reflexes, clasifications, and functions.

REFLEX
CONTENTS:
 DEFINITION
 REFLEX ARC
 TYPES/CLASSIFICATION OF
REFLEXES
 STRETCH REFLEX
 MUSCLE SPINDLE
 PROPERTIES OF REFLEXES26-Jan-16 1Dr. Ashok Solanki

Nerve pathways
Ascending Tracts
Tract Signal function
Dorsal columns
Vibration, tactile sensation, conscious
proprioception
Spinocerebeller Proprioception
Spinothalamic (lateral and
anterior)
Pain, temperature, itch (lateral), crude
touch (anterior)
Spinoreticular Pain
Spinomesencephalic Pain
Spino-cervico-thalamic Pain (touch?)
Spinohypothalamic Pain

Structure of spinal cord
26-Jan-16 Dr. Ashok Solanki 5

 Fetal 3rd month: ends at
coccyx
 Birth: ends at L3
 Adult position at approx L1-2
during childhood
 End: conus medullaris
 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)
Spinal cord
http://www.apparelyzed.com/spinalcord.html

Spinal nerves continued
 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

Classified as
According to centre IN THE SPINAL CORD-
seg, inter, supra.
According to function-
flexor, extensor, postural R.
Clinically-
supreficial, deep, visceral
No. of synapse involved.
Mono and polysynaptic
According to origin–
spinal cord, brain stem, cortical etc.
Conditional and unconditional – since birth
 Rapid, stereotyped, invountary response to a sensory stimuli consciouslly or unconsciouslly.
826-Jan-16 Dr. Ashok Solanki

CLASSIFICATION
 CONDITIONED (ACQUIRED)/
UNCONDITIONED(SINCE BIRTH)
 CEREBELLER, CORTICAL, MIDBRAIN,
SPINAL
 SOMATIC:FLEXOR , EXTENSOR
VISCERAL: AUTONOMIC
 MONOSYNAPTIC , POLYSYNAPTIC
 SUPERFICIAL, DEEP, VISCERAL,
PATHOLOGICAL
 SEGMENTAL, INTERSEGMENTAL,
SUPRASEGMENTAL
26-Jan-16 9Dr. Ashok Solanki

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

REFLEX ARC
 ANATOMICAL NERVOUS PATHWAY OF
REFLEX IS CALLED REFLEX ARC.
RECEPTOR
SENSORY / AFFERENT NERVE
CENTER
EFFERENT / MOTOR NERVE
EFFECTOR ORGAN
* BELL-MAGENDIE LAW: DORSAL ROOTS ARE
SENSORY & VENTRAL ROOTS ARE MOTOR.

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 REFLEX26-Jan-16 14Dr. Ashok Solanki

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

Reflex Arc
 Specific nerve impulse pathway
 5 components of reflex arc
 receptor
 sensory neuron
 integrating center
 motor neuron
 effector
Dr. Ashok Solanki 1626-Jan-16

PROPERTIES
 ONE WAY CONDUCTION
 SUMMATION: SPATIAL, TEMPORAL
 OCCLUSION
 SUBLIMINAL FRINGE
 RECRUITMENT
 AFTERDISCHARGE
 REBOUND PHENOMENON
 FATIGUE
 RECIPROCAL INNERVATION AND
RECIPROCAL INHIBITION

Flexor (withdrawal) Reflex
 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

Crossed Extensor Reflex
 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

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)

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 I-
b stimulates the I-b afferents
 stimulate the inhibitory interneurons
 inhibit the α-motoneuron discharge to 2126-Jan-16 Dr. Ashok Solanki

INVERSE STRETCH REFLEX/
AUTOGENIC INHIBITION
 WHEN A MUSCLE IS STRETCHED, IT
CONTRACTS BUT IF THE STRETCH IS
MAINTAINED (CONTINUED), THE
MUSCLE RELAXES.

UMN lesions
•weakness, paralysis
•spasticity
• tendon reflexes
•+ Babinski sign
•little,if any,muscle
atrophy
•no fasiculation
LMN lesions
•weakness, paralysis
•flaccidity, hypotonia
•Hypo- /no tendon
reflex
• - Babinski sign
•muscle atrophy
•fasiculation of
involved muscle

VISCERAL REFLEXES
 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

PATHOLOGICAL REFLEXES
 BABINSKI’S SIGN +
Dorsiflexion of great toe and fanning of
other toes.
 CLONUS
 PENDULAR MOVEMENTS

Flexor reflex (Withdrawal, "hot stove")1. receptors sense
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

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.
Normal tone is due to continuous dischrge

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)

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

Importance or use of stretch
reflex:
 1. Tone maintenance
 2. Maintenance of posture
 3. Control of voluntary movements

What are the components of reflex
action?
 Components of reflex
forms
reflex arc involving
1. receptor- sensory organ
2. afferent neuron-
3. centre
4. efferent neuron
5. effector organ

Reflex arc
 Diagram showing complete reflex arc

2. 5 Essential Components
of the Reflex Arc
39
Dr. Ashok Solanki
Stimulus at distal
end of neuron
Skin Spinal cord
(in cross section)
Interneuron
Receptor
Effector
Sensory neuron
Motor neuron
Integration
center
(a)

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