reflexes

1. MOTOR SYSTEM

2. TRANSVERS SECTION OF SPINAL CORD

3. MOTOR UNIT

4. Types of motor neuron
• α – motor neuron
• γ - motor neuron

5. Types of muscle fibers
• Extrafusal muscle fibers ( cause muscle
contraction supplied by α - motor neuron)
• Intrafusal muscle fibers or muscle spindle
(receptor for stretch reflex, supplied by
γ - motor neuron)

6. MUSCLE SPINDLE (INTRAFUSAL FIBERS)

7. MUSCLE EXTRAFUSAL FIBERS
MUSCLE INTRAFUSAL FIBERS

8. Muscle spindle
• Nuclear bag fiber
• Nuclear chain fiber
Sensory innervations of muscle spindle
• Ia – nuclear bag & nuclear chain fibers
• II – nuclear chain fibers
Motor supply – γ motor neuron
Dynamic & Static

9. Reflex
• Definition
• Components of reflex arc
Receptor
Afferent pathway
Center
Efferent pathway
Effector organ

10. Components of reflex arc

11. Classification of reflexes
• Monosynaptic or stretch reflex or tendon jerk
eg. Bicep jerk tricep jerk, supinator jerk
knee jerk, ankle jerk
• Polysynaptic reflex
eg. Withdrawal reflex
Abdominal reflex
Plantar reflex
• Visceral reflex
eg. Micturation, defecation reflex
Jendressik Phenomenon

12. KNEE JERK – MONOSYNAPTIC REFLEX

15. POLYSYNAPTIC REFLEX

16. WITDRAWEL REFLEX - POLYSYNAPTIC REFLEX

17. DIFFERENT
REFLEXES
SHOWN

22. • Motor cortex
• corticospinal (pyramidal tract)
• Upper motor neuron (pyramidal &
extrapyramidal tracts)
• Lower motor neuron
• Difference between upper & lower motor
neuron lesion (UMNL & LMNL)

26. MOTOR TRACTS

28. DIFFERENCE BETWEEN UPPER & LOWER
MOTOR NEURON LESION
UMN LESION
• Paralysis affect
movement rather than
muscles
• Muscle wasting is only
from disuse, therefore
slight. Occasionally
marked in chronic
severe lesions.
• Spasticity of clasp-
knife’ type. Muscles
hypertonic.
LMN LESION
• Individual muscle or
group of muscles are
affected.
• Wasting pronounced.
• Flaccidity. Muscles
hypotonic.

29. • Tendon reflexes
increased. Clonus
often present.
• Superficial reflexes
diminished or
modified.
Abdominal reflex
absent.
Babinski’s sign +ve,
Increased jaw jerk.
• Tendon reflexes
diminished or absent.
• Superficial reflexes
often unaltered.