reflexes, clasifications, and functions.

May 2, 2023 Dr. Ashok Solanki 1

REFLEX CONTENTS:

DEFINITIONREFLEX ARCTYPES/CLASSIFICATION OF

REFLEXESSTRETCH REFLEXMUSCLE SPINDLEPROPERTIES OF REFLEXES



Nerve pathwaysAscending Tracts

Tract Signal functionDorsal 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

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.


CLASSIFICATIONCONDITIONED (ACQUIRED)/

UNCONDITIONED(SINCE BIRTH)CEREBELLER, CORTICAL, MIDBRAIN,

SPINALSOMATIC:FLEXOR , EXTENSOR

VISCERAL: AUTONOMICMONOSYNAPTIC , POLYSYNAPTICSUPERFICIAL, DEEP, VISCERAL,

PATHOLOGICALSEGMENTAL, INTERSEGMENTAL,

SUPRASEGMENTAL


Dr. Ashok Solanki


Functions or reflex action Maintain the homeostasis- b.p regulation,

heart rate, digestive , autonomic reflexesAutomatic actionsBalance and posture Reflex maintining the movements -eyes


REFLEX ARC ANATOMICAL NERVOUS PATHWAY OF

REFLEX IS CALLED REFLEX ARC.RECEPTORSENSORY / AFFERENT NERVECENTEREFFERENT / MOTOR NERVEEFFECTOR ORGAN

* BELL-MAGENDIE LAW: DORSAL ROOTS ARE SENSORY & VENTRAL ROOTS ARE MOTOR.


SUPERFICIAL REFLEXESCORNEAL AND CONJUNCTIVAL

REFLEXPHARYNGEAL REFLEXPALATAL REFLEXABDOMINAL RELEXPLANTAR 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


DEEP REFLEXESJAW JERK: 5TH CRANIAL NV NUCLEI BICEPS JERK: C5,6TRICEPS JERK: C6,7SUPINATOR JERK: C5,6KNEE JERK: L2,3,4ANKLE JERK: S1,2

May 2, 2023

Reflex ArcSpecific nerve impulse pathway5 components of reflex arc

receptor sensory neuronintegrating centermotor neuroneffector

Dr. Ashok Solanki 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

Dr. Ashok Solanki 18May 2, 2023

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

Dr. Ashok Solanki 19May 2, 2023

May 2, 2023

Clinical ConsiderationsChecking a patient’s reflexes may help

to detect disorders/injuryPlantar flexion reflex -- stroke the lateral

margin of the solenormal response is curling under the toesabnormal response or response of children

under 18 months is called Babinski sign (upward fanning of toes due to incomplete myelination in child)

Dr. Ashok Solanki 20


Inverse stretch reflexGolgi tendon organ- 2 to 15 in each

muscle.Responds to tension and not the lengthThe Golgi tendon reflex is a protective

reflexrise 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

the muscleThis reflex relaxation of the extrafusal

muscle fibers


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 REFLEXINDIRECT 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.

CLONUSPENDULAR MOVEMENTS




Flexor reflex (Withdrawal, "hot stove")

1. receptors sense pain2. sensory impulse to

spinal cord3. synapse to

association neuron, synapse to motor neurons

polysynaptic4. motor neurons to

flexor muscles to 5. withdraw offended

body part from stimulusMay 2, 2023 Dr. Ashok Solanki 29



Spinal reflexes

Static stretch reflex- maintain the toneMaintain 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 of gamma m. n.


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

Staticcontinuous 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 maintenance2. Maintenance of posture3. Control of voluntary movements


What are the components of reflex action?

Components of reflex forms reflex arc involving 1. receptorsensory organ 2. afferent neuron- 3. centre 4. efferent neuron 5. effector organ


Reflex arcDiagram showing complete reflex arc




2. 5 Essential Components of the Reflex Arc

Dr. Ashok Solanki

Stimulus at distalend of neuron

Skin Spinal cord(in cross section)

Interneuron

Receptor

Effector

Sensory neuron

Motor neuron

Integrationcenter

(a)



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