1. SENSORY AND MOTOR SYSTEMS: REFLEXES
D. C. Mikulecky
Professor of Physiology
Objectives:
1. Associate receptors with the adequate stimulus for those receptors and classify them by the type of energy handled.
2. Identify the various steps in the transduction of a signal into action potentials in sensory nerves.
3. Identify the various ways a signal can be encoded into the all or none responses of the nervous system.
4. Identify the relation ship between sensory units, the size of their receptor field, and sensory acuity. Relate to two point discrimination as an example.
5. Describe the hierarchical and parallel organization of the motor system.
6. Describe somatotopic organization and relate it to the anatomical and functional aspects of both the sensory and the motor systems.
7. Describe the organization of the spinal cord with respect to sensory and motor function.
8. Relate the proprioceptors to the function of the motor system.
9. Describe some simple reflexes.

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 GENERATOR POTENTIAL ACTION
MEMBRANE
CONDUCTANCE
CHANGE
GENERATOR
POTENTIAL
ACTION
POTENTIAL

8. See pages in text

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 MORE PRESSURE LOW FREQUENCY HIGHER

13. POPULATION CODING
LIGHT PRESSURE
MORE PRESSURE

14. THE LABELED LINE CODE OF STIMULUS QUALITY NOSE SMELL EYE VISION TONGUE
NEOCORTEX
LIMBIC
CORTEX
NOSE
SMELL
THALAMUS
EYE
VISION
TONGUE
TASTE
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
See chapter 55 in text

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

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
See chapter 56 in text

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. THE ROLE OF GAMMA MOTOR NEURONS IN REGULATING MUSCLE SPINDLE RESPONSE
STIMULATE
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