classification, ref arc, clinical significance of reflexes.

1. REFLEX
CONTENTS:
DEFINITION
 REFLEX ARC
 TYPES/CLASSIFICATION OF
REFLEXES
 STRETCH REFLEX
 MUSCLE SPINDLE
 PROPERTIES OF REFLEXES
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4. Nerve pathways
Ascending Tracts
Tract
Signal function
Dorsal columns
Vibration, tactile sensation, conscious
proprioception
Spinocerebeller
Spinothalamic (lateral and
Proprioception
anterior)
Spinoreticular
Spinomesencephalic
Spino-cervico-thalamic
Spinohypothalamic
Pain, temperature, itch (lateral), crude
touch (anterior)
Pain
Pain
Pain (touch?)
Pain

5. Structure of spinal cord
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6. Spinal cord
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Fetal 3rd month: ends at
coccyx
Birth: ends at L3
Adult position at approx L1-2
during childhood
End: conus medullaris
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This tapers into filum terminale
of connective tissue, tethered
to coccyx
Spinal cord segments are
superior to where their
corresponding spinal nerves
emerge through intervetebral
foramina (see also fig 17.5, p
288)
Denticulate ligaments: lateral
shelves of pia mater anchoring
to dura (meninges: more later)
http://www.apparelyzed.com/spinalcord.html

7. Spinal nerves continued
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Divided based on vertebral locations
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
Cauda equina (“horse’s tail”): collection of nerve
roots at inferior end of vertebral canal

8. Classified as
According to centre IN THE SPINAL CORDseg, inter, supra.
According to functionflexor, extensor, postural R.
Clinicallysupreficial, deep, visceral
No. of synapse involved.
Mono and polysynaptic
According to origin–
spinal cord, brain stem, cortical etc.
Conditional and unconditional – since birth
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Rapid, stereotyped, invountary response to a sensory stimuli
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consciouslly or unconsciousllySolanki
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9. CLASSIFICATION
CONDITIONED (ACQUIRED)/
UNCONDITIONED(SINCE BIRTH)
 CEREBELLER, CORTICAL, MIDBRAIN,
SPINAL
 SOMATIC:FLEXOR , EXTENSOR
VISCERAL: AUTONOMIC
 MONOSYNAPTIC , POLYSYNAPTIC
 SUPERFICIAL, DEEP, VISCERAL,
PATHOLOGICAL
 SEGMENTAL, INTERSEGMENTAL,
SUPRASEGMENTAL
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12. Functions or reflex action
Maintain the homeostasis- b.p regulation,
heart rate, digestive , autonomic reflexes
 Automatic actions
 Balance and posture
 Reflex maintining the movements -eyes
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13. REFLEX ARC
ANATOMICAL NERVOUS PATHWAY OF
REFLEX IS CALLED REFLEX ARC.
RECEPTOR
SENSORY / AFFERENT NERVE
CENTER
EFFERENT / MOTOR NERVE
EFFECTOR ORGAN
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* BELL-MAGENDIE LAW: DORSAL ROOTS ARE
SENSORY & VENTRAL ROOTS ARE MOTOR.
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14. SUPERFICIAL REFLEXES
CORNEAL AND CONJUNCTIVAL
REFLEX
 PHARYNGEAL REFLEX
 PALATAL REFLEX
 ABDOMINAL RELEX
 PLANTAR REFLEX: Scratch over the
outer edge of sole cause plantar flexion
and adduction of all toes and dorsiflexion
and inversion of foot.( L5,S1)
 ANAL REFLEX
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15. DEEP REFLEXES
JAW JERK: 5TH CRANIAL NV NUCLEI
 BICEPS JERK: C5,6
 TRICEPS JERK: C6,7
 SUPINATOR JERK: C5,6
 KNEE JERK: L2,3,4
 ANKLE JERK: S1,2
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16. Reflex Arc
Specific nerve impulse pathway
 5 components of reflex arc

