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

1. Stretch reflex2. Tendon reflex3. Flexor (withdrawal reflex)4. Crossed extensor reflex

1. 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

Patellar reflex

Achilles reflex

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

MUSCLES: 1. Extrafusal 2. Intrafusal (muscle spindle) fibres

MUSCLE SPINDLE:1. Nuclear bag fibre2. Nuclear chain fibre

SENSORY NEURONS:1. Nuclear bag fibre Ia afferent fibres2. Nuclear chain fibre Ia and II afferent fibres

MOTOR NEURONS:1. Extrafusal fibres Alpha motor neuron2. 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 relaxesb.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

WITHDRAWALREFLEX:

- 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

1. Muscle tone - Poliomyelitis hypotonia/ atonia - Stroke hypertonia - Muscle spasm (broken bone, peritonitis), cramps

2. 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 reflex6. Pupillary light reflex (autonomic reflex) brain injury

indicator7. 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.