Interneuronal spinal circuits

Question 1

Renshaw cells

Answer 1

interneurons - bring contraction levels of opposing muscles into closer approximation - co contraction and co activation

Question 2

reciprocal innervation

Answer 2

innervate AG/ANT muscle groups from same neuron source because the reciprocal Ia has numeral collaterals

Question 3

2 characteristics of co-activation

Answer 3

allows for direction reversals - from transition of flexion to extension
increases stiffness across joints - permits precision of movement and joint mobilization

Question 4

connectivity of renshaw cells

Answer 4

class of inhibitory interneurons
action/output is inhibitory to alpha MN and Ia MN
input is from alpha MN and descending commands - receives stimulating collaterals of alpha MN that receives their inhibitory action - -recurrent collateral -> recurrent inhibition

Question 5

2 methods of co contraction

Answer 5

renshaw activation will decrease AG alpha MN output, and increase ANT alpha MN output
1-descending stim to renshaw interneuons - inhibition AG/disinhibition(less inhib) ANT = recurrent collateral carries no function, AG alpha MN inhibited, no AP directed to collateral
2- descending stim to alpha MN with recurrent collateral - inhibition AG, disinhibition ANT via renshaw activation, neg fdbk loop = reduced output of alpha MN

Question 6

disinhibition

Answer 6

diabling inhibition - inhibit the inhibition interneuron

Question 7

renshaw activation will always 1-3

Answer 7

decrease alpha MN output - during co-activiation of muslce activity during dynamic tasks - inhib alpha MN that caused its action, alpha MN of synergists, |a Inhib of antagonist

Question 8

field fote ad tepavac 2002 - improved interlimb coordination in people with incomplete spinal cord injury following training with body weight support and electrical stim - what did they do and 3 results

Answer 8

electrical stim applied to common peroneal nerve to elicit a flexion withdrawal response to assist with stepping in weaker limb
1. strong joint coupling without injury
2. no joint coupling for pre trained
3. improved for post
both ground walking speed and treadmill improved -

Question 9

driving

Answer 9

AP induced in response to every cycle of vibration

Question 10

clinical application of TVR

Answer 10

eval of muscle relaxant drugs
sensitivity of gamma MN system - strength of reflex
element of surprise to evaluate functioning of reflex pathways as an alternative way
therapeutic application in augmentation of weak voluntary contractions

Question 11

whole body vibration may have

Answer 11

detrimental health effects - may be a way for old and disabled ind.

Question 12

kinesthetic illusions

Answer 12

misperceptions of body positions or movement
vibration - stim of spindle afferents - reflexive/tonic contraction of muscle but continued vibration- CNS interprets Ia afferent flow to indicate lengthening muslce - in absence of overriding info, generates transient illusion of new/changing jt position

Question 13

Lackner 1988

Answer 13

vibrations of muscles produces reflexive contractions
passive resistance to contraction will produce perceptions of continued muslce lengthening - illusions of physically impossible limb configurations - lackners pinocchio effect - transient, but completing impression of the growth of ones nose, accomplished by vibration of biceps