receptor
 sensory neuron
 integrating center
 motor neuron
 effector
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17. PROPERTIES
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ONE WAY CONDUCTION
SUMMATION: SPATIAL, TEMPORAL
OCCLUSION
SUBLIMINAL FRINGE
RECRUITMENT
AFTERDISCHARGE
REBOUND PHENOMENON
FATIGUE
RECIPROCAL INNERVATION AND
RECIPROCAL INHIBITION
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18. Flexor (withdrawal) Reflex
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Step on tack (pain fibers send
signal to spinal cord
Interneurons branch to different
spinal cord segments
Motor fibers in several
segments are activated
More than one muscle group
activated to lift foot off of tack
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19. Crossed Extensor Reflex
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Lifting left foot requires
extension of right leg to
maintain one’s balance
Pain signals cross to opposite
spinal cord
Contralateral extensor muscles
are stimulated by interneurons
to hold up the body weight
Reciprocal innervation - when
extensors contract flexors
relax, etc
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20. Clinical Considerations
Checking a patient’s reflexes may help
to detect disorders/injury
 Plantar flexion reflex -- stroke the lateral
margin of the sole

normal response is curling under the toes
 abnormal response or response of children
under 18 months is called Babinski sign
(upward fanning of toes due to incomplete
myelination in child)
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21. Inverse stretch reflex
Golgi tendon organ- 2 to 15 in each
muscle.
 Responds to tension and not the length
 The Golgi tendon reflex is a protective
reflex
 rise in tension is sensed by the Golgi
tendon a which stimulates the Ib stimulates the I-b afferents
 stimulate the inhibitory interneurons
 inhibit the α-motoneuron discharge to
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22. INVERSE STRETCH REFLEX/
AUTOGENIC INHIBITION
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WHEN A MUSCLE IS STRETCHED, IT
CONTRACTS BUT IF THE STRETCH IS
MAINTAINED (CONTINUED), THE
MUSCLE RELAXES.
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23. UMN lesions
LMN lesions
•weakness, paralysis
•weakness, paralysis
•spasticity
•flaccidity, hypotonia
• tendon reflexes
•Hypo- /no tendon
•+ Babinski sign
reflex
•little,if any,muscle
• - Babinski sign
atrophy
•muscle atrophy
•no fasiculation
•fasiculation of
involved muscle
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24. VISCERAL REFLEXES
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PUPILLARY REFLEXES:
DIRECT LIGHT REFLEX
INDIRECT OR CONSENSUAL LIGHT REFLEX
ACCOMODATION REFLEX: CONSTRICTION
OF PUPIL, CONVERGENCE OF EYE BALLS,
INCREASE IN ANTERIOR CURVATURE OF
LENS
CILIOSPINAL REFLEX: STIMULATION OF
SKIN IN NECK –DILATATION OF PUPILS
OCULOCARDIAC REFLEX: PRESSURE OVER
EYEBALLS - BRADYCARDIA
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25. PATHOLOGICAL REFLEXES
BABINSKI’S SIGN +
Dorsiflexion of great toe and fanning of
other toes.
 CLONUS
 PENDULAR MOVEMENTS
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29. 1. receptors sense
Flexor reflex (Withdrawal, "hot stove")
pain
2. sensory impulse to
spinal cord
3. synapse to
association neuron,
synapse to motor
neurons

polysynaptic
4. motor neurons to
flexor muscles to
5. withdraw offended
body part from
stimulus
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31. Spinal reflexes
Static stretch reflex- maintain the tone
Maintain constant degree of muscle
contraction (Tone)
Continuous static receptor signal →
transmitted via both primary and
secondary neurons → S.C → continuous
command by static gamma motor
neurons → Tone.
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Normal tone is due to continuous dischrge
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32. Stretch reflex 2 types
-Response that is transmitted:
Dynemic:
-when there is change in the length of the spindle
receptor (stretching of the sensory receptor area of the
muscle spindle by stretching of the muscle spindle or the
whole muscle). Detect Change in length.
-transmitted by the primary fiber Aα type
Static
continuous information about the length of the muscle
(not the change in length).
transmitted by both the primary Aα and secondary (Aβ
and Aγ)
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33. APPLIED:
Decreased (hypoactive) stretch reflex:
Destruction of sensory or motor nerve to the
muscle
Stimulation of inhibitory areas in brain
Inhibition of facilitatory areas in the brain
Hypothyroidism
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34. Importance or use of stretch
reflex:
 1.
Tone maintenance
 2. Maintenance of posture
 3. Control of voluntary movements
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35. What are the components of reflex
action?

Components of reflex
forms
reflex arc involving
1. receptor- sensory organ
2. afferent neuron3. centre
4. efferent neuron
5. effector organ
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36. Reflex arc
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Diagram showing complete reflex arc
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39. 2. 5 Essential Components
of the Reflex Arc
Skin
Stimulus at distal
end of neuron
Spinal cord
(in cross section)
Sensory neuron
Receptor
Motor neuron
(a)
Integration
center
Interneuron
Effector
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