Nerves

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Nerves

  1. 1. Neural Anatomy and Function
  2. 2. NERVOUS SYSTEMS• Central nervous system• Peripheral nervous system
  3. 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. 4. PERIPHERAL NERVOUSSYSTEM• Somatic – Sensory (Gamma) Nerves – Motor (Alpha) Nerves• Autonomic [FYI] – Parasympathetic – Sympathetic
  5. 5. Spinal Nerves p. 35
  6. 6. NERVE ANATOMY•A single nerve cell is called a neuron•A bundle or group of neurons make up anerve•A nerve contains both afferent and efferentnerves
  7. 7. Afferent Neuron• Carry impulse towards the CNS (e.g. sensory nerves)• Synapse Towards CNS
  8. 8. Efferent Neuron• Carry impulse away from the CNS (e.g. motor nerves)2. Stimulatory3. Inhibitory
  9. 9. NEURON ANATOMY• Dendrite• Cell Body• Axon
  10. 10. AXON1. Conduction2. Myelin sheath3. Synapse4. Neurotransmitter
  11. 11. CONDUCTIONResting State: Na outside, K inside
  12. 12. CONDUCTION4. Na K Pump 1. Depolarization3. Repolarization 2. Propagation
  13. 13. MYELIN SHEATH
  14. 14. SYNAPSE
  15. 15. SYNAPSE
  16. 16. SYNAPSE•Quick Time Movie
  17. 17. NEUROMUSCULAR JUNCTION
  18. 18. NEUROMUSCULARJUNCTION
  19. 19. MOTOR UNIT• Motor unit = one motor nerve + all the muscle fibers it innervates.• Types – Fast (alpha -1) – Slow (alpha -2)
  20. 20. 31 2
  21. 21. MOTOR UNITFast Fast Slow
  22. 22. MUSCLE TENSION or FORCE or STRENGTH1. Number of MU stimulated2. Frequency of stimulation to each MU3. Type of MU stimulated
  23. 23. MUSCLE STIMULATION: How does it begin?
  24. 24. 1. Volitional Control (Motor Cortex)1. Motor cortex2. Motor neurons3. Muscles
  25. 25. 2. Reflex Control1. Afferent neuron – Sensory neuron2. Efferent neuron – Motor neuron
  26. 26. PROPRIOCEPTION & KINESTHESIS p. 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. 27. PROPRIOCEPTION• Proprioceptors of the joints and skin – Meissner’s corpuscles – Ruffini’s corpuscles – Pacinian corpuscles – Krause’s end-bulbs
  28. 28. PROPRIOCEPTION• Proprioceptors of the muscles – Muscle spindles – Golgi tendon organs
  29. 29. Muscle Spindles
  30. 30. musclespindle
  31. 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. 32. Golgi Tendon Organs
  33. 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. 34. Neuromuscular Summary•An example from baseball.•A pitcher throws a curve ball toSammy Sosa•Sammy’s eyes see the ball comingtowards him and is able to identifythe pitch as a curve ball•Sensory nerves (afferent) send thatinformation to the CNS•In the CNS the sensory nervesynapses with motor nerves•The motor nerves in turn stimulatesthe muscles (deltoid and pectoralismajor) required to swing the bat inthe proper position to hit the ball
  35. 35. Neuromuscular Summary•Inside the fibers of the deltoid andpectoralis major, calcium isreleased•The calcium allows myosin headsto attach to actin•When the heads swivel the fibersof the deltoid muscle will shorten•The shortening of the fibers willpull on the humerus causingSammy to swing the bat•The muscle spindles “tell” theCNS when the arm is in thecorrect position•If all goes as planned, the deltoidand pectoralis major will move hisarms into a position to hit the ball
  36. 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. 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. 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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