1 - Zill - Spinal Reflexes

Question 1

Reflex: Stretch (Myotatic, Deep Tendon)

Purpose:

Stimulus/Sense Organ Excited:

Normal Response:

Upper Motor Neuron Disorder:

Answer 1

Reflex: Stretch (Myotatic, Deep Tendon)

Purpose: Compensation; “riding on a bus”

Stimulus/Sense Organ Excited: Rapid stretch of muscle (test: tendon tap); Excites Ia, II sensory; not Gogli

Normal Response: Stretched muscle contracts rapidly; Excite Synergist/Inhibit Antagonist; Gamma motor neurons can enhance–“Relax patient!”

Upper Motor Neuron Disorder:

1. Hyperreflexia (increase) - Upper Motor Neuron (spinal cord, damage corticospinal tract)
2. Clonus - Hyperreflexia w/repetitive or sustained contractions

Question 2

Reflex: Autogenic Inhibition

Purpose:

Stimulus/Sense Organ Excited:

Normal Response:

Upper Motor Neuron Disorder:

Answer 2

Reflex: Autogenic Inhibition

Purpose: Inhibition - limits muscle tension

Stimulus/Sense Organ Excited: Large force on tendon excites Golgi Tendon Organ Ib (Test: Pull on resisted muscle)

Normal Response: Muscle tension decreases; inhibit synergist muscles, excite antagonistic

Upper Motor Neuron Disorder: Clasped Knife Reflex, occurs in upper motor neuron lesions

Question 3

Reflex: Flexor Reflex

Purpose:

Stimulus/Sense Organ Excited:

Normal Response:

Upper Motor Neuron Disorder:

Answer 3

Reflex: Flexor Reflex

Purpose: Protective Avoidance Reflex “step on a nail”

Stimulus/Sense Organ Excited: Sharp painful stimulus, Excite Cutaneous and pain receptors (stroke foot with pointed object)

Normal Response: Limb rapidly withdraws; Crossed Extensor Reflex (inhibit same/excite opposite)

Upper Motor Neuron Disorder: Test - Babinski Sign - normally toes flex to sole, abnormal toes extend away

Question 4

Pupillary light Reflex

Cranial Nerves?

Stimulus?

Sensory?

Response?

Clinical?

Answer 4

Cranial Nerves II / III

Stimulus: Shine light in eye

Sensory: Light detected by optic nerve

Response: Optic Nerve (CN II) detects light; Excite Constrictor of pupil of eye (CN III - Short Ciliary Nerves, Smooth Muscle Parasympathetics)

Clinical: Extensively used to check CN II; Absence of Pupillary Light Reflex can indicate catastophe (brain herniation)

Question 5

Corneal Reflex

Cranial Nerves?

Stimulus?

Sensory?

Response?

Clinical?

Answer 5

Cranial Nerves: V / VI

Stimulus: Touch cornea of eye with cotton

Sensory: Touch detected by Long Ciliar nerves (V1), Somatic Sensory

Response: Close Eye (VII to Orbicularis Oculi M.) Branchiomotor

Clinical: Absence of Corneal Reflex - Test for damage to V1 sensory, VII motor

Question 6

Gag Reflex

Cranial Nerves?

Stimulus?

Sensory?

Response?

Clinical?

Answer 6

Gag Reflex

Cranial Nerves: CN IX, X

Stimulus: Touch posterior tongue, oropharynx

Sensory: Excite Visceral Sensory in Glossopharyngeal N. (IX)

Response: Excite muscles of pharynx, palate: Vagus N. (X) Branchiomotor

Clinical: Other symptoms of Vagus damage - “Say Ahh” soft palate not elevated on isilateral side (paralyze Levator Palati); Uvula deviated away from side of lesion

Question 7

Jaw Jerk

Cranial Nerves?

Stimulus?

Sensory?

Response?

Clinical?

Answer 7

Jaw Jerk

Cranial Nerves: Deep Tendon Reflex - Trigeminal Sensory AND Motor - V3

Stimulus: Tap down on mandible, stretch muscles of mastication

Sensory: Excite muscle spindle sensory neurons in Trigeminal (V)

Response: Contract muscles that elevate Mandible Motor - V3

Clinical: Hyporeflexia - indicates Trigeminal nerve damage

Question 8

Pattern Generator

Answer 8

Group of interneurons that are interconnected

Produce rhythmic behavior (baby walking on treadmill)

Question 9

Stretch Reflex

Autogenic Inhibition

Flexion Reflex

Answer 9

Stretch - Activate muscle spindles, postural stability, excite syn, inhibit antag

Autogenic - Activate golgi tendon, prevents damage to tendons/bone, excite ant, inhibit syn

Flexion - Actiave cutaneous pain afferents, excite/inhibit reverse contralaterally

Question 10

Increase in Tonus

Answer 10

Occurs after Upper Motor Neuron Lesion (stroke)

Due to loss of modulation of reflex

Question 11

Upper vs Lower Motor Neuron Lesion

Answer 11

Hyporeflexia (decrease) - Lower Motor Neuron

Hyperreflexia (increase) - Upper Motyor Neuron

Question 12

Renshaw Cell

Answer 12

Interneurons that can limit motor neuron firing, which can dampen or refuce reflexes