exam 1 and 2 mvs 320

exam 1 and 2 mvs 320 - 2 Fundamental differences between...

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2. Fundamental differences between semicircular canals and otolith organs. Otilith organs: utricle and saccule: suspended in perilymph and house the macula which is a spot of sensory epithelium, contains receptor cells and monitors head position when still. Utricles contain horizontally aligned macula and succules contain vertically aligned macula. Utricles are bilateral so brain receives additional information from the contralateral labyrinth. Saccules are most sensitive to vertical accelerations and gravity. Linear acceleration Semicircular canals angular acceleration. Contain semicircular ducts. Houses cupula. 3. Muscle activation patterns for ankle vs. hip postural strategies. - For ankle postural strategies if the movement is forward then posterior muscles will be activated. Where as, if the movement is backwards then anterior muscles are activated. Also, ankle activation patterns work in a distal to proximal fashion. Where as hip postural activations work in a proximal to distal manner. If the movement is forwards then anterior muscles are activated and if it is backwards then posterior muscles are activated. 4. Effect of descending input to Renshaw cells on subsequent alpha motorneuron activity. - Renshaw cells are involved in regulation of force: recurrent inhibition. Increased mn activity leads to increased renshaw firing, leads to decreased mn activity. Circuit can be modulated by higher motor control centers, and can disinhibit antagonistic muscles by removing inhibitory drive to neurons therefore allowing more excitability. Disinhibition of 1a inhibitory interneuron 5. The adaptive properties and receptive field types of cutaneous receptors. -Meissner’s and Merkel’s receptors are superficial; Meissner’s account for spatial acuity and Merkel’s account for pressure. The deeper receoptors are Ruffini, which detect movement and skin stretch, and pacininian, which detect deeop pressure and vibration. The Merkel’s receptors respond to light stimulus; hairless fields such as skin of palms, face, and bottom of feet contain Merkel receptors. Meissner’s corpuscles also respond to light touch. Ruffini’s corpuscle’s respond to directional information and sensations on the skin, and pacinian corpuscles respond to intense stimuli such as deep pressure and vibration. Meissner’s and pacinian corpuscles are rapidly adapting mechanoreceptors. Merkel’s and Ruffini’s are slowly adapting mechanoreceptors. 6. Myasthenia gravis: This is an autoimmune disease where the synaptic cleft is widened, there is a loss of junctional folds, and there is a reduced number and density of Ach receptors. One symptom is one eye droops (ptosis). It is best treated with immunosuppressive drugs and anticholinesterases.
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This note was uploaded on 03/15/2012 for the course MVS 320 taught by Professor Drew during the Fall '11 term at University of Michigan.

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exam 1 and 2 mvs 320 - 2 Fundamental differences between...

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