Lecture 31: Reflexes

Question 1

Define reflex and list the five components

of a reflex arc.

Answer 1

• reflex: rapid autonomic response to a stimulus
• components
  1. sensory receptor
  2. sensory neuron
  3. integrating center
  4. motor neuron
  5. effector

Question 2

Differentiate between ipsilateral and
contralateral, somatic and autonomic,
monosynaptic and polysynaptic reflexes.

Answer 2

• ipsilateral: reflex and stimulus on same side
• contralateral: reflex and stimulus on opposite sides
• somatic: skeletal muscle (voluntary)
• autonomic: cardiac and smooth muscle, glands (involuntary)
• monosynaptic: direct communication between sensory and motor neuron
• polysynaptic: interneuron facilitates communication between sensory and motor neuron

Question 3

Diagram and describe the 4
representative reflex arcs discussed in
lecture.

Answer 3

• Stretch reflex: prevent over-stretching a muscle, muscle spindle senses and causes contraction of stretched muscle
• Tendon reflex: prevent damage from too much tension, Golgi tendon organ inhibits muscle that is contracting
• Flexor reflex: protect a part of the body from further injury, nocioreceptors cause flexion of affected limb
• Crossed extensor reflex: stabilize a position when a painful stimulus results in flexion of opposite limb, nocioreceptors cause extension of opposite limb

Question 4

Stretch Reflex

Answer 4

• reflex classification: monosynaptic, ipsilateral, spinal, somatic
• stimulus: stretching
• sensory receptor: muscle spindle
• response to the stimulus:
  1. agonist: contracts to relieve stretching
  2. antagonist: inhibited by interneuron

Question 5

Tendon Reflex

Answer 5

• reflex classification: polysynaptic, ipsilateral, spinal, somatic
• stimulus: tension
• sensory receptor: Golgi tendon organ
• response to the stimulus
  1. agonist: inhibited
  2. antagonist: muscle relaxes (nerve excited) to relieve excess tension

Question 6

Flexor Reflex

Answer 6

• reflex classification: polysynaptic, ipsilateral, spinal, somatic
• stimulus: pain
• sensory receptor: nocioceptor
• response to the stimulus: flexor muscles contract and withdraw limb

Question 7

Crossed Extensor Reflex

Answer 7

• reflex classification: polysynaptic, contralateral, spinal, somatic
• stimulus: pain
• sensory receptor: nocioceptor
• response to the stimulus: extensor muscles contract and extend opposite limb