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Neural Anatomy and Function

Neural Anatomy and Function. NERVOUS SYSTEMS. Central nervous system Peripheral nervous system. CENTRAL NERVOUS SYSTEM p. 33. Brain Cerebral Cortex/Cerebrum Motor cortex Basal Ganglia/Diencephalon – sensory input Cerebellum – motor control Brain stem – sensory input Spinal Cord.

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Neural Anatomy and Function

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  1. Neural Anatomy and Function

  2. NERVOUS SYSTEMS • Central nervous system • Peripheral nervous system

  3. CENTRAL NERVOUS SYSTEM p. 33 • Brain • Cerebral Cortex/Cerebrum • Motor cortex • Basal Ganglia/Diencephalon – sensory input • Cerebellum – motor control • Brain stem – sensory input • Spinal Cord

  4. PERIPHERAL NERVOUS SYSTEM • Somatic • Sensory (Gamma) Nerves • Motor (Alpha) Nerves • Autonomic [FYI] • Parasympathetic • Sympathetic

  5. Spinal Nerves p. 35

  6. NERVE ANATOMY • A single nerve cell is called a neuron • A bundle or group of neurons make up a nerve • A nerve contains both afferent and efferent nerves

  7. Afferent Neuron • Carry impulse towards the CNS (e.g. sensory nerves) • Synapse Towards CNS

  8. Efferent Neuron • Carry impulse away from the CNS (e.g. motor nerves) • Stimulatory • Inhibitory

  9. NEURON ANATOMY • Dendrite • Cell Body • Axon

  10. AXON • Conduction • Myelin sheath • Synapse • Neurotransmitter

  11. CONDUCTION Resting State: Na outside, K inside

  12. CONDUCTION 4. Na K Pump 1. Depolarization 3. Repolarization 2. Propagation

  13. MYELIN SHEATH

  14. SYNAPSE

  15. SYNAPSE

  16. SYNAPSE • Quick Time Movie

  17. NEUROMUSCULAR JUNCTION

  18. NEUROMUSCULAR JUNCTION

  19. MOTOR UNIT • Motor unit = one motor nerve + all the muscle fibers it innervates. • Types • Fast (alpha -1) • Slow (alpha -2)

  20. 3 1 2

  21. MOTOR UNIT Fast Fast Slow

  22. MUSCLE TENSION or FORCE or STRENGTH • Number of MU stimulated • Frequency of stimulation to each MU • Type of MU stimulated

  23. MUSCLE STIMULATION: How does it begin?

  24. Volitional Control (Motor Cortex) • Motor cortex • Motor neurons • Muscles

  25. 2. Reflex Control • Afferent neuron • Sensory neuron • Efferent neuron • Motor neuron

  26. PROPRIOCEPTION & KINESTHESISp. 37 • Proprioception • The ability to sense the position and location and orientation and movement of the body and its parts • Kinesthesis • The ability to feel movements of the limbs and body

  27. PROPRIOCEPTION • Proprioceptors of the joints and skin • Meissner’s corpuscles • Ruffini’s corpuscles • Pacinian corpuscles • Krause’s end-bulbs

  28. PROPRIOCEPTION • Proprioceptors of the muscles • Muscle spindles • Golgi tendon organs

  29. Muscle Spindles

  30. muscle spindle

  31. Muscle Spindles • Provide proprioception • Sense the amount of stretch and the rate of stretch • Reflexes involving the muscle spindles is how we ‘feel’ a movement was done correctly • Spindles are a part of learning; we develop such reflexes as we practice skills and movements

  32. Golgi Tendon Organs

  33. Golgi Tendon Organs • Sensitive to muscle tension and active contraction • Protect muscle from excess contraction force • Stimulation of GTO an afferent impulse is sent to the central nervous system • In turn, efferent impulses are sent to the… • Agonist muscle causing it to relax • Antagonist muscle causing it to contract

  34. Neuromuscular Summary • An example from baseball. • A pitcher throws a curve ball to Sammy Sosa • Sammy’s eyes see the ball coming towards him and is able to identify the pitch as a curve ball • Sensory nerves (afferent) send that information to the CNS • In the CNS the sensory nerve synapses with motor nerves • The motor nerves in turn stimulates the muscles (deltoid and pectoralis major) required to swing the bat in the proper position to hit the ball

  35. Neuromuscular Summary • Inside the fibers of the deltoid and pectoralis major, calcium is released • The calcium allows myosin heads to attach to actin • When the heads swivel the fibers of the deltoid muscle will shorten • The shortening of the fibers will pull on the humerus causing Sammy to swing the bat • The muscle spindles “tell” the CNS when the arm is in the correct position • If all goes as planned, the deltoid and pectoralis major will move his arms into a position to hit the ball

  36. Neuromuscular Summary • An example from weight training. • A man is having his muscular strength tested on the bench press • For his first lift, 50 pounds is put on the bar • He will be using his pectoralis major muscle with has 500 motor units (300 slow twitch and 200 fast twitch) and his triceps muscle • His CNS stimulates 280 motor units leading to his pectoralis major muscle (180 slow twitch and 100 fast twitch) • End nerve ending stimulates a separate muscle fiber

  37. Neuromuscular Summary • Calcium is released, myosin attaches to actin and swivels. • The pectoralis major and triceps muscles shortens and his arm extends outward raising the bar with 50 pounds on it. • After a few minutes of rest, 100 pounds is place on the bar • This time he stimulates 380 motor units (260 slow twitch and120 fast twitch) • The weight is successfully lifted • After a few minutes of rest, 150 pounds is place on the bar

  38. Neuromuscular Summary • This time he stimulates 460 motor units (280 slow twitch and 180 fast twitch) • As the pectoralis major muscle contracts the GTO in the pectoralis major are stimulated • They stimulate a sensory nerve leading to the CNS • In the CNS, the sensory nerve synapses with a motor nerve that will inhibit (relax) the pectoralis major muscle • The man is unable to successfully lift the 150 pounds.

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