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NESC 2470 (13)

Lecture 1, Nov 9th 2011.docx

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NESC 2470

Lecture 1, Nov 9th 2011 November-22-11 5:36 AM 3 Levels of control  Individual nerve cells  Spinal cord  Forebrain control Types of muscle  Smooth muscle o Digestive tract o Arteries o Innervated by nerve fibres from the ANS o Plays role in peristalsis, control of blood pressure and blood flow  Striated muscle (Striped looking) o Cardiac Muscle  Heart muscle  Can contract without innervation  Innervation from ANS allows speed to be controlled o Skeletal muscle  Each fibre innervated by 1 axon branch of a lower motor neuron  Each motor neuron can connect to many muscle fibres Somatic nervous system  Under voluntary control  Generates behaviour Flexion  Closing Joint Extension  Extending joint Muscles from each of these groups working against each other are called antagonists Synergists  Muscles that work together to move joint in same direction Muscles tend to be grouped into 3 categories  Axial o Control trunk o Posture regulating muscles  Proximal o Shoulder, elbow, knee, pelvis o Involved in locomotive control o Neuronal location in the spine in cervical (arms) and lumbar-sacral (legs) segments  Distal o Hand, foot, finger, toe o Involved in the control of object manipulation o Neuronal location in the spine in cervical (arms) and lumbar-sacral (legs) segments Lower motor neurons  Cell bodies in spinal cord  Leave muscle through ventral route  Connects to muscle at neuromuscular junction  Innervate the somatic musculature in the ventral horn of the spinal cord  Only these directly command muscle contraction Ventral Horns  Larger at cervical enlargement o Arm control  And lumbar enlargement o Leg control Spinal segments  Cervical  Thoracic  Lumbar  Sacral Muscle cells  Controlled by lower motor neurons o Alpha motor neurons  Directly trigger the generation of force by muscles One alpha motor neuron and all the muscle fibers it innervates collectively make up  the elementary component of motor control, called a motor unit  Communicates with muscle fibre by releasing Ach at neuromuscular junction Motor unit  Lower motor neuron and muscle fibres connected to it  Come in many different sizes  Muscles with more small motor units can be more finely controlled  Small units have small alpha motor neurons Motor neuron pool  All of the motor neurons that control 1 muscle Force of exertion control  Rate of alpha motor neuron firing  Recruitment of additional synergistic motor units  Best motor control occurs when motor unit is very small Henneman's size principle  Small motor units turn on first  Large ones only come on as needed Alpha motor neuron input  Excite skeletal muscles  Muscle spindles o Innervated by dorsal root ganglion cells o Provides feedback about muscle length  Upper motor neurons o Located in the motor cortex and brain stem o Conscious voluntary control  Interneurons o Located in spinal cord o Largest input o Part of circuit that generates the spinal motor programs Red motor unit (Slow motor units)  More mitochondria  Slow contracting  Take long time to fatigue  Found in anti-gravity muscles, wings, legs  Contain smaller diameter, more slowly conducting axons  Fire less frequently White motor un
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