Podcast
Questions and Answers
Central pattern generators in the spinal cord are incapable of adjusting rhythmic movements in response to altered circumstances.
Central pattern generators in the spinal cord are incapable of adjusting rhythmic movements in response to altered circumstances.
False
During locomotion, the swing phase involves the limb being extended and placed in contact with the ground.
During locomotion, the swing phase involves the limb being extended and placed in contact with the ground.
False
Increases in the speed of locomotion are primarily due to a reduction in the duration of the swing phase.
Increases in the speed of locomotion are primarily due to a reduction in the duration of the swing phase.
False
In both cats and humans, the first extension (E1) phase occurs while the foot is in contact with the ground during the stance phase.
In both cats and humans, the first extension (E1) phase occurs while the foot is in contact with the ground during the stance phase.
Signup and view all the answers
During the flexion (F) phase of locomotion, the hip, knee, and ankle joints extend.
During the flexion (F) phase of locomotion, the hip, knee, and ankle joints extend.
Signup and view all the answers
The E1 phase is characterized by flexion at the knee and ankle with concurrent extension at the hip.
The E1 phase is characterized by flexion at the knee and ankle with concurrent extension at the hip.
Signup and view all the answers
During the E2 phase, extensor muscles lengthen even as they are contracting strongly.
During the E2 phase, extensor muscles lengthen even as they are contracting strongly.
Signup and view all the answers
The yielding of extensor muscles during the E2 phase impedes smooth body movement over the foot and is counterproductive to an effective gait.
The yielding of extensor muscles during the E2 phase impedes smooth body movement over the foot and is counterproductive to an effective gait.
Signup and view all the answers
A flexion reflex can lead to an animal collapsing if its weight is supported by the limb, demonstrating phase-dependent reflex reversal.
A flexion reflex can lead to an animal collapsing if its weight is supported by the limb, demonstrating phase-dependent reflex reversal.
Signup and view all the answers
The tonic electrical stimulation of the mesencephalic locomotor region has no effect on the speed of locomotion in animals on a freely moving treadmill.
The tonic electrical stimulation of the mesencephalic locomotor region has no effect on the speed of locomotion in animals on a freely moving treadmill.
Signup and view all the answers
Descending noradrenergic pathways from the locus ceruleus are essential for initiating locomotion in animals.
Descending noradrenergic pathways from the locus ceruleus are essential for initiating locomotion in animals.
Signup and view all the answers
The motor cortex, cerebellum, and brain stem all play distinct roles in the regulation of locomotor function.
The motor cortex, cerebellum, and brain stem all play distinct roles in the regulation of locomotor function.
Signup and view all the answers
Stronger electrical stimulation during locomotion should always produce a walking gait without progressing to faster gaits like trotting and galloping.
Stronger electrical stimulation during locomotion should always produce a walking gait without progressing to faster gaits like trotting and galloping.
Signup and view all the answers
Synaptic depression is characterized by an immediate onset of activity after a depolarization.
Synaptic depression is characterized by an immediate onset of activity after a depolarization.
Signup and view all the answers
Mutual inhibition involves interneurons that fire in-phase with each other, reciprocally coupled by inhibitory connections.
Mutual inhibition involves interneurons that fire in-phase with each other, reciprocally coupled by inhibitory connections.
Signup and view all the answers
The speed of stepping in spinal cats always remains constant, even if the speed of the treadmill belt changes.
The speed of stepping in spinal cats always remains constant, even if the speed of the treadmill belt changes.
Signup and view all the answers
As the stepping rate increases, the duration of the stance phase increases, while the swing phase duration remains constant.
As the stepping rate increases, the duration of the stance phase increases, while the swing phase duration remains constant.
Signup and view all the answers
Stretching hip extensor muscles inhibits the extensor half-center, thus promoting flexor motor neuron activity.
Stretching hip extensor muscles inhibits the extensor half-center, thus promoting flexor motor neuron activity.
Signup and view all the answers
Rapid extension at the hip joint leads to contractions of the extensor muscles in chronic spinal cats.
Rapid extension at the hip joint leads to contractions of the extensor muscles in chronic spinal cats.
Signup and view all the answers
Preventing hip flexion in a limb suppresses stepping in that limb.
Preventing hip flexion in a limb suppresses stepping in that limb.
Signup and view all the answers
During entrainment, extensor motor neuron activity is initiated in synchrony with hip extension.
