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Biomechanics Chp 4

Chapter 4

QuestionAnswer
What are sensory neurons? Nerves that enter the spinal cord on the posterior side because they transmit info from the muscle to the system.
What are motor neurons? These neurons exit on the anterior side of the spinal cord because they transmit info from the system to the muscle.
CNS Central Nervous System.
What does the CNS consist of? Brain, and Spinal Cord.
What does the CNS do? Is where human movements is initiated, controlled and monitored.
PNS Peripheral Nervous System.
What is the PNS? Consists of all of the branches of nerves that lie outside of the spinal cord.
How many pairs of spinal nerves are in the cervical region? 8 pairs
How many pairs of spinal nerves are in the thoracic region? 12 pairs
How many pairs of spinal nerves are in the lumbar region? 5 pairs
How many pairs of spinal nerves are in the sacral region? 5 pairs
How many pairs of spinal nerves are in the coccygeal region? 1 pair
What are the structures of a motor neuron? Soma, Ganglia, Dendrites, Axon, Alpha motor neuron, myelination, Node of Ranvier, and Schwann cells.
What is the all or none principle? When motor units receive sufficient stimulation, all fibers of a motor unit produce tension together.
Does one motor unit innervate all of the fibers in one fascicle? Why or Why not? Each motor unit goes to a different fiber. Motor end plates go to different fibers in different fascicles.
What is an Alpha Motor Neuron? Really long axon that goes to the muscle that is being innervated.
What is a reflex? Involuntary response to stimuli.
What is the contraction speed for Type 1 muscle fiber type? Slow.
What is the contraction speed for Type IIa muscle fiber type? Fast.
What is the contraction speed for Type IIb muscle fiber type? Fast.
The number of fibers in Type I muscle fiber type? Few.
The number of fibers in Type IIa muscle fiber type? Many.
The number of fibers in Type IIb muscle fiber type? Many.
The force of unit in Type I muscle fiber type? Low.
The force of unit in Type IIa muscle fiber type? High.
The force of unit in Type IIb muscle fiber type? High.
Fatigability in Type 1 muscle fiber type? Low.
Fatigability in Type IIa muscle fiber type? Medium.
Fatigability in Type IIb muscle fiber type? High.
Describe type I muscle fiber type. Slow contraction times (>70 ms). Generates little tension. Highly fatigable resistant. Maintaining posture. Distance runners.
Describe type IIa muscle fiber type. Fast contraction times (30-50 ms). More fatigue resistant than type IIb. Swimming, bicycling.
Describe type IIb muscle fiber type. Rapid contraction times (30-40ms). Innervated by alpha motor neurons. Larger neuron-to-fiber ratios. Sprinting, jumping, weightlifting.
What is recruitment? The order of activation of the motor units, is the prime mechanism for force production in the muscles.
What order does recruitment follow? (AKA Size principle.) Small, slow-twitch motoneurons are recruited first, followed by recruitment of the fast twitch oxidative and finally the large, fast twitch glycolytic motor units.
What is frequency coding? The amount of force or tension developed by the muscle. Involves intermittent high-frequency bursts of action potentials or impulses ranging from 30 -120 impulses per second.
Recruitment in small muscles. All units are recruited and activated when the external force of the muscle is at levels of only 30% to 50% of the maximum voluntary contraction level.
Recruitment in large muscles. Recruitment of motor units takes place all through the total force range, so that some muscles are still recruiting more motor units at 100% of maximum voluntary contraction.
What is the flexor reflex? Initiated by painful stimulus, causes quick withdrawal/flexion of the limb. Ex: touching a stove.
Propiospinal reflexes? Reflexes processed on both sides and at different levels of the spinal cord.
Crossed Extensor reflex? Causes extension of flexed limb when contralateral limb rapidly flexes. Initiated by receiving or expecting to receive painful stimuli.
Tonic Neck Reflex? Stimulated by movements of the head that create a motor response in the arms. When the head is rotated to the left this stimulates a asymmetric response of extension of the same-side arm (left)and a flexion of the opposite arm. ATNR reflex seen in infants
Supraspinal reflex? Brings information into the spinal cord and processes it in the brain.
Labyrnthine Righting reflex? Ex of Supraspinal reflex. Stimulated by leaning, being upside down, or falling of an upright posture.
Proprioceptors? Sensory receptors in the musculoskeletal system that that transform mechanical distortion in the muscle or joint.
Muscle Spindle? A proprioceptor found in higher abundance in the belly of the muscle lying parallel to the muscle fibers and actually connecting into the fascicles via connective tissue.
Intrafusal fibers? Contained within a capsule, forming a spindle shape.
Gamma Motor Neuron? Innervates contractile ends of muscle spindle. Innervates multiple muscle spindles.
Nuclear Bag Fiber? Has a large cluster of nuclei in its center. Thicker and its fibers connect to the capsule and to the actual connective tissue of the muscle fiber.
Nuclear Chain Fiber? Is smaller with the nuclei arranged in rows in the equatorial region. Does not connect to the actual muscle fiber but only makes connection with the spindle capsule.
Reciprocal Inhibition? Relaxation of antagonist(s) while agonist produce joint action.
Autogenic Facilitation? Internally generated excitation of the alpha motor neurons through stretch or other input.
Golgi Tendon Organ? Proprioceptor significantly influencing muscular action. Lies at the musculoskeletal junction.
Extrafusal Fibers? Collagen fibers of the GTO
Proprioceptive neuromuscular facilitation? Technique used to stimulate relaxation of the stretched muscle so that the joint can be moved through a greater range of motion.
Created by: czap
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