block 6- CPG Flashcards

Question

in conclusion How is activity in unitary oscillators coordinated?-CHEAT SHEAT?

Answer 1

Coordination between unitary oscillators relies on a gradient of excitability, fine-tuned by neurotransmitter action

Answer 2

Highest numbers of axons originate from: Dorsolateral commissural interneurons (dlc) Dorsolateral ascending interneurons (dca) Descending interneurons (dIN) Concentration is highest at rostral end of spinal cord and gets less and less as you go along ➔ Supports rostral-caudal excitability gradient -the more axons you have

Answer 3

Lamprey swimming involves rhythmic, undulatory body movements coordinated along the spinal cord. The swim rhythm is generated by a central pattern generator (CPG) with a half-centre oscillator structure. The spinal cord functions as a chain of unitary oscillators, each segment capable of generating rhythm. Even when isolated, spinal segments can produce rhythmic activity — but overall rhythm slows down. Phase lag per segment remains consistent, preserving the head-to-tail wave even if rhythm is slower. Glutamate (via NMDA receptors) is the key excitatory neurotransmitter in rhythm generation. Changing NMDA levels in different spinal regions can reverse or split the direction of the wave: Equal NMDA → normal rostral-caudal wave (forward swim). High NMDA caudally → caudal-rostral wave (backward swim). High NMDA in the middle → waves go both rostrally and caudally. This supports the leading oscillator hypothesis: the fastest oscillator sets the rhythm and coordinates the rest

Answer 4

Walking is a coordinated activity, and we can think of it as a repetitive "step cycle" that involves two main parts: Stance (Support) Phase: This is when your foot is in contact with the ground, supporting your body weight. The leg moves from the front (anterior) to the back (posterior) of your body. During this phase, the leg is also helping to push the body forward (propulsive force). Swing (Transfer) Phase: After the stance phase, the leg lifts off the ground and swings forward, moving from the back (posterior) to the front (anterior). This phase gets the leg ready to land again. Walking is not like a simple swinging motion, like a pendulum. It involves the hip, knee, and ankle joints all working together in a controlled way to make sure that the leg moves smoothly and efficiently.

Answer 5

When walking speed changes, the body adjusts in different ways: Moderate Speed Changes: Stance Phase: The biggest change happens in how long the foot stays on the ground (stance phase). This is where the duration of time spent with your foot planted changes when you walk faster or slower. Swing Phase: There is a smaller change in how long the leg swings through the air before it touches the ground. -When you change speed significantly, the coordination between limbs also changes.

Answer 6

-Each limb is controlled by its own controller. There is evidence in both humans and animals -various gaits (pattern of coordination) are controlled by a single neuronal network. again evidence -Even though each limb has its own "controller," all of these "controllers" are connected and work together through a single network of neurons in the brain and spinal cord. This network coordinates the movements of the limbs to produce different gaits or patterns of movement

Answer 7

The basic neuronal network for walking is located in the spinal cord, posterior brainstem, and cerebellum, rather than in the higher brain regions. This was shown through transection experiments, where cutting the spinal cord at the superior colliculus level still allowed cats to walk, though in a machine-like manner. However, when the spinal cord was severed at more caudal level(lower levels), spontaneous walking did not recover. This demonstrated that the lower brainstem and spinal cord are crucial for locomotion, and the Mesencephalic Locomotor Region (MLR) is key for initiating walking

Answer 8

The Mesencephalic Locomotor Region (MLR) plays a key role in controlling muscle force and limb coordination during walking, but it doesn't directly control the frequency of the step cycle. This was shown in two experiments: When the MLR was stimulated at a constant level while the treadmill speed decreased, the step cycle frequency also decreased, showing that the MLR does not regulate cycle frequency. When the MLR was stimulated at increasing levels while keeping treadmill speed constant, there was an increase in force and a change in gait pattern, but no change in cycle frequency. In conclusion, MLR activity influences muscle force and limb coordination, but not the frequency of the walking cycle. its control by the feedback cycle

Answer 9

"Low spinal cats" have had their spinal cords cut at the thoracic level, meaning the brain is disconnected from the lower spinal cord. Despite this, when these cats are: Supported in a harness and Placed on a treadmill, they can still show stepping movements with their hind legs. 💡 Why Is This Important? This tells us something critical: 🧠 The spinal cord itself contains circuitry for generating basic walking movements — even without input from the brain. These spinal circuits are called Central Pattern Generators (CPGs) — they can produce rhythmic patterns like walking or swimming. 🦵 But There’s a Catch: The stepping in these spinalized cats is weak and uncoordinated. However, when given clonidine (a drug that activates α2-adrenergic receptors), the movements become: Stronger More coordinated 🧬 What Does This Mean? The core locomotor controller (the CPG for walking) is located in the spinal cord, specifically in the lumbosacral enlargement, where leg motor neurons are concentrated. The poor movement quality in spinal cats is due to lack of excitatory drive (e.g., from brainstem or neuromodulators). Clonidine provides this missing excitatory input by enhancing noradrenergic signaling, allowing the CPG to function more effectively. ✅ Key Takeaway: The spinal cord can independently generate stepping rhythms, but it needs excitatory input (like from the brain or drugs) to work properly. The lumbosacral spinal cord houses this essential walking circuitry.

Answer 10

-Even without sensory feedback, the spinal cord can still produce rhythmic activity for stepping. This suggests that the spinal cord has the capacity to generate walking movements without needing continuous sensory input. -Sensory feedback is not required for the spinal cord to generate rhythmic stepping activity, meaning that the spinal cord has an intrinsic ability to control stepping, likely due to central pattern generators (CPGs) within the spinal cord.

Answer 11

- refers to the idea that even though each part of the body has its own CPG, they work together through coordination to produce one overall rhythmic movement, like the coordinated action of the limbs during walking. -Destruction of grey matter in specific spinal cord regions (L3/L4 + L6/L7) still allows for rhythmic activity, indicating that local oscillatory networks (CPGs) in the spinal cord control stepping. This shows that individual CPGs can work together as part of a larger rhythm generator, with L5 still capable of generating rhythmic activity.

Answer 12

Identifying Limb CPG Neurons: Limb CPGs can be identified using techniques like activity-dependent labeling, genetic approaches, and electrophysiology. Only about 0.1% of spinal cord neurons are part of the CPG.

Answer 13

Endogenous Bursting Neurons (Hb9 interneurons): Some neurons have endogenous bursting properties that help generate rhythmic activity, especially during locomotion. At the start of locomotion, rhythmic activity is generated by network interactions. During slow locomotion, it's a combination of network interactions and pacemaker activity. During fast locomotion, rhythmic activity is mainly driven by pacemaker activity.

Answer 14

CPGs for Individual Joints: There are individual spinal CPGs for each joint and muscle group, which combine to create a limb CPG. Limb CPGs interact to coordinate overall limb movement. These limb CPGs are activated by commands from the brainstem and higher control centers.

block 6- CPG Flashcards

(38 cards)