Spinal Level Reflexes

Authors

Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

Overview

• Onset: birth or earlier
• Integration: 1-2 months ( 2 exceptions)

There are 3 main types:

Table 1: Muscle reflexes¹

Type of Reflex (Example)	Number of Synapses	Stimulus for Reflex	Sensory Afferent Fibers	Responses
Stretch-reflex	1	Stretch (lengthening) of the muscle	Ia Contraction of the muscle
Golgi tendon reflex (clasp knife)	2	Contraction (shortening) of the muscle	Ib	Relaxation of the muscle
Flexor-withdrawal reflex (touching a hot stove)	Multiple	Pain; temperature	II, III, and IV	Ipsilateral flexion and contralateral extension

Figure 1: Motor response²

Stretch-Reflex

Proprioceptive Placing

Timing

• Onset:
  • UE: birth
  • LE- 35 weeks gestational age
• Integration: 2 months

Testing

• Test position: Hold infant vertical
• Test procedure: Brush dorsum of hand/foot against table
• Positive response: Lifts hand/foot on table
• Negative response: Hand/foot remains relaxed

Significance

• Significance: precursor to hand/food placement in activities
• Foot placing is elicited by touching the shinbone and the dorsal side of the foot against a hard surface such as the edge of a table. The newborn makes a quick lifting motion, as if to step onto the table. This reaction is present between the 3rd and 6th month of age.

Flexor Withdrawal

Timing

Onset: 28 weeks GA Integration: 1-2 months

Testing

• Test position: supine , head in midline
• Test procedure: noxious stimulus to sole of foot
• Positive response: none or volitional withdrawal from stimulus

Significance

Significance: develops protective balance between flexor and extensor, persistence interferes with weight bearing and walking

Crossed Extension

Timing

• Onset : 28 weeks
• Integration: 1-2 months

Testing

• Test position: supine, test LE extend
• Test procedure: noxious stimulus to sole of foot
• Positive response: flexion of stimulated leg and then extension of oppo leg w adduction
• Negative response: no mvmt of flexed leg

Significance

• Persistence interferes with weight bearing and walking

Palmar grasp

Timing

• Onset: 28 wks GA-weak, 36 wks GA-full response
• Integration: 4-7 months

Testing

• Test position: Supine, head in midline
• Test procedure: Pressure on palm of hand
• Positive response: Fingers flex and grasp finger (baby can be lifted off surface)
• Negative response: Hand remains relaxed

Significance

• Signif: persistence interferes with volitional grasp and release

Plantar grasp

Timing

• Onset 28 weeks
• Integration 9 months

Testing

• Test position: supine, head in midline, LE relaxed
• Test procedure: supported standing on feet or pressure on sole of foot just distal to MT heads
• Positive response: flexion or curling of toes
• Negative response: toes remain relaxed

Significance

Persistence interferes w stance, balance and walking

References

1.

Costanzo LS. Costanzo Physiology. 7. edition. Elsevier; 2022.

2.

Betts JG, Blaker W. Anatomy and Physiology. 2nd ed. OpenStax; 2022. https://openstax.org/details/books/anatomy-and-physiology-2e/?Book%20details