1. Illinois State University Neurological Control of Movement Chapter 20 n Individual nerve fibers are called neurons. n A typical neuron is composed of three regions:

2. Illinois State University Regions of a Neuron n 1. The cell body, or soma. –Contains the nucleus. n 2. The dendrites. –Carry the impulses toward the cell body. n 3. The axon. – The neuron’s transmitter.

3. Illinois State University Nerve Function n Axon hillock. –Cone-shaped region of axon –Impulse conduction

4. Illinois State University Nerve Function n Nerve impulse - an electrical charge. n Resting membrane potential (-70 mV)

5. Illinois State University Sodium-potassium pump

6. Illinois State University Nerve Function n Depolarization. (Excitation) n Hyperpolarization. (Inhibition)

7. Illinois State University Graded potentials n localized changes in the membrane potential.

8. Illinois State University Threshold of excitation n Voltage above which an impulse must go to excite a cell.

9. Illinois State University Action potential n a rapid and substantial depolarization of the neuron’s membrane.

10. Illinois State University The chain of events for an action potential are: n increased sodium permeability through opening of the sodium gates. n decreased sodium permeability as the gates close n and opening of the potassium gates and repolarization.

11. Illinois State University Nerve Transmission n Myelinated neurons - the impulse travels through the axon by jumping between nodes of Ranvier (gaps between the cells that form the myelin sheath).

12. Illinois State University This process, saltatory conduction, is 5 to 50 times faster than in unmyelinated fibers of the same size.

13. Illinois State University Nerve Transmission n Impulses also travel faster in neurons of larger diameters.

14. Illinois State University Nerve Communication n Neurons communicate with each other across synapses.

15. Illinois State University A synapse involves: n the axon terminals of the presynaptic neuron n the postsynaptic receptors on the dendrite or cell body of the next neuron n the space (the synaptic cleft) between two neurons.

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17. Nerve Communication n A nerve impulse causes chemicals called neurotransmitters to be released from the presynaptic axon terminals into the synaptic cleft.

18. Illinois State University Nerve Communication n Neurotransmitters diffuse across the cleft and are bound to the postsynaptic receptors.

19. Illinois State University Nerve Communication n Once neurotransmitters are bound, the impulse has been successfully transmitted and the neurotransmitter is then either destroyed by enzymes or actively returned to the presynaptic neuron for future use.

20. Illinois State University Nerve Communication n Neurotransmitter binding at the postsynaptic receptors opens ion gates in that membrane and can cause depolarization (excitation) or hyperpolarization (inhibition), depending on the specific neurotransmitter and the receptors to which it binds.

21. Illinois State University Nerve Communication n Neurons communicate with muscle cells at neuromuscular junctions. n These involve presynaptic axon terminals (motor endplates), the synaptic cleft, and receptors on the sarcolemma of the muscle fiber. n The neuromuscular junction functions much like a neural synapse.

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24. Nerve Communication n The neurotransmitters most important to regulation of exercise are acetylcholine and norepinephrine.

25. Illinois State University Summation n Excitatory postsynaptic potentials (EPSPs) are depolarizations of the postsynaptic membrane. n Inhibitory postsynaptic potentials (IPSPs) are hyperpolarizations of that membrane.

26. Illinois State University Summation n A single presynaptic terminal cannot generate enough of a depolarization to fire an action potential. –Multiple signals are needed. n These may come from numerous neurons or from a single neuron when numerous axon terminals release neurotransmitters repeatedly and rapidly.

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28. Summation n The axon hillock keeps a running total of all EPSPs and IPSPs. n When their sum meets or exceeds the threshold for depolarization, an action potential occurs. n This process of accumulating incoming signals is known as summation.

29. Illinois State University Central Nervous System n The central nervous system is composed of the brain and the spinal cord. n The four major divisions of the brain are –the cerebrum, –the diencephalon, –the cerebellum, –and the brain stem.

