Neural Anatomy and Function

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

7. 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

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

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

10. NEURON ANATOMY • Dendrite • Cell Body • Axon

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

12. CONDUCTION Resting State: Na outside, K inside

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

14. MYELIN SHEATH

15. SYNAPSE

16. SYNAPSE

17. SYNAPSE • Quick Time Movie

18. NEUROMUSCULAR JUNCTION

19. NEUROMUSCULAR JUNCTION

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

22. 3 1 2

23. MOTOR UNIT Fast Fast Slow

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

25. MUSCLE STIMULATION: How does it begin?

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

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

29. 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

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

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

32. Muscle Spindles

33. muscle spindle

35. 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

36. Golgi Tendon Organs

38. 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

39. 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

40. 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

41. 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

42. 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

43. 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.