Neurology · MU Sofia

1. Reflexes: classification, reflex arc, examination of normal reflexes

Explains what a reflex is and the five components of a reflex arc, from receptor to effector. Classifies reflexes by effector organ, number of synapses, development, receptor location and clinical grouping into superficial, deep tendon and visceral types. Walks through how to examine the biceps, knee, ankle, corneal, abdominal, cremasteric and plantar reflexes, including segmental levels, nerves and normal responses. A table grades reflex responses from absent to clonus.

Inside: 1 section · 1 labelled picture · 1 table · 15 flashcards · 4 min

Topic 1 of 88 in the MU Sofia syllabus for Neurology (Medicine, Year 4). The free AceMed note covers it in 1 section, about 616 words (4 min of reading), with 15 flashcards.

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  1. Reflexes - classifcaiton, reflex arc, examination of normal reflexes

Reflexes - classifcaiton, reflex arc, examination of normal reflexes

Definition of a Reflex

A reflex is an involuntary, rapid, stereotyped response of the body to a specific stimulus, mediated through the nervous system without conscious control.

Reflexes are important in clinical neurology because they help assess the integrity of the: Peripheral nerves. Spinal cord segments. Brainstem. Descending motor pathways

Reflex Arc: The reflex arc is the anatomical and physiological pathway through which a reflex occurs.

Components of a Reflex Arc

  1. 1. Receptor: Receives the stimulus.
  • Examples: Muscle spindle (stretch reflex). Skin receptors. Tendon receptors
  1. 2. Afferent (Sensory) Neuron: Carries impulses from the receptor to the CNS.
  2. 3. Integration Center
  • Located in: Spinal cord. Brainstem
  • May involve: One synapse (monosynaptic). Several synapses (polysynaptic)
  1. 4. Efferent (Motor) Neuron: Conducts impulses from CNS to effector.
  2. 5. Effector Organ: Produces the response.
  • Examples: Skeletal muscle. Smooth muscle. Glands

Classification of Reflexes

Reflexes can be classified according to several criteria.

A. According to Effector Organ

  1. 1.Somatic Reflexes: Effectors are skeletal muscles.
  • Examples: Biceps reflex. Triceps reflex.Patellar reflex
  1. 2.Autonomic (Visceral) Reflexes: Effectors are smooth muscles. Cardiac muscle. Glands
  • Examples: Pupillary light reflex.Accommodation reflex. Salivary reflex

B. According to Number of Synapses

  1. 1.Monosynaptic Reflexes: Contain only one synapse between sensory and motor neuron.
  • Example: Stretch (myotatic) reflex. Patellar reflex. Achilles reflex
  • Characteristics:Fastest reflexes. Simple pathway
  1. 2.Polysynaptic Reflexes: Contain one or more interneurons.
  • Examples: Withdrawal reflex. Corneal reflex. Plantar reflex
  • Characteristics: More complex.Slower

C. According to Development

  1. 1.Unconditioned (Innate) Reflexes: Present at birth.
  • Examples: Deep tendon reflexes. Corneal reflex.Pupillary reflex
  1. 2.Conditioned (Acquired) Reflexes: Develop through learning and experience.
  • Example: Pavlovian conditioned reflex

D. According to Receptor Location

  1. 1.Exteroceptive Reflexes: Stimulus originates outside the body.
  • Examples: Corneal reflex. Abdominal reflexes.
  1. 2.Proprioceptive Reflexes: Stimulus arises from muscles, tendons, joints.
  • Examples: Patellar reflex. Achilles reflex
  1. 3.Interoceptive (Visceral) Reflexes: Stimulus originates in internal organs.
  • Examples: Micturition reflex.Defecation reflex

Clinical Classification of Reflexes

For neurological examination, reflexes are divided into:

  1. A. Superficial Reflexes: Produced by stimulation of skin or mucous membranes.
  • Examples: Corneal reflex. Abdominal reflexes.Cremasteric reflex.Plantar reflex
  1. B. Deep Tendon Reflexes (DTRs): Produced by tapping tendons.
  • Examples: Biceps reflex. Triceps reflex.Brachioradialis reflex.Patellar reflex.Achilles reflex
  1. C. Visceral Reflexes
  • Examples: Pupillary light reflex.Accommodation reflex

Examination of Normal Reflexes

  • General Principles

Patient should be: Relaxed. Comfortable. Symmetrical position

  • Equipment: Reflex hammer
  • Compare: Right vs left side. Symmetry of response

Deep Tendon Reflexes

1. Biceps Reflex

  • Spinal Segments: C5–C6
  • Nerve: Musculocutaneous nerve
  • Technique: Flex elbow partially. Place thumb on biceps tendon. Strike examiner's thumb

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