1. Peripheral Nervous System and Reflex Physiology

3. PNS Components: ► All Nerves extending from the brain and spinal cord (CNS). ► Reminder: What’s a nerve? What’s a nerve? A bundle of axons (fibers)!

5. Categories of Nerves ► Motor (efferent) nerves conduct impulses from CNS ► Sensory (afferent) nerves conduct impulses toward CNS conduct impulses toward CNS ► Mixed nerves have both motor and sensory fibers have both motor and sensory fibers * the most common type of nerve!!! * the most common type of nerve!!!

6. The Cranial Nerves ► connect directly with the BRAIN ► 12 pairs  1 st 2 pairs connect to cerebrum  All others connect to brain stem  Extend to areas in the head/neck only (with one exception!) (with one exception!)

10. Cranial Nerve Names I.OLFACTORY SMELL (SENSORY)

11. II.OPTIC VISION / SENSORY SIGHT

12. III.OCULOMOTORIV.TROCHLEAR Moves MOTOR eyeballs Moves MOTOR eyeballs

13. V. TRIGEMINAL SENSORY (face) MOTOR (chewing)

14. VI.ABDUCENS Moves MOTOR Eye

15. VIIFACIAL Facial MOTOR Expression TasteSENSORY

16. VIII.AUDITORY Hearing/ SENSORY balance

17. IXGLOSSOPHARYNGEAL Tongue/ SENSORY Pharynx MOTOR

18. X. VAGUS Organs of SENSORY Chest/ MOTOR abdomen

19. XI.ACCESSORY Head / Neck MOTOR Muscles

20. XII.HYPOGLOSSAL Tongue MOTOR movement

21. REFLEXES ► Definition:   rapid, involuntary response to stimulus ► Reflexes can be :  Pre-programmed for survival!  Learned / Acquired

22. ► Reflex Arcs:  Neuron pathways that carry impulses involved in generating a reflex

23. Reflex Arc Components ► Receptor ► A sensory (afferent) neuron ► Integration center ► Synapse ► interneuron(s) ► A motor (efferent neuron) ► Effector of some sort (usually muscle)

25. Two Major Reflex Categories 1. SOMATIC REFLEXES: Result in activation of skeletal muscles Result in activation of skeletal muscles 2. VISCERAL REFLEXES: Result in activation of internal organs/effectors

26. Reflex Examples ► Stretch Reflex:  Muscle contracts to counteract stretch stimulus

27. ► Withdrawal Reflex  Stimulus (Pain or Perceived threat) leads to withdrawal of threatened body part!

30. ► Plantar Reflex  normal ► Babinski Reflex  infants

31. others Abdominal Reflexes Blink Reflexes Reaction-time Reflexes Pupillary Reflexes