Motor Control: Reflexes - K Flashcards
What neuron conducts the affarent part of the myotactic/stretch reflex and to where does it go?
Myelinated 1a-fiber to the dorsal root of the SC
What neuron conducts the efferent part of the myotactic/stretch reflex and where does it go to?
Gamma-motor neuron to the intrafusal fibers of the associated muscle
What is reciprocal inhibition regarding the stretch/myotactic reflex? What’s an example?
When the 1a-fiber simultaneously activates an inhibitory interneuron that will synapse with the alpha-motor neuron of the antagonist muscle causing it to relax/lengthen
If your biceps are too stretched, to contract them and protect them.. The triceps must be relaxes then.
What is the golgi tendon reflex? What is it initiated by?
The inverse of stretch/myotactic, an autogenic inhibition that appears as a sudden relaxation of a contracted muscle when too much force is being exerted on the muscle
Golgi tendon organ
What is the golgi tendon organ, and where is it located/what does it innervate?
Collection of bare n endings located in.. Tendons!
What increases action potential activity in the golgi tendon organs?
Increased tension
What fiber carries the AP’s from the golgi tendon organ to the SC? What does it synapse on?
1b-fiber
Interneurons
What is the primary difference between a reflex and volitional response?
Reflex is mediated at all levels of the CNS
Volitional originates from cortical areas based on judgment, initiative, and motor control
What are the characteristics of an alpha motor receptor?
Large and heavily myelinated
Innervates/activates skeletal m at NMJs
Directly leads to motion
What are the characteristics of a gamma-motor neuron?
Smaller and slower than alphas
Innervates the contractile components of muscle spindles (intrafusal fibers) at the NMJ
These control the sensitivity of muscle spindles
Activity doesn’t lead directly to motion
Decerebrate Posturing is due to what, and what does it lead to?
Loss of all structures rostral to the pons, a severe brain injury
Contractions of anti-gravity muscles, spasticity (gamma, one direction) or rigidity (alpha, all directions)
Decorticate Posturing is due to what, and leads to what symptoms?
Upper mid-brain damage and loss of cortical input from structures rostral to the pons
Rigidity that’s based on the position of the head! Decerebate is not based on head position, flexion of UE and extension of LE
May be bilateral or unilateral (due to strokes)
What is the stretch/myotatic reflex? What R’s are being activated here?
Contraction of a stretched muscle to protect it from tearing
Nuclear bag and chain R’s
