Exercise 22: Exercise 22: Reflex Reflex

PhysiologyPhysiology

WHAT is a REFLEX?WHAT is a REFLEX? Rapid, predictable, unlearned, Rapid, predictable, unlearned, involuntaryinvoluntary motormotor response to a response to a stimulusstimulus

REFLEX ARCREFLEX ARC Chain of events in neural pathwayChain of events in neural pathway Sensory to motorSensory to motor

Receptor Receptor Sensory neuron Sensory neuron Integration Center in CNS Integration Center in CNS Response through Motor neuron Response through Motor neuron EffectorEffector

Reflexes: 5 StepsReflexes: 5 Steps

1.1. Arrival of a stimulus, activation Arrival of a stimulus, activation of receptorof receptor

2.2. Activation of sensory neuronActivation of sensory neuron3.3. Information processing: Information processing:

integration centerintegration center4.4. Activation of motor neuronActivation of motor neuron5.5. Response by an effector Response by an effector

Know the steps & the diagram!!

Somatic vs. AutonomicSomatic vs. Autonomic Somatic ReflexesSomatic Reflexes

Conscious control—skeletal musclesConscious control—skeletal muscles Autonomic ReflexesAutonomic Reflexes

Not conscious—smooth, cardiac, Not conscious—smooth, cardiac, glandsglands

16-2

Somatic: Patellar Reflex = Somatic: Patellar Reflex = stretch reflexstretch reflex

13-20

Tap tendonTap tendonStimulates muscle Stimulates muscle Reflex contraction of Reflex contraction of the stretched musclethe stretched muscle

13-22

(Flexor reflex) Crossed-extensor reflex

Flexor reflex + extension reflex of Flexor reflex + extension reflex of opposite limbopposite limb

Plantar ReflexPlantar Reflex Longitudinal stroking of sole of Longitudinal stroking of sole of

footfoot Tibial nerveTibial nerve Normal response: curling of toesNormal response: curling of toes

13-23

Babinski’s Sign Babinski’s Sign (positive Babinski reflex)(positive Babinski reflex)

Same stimulus—but response is Same stimulus—but response is fanning of toesfanning of toes

Seen in infants; disappears if Seen in infants; disappears if descending motor pathways descending motor pathways develop properly—if seen in develop properly—if seen in adult, often a CNS injuryadult, often a CNS injury

13-23

AUTONOMIC REFLEXESAUTONOMIC REFLEXES Pupillary reflexPupillary reflex

Receptor: retina Receptor: retina optic nerve optic nerve brain/s cord brain/s cord oculomotor nerve oculomotor nerve

Smooth muscle controls irisSmooth muscle controls iris Dilation = biggerDilation = bigger Constriction = smallerConstriction = smaller

AUTONOMIC REFLEXESAUTONOMIC REFLEXES Salivary reflexSalivary reflex

Salivary glands are effectorsSalivary glands are effectors