1. SENSORY AND MOTOR SYSTEMS: REFLEXES D. C. Mikulecky Professor of Physiology

2. ADEQUATE STIMULUS • A SPECIFIC STIMULUS UNIQUE TO A SENSORY RECEPTOR • FOR EXAMPLE, PHOTORECEPTORS IN THE EYE RESPOND ONLY TO ELECTROMAGNETIC RADIATION

3. TYPES OF ENERGY TRANSDUCED

4. GRADED VS ALL OR NONE • A RECEPTOR’S RESPONSE TO A STIMULUS IS GRADED • IF THRESHOLD IS EXCEEDED, THE ACTION POTENTIAL RESULTING IS ALL OR NONE

5. SENSORY TRANSDUCTION ADEQUATE STIMULUS MEMBRANE CONDUCTANCE CHANGE GENERATOR POTENTIAL ACTION POTENTIAL

9. EXAMPLE: THE PACINIAN CORPUSCLE • PRESSURE RECEPTOR • PRESSURE DISTORTS THE CAPSULE, STRETCHING THE CELL MEMBRANE • SODIUM CHANNELS OPEN, DEPOLARIZING THE MEMBRANE • IF BEYOND THRESHOLD, ACTION POTENTIAL RESULTS

11. HOW IS THE INTENSITY OF THE STIMULUS ENCODED? • FREQUENCY CODING • POPULATION CODING

12. FREQUENCY CODING LIGHT PRESSURE LOW FREQUENCY MORE PRESSURE HIGHER FREQUENCY

13. POPULATION CODING LIGHT PRESSURE MORE PRESSURE

14. THE LABELED LINE CODE OF STIMULUS QUALITY NEOCORTEX LIMBIC CORTEX NOSE SMELL THALAMUS EYE VISION TASTE TONGUE BRAIN STEM EAR AUDITION SKIN SOMATIC SPINAL CORD

15. LOCALIZATION, DISTRIBUTION, AND ACUITY • CODING OF LOCATION DEPENDS ON RECEPTOR LOCATION • AREA COVERED BY RECEPTORS IN A SENSORY UNIT IS A RECEPTIVE FIELD • ACUITY DEPENDS ON THE DENSITY OF RECEPTORS

17. GENERAL FEATURES OF THE MOTOR SYSTEM • HIERARCHICAL ORGANIZATION • VS • PARALLEL ORGANIZATION

18. HIERARCHICAL ORGANIZATION MOTOR CORTEX CEREBELLUM AND BASAL GANGLIA BRAIN STEM SPINAL CORD SKELETAL MUSCLE

19. PARALLEL ORGANIZATION MOTOR CORTEX BRAIN STEM SPINAL CORD SKELETAL MUSCLE

20. THE MOTOR UNIT • A SINGLE MOTOR NEURON AND ALL THE MUSCLES IT INNERVATES • THE FUNCTIONAL UNIT OF THE MOTOR SYSTEM • CORRESPONDS TO THE SENSORY UNIT/RECEPTIVE FIELD RELATIONSHIP • SIZE OF MOTOR UNIT DETERMINES FINENESS OF MOTOR RESPOSE

21. THE MOTOR RESPONSE SYSTEM: SPINAL LEVEL • THE ORGANIZATION OF MOTOR NERVES IN THE SPINAL COLUMN • THE ROLE OF INTERNEURONS • THE ROLE OF LOCOMOTOR GENERATORS

22. THE ORGANIZATION OF MOTOR NERVES IN THE SPINAL COLUMN • DORSAL AREA OF VENTRAL HORN: FLEXOR MOVEMENTS • VENTRAL AREA OF VENTRAL HORN: EXTENSOR MOVEMENTS • DORSOLATERAL AREA OF VENTRAL HORN: INNERVATE EXTREMITIES • VENTROMEDIAL REGION: AXIAL MUSCLES TO MAINTAIN POSTURE

23. LOCATION OF CELL BODIES FOR EXTENSORS AND FLEXORS FLEXORS EXTENSORS

24. THE ROLE OF INTERNEURONS • LOCATED IN THE INTER MEDIATE ZONE OF THE SPINAL CORD • LATERAL SIDE NEURONS SYNAPSE IPSILATERALLY (TO DISTAL LIMB MUSCLES) • MIDLINE NEURONS SYNAPSE BOTH SIDES (MUSCLES FOR POSTURE) ALPHA MOTOR NEURONS:EXCITE SYNERGISTIC AND INHIBIT ANTAGONISTIC

