 min. Fearing the worst, Cheryl heads to the hospital, where she learns that Angel's Trumpet pollen contains an anticholinergic agent that entered her systemic circulation via her eye and likely led to all symptoms. Soon she will be back to normal. As a medical resident at the hospital, you are asked to answer the following The receptors for which neurotransmitter would be affected by the pollen? How would blocking these receptors result in the observed symptoms? Sensory information to the CNS follows the "law of specific nerve energies". Define this law. Clearly explain how the following examples these illustrate this law. Hitting your funny bone Phantom limb pain Why are all muscle fibers of a given motor units of the same type? Why are smaller motor units and slow-twitch muscle fibers used more frequently than larger motor units and fast-twitch fibers' Use an example in your explanation.Explanation / Answer
Answer:
2. Law of specific nerve energies states that each type of sensory nerve ending, however stimulated (electrically, mechanically, etc.), gives rise to its own specific sensation; moreover, each type of sensation depends not upon any special character of the different nerves but upon the part of the brain in which their fibres terminate.
a. The ulnar nerve, which travels on the outside of the elbow joint and is particularly badly protected compared to other nerves in the body, is struck and sends strong signals up to the brain.
Due to the law of specific nerve energies, the brain can't tell apart a signal originating from the end-point of a nerve and a signal beginning in the middle of the nerve, so it has to assume that the jolts coming up through the nerve bundle originated in all the places the nerve enervates, meaning the entire lateral side (where the little finger is) of the arm lights up like a christmas tree of tingling.
b. According to the law of projection, if a particular sensory pathway along its course to the cortex is stimulated, the sensation produced is referred back to the location of the receptor. Example: When a limb is amputed, the patient complaints of pain even when the limb is absent.
Experiments on patients with phantom limbs suggest that neural connections in the adult human brain are much more malleable than previously assumed. Three weeks after amputation of an arm, sensations from the ipsilateral face are referred to the phantom.
This effect is caused by the sensory input from the face skin ‘invading’ and activating deafferented hand zones in the cortex and thalamus. The study on phantom limbs thus challenge long held theoretical assumptions about sensory function of 'Muller’s law of specific nerve energies'.
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