Exam 2 Prep Flashcards
(211 cards)
What is locomotion?
An action initiated by the brain, but yet are maintained in its steady-state execution by mostly spinal mechanisms (CPG) with the interaction of peripheral afferent contributions
What is the evidence for CPG in human spinal cord injuries?
-Involuntary LE stepping-like movements were expressed spontaneously
-In supine: rhythmic, alternating, and forceful muscle contractions bilaterally
-Rhythmic movements
-Spontaneous rhythmic patterns
What movements does the CPG control?
-Protective reflexes
-Locomotion
What is the central pattern generator (CPG)? What is its function?
-The rhytmic timing and coordination of muscles generated by the CPG and is located in the spinal cord
-It initiates gait, a locomotor command is generated levels above the spinal cord (brain)
What is the grand initiator of gait that is also involved in the choice and emotion behind gait?
-Basal ganglia
-Mesencephalic locomotor region
How is the basal ganglia involved with initiation of gait?
It selects the pattern
How is the mesencephalic locomotor region (MLR) involved with the initiation of gait?
-It modulates the spinal cord
-Initiates info to the brainstem
-Initiator of neurons
Where does the CPG get sensory feedback from?
-Muscle spindle (muscle length)
-Golgi tendon (muscle force)
-Joint receptors
How are the reticulospinal neurons involved in locomotion?
They innervate the gamma and alpha motor neurons
What is the order in which locomotion is initiated?
-Cortex, basal ganglia, and cerebellum select limb pattern
-Mesencephalic locomotor region initiates the neurons
-Reticulospinal neurons integrate whole body movement and innervate gamma and alpha motor neurons
-Central pattern generator
How does the basal ganglia communicate with the MLR to initiate the gait process?
It releases dopamine into the MLR
What are burst generators?
They activate synergist muscle at each limb joint and ensure it is appropriately timed
What are locomotor networks composed of?
Distributed and interconnected unit burst generators that are selectively recruited to produce specific locomotor patterns
How does alternation of limbs via inhibition and activation of neurons occur?
-During locomotion, flexor and extensor neurons receive inhibitory and excitatory input
-Receive inhibitory input from Renshaw cells and reciprocal Ia interneurons
What are Renshaw cells?
-A population of inhibitory interneurons that project onto motor neurons
-Can synapse onto two motor neurons
How much does Ia and Ib increase extensor activity?
By 50%
How does Ib (GTO) increase extensor activity during gait?
It enhances muscular contraction of extensors during the stance phase and resets when activated during the swing phase (ask Dr. Rivera to explain more)
How does Ia (muscle spindle) increase extensor activity during gait?
Establishes monosynaptic connection with synergistic alpha motor neurons
How is the hip involved with the step cycle? Why is it important?
-The hip movement/position during the step cycle signals which part of the step cycle the limb is at any given moment
-Signals from afferents are influenced by hip position and help regulate the step cycle at the spinal cord level
How are the signals from the hip regarding the step cycle regulated and transmitted to the brain?
-The signal is sent to the spinal cord
-Then the signal is transmitted to the cerebellum via the dorsal spinocerebellar tract
Why is loading in mid to terminal stance a key component of sensory input?
-The longer the loading and increase in hip extension, the more sensory input
-Provides a greater opportunity for pre-swing and trailing limb
-Leads to greater stride length
How does the hip position regulate the transition from stance to swing phase?
Regulates the termination of extensor activity and onset of flexor activity
What is the swing phase mediated by?
-The trailing limb, 20-30 degrees of hip extension
-A quick stretch (extension) is needed to activate the muscle spindle
-Aids in the propulsion of the limb in space
What are the three inputs to help in gait training?
-Input 1: higher the mid-stance load, the more swing phase is improved
-Input 2: Hip position, hip extension and achieve trailing limb
-Input 3: erect posture