During entrainment, extensor motor neuron activity is initiated in synchrony with hip extension.
Signup and view all the answers
The afferents primarily responsible for signaling hip angle for swing initiation arise from the Golgi tendon organs in hip flexor muscles.
The afferents primarily responsible for signaling hip angle for swing initiation arise from the Golgi tendon organs in hip flexor muscles.
Signup and view all the answers
Stimulation of the Golgi tendon organs and muscle spindles of flexor muscles prolongs the stance phase.
Stimulation of the Golgi tendon organs and muscle spindles of flexor muscles prolongs the stance phase.
Signup and view all the answers
During the E3 phase, the hip, knee, and ankle all flex to provide a propulsive force for forward movement.
During the E3 phase, the hip, knee, and ankle all flex to provide a propulsive force for forward movement.
Signup and view all the answers
Contractions of extensor muscles typically occur during the F phase of the stepping cycle.
Contractions of extensor muscles typically occur during the F phase of the stepping cycle.
Signup and view all the answers
The semitendinosus muscle, a flexor, briefly contracts at the beginning of each stance phase.
The semitendinosus muscle, a flexor, briefly contracts at the beginning of each stance phase.
Signup and view all the answers
The complex sequence of muscle contractions involved in stepping is referred to as the 'motor program for gait'.
The complex sequence of muscle contractions involved in stepping is referred to as the 'motor program for gait'.
Signup and view all the answers
In spinal preparations, the spinal cord is transected at the upper cervical level, isolating the hind limb musculature.
In spinal preparations, the spinal cord is transected at the upper cervical level, isolating the hind limb musculature.
Signup and view all the answers
Locomotor activity in chronic spinal preparations returns with drug treatments, within a few weeks following cord transvection.
Locomotor activity in chronic spinal preparations returns with drug treatments, within a few weeks following cord transvection.
Signup and view all the answers
In decerebrate preparations, the brain stem is transected precisely at the level of the pons.
In decerebrate preparations, the brain stem is transected precisely at the level of the pons.
Signup and view all the answers
In premammillary decerebrate preparations, spontaneous walking can occur and in postmammilary sections, electrical stimulation of the mesencephalic locomotor region is required to evoke stepping
In premammillary decerebrate preparations, spontaneous walking can occur and in postmammilary sections, electrical stimulation of the mesencephalic locomotor region is required to evoke stepping
Signup and view all the answers
In decerebrate preparations, coordination of fore and hind limbs is observed, but the rate of stepping is unchangeable.
In decerebrate preparations, coordination of fore and hind limbs is observed, but the rate of stepping is unchangeable.
Signup and view all the answers
Rhythmic locomotor patterns require sensory input from the moving limbs to be generated
Rhythmic locomotor patterns require sensory input from the moving limbs to be generated
Signup and view all the answers
Stimulation of afferent receptors from the Golgi tendon organs (GTO) shortens the stance phase during locomotion.
Stimulation of afferent receptors from the Golgi tendon organs (GTO) shortens the stance phase during locomotion.
Signup and view all the answers
Extensor motor neurons require high forces exerted by the extensor muscles to initiate the swing phase.
Extensor motor neurons require high forces exerted by the extensor muscles to initiate the swing phase.
Signup and view all the answers
The monosynaptic pathway from Ia fibers is one of the three excitatory pathways that transmit information to extensor motor neurons.
The monosynaptic pathway from Ia fibers is one of the three excitatory pathways that transmit information to extensor motor neurons.
Signup and view all the answers
Proprioceptive feedback from muscle spindles and Golgi tendon organs disrupts the burst activity in extensor motor neurons.
Proprioceptive feedback from muscle spindles and Golgi tendon organs disrupts the burst activity in extensor motor neurons.
Signup and view all the answers
The stumbling-corrective reaction is exclusive to dogs and has not been observed in other animals.
The stumbling-corrective reaction is exclusive to dogs and has not been observed in other animals.
Signup and view all the answers
Placing reflex leads to rapid flexion of the paw away from a stimulus during the stance phase.
Placing reflex leads to rapid flexion of the paw away from a stimulus during the stance phase.
Signup and view all the answers
An identical mechanical stimulus during the stance phase excites extensor muscles and inhibits flexor muscles.
An identical mechanical stimulus during the stance phase excites extensor muscles and inhibits flexor muscles.
Signup and view all the answers
The central rhythm generator for walking is influenced solely by proprioceptors and does not involve exteroceptors.
