Ginus Partadiredja Department of Physiology REFLEX Ginus Partadiredja Department of Physiology

REFLEX: A Fast, automatic, predictable involuntary response to a particular stimulus REFLEX: - Inborn (pulling hand away from a hot surface) - Acquired (Driving expertise) REFLEX: 1. Somatic (skeletal muscle) 2. Autonomic (glands, cardiac & smooth muscle) REFLEX: 1. Spinal reflex 2. Cranial reflex

REFLEX ARC COMPONENTS: Sensory receptor  Sensory/ afferent neuron  Integrating center  Motor/ Efferent neuron  Effector REFLEX: 1. Monosynaptic reflex (e.g. stretch reflex) 2. Polysynaptic reflex (e.g. withdrawal reflex)

SOMATIC SPINAL REFLEXES Stretch reflex Tendon reflex Flexor (withdrawal reflex) Crossed extensor reflex STRETCH (MYOTATIC) REFLEX Control muscle length  muscle contraction response Monosynaptic reflex Tapping tendons at the elbow (biceps & triceps reflexes), wrist, knee (knee jerk/ patellar reflex), ankle (Achilles reflex)

Biceps reflex Triceps reflex  Achilles reflex Patellar reflex 

PATELLAR REFLEX: Tendon  Muscle spindle  Ia afferent neuron  Spinal cord   motor neuron excited Monosynaptic, ipsilateral reflex Reciprocal innervation  polysynaptic  antagonistic muscle inhibited

MUSCLES: Extrafusal Intrafusal (muscle spindle) fibres MUSCLE SPINDLE: Nuclear bag fibre Nuclear chain fibre SENSORY NEURONS: Nuclear bag fibre  Ia afferent fibres Nuclear chain fibre  Ia and II afferent fibres MOTOR NEURONS: Extrafusal fibres  Alpha motor neuron Intrafusal fibres  Gamma motor neuron

Nuclear bag fibres  dynamic stretch reflex stretch Nuclear chain fibres  static stretch reflex reflex GAMMA MOTOR NEURON: Regulated by the brain, voluntary Smooth out the movement during muscle contractions Preventing jerky movements Alpha & gamma motor neurons are stimulated simultaneously

2. TENDON REFLEX Control muscle tension  muscle relaxation response Polysynaptic, ipsilateral Golgi tendon organs  Ib afferent neuron  Spinal cord  a.Inhibitory interneuron  Motor neuron inhibited/ muscle relaxes b.Excitatory interneuron Motor neuron excited/ antagonistic muscle contracts

3. FLEXOR REFLEX Withdrawal reflex Polysynaptic, ipsilateral, intersegmental Pain receptor  Sensory neuron  Integrating center  Interneuron  Motor neuron  Ipsilateral flexor muscles - Reciprocal innervation  extensor muscles

WITHDRAWAL REFLEX: Polysynaptic Ipsilateral Intersegmental

4. CROSSED EXTENSOR REFLEX Polysynaptic, contralateral, intersegmental Contralateral reflex arc Pain receptor  Sensory neuron  Integrating center  Interneuron  Motor neuron  Contralateral extensor muscles Reciprocal innervation  Flexor muscles

DIAGNOSTICS Muscle tone - Poliomyelitis  hypotonia/ atonia - Stroke  hypertonia - Muscle spasm (broken bone, peritonitis), cramps Reflex - Afferent fibers/ lower motor neuron lesions (e.g. poliomyelitis, diabetes, syphilis)  hyporeflexia - Descending motor pathways from the brain (e.g. stroke)  hyperreflexia - Mass reflex

3. Patellar reflex Diabetes mellitus, neurosyphilis  decrease/ absent Motor tracts descending from the brain disorders  increase/ hyperreflexia 4. Achilles reflex Diabetes mellitus, neurosyphilis, alcoholism, subarachnoid hemorrhages  decrease/ absent Cervical cord compression, motor tracts lesion  increase 5. Abdominal reflex 6. Pupillary light reflex (autonomic reflex)  brain injury indicator 7. Babinski sign

References Carola R, Harley JP, Noback, CR (1990). Human Anatomy and Physiology, Chapter 12, Pages: 346-450. Ganong WF (2005). Review of Medical Physiology, 22nd ed. Chapter 6, Pages: 129-137. Guyton AC & Hall JE (2006). Textbook of Medical Physiology, 11th ed. Chapter 54, Pages: 673-684. Tortora GJ & Derrickson B (2006). Principles of Anatomy and Physiology, 11th ed. Chapter 13, Pages: 460-467.