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Reflex Arc

Reflex Arc. The Reflex Arc. Includes Receptor Sensory Neuron Motor Neuron Effectors Involved in a particular reflex interneurons may or may not be present The arc makes a REFLEX possible- or “rapid automatic responese to stimuli”

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Reflex Arc

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  1. Reflex Arc

  2. The Reflex Arc • Includes • Receptor • Sensory Neuron • Motor Neuron • Effectors Involved in a particular reflex • interneurons may or may not be present The arc makes a REFLEX possible- or “rapid automatic responese to stimuli” Reflexes make RAPID ADJUSTMENTS in the functions of organs or organ systems

  3. Kinds of Reflexes Reflexes are categorized in several ways: 1) on the basis of DEVELOPMENT a) INNATE REFLEXES- result from the connection of neurons that form during normal development Are genetically determined Include: withdrawal from pain, blinking and sucking

  4. b) ACQUIRED REFLEXES are still rapid, and automatic but are LEARNED responses • -by MOTOR RESPONSES- • SOMATIC REFLEXES control activities of the muscular system • VISERAL REFLEXES or autonomic involuntary reflexes- control the actions of smooth and cardiac muscles and glands

  5. 3) - by PROCESSING SITE- a) SPINAL REFLEXES - control the activities of the muscular system b) CRANIAL REFLEXES - are reflexes processed in the brain

  6. 4) – by the COMPLEXITY OF THE CIRCUIT- a) Monosynaptic Reflexes - in which the sensory neuron synapses DIRECTLY with the motor neuron - there is little delay between sensory input and motor output - control the most RAPID reflexes

  7. Polysynaptic Reflexes - involves a sensory neuron an interneuron and… a motor neuron - the involvement of interneuron's allows for the motor control of several different muscle groups - polysynaptic reflexes allow for more complicated responses

  8. Classification of Reflexes can be Combined • Examples: • Monosynaptic (complexity of circuit) spinal (processing site) reflex - The stretch reflex -provides automatic regulation of skeletal muscle length - is responsible for muscle tone -the STIMULUS is the stretching of the muscle - the RECEPTORS are in the muscle cells - the SENSORY NEURON synapses directly with - the MOTOR NEURON which triggers and immediate response in the -EFFECTOR = the muscle

  9. The Knee Jerk or PATELLAR REFLEX is an example of a MONOSYNAPTIC REFLEX by passive (relaxed) muscles

  10. Postsynaptic Reflexes • Can be one of two types: IPSILATERAL- the sensory stimulus and motor response are on the same side of the body ……or….. CONTRALATERAL- the motor response is required on the opposite side of the body

  11. Five Basic Characteristics of Postsynaptic Reflexes • They involve “pools” of neurons • They are “intersegmental” involve more than one pair of spinal nerves • They involve reciprocal innervations e.g. the contraction of one group of muscles is opposed by the inhibition of another group of opposing muscles • The contraction of a flexing muscle may trigger the STRETCH REFLEX of another muscle • They have reverberating circuits that PROLONG the reflex motor response even after the initial stimulus has failed • Several reflexes may cooperate to produce a coordinated controlled response Example: Stepping on a Tack with your bare foot

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