Neural Anatomy and Function NERVOUS SYSTEMS вЂў Central nervous system вЂў Peripheral nervous system CENTRAL NERVOUS SYSTEM p. 33 вЂў Brain вЂ“ Cerebral Cortex/Cerebrum вЂў Motor cortex вЂ“ Basal Ganglia/Diencephalon вЂ“ sensory input вЂ“ Cerebellum вЂ“ motor control вЂ“ Brain stem вЂ“ sensory input вЂў Spinal Cord PERIPHERAL NERVOUS SYSTEM вЂў Somatic вЂ“ Sensory (Gamma) Nerves вЂ“ Motor (Alpha) Nerves вЂў Autonomic [FYI] вЂ“ Parasympathetic вЂ“ Sympathetic Spinal Nerves p. 35 NERVE ANATOMY вЂўA single nerve cell is called a neuron вЂўA bundle or group of neurons make up a nerve вЂўA nerve contains both afferent and efferent nerves Afferent Neuron вЂў Carry impulse towards the CNS (e.g. sensory nerves) вЂў Synapse Towards CNS Efferent Neuron вЂў Carry impulse away from the CNS (e.g. motor nerves) 1. Stimulatory 2. Inhibitory NEURON ANATOMY вЂў Dendrite вЂў Cell Body вЂў Axon AXON 1. 2. 3. 4. Conduction Myelin sheath Synapse Neurotransmitter CONDUCTION Resting State: Na outside, K inside CONDUCTION 4. Na K Pump 3. Repolarization 1. Depolarization 2. Propagation MYELIN SHEATH SYNAPSE SYNAPSE SYNAPSE вЂўQuick Time Movie NEUROMUSCULAR JUNCTION NEUROMUSCULAR JUNCTION MOTOR UNIT вЂў Motor unit = one motor nerve + all the muscle fibers it innervates. вЂў Types вЂ“ Fast (alpha -1) вЂ“ Slow (alpha -2) 3 1 2 MOTOR UNIT Fast Fast Slow MUSCLE TENSION or FORCE or STRENGTH 1. Number of MU stimulated 2. Frequency of stimulation to each MU 3. Type of MU stimulated MUSCLE STIMULATION: How does it begin? 1. Volitional Control (Motor Cortex) 1. Motor cortex 2. Motor neurons 3. Muscles 2. Reflex Control 1. Afferent neuron вЂ“ Sensory neuron 2. Efferent neuron вЂ“ Motor neuron PROPRIOCEPTION & KINESTHESIS p. 37 вЂў Proprioception вЂ“ The ability to sense the position and location and orientation and movement of the body and its parts вЂў Kinesthesis вЂ“ The ability to feel movements of the limbs and body PROPRIOCEPTION вЂў Proprioceptors of the joints and skin вЂ“MeissnerвЂ™s corpuscles вЂ“RuffiniвЂ™s corpuscles вЂ“Pacinian corpuscles вЂ“KrauseвЂ™s end-bulbs PROPRIOCEPTION вЂў Proprioceptors of the muscles вЂ“Muscle spindles вЂ“Golgi tendon organs Muscle Spindles muscle spindle Muscle Spindles вЂў Provide proprioception вЂў Sense the amount of stretch and the rate of stretch вЂў Reflexes involving the muscle spindles is how we вЂ�feelвЂ™ a movement was done correctly вЂў Spindles are a part of learning; we develop such reflexes as we practice skills and movements Golgi Tendon Organs Golgi Tendon Organs вЂў Sensitive to muscle tension and active contraction вЂў Protect muscle from excess contraction force вЂў Stimulation of GTO an afferent impulse is sent to the central nervous system вЂў In turn, efferent impulses are sent to theвЂ¦ вЂ“ Agonist muscle causing it to relax вЂ“ Antagonist muscle causing it to contract Neuromuscular Summary вЂўAn example from baseball. вЂўA pitcher throws a curve ball to Sammy Sosa вЂўSammyвЂ™s eyes see the ball coming towards him and is able to identify the pitch as a curve ball вЂўSensory nerves (afferent) send that information to the CNS вЂўIn the CNS the sensory nerve synapses with motor nerves вЂўThe motor nerves in turn stimulates the muscles (deltoid and pectoralis major) required to swing the bat in the proper position to hit the ball Neuromuscular Summary вЂўInside the fibers of the deltoid and pectoralis major, calcium is released вЂўThe calcium allows myosin heads to attach to actin вЂўWhen the heads swivel the fibers of the deltoid muscle will shorten вЂўThe shortening of the fibers will pull on the humerus causing Sammy to swing the bat вЂўThe muscle spindles вЂњtellвЂќ the CNS when the arm is in the correct position вЂўIf all goes as planned, the deltoid and pectoralis major will move his arms into a position to hit the ball Neuromuscular Summary вЂў An example from weight training. вЂў A man is having his muscular strength tested on the bench press вЂў For his first lift, 50 pounds is put on the bar вЂў He will be using his pectoralis major muscle with has 500 motor units (300 slow twitch and 200 fast twitch) and his triceps muscle вЂў His CNS stimulates 280 motor units leading to his pectoralis major muscle (180 slow twitch and 100 fast twitch) вЂў End nerve ending stimulates a separate muscle fiber Neuromuscular Summary вЂў Calcium is released, myosin attaches to actin and swivels. вЂў The pectoralis major and triceps muscles shortens and his arm extends outward raising the bar with 50 pounds on it. вЂў After a few minutes of rest, 100 pounds is place on the bar вЂў This time he stimulates 380 motor units (260 slow twitch and120 fast twitch) вЂў The weight is successfully lifted вЂў After a few minutes of rest, 150 pounds is place on the bar Neuromuscular Summary вЂў This time he stimulates 460 motor units (280 slow twitch and 180 fast twitch) вЂў As the pectoralis major muscle contracts the GTO in the pectoralis major are stimulated вЂў They stimulate a sensory nerve leading to the CNS вЂў In the CNS, the sensory nerve synapses with a motor nerve that will inhibit (relax) the pectoralis major muscle вЂў The man is unable to successfully lift the 150 pounds.