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Lecture 3

KINE 1020-Week 2- Lecture 3 and 4

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York University
Kinesiology & Health Science
KINE 1020
Angelo Belcastro

Lecture 3 Jan0912 Muscle weakness failure to develop an expected force which can be attributed any one of the processes required for force generation This is associated with all types and examples of muscle diseases disorders Muscle contraction results from a chain of events that begins with a 1 Nerve impulse traveling in the up motor neuron from the cerebral cortex in the brain to spinal cord 2 The nerve impulse then travels in the lower motor neuron from spinal cord to neuromuscular junction 3 Where the neurotransmitter acetylcholine is released Acetylcholine diffuses across the neuromuscular junction stimulating acetylcholine receptors depolarize the muscle membrane 4 The result is the contraction of the muscle fibre Contraction depends on the integrity of each of these parts disease or disorder in any part causes muscle weakness Classification a Upper Motor Neuron Disease a problem from cerebral cortex down to the spinal cord y CV stroke producing weakness of one side of the body The arm is flexed leg extended and the limbs have increased tone y With the upper motor neuron disease the muscle bulk is usually well preserved y Other causes of upper motor neuron disorders include tumours and spinal cord injury b Lower motor neuron disease flaccid muscle weakness can happen at two levels spinal cord and peripheral nerves 1Spinal cord motor neurons are lying in the spinal cord you get muscle wastingshrinkage and eventual death of neurons and denervationy Generally between 50 70 years of age and have upper and lower motor neuron weakness paralysis progresses rapidly and death within three years y Infant amyotrophic lateral sclerosis is fatal within one year y No cause is yet known and no cure 2 Peripheral Nerves Disease peripheral neuropathies or polyneuropathies y Symptoms usually begin in the hands and feet and progress toward the body also associated with sensory disturbances y Peripheral neuropathies degeneration of the axons o Axons can regenerate but only at a rate of one to two millimetres per day o Damage to blood vessels nerves can cause these peripheral neuropathies y Myelin Sheath can degenerate o Symptoms are similar to axonal neuropathiesMajor difference is muscles rarely atrophy o Recovery can be very quick o Causes diabetes heredityc NM junction disease y These disease are associated with weakness and fatigability with exercise
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