25. THE ROLE OF LOCOMOTOR GENERATORS • RHYTHMIC ACTION OF ALTERANATING FLEXION AND EXTENSION INVOVED IN WALKING MOVEMENTS (CHICKEN WITH ITS HEAD CUT OFF) • SPINAL TRANSECTED ANIMALS CAN WALK ON TREADMILL • UNDER CONTROL OF LOCOMOTOR COMMAND CENTER IN THE BRAIN STEM

26. SENSORY FIBERS IN THE MUSCLE • THE MUSCLE SPINDLE AS LENGTH DETECTOR • GOGLI TENDON ORGANS: TENSION RECEPTORS

27. THE MUSCLE SPINDLE AS LENGTH DETECTOR(SENSORY FIBERS) • TYPE Ia NERVE FIBERS: TRANSMIT INFORMATION ABOUT LENGTH AND VELOCITY TO THE CNS • TYPE II NERVE FIBERS:TRANSMIT INFORMATION ABOUT MUSCLE LENGTH TO CNS

28. TWO TYPES OF INTRAFUSAL FIBERS TYPE IA SENSORY FIBER TYPE II SENSORY FIBER NUCLEAR CHAIN FIBER NUCLEAR BAG FIBER

29. TWO TYPES OF MOTOR NEURON • ALPHA MOTOR NEURON: INNERVATES EXTRAFUSAL FIBER • GAMMA MOTOR NEURON: INNERVATES INTRAFUSAL FIBERS

30. STRETCHING AN INTRAFUSAL FIBER SENDS SIGNALS TO CNS

31. THE ROLE OF GAMMA MOTOR NEURONS IN REGULATING MUSCLE SPINDLE RESPONSE STIMULATE RECORD RECORD Afferent Activity Muscle Force

32. STIMULATE THE ROLE OF GAMMA MOTOR NEURONS IN REGULATING MUSCLE SPINDLE RESPONSE RECORD RECORD STIMULATE Afferent Activity Muscle Force

33. GOGLI TENDON ORGANS: TENSION RECEPTORS • IN SERIES WITH EXTRAFUSAL FIBERS • TRANSMITS INFORMATION ABOUT FORCE OR TENSION TO CNS • FREQUENCCY CODING

34. SPINAL REFLEXES • THE STRETCH REFLEX • THE INVERSE MYOTACTIC REFLEX • THE FLEXOR WITHDRAWAL REFLEX

35. THE STRETCH REFLEX (KNEE JERK REFLEX) • TAP PATELLAR TENDON BELOW KNEE • SENSORY SIGNALS FROM MUSCLE SPINDLE INDICATE FLEXION OF LEG • FLEXOR IS INHIBITED • EXTENSOR ACTIVATED • LEG EXTENDS

36. KNEE JERK REFLEX EXTENSOR ACTIVATED SENSORY NEURON FROM MUSCLE SPINDLE DETECTS STRETCH SPINAL CORD FLEXOR INHIBITED

37. INVERSE MYOTACTIC REFLEX ARM EXTENDS BICEPS & SYNERGYSTIC MUSCLE RELAXEDEXTENSOR CONTRACTED WEIGHT RELEASED

38. THE FLEXOR WITHDRAWAL REFLEX • PAINFUL STIMULUS DETECTED • IPSILATERAL EXTENSORS INHIBITED • IPSILATERAL EXTENSORS EXCITED • LIMB IS WITHDRAWN • IF INVOLVING ONE FOOT WHILE STANDING, CONTRALATERAL SIDE EXTENSORS ACTIVATED AND FLEXORS INHIBITED TO SUPPORT GREATER WEIGHT

39. FLEXOR WITHDRAWAL REFLEX SENSORY SIGNAL TO SPINE STEPON TACK VIA INTERNEURONS IPSILATERAL EXTENSORS INHIBITED IPSILATERAL FLEXORS CONTRACT-LEG LIFTS CONTRALATERAL EXTENSORS CONTRACT CONTRALATERAL FLEXORS INHIBITED- MAINTAIN BALANCE AND SUPPORT WEIGHT