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31. Central Nervous System n The cerebral cortex is your conscious brain. n The diencephalon includes the thalamus, which receives all sensory input entering the brain, and the hypothalamus, which is a major control center for homeostasis.

32. Illinois State University Central Nervous System: n The cerebellum, which is connected to numerous parts of the brain, is critical to movement. n The brain stem is composed of the midbrain, the pons, and the medulla oblongata.

33. Illinois State University Central Nervous System n The spinal cord carries both sensory (afferent) and motor (efferent) fibers between the brain and the periphery.

34. Illinois State University Central Nervous System n The brain has a pain control system called an analgesia system. The enkephalins and  -endorphins are important opiate substances that act on the opiate receptors in the analgesia system to help reduce pain. The enkephalins and  -endorphins are important opiate substances that act on the opiate receptors in the analgesia system to help reduce pain. n Exercise of long duration has been postulated to increase the natural levels of these opiate substances.

35. Illinois State University Peripheral Nervous System n The peripheral nervous system contains 43 pairs of nerves: 12 cranial and 31 spinal. n The PNS can be subdivided into the sensory and motor divisions. n The motor division also includes the autonomic nervous system.

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37. Peripheral Nervous System n The sensory division carries information from sensory receptors to the CNS so that the CNS is constantly aware of your current status and your environment. n The motor division carries motor impulses out from the CNS to the muscles.

38. Illinois State University Peripheral Nervous System n The autonomic nervous system includes the sympathetic nervous system, which is your fight-or-flight system, and the parasympathetic system, which is your housekeeping system. –Though these systems often oppose each other, they always function together.

39. Illinois State University Sensory-Motor Integration n Sensory-motor integration is the process by which your PNS relays sensory input to your CNS, your CNS interprets this information, and then it sends out the appropriate motor signal to elicit the desired motor response.

40. Illinois State University Sensory-Motor Integration n Sensory input can terminate at various levels of the CNS. Not all of this information reaches the brain.

41. Illinois State University Sensory-Motor Integration n Reflexes are the simplest form of motor control. –These are not conscious responses. –For a given sensory stimulus, the motor response is always identical and instantaneous.

42. Illinois State University Sensory-Motor Integration n Muscle spindles trigger reflexive muscle action when the muscle spindle is stretched.

43. Illinois State University Sensory-Motor Integration n Golgi tendon organs trigger a reflex that inhibits contraction if the tendon fibers are overstretched.

44. Illinois State University Sensory-Motor Integration n The primary motor cortex, located in the frontal lobe, is the center of conscious motor control.

45. Illinois State University Sensory-Motor Integration n The basal ganglia, in the cerebral white matter, help initiate some movements (sustained and repetitive ones) and help control posture and muscle tone.

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47. Sensory-Motor Integration n The cerebellum is involved in all rapid and complex movement processes and assists the primary motor cortex and the basal ganglia.

48. Illinois State University Cerebellum n It is an integration center that decides how to best execute the desired movement given your body’s current position and your muscles’ current status.

49. Illinois State University Sensory-Motor Integration n Though not well understood, engrams are memorized motor patterns, stored in both the sensory motor areas of the brain, that are called upon as needed.

50. Illinois State University Motor Units n Each muscle fiber is innervated by only one neuron, but each neuron may innervate up to several thousand muscle fibers.

51. Illinois State University Motor Units n All muscle fibers within a single motor unit are of the same fiber type. n Motor units are recruited in an orderly manner, so that specific ones are called on each time a specific activity is performed.

52. Illinois State University Motor Units n Motor units with smaller neurons (slow- twitch units) are called on before those with larger neurons (fast twitch).

53. Illinois State University Fiber Recruitment n Neuromuscular activity is graded on the basis of a fixed order of recruitment from the available pool of motor units. n The more force that is needed to execute a certain movement, the more motor units are recruited.

54. Illinois State University Low Force Moderate Force Maximal Force