1. Nervous System Applications: Exercise Responses And Regulation

2. In General: Acute Exercise is an “Homeostatic Emergency” The SNS acts as “Rescuer” in acute emergencies:

3. Acute Exercise: SNS acts on: Heart: Increases HR, Contractility, opens myocardial blood vessels Lungs: Relaxes airways for better air flow Liver: Increases glycogenolysis Adipose Tissue: Mobilizes fat

4. Exercise: SNS Skeletal Muscles: Initial Vasoconstriction of most blood vessels, and mobilization of glycogen stores Skin: Vasoconstriction, and increased sweating… Vasoconstriction?

5. Exercise and PSNS: “Backs off” during acute exercise… Training effect: At rest, increased Vagal tone keeps HR low: *But PSNS with- draws inhibition more efficiently in trained people

6. Training Effect: Nervous System Adaptation Nervous System is already designed to EXCEED most demands: BUT Some adaptation seen in Autonomic Nervous System Some adaptation seen in the neuromuscular junction Definite adaptation in motor control pathways

7. The Nervous System and Motor Control “Smooth Moves” are possible because the nervous system is able to integrate signals and information to generate coordinated movement… But HOW???

8. What Do You Know About Proprioceptors? Give us information from internal sensory receptors about: Limb Position and movement is sensed from the Somatosensory system Head position and movement is located in the Vestibular System

9. Example: You are playing volleyball - outside set is to you! It’s up there, you’re ready, you begin your approach - Information about the floor, speed of approach, arm swing velocity => Variety of Proprioceptors

10. Muscle Spindles Provide detailed information about muscle length:**Most important contributor to Motor Control Sense contracting, relaxing, and inappropriate stretch Dual function: Sense -> stretch reflex (motor)

11. Golgi Tendon Organs: GTO Located in the muscle-tendon junction Rather than feeling “stretch or length”, they feel “tension” Protect muscle from overload via reflex arc

12. Joint Receptors Located in Joint capsules and ligaments Sense only “Extreme” position -> Pain Contribution is minor to motor control Bo Jackson’s hip

13. Vestibular System Located in the inner ear: Semicircular canals Involved in Dynamic balance Head orientation, acceleration and position Vertigo: dysfunction of the Vestibular System

14. Demo Time: Get the Bat! What happens to “head” and “body” awareness when we dismantle the Vestibular system?

15. Motor Neurons and Muscle Spindles:  Motor Neurons: Signal all muscle cells in the motor unit to contract: Impulse originates in CNS  -Motor Neuron: Parallel Signal sent to the muscle spindle: Muscle spindle SENSES “stretch”

16. Try This: Close your eyes Prepare to “Lift” a 5 pound weight Instead Substitute a 25 pound weight

17. Saved by the  Coactivation! Both neurons sent down parallel signals: The muscle spindle shortened But not enough motor units were recruited to shorten the bicep…

18. And… The muscle spindle “sensed” stretch It sent an afferent signal to the CNS that the mission was not accomplished A Reflex arc/voluntary CNS signal recruited more motor units to get the job done

19. Motor Neurons and Muscle Fiber Types Initial strength gains are usually due to improved motor neuron recruitment and GTO inhibition Training cannot modify fiber types except to increase oxidative capacity of FT fibers Fiber type is determined by motor nerve type

20. That’s All For The Nervous System: Read More About Proprioception: Chapter 9:248-252 – Vestibular System and Balance/Equilibrium Monday: Review for Exam I Read Class Notes, Chapter 8, Summary BEFORE CLASS!