Test 3 - Lecture 2 (Proprioception) Flashcards
Determines joint angles & or angles of joint rotation
Muscle length
Provides counteracting force against the external load to stabilize joint positions
Active tension
Convey centrally programmed motor commands into the ventral horn of the spine
Descending corticospinal tracts
_____ fibers comprise the main bulk of skeletal muscle, generate force during muscle contraction
Extrafusal
Each extrafusal fiber is innervated by a ________, located in the _______ of the spinal cord
Alpha motor neuron, ventral horns
The strength of signaling from the alpha motor neurons is determined through
Synaptic integration
Is determined by the accumulation of signals (excitatory or inhibitory) that provide input to a alpha motor neurons innervating the muscle
Level of muscle activation
Provides information concerning current position & movement of the muscles & joints
Proprioception
What are the two main proprioceptors
Muscle spindles, golgi tendon organs
Motor neurons that innervate the intrafusal muscle fibers
Gamma motor neurons
Are arranged in parallel with the extrafusal fibers; reports the muscle length, along with changes in length
Muscle spindles
Are arranged in series with the extrafusal fibers of the associated skeletal muscle
Google tendon organs
Sensory nerve ending wrapping around the central part of the intrafusal fiber
Annulospiral ring
Stretching of the annulospiral ring activates mechanosensitve channels causing
Depolarization of the sensory neuron
The rate of firing from sensory neurons is ______ proportional to the amount of stretch
Directly
Characterized by a large number of nuclei packed within the mid-portion
Nuclear bag fibers (dynamic/static)
Characterized by nuclei arranged in a longitudinal row
Nuclear chain fibers (more numerous than nuclear bag fibers)
Arise from the annulospiral rings surrounding all three fiber types; largest fibers, fastest conducting, rapidly adapting (mainly report changes in length)
Type 1a (primary) afferents
Arise from nerve endings located distal to the center of nuclear chain & static nuclear bag fibers; intermediate diameter, relatively fast conducting, slowly adapting (mainly report static length)
Type II (secondary) afferents
During the lengthening of a muscle… the type ____ fiber reports the largest signaling
Ia
_____ fibers contribute to the force the muscle is putting out
Extrafusal
Nerve terminals are called plate endings; innervate dynamic nuclear bag fibers
Dynamic gamma motor neurons
Nerve terminals are called trail endings; innervate static nuclear bag fibers, as well as nuclear chain fibers
Static gamma motor neurons
Provides sensory input for the CNS to continually monitor the length & changes of length in the muscle
Muscle spindle
T/F: co-activation is the theory that gamma motor neurons that innervate intrafusal fibers HAVE to contract when the alpha motor neurons contract the extrafusal fibers for a muscle to function properly
True
Activating ____ motor neurons during a muscle contraction maintains sufficient tension on the mechanoreceptive nerve endings to allow them to continue to signal the rate & extent of change in muscle length
Gamma
The amount of dynamic & static activity during a certain movement is called
Level of fusimotor activity (fusimotor system)
Report the force & tension generated by a muscle, arising from its extrafusal fibers contracting against the external load; give rise to type Ib afferent fibers
Golgi tendon organs
Functional unit for a reflex consists of…
- sensor (proprioceptors)
- afferent pathway (type Ia or II sensory nerves)
- integrating center (synaptic relay through spinal interneurons & motor neurons)
- effector pathway (motor nerves)
- effector (skeletal muscles)
Stereotypic motor response to a particular sensory input
Motor reflex
Two factors that effect “lowering the cup”
- increase in the load
Or - reduction in the level of activation to the flexor
Two factors which result in “raising the cup”
- reduction in the load
Or - increase in the level of activation
To maintain stable position: the muscles starts to lengthen = _____ activation, to counteract
Increase
To maintain stable position: the muscles starts to shorten = _____ activation, to counteract
Decrease
The act of counteracting a disturbance to a stable position or tension
Reflex
To maintain stable tension: the tension starts to increase = _____ activation, to counteract
Decrease
To maintain stable tension: the tension starts to decrease = _____ activation, to counteract
Increase
Two alpha motor neuron reflexes
Myotatic & inverse myotatic reflex
In response to input from muscle spindles; length (reflex for stabilization of muscle length)
Myotatic reflex
In response to input from golgi tendon organ; tension (reflex for stabilization of muscle tension)
Inverse myotatic reflex
Ia afferent fibers provide _______ input to motor neurons interacting the ______ & ______ muscles
- monosynaptic excitatory
- homonymous
- synergist
Fiber types used in myotatic muscle reflex
Ia (excitatory input)
- increase in Ia signaling - increased motor signaling to muscles (leading to muscle shortening)
Fiber used in inverse myotatic muscle reflex
Ib (inhibitory input)
- increase Ib signaling - decreased motor signaling (release of tension)
Ib afferent fibers provide _______ input to motor neurons interacting the ______ & ______ muscles
- inhibitory interneurons
- homonymous
- synergist
Contributes to an appropriate balancing between the agonist & antagonist muscles acting upon the joint
Reciprocal innervation
Ia afferent input _______ to provide input to multiple motor neurons for the homonymous & synergist muscles
Diverges
afferent proprioceptive sensory input combines with the descending efferent motor commands that are all ______ upon an alpha motor neuron
Convergent
Inhibitory interneuron that is stimulated by fibers branching off the motor nerve, to synapse upon the motor neuron from which that motor nerve arose
Renshaw cell interneuron
Circuit serves to restrain motorneuron firing relative to its excitatory inputs; stabilize the current output relative to the current input
Recurrent feedback inhibition
