quiz_2_study_sheet3 - Quiz 2 Study Sheet Reflex A response...

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Reflex: A response that occurs automatically, without any brain involvement, to protect the body. Stimulus to response mediated by a neural pathway known as the reflex arc Reflex arc: Neural pathway that does not include the brain in order to decrease reaction time to stimulus. Components of reflex arc are: 1. Receptor: Responds to stimulus, such as physical or chemical change in environment 2. Afferent pathway: Relays action potential produced by receptor in response to stimulus 3. Integrator: Processes action potential from receptor and signals from all other inputs to “make a decision” about the appropriate response. 4. Efferent pathway: Transmits instructions for the “integrating center” to the effector 5. Effector: Carries out desired response Tip: Afferent neurons cause sensation to ascend to the brain. Efferent neurons send impulses out of the brain to effect action Reflexes are useful for: Automatic protective responses (pain withdrawl) Postural maintenance o Proprioception : mostly subconscious perception of movements and limb positions independent of vision Monosynaptic Reflex : Simplest type, only one synapse in spinal cord between sensory (afferent) and motor (efferent) neurons. Polysynaptic Reflex :Multiple synapses between afferent and efferent neurons. Muscle Spindle : Specialized muscle structure innervated by both sensory and motor neurons. Consist of specialized muscle fibers known as intrafusal muscle fibers Embedded in extrafusal muscle fibers, found within fleshy portions of muscle Each has o Afferent Ia-neuron: Innervates intrafusal muscle fibers of muscle spindle o Efferent γ-motorneuron: Innervates intrafusal muscle fibers and relieves stretch in muscle fiber o Efferent α –motoneuron: Innervates extrafusal muscle fibers Muscle spindles respond to: 1) changes in length, 2) rate of length change Stretch Reflex : Local negative-feedback mechanism to resist passive changes in muscle length to maintain optimal resting length Muscle stretched Primary sensory fibers (Ia afferent) sent to spinal cord and secondary (II afferent) send to CNS
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quiz_2_study_sheet3 - Quiz 2 Study Sheet Reflex A response...

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