Kinesiology Week 5
Kinesiology Week 5 3824
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This 6 page Class Notes was uploaded by Sydney Notetaker on Thursday September 22, 2016. The Class Notes belongs to 3824 at Virginia Polytechnic Institute and State University taught by Dr. Williams in Fall 2016. Since its upload, it has received 115 views. For similar materials see Kinesiology in HNFE at Virginia Polytechnic Institute and State University.
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Date Created: 09/22/16
Week 5 Tuesday, August 23, 2016 9:33 AM Neuro 1 Part 2 What to know which nerve region innervates a nerve and what it does Phrenic Nerve • Come out of the cervical region and innervates the diaphragm muscle which is involuntary and it controls our breathing Axillary, Musculocutaneous, radial, ulnar, and median nerves • Come out of the brachial plexus and innervate muscles associated with the arm Axillary nerve comes out and around the scapula • Innervates the deltoid muscle Musculocutaneous muscle • Innervates the biceps Radial Nerve • Helps with elbow extension • And runs along the radial bone • Wrist, finger, and thumb extension • Innervates the triceps muscle Median Nerve • Innervates flexor muscles on the radial side associated with the wrist, fingers, and thumb Ulnar nerve Passes behind the elbow Ulnar side of hand is the strongest side of your grip Lumbar Nerves Comes out of the lower back Femoral Nerve Innervates the hip flexor muscles If loss of function of nerve, there will be weakened hip flexion and Ulnar side of hand is the strongest side of your grip Lumbar Nerves Comes out of the lower back Femoral Nerve Innervates the hip flexor muscles If loss of function of nerve, there will be weakened hip flexion and knee extension Obturator nerve Innervates all hip adductors or groin muscles (medial side of thigh) If the nerve is damaged there will loss of adduction Sciatic Nerve Exits at lower area of lumbar vertebrae and part of the sacral region Comes through pelvis on posterior side of hip Innervates hamstring muscles Loss of this nerve prohibits knee flexion and hip extension Splits into Tibial and Peroneal nerve Tibial Nerve Innervate plantar flexion If there is damage, there will be a loss of plantar flexion Runs on medial side of leg Peroneal Nerve Innervates dorsiflexion muscles (picking toe up off the ground) Sciatic Nerve damage can cause weakness or paralysis, this can also impinge a receptor somewhere else the body and can send a signal to the brain ○ Referred pain-impingement of receptor somewhere else in the body Neuro 2 Tuesday, September 20, 2016 10:04 AM Motor Unit • Innervates thousands of muscle fibers at a time • Motor neuron equally controls all muscle fibers Each motor neuron in the gastrocnemius muscle may innervate 2000 fibers because its ratio is 1:2000 Extraocular muscles have a small innervation ratio so they have fine control over the • Motor neuron equally controls all muscle fibers Each motor neuron in the gastrocnemius muscle may innervate 2000 fibers because its ratio is 1:2000 Extraocular muscles have a small innervation ratio so they have fine control over the eye muscles Innervation ratio- number of muscle fibers per motor unit • Slower motor units have a much smaller motor body and are slower • Large motor units have a large motor body and are faster Motor neurons are important in determining muscle fiber types In a study they took the fast neurons and hooked them up to the small fibers and took the slow neurons and hooked them up to the large fibers ○ Cross innervation • They found that the neuron is important in determining the fiber type characteristics and activity patterns • Use determines functions and function determines use Control muscle force by the size principle • It takes less of a stimulus to activate the small motor neuron than it does to activate the large motor neuron Size Principle • We activate more and more units based on the their size ○ The small (slow) motor units are activated first, then intermediate motor units, and lastly the large (fast) motor units We don’t have the ability to selectively recruit the fast ones before the slow ones Can we fully activate the motor unit pool? • Do we need to be under stress in order to become a "superhuman" The more motor units activated the more force we have If the motor units are sitting around and have never been activated in my lifetime, what happens to them? • They atrophy and become weak Violating the size principle • We as humans can't, but some species can ○ A Cat, when its paw gets wet and he flicks his paw very fast to get lifetime, what happens to them? • They atrophy and become weak Violating the size principle • We as humans can't, but some species can ○ A Cat, when its paw gets wet and he flicks his paw very fast to get the water off ○ A fish, when he flicks his tail to get away quickly Rate Coding • Motor control • If second stimulus is sent before the muscle relaxes it sums the first one and gives it a little more force (summation) • Incomplete tetanus- you can still see some individual contractions • Complete tetanus - you can't really see any individual contractions Reflexes • Proprioceptor • Help us recruit or prevent motor units Proprioceptors • Monitor the environment • Senses position of body and strength of effort being used in the movement • The pain receptor sends a signal to the spinal cord, and will activate the muscles that cause the elbow the flex and inhibit the ones that cause it to extend Interneuron • Within the spinal cord • Some are inhibitory and some are excitatory • If you touch a hot stove the sensory neuron will activate excitatory neurons to flex the elbow Why are reflexes important? • To make sure the neural periphery is working and intact ○ Babinski reflex § Tickle baby's foot and they spread their toes ○ Moro reflex § Act like you are going to drop the baby and this triggers their arms to go out Stretch (knee jerk) Reflex • Excitatory reflex ○ Moro reflex § Act like you are going to drop the baby and this triggers their arms to go out Stretch (knee jerk) Reflex • Excitatory reflex • Muscle spindle gets stretched ○ Tapping on patella tendon invokes a small stretch on the quadriceps muscle ○ Monosynaptic Muscle spindle • Sits in between muscle fibers • Nerves are wrapped around spindle like a spring • When it stretches the nerves get pulled apart and send a signal to the spinal cord and the brain Contractile region • Regulates length of the sensory region - Slow stretching the contractile region stretches and no reflex - The rapid stretching the sensory region contract and you get a reflex Recurrent inhibition • A motor neuron activates the Renshaw cell and it begins to inhibit the stretched muscle ○ The muscle shortens then relaxes Reciprocal inhibition • The interneuron inhibits the antagonist muscle Stretch Reflex Importance • If we didn't have stretch reflex there wouldn't be enough time to process that we have a heavy object in our hand and we would drop it Also helps with injury prevention • If I decide I want to flex my elbow at 90 degrees I set the movement up using the muscle spindle • It activates the stretch reflex to shorten the muscle If I decide I want to flex my elbow at 90 degrees I set the movement up using the muscle spindle • It activates the stretch reflex to shorten the muscle
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