1. The Sectional Organization of the Spinal Cord

2. An introduction to reflexes
Reflexes are rapid automatic responses to stimuli
Neural reflex involves sensory fibers to CNS and motor fibers to effectors

3. Reflex arc Wiring of a neural reflex Five steps
Arrival of stimulus and activation of receptor
Activation of sensory neuron
Information processing
Activation of motor neuron
Response by effector

4. Components of a Reflex Arc

5. Reflex classification
According to
development
Site of information processing
Nature of resulting motor response
Complexity of neural circuit

6. Methods of Classifying Reflexes

7. reflex classifications
Innate reflexes
Result from connections that form between neurons during development
Acquired reflexes
Learned, and typically more complex

8. More reflex classifications
Cranial reflexes
Reflexes processed in the brain
Spinal reflexes
Interconnections and processing events occur in the spinal cord

9. still more reflex classifications
Somatic reflexes
Control skeletal muscle
Visceral reflexes (autonomic reflexes)
Control activities of other systems

10. and more reflex classifications
Monosynaptic reflex
Sensory neuron synapses directly on a motor neuron
Polysynaptic reflex
At least one interneuron between sensory afferent and motor efferent
Longer delay between stimulus and response

11. Neural Organization and Simple Reflexes

12. Spinal Reflexes
Range from simple monosynaptic to complex polysynaptic and intersegmental
Many segments interact to form complex response

13. Monosynaptic Reflexes
Stretch reflex automatically monitors skeletal muscle length and tone
Patellar (knee jerk) reflex
Sensory receptors are muscle spindles
Postural reflex maintains upright position

14. Components of the Stretch Reflex

15. The Patellar Reflex

16. Intrafusal Fibers

17. Polysynaptic reflexes
Produce more complicated responses
Tendon reflex
Withdrawal reflexes
Flexor reflex
Crossed extensor reflex

18. The Flexor and Crossed Extensor Reflexes

19. Polysynaptic reflexes
Involve pools of interneurons
Are intersegmental in distribution
Involve reciprocal inhibition
Have reverberating circuits to prolong the motor response
Several reflexes may cooperate to produce a coordinated response

20. Reinforcement and inhibition
Reinforcement = facilitation that enhances spinal reflexes
Spinal reflexes can also be inhibited
Babinski reflex replaced by planter reflex

21. The Babinski Reflexes