What is a reflex?What is a reflex?
Functional unit of CNS, involuntary Functional unit of CNS, involuntary response to a stimulusresponse to a stimulus
-example/pinprick-example/pinprick
Reflex ArcReflex Arc--DIFDIF//
- -formed offormed of ::
--Sense organ (receptor)Sense organ (receptor)..
--An afferent neuronAn afferent neuron . .
--One or more synapses (CNS)One or more synapses (CNS) . .
--An efferent neuronAn efferent neuron . .
--An effector organAn effector organ
--Bell-Magendi lawBell-Magendi law
****-Afferent neuron-Afferent neuron
- Afferent neurons undergo:- Afferent neurons undergo:
1- 1- DivergenceDivergence WHY? WHY? 2-2- ConvergenceConvergence WHY? WHY?
**- Interneurons**- Interneurons ( (excitatoryexcitatory or or inhibitoryinhibitory). ).
- (Two types of circuits formed by inter neurons- (Two types of circuits formed by inter neurons
(parallel and reverberating circuits).(parallel and reverberating circuits).
Reverberating circuitsReverberating circuits--Function-Function-- In brain and spinal cord- In brain and spinal cord--- RespirationRespiration&&WakefulnessWakefulness
Renshaw cells
- - located in anterior horn with motor neuronslocated in anterior horn with motor neurons . .
--inhibitoryinhibitory ((presynaptic inhibitionpresynaptic inhibition,, negative negative feedback fashion)feedback fashion)
& & lateral inhibitionlateral inhibition to nearby neurons to nearby neurons..
Efferent neuronEfferent neuron
--
1.1. alphaalpha motor neurons motor neurons
2.2. GammaGamma motor neurons motor neurons
Stretch reflexStretch reflex
-Components:--Components:-
Receptor Receptor ::
AfferentAfferent
AHCAHC
EfferentEfferent
EffectorEffector
Stretch reflex receptor ( Muscle Spindle)Stretch reflex receptor ( Muscle Spindle)
Structure of Muscle SpindleStructure of Muscle Spindle-:-:
Two types of intrafusal fibresTwo types of intrafusal fibres:: . .
Innervation of the muscle spindleInnervation of the muscle spindle11--Sensory Afferent fibresSensory Afferent fibres::
22--Efferent fibres to spindleEfferent fibres to spindle
Types of responsesTypes of responses Component of stretch reflexComponent of stretch reflex
.1.111--Dynamic stretch reflex (Dynamic stretch reflex (dynamic or phasicdynamic or phasic
responseresponse))
22 - -Static stretch reflex( static responseStatic stretch reflex( static response
Muscle Tone:- Static stretch reflexStatic stretch reflex
Dif/ resistance of muscle to stretch-Stimuli for muscle tone
-Present in ?
-hypotonic or flacidity
-hypertonic,spastic muscle
Reciprocal inhibitionReciprocal inhibition
IN KNEE JERK/
contraction of EXTENSOR of thigh >>>>>>>
relaxation of FLEXORS
Higher control on gamma efferent Higher control on gamma efferent dischargedischarge-: -:
1-Cortical areas.
2-Basal ganglia.
Lengthening Reaction:-Lengthening Reaction:- response of spastic muscle to response of spastic muscle to lengtheninglengthening
Clonus:- Clonus:- as as Ankle clonusAnkle clonus
Clinical significance of stretch Clinical significance of stretch reflex:-reflex:---Tendon jerksTendon jerks
Withdrawal reflexWithdrawal reflex(flexor reflex)(flexor reflex)
--Properties of withdrawal RProperties of withdrawal R - -crossed extensor reflexcrossed extensor reflex
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