PowerPoint Presentation - movement

1)Action Potential in Motor Axon2) End Plate Potential at Neuromuscular Junction3) Action Potential in Muscle Fiber.4) The AP induces, after a small latency, a twitch in the muscle fiberTwitch - transient all-or-none contraction
Muscle Excitation-Contraction

1. spindle stretch activates sensory neuron. 2. sensory neuron synapses on ventral cord motor neurons and interneurons3. increase in motor neuron activity innervates same and synergistic muscles.4. inhibits motor neurons that innervate antagonistic muscles

Stretch reflex

Types of motor neurons
a motor neurons- innervate the extrafusal muscle fibers that generate the forces needed for movement and posture. g motor neurons - innervate muscle spindles in intrafusal muscle fibers. These fibers regulate the sensory input from spindles by setting the muscle fibers to an appropriate length.

g motor Neuron Activity Affects Reponses of Muscle Spindles
Gamma neurons regulate excitation of spindles so they can activate the muscle indirectly through the stretch reflex.

Golgi tendon organ
Encapsulated afferent nerve endings located at the junction of the muscle and tendon.Fire when muscle contracts and are less sensitive (not completely insensitive) to passive stretch of the muscle.axons from Golgi tendon organs inhibit neurons in the spinal cord that synapse with the a motor neurons that innervate the same muscle.Helps prevent fatigueProtects muscle from large forcesMaintains steady level of muscle force

Golgi Tendon Organs

Comparison of the Function of Muscle Spindles and Golgi Tendon Organs

Comparison of the Function of Muscle Spindles and Golgi Tendon Organs

Negative Feedback Regulation of Muscle Tension By Golgi Tendon Organs
Negative feedback byGolgi tendon organs
When muscle contracts, feedbackinhibits additional contractions prevents damage and fatigue.

Flexion reflex
Reflexes that compensate posture when one withdraws from pain.involves several synaptic linksexcitation of nociceptor leads to ipsilateral and contralateral responses. flexion reflex. Stimulation of cutaneous receptors in the foot leads to activation of spinal cord local circuits that withdrawal stimulated (pained) side and extend other side to provide compensatory support.

Spinal Cord Circuitry Responsible for the Flexion Reflex