Locomotion Flashcards
Which species locomote?
all
TRUE or FALSE: lower vertebrates contract muscles of the 4 limbs at the same time (co-contractors)
FALSE:
- lower vertebrates use sinusoidal body contractions for locomotion
- avian species contract muscles of the 4 limbs at the same time (co-contractors)
What are the 2 phases of locomotion?
- swing = flexion (i.e. flexor muscles are active)
- stance = extension (i.e. extensor muscles are active)
When does the beginning of the locomotion cycle occur?
when leg hits the ground (going from swing to stance)
TRUE or FALSE: locomotion is all or none
FALSE: specific pattern of muscle activation is more complex
TRUE or FALSE: locomotion is controlled by the spinal cord
TRUE
During which phase do flexors BEGIN to activate?
stance phase
What is spinalization and what was it used to demonstrate?
- cut all afferent inputs to spinal cord
- prove that theory that afferents cause locomotion is WRONG
TRUE or FALSE: activation of extensor half center will inhibit flexor half center
TRUE
What does the locomotor CPG do?
generate complex locomotor patterns
(CPG = central pattern generator)
Describe the stumbling corrector response after tripping. Is this response activated by the brain or the spinal cord?
- tripping activates the stumbling corrector response
- this response increases knee and hip FLEXION & ankle hyper-EXTENSION
- activated by the spinal cord
TRUE or FALSE: the locomotor CPG does not require assistance
FALSE: locomotor CPG requires assistance (e.g. visual and sensory info)
TRUE or FALSE: although supraspinal/sensory structures are not necessary for basic locomotor rhythm generation, they are responsible for stopping activity within the locomotor CPG and modulating its output to suit the environment
FALSE: responsible for INITIATING and modulating CPG activity
The locomotor CPG is ________________ (initiated/modulated) by descending input and ________________ (initiated/modulated) by sensory input.
- initiated by motor input
- modulated by sensory input
What is an example of descending input and sensory input affecting locomotor CPG in the SC?
- descending input = DECISION to perform locomotion (activate CPG)
- sensory input = going DOWNSTAIRS (i.e. consider the environment of locomotion)
how many cervical nerves are there? thoracic? lumbar? sacral?
- C1-C8
- T1-T12
- L1-L5
- S1-S5
How are grey and white matter arranged in the spinal cord?
grey matter on the inside (unmyelinated)
Where are 2 locations on the spinal cord that you can find more grey matter?
cervical and lumbar enlargements
In which enlargement of the spinal cord is the locomotor CPG found?
lumbar enlargement
Mammalian spinal cord has a laminar distribution. What does this mean?
neurons in different lamina have related functions
Which spinal cord lamina are associated with the dorsal horn? intermediate nucleus? ventral horn?
- dorsal horn = lamina I - V
- intermediate nucleus = lamina VI - VIII
- ventral horn = lamina IX
What kind of neurons are found in lamina I - V? Which part of the spinal cord is this?
- sensory-related interneurons
- dorsal horn
What kind of neurons are found in lamina VI - VIII? Which part of the SC is this?
- sensory and motor-related interneurons (excitatory and inhibitory)
- intermediate nucleus
What kind of neurons are found in lamina IX? Which part of the SC is this?
- motor neurons
- ventral horn
Which part of the spinal cord controls locomotion?
a) dorsal horn
b) intermediate nucleus
c) ventral horn
Which lamina control locomotion?
b) intermediate nucleus (lamina VI - VIII)
TRUE or FALSE: interneurons with variable functions are intermingled in the the intermediate and dorsal spinal cord.
FALSE: intermediate and VENTRAL spinal cord
What are the different types of cells and their subtypes that exist in the SC?
- glia (astrocytes, oligodendrocytes)
- neuron (motor neuron, interneuron (+/-))
Describe the first spinalized cat preparations and what it demonstrated. (hint: were the first studies physiological?)
- first studies were NOT PHYSIOLOGICAL (drugs and spinalization and stimulation of PNS to generate locomotion)
- after application of L-DOPA stimulation of flexor reflex afferents –> left-right alternation of hindlimbs similar to stepping (slow locomotor pattern)
- first studies showed that the locomotor CPG was found in the INTERMEDIATE NUCLEUS, as majority of the interneurons that receive input from FRA are found here
In comparison to spinalization to evoke locomotion, what was another experiment done to activate the locomotor CPG more physiologically? Describe this experiment.
- electrical brainstem stimulation
- site in the midbrain of cats was identified that could evoke locomotion when electrically stimulated
- site = MESENCEPHALIC LOCOMOTOR REGION (MLR)
MLR vs CPG?
- MLR = initiation of stepping in locomotion
- CPG = generation of locomotor patterns
How does increasing stimulation strength affect in vivo fictive locomotor activity?
increasing stimulation = increasing speed of locomotion
How are the MLR and CPG anatomically related?
MLR –> reticular formation –> reticulospinal tract –> locomotor CPG