The central rhythm generator for walking is influenced solely by proprioceptors and does not involve exteroceptors.
Signup and view all the answers
The extensor half-center of the central rhythm generator has no control over the stance phase in locomotion.
The extensor half-center of the central rhythm generator has no control over the stance phase in locomotion.
Signup and view all the answers
In response to unexpected loading of the leg, proprioceptive feedback enables automatic adjustment of force and length in extensor muscles.
In response to unexpected loading of the leg, proprioceptive feedback enables automatic adjustment of force and length in extensor muscles.
Signup and view all the answers
Study Notes
Locomotion
- Local circuits in the spinal cord, called central pattern generators, control rhythmic movements like locomotion and swimming
- These circuits can fully control the timing and coordination of complex movements and adjust them to changing situations
- Locomotion cycles consist of stance and swing phases
- Stance: limb extended, contacting the ground for propulsion
- Swing: limb flexed, lifted from the ground and brought forward
- Increased locomotion speed correlates with shorter stance phases while swing phases remain relatively constant
- Locomotion in humans and cats can be divided into four phases:
- Flexion (F)
- First extension (E1)
- Second extension (E2)
- Third extension (E3)
- F and E1 occur during the swing phase (foot off ground)
- E2 and E3 occur during the stance phase (foot on ground)
- E2 is characterized by knee and ankle flexion resulting from body weight
- During E3, all three joints extend, providing propulsive force to move the body forward
Spinal Preparations
- Spinal cord is transected at the lower thoracic level, isolating hind limb segments from the rest of the central nervous system
- This allows for the study of spinal circuits in generating rhythmic locomotor patterns.
- Preparations may be maintained for weeks or months, allowing locomotor re-emergence without treatment over time
Decerebrate model
- The brain stem is completely transected
- This prevents rostral brain centers from influencing locomotor patterns
- Examines the role of the cerebellum and brain stem structures in controlling locomotion
- Spontaneous or electrically stimulated locomotor rhythms can be examined depending on the level of decerebration
Deafferented Preparations
- All sensory input from moving limbs is removed by transecting the dorsal roots (sensory axons only)
- Motor pathways remain intact
- Locomotor patterns are still generated, reflecting a degree of central rhythmic generation independent of sensory feedback
- The reduction in interneuron and motor neuron excitability may contribute to observed changes in locomotor patterns
Immobilized preparation
- Muscles are paralyzed (e.g., with curare) to prevent movement during 'fictive locomotion'
- This removes proprioceptive reflexes while keeping tonic sensory input
- Allows direct examination of spinal cord neuron activity during the simulated movement
Neonatal Rats
- Spinal cord removal from neonatal rats and maintenance in a saline bath permits coordinated leg motor neuron activity when exposed to NMDA and serotonin.
- This preparation enables detailed analysis of the rhythm-generating network
Central Pattern Generators (CPGs)
- CPGs are neuronal networks that generate rhythmic motor activity in the absence of sensory input
- CPGs are involved in rhythmic behaviors such as walking, swimming, and feeding, and are usually modified by sensory feedback and central nervous system signals
- CPGs depend on factors such as cellular properties within the network, synaptic properties, and interneuronal connections.
Sensory Input
- Somatosensory input from muscle and skin receptors, vestibular apparatus input for balance, and visual input are all used to regulate and modify stepping
- Proprioceptive feedback from limbs helps control the timing and amplitude of stepping patterns adjusting stance duration in relation to limb speed
- The Golgi tendon organs (measuring load on leg), and muscle spindles (monitoring muscle length) modify stance phase and delay swing initiation until leg unloading and low extensor muscle force.
- Exteroceptors provide valuable information to modify stepping patterns in response to obstacles, such as the 'placing reflex' in cats
- These reflexes adjust stepping movements to avoid external obstacles
Descending Pathways
- Signals from the brainstem and brain initiate locomotion
- The mesencephalic locomotor region (MLR) plays a role in initiating and controlling locomotion speed
- The motor cortex is involved in fine-tuning stepping movements, especially in visuomotor coordination tasks such as walking over barriers
- The cerebellum adjusts stepping movements in response to proprioceptive input while preventing gait deviation ('ataxia')
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the mechanics behind locomotion, focusing on how central pattern generators in the spinal cord manage rhythmic movements. Understand the phases of locomotion and how speed impacts stance and swing phases in humans and cats. This quiz will challenge your understanding of locomotion dynamics and related anatomical processes.
