Spinal Reflexes Flashcards
What are the two types of muscle fibers?
Intrafusal and extrafusal
If you increase the length of a muscle you cause it to contract via negative feedback that maintains muscle length describes what?
Tendon stretch myotatic
Intrafusal fibers contain what type of motor neuron?
Gamma motor neuron
Extrafusal fibers contain what type of motor neurons?
Alpha motor neurons
What are the two types of extrafusal muscle fibers?
Type I and type II
Slow twitch aerobic fibers describe what kind of fibers?
Type I
Fast twitch anaerobic fibers describe what kind of fibers?
Type II
All neurons that innervate a muscle (including alpha and gamma motor neurons) describe what?
Motor neuron pool
All muscle fibers that are innervated by an alpha motor unit describe what?
Motor unit
Small neurons have a lower threshold for synaptic inputs describes what?
Size principle
What are the smallest motor neurons, first ones recruited, innervate intrafusal muscle fibers which produce negligible force, don’t fatigue?
Gamma motor neurons
What neurons innervate type I muscle fibers, produce small force, don’t fatigue?
Small alpha motor neuron
What neuron innervates type II muscle fibers, produce large force, fatigue rapidly?
Large alpha motor neuron
What give information about the position of the body in space?
Propioceptors
What measure muscle length and the velocity of shortening?
Muscle spindles
What measures muscle force?
Golgi tendon organs
What measures the angles of joints?
Joint angle receptors
What type of muscle fibers have muscle spindles w/ cell bodies in the dorsal root ganglia that synapse in the spinal cord?
Intrafusal muscle fibers
What are the two types of intrafusal muscle fibers?
Static and dynamic
What are the two types of muscle spindle receptors?
Primary and secondary
What type of spindle receptors are wrapped around static and dynamic intrafusal muscle fibers, type Ia fibers?
Primary spindle receptors
What type of spindle receptors wrap around only static intrafusal muscle fibers, type II fibers?
Secondary spindle receptors
What type of muscle fiber gives information about velocity and length?
Type Ia
What type of muscle fiber gives information about length only?
Type II
What controls the sensitivity of spindle receptors?
Gamma motor neurons
What modulate the stretch reflex but are not directly apart of it, exist in the tendon of the muscle, are situated in a good position to measure force, and are sensitive to active contraction?
Golgi tendon organs
What are primarily involved in the stretch reflex?
Muscle spindles
An increase in muscle length leads to an increase in muscle firing leads to an increase in activity of the alpha motor neuron which leads to contraction describes what?
Homonymous stretch reflex
In the homonymous stretch reflex afferents control what?
Spindle fibers
In the homonymous stretch reflex efferents control what?
Alpha motor neurons
What is important for muscle tone and can induce spasticity?
Homonymous stretch reflex
Low threshold gamma interneurons fire, activation of intrafusal muscle fibers which stretch muscle spindle, increase activity of spindle fibers, combination of spindle afferents with w/ descending alpha neuron afferents bring neuron to threshold, contraction of extrafusal muscle fibers describes what?
Alpha gamma co activation -voluntary movement
What type of muscles increase the activity of the stretch reflex on each other?
Synergists
What type of muscles decrease the activity of the stretch reflex on each other?
Antagonistic muscles
Interneuron GABA release that activates GABAb receptor which blocks calcium channel in presynaptic junction describes what?
Antagonistic muscle decreased reflex
What GABAb agonist decrease stretch reflexes and motor spasticity?
Baclofen
