CHAPTER 15

• What are sensory pathways?

  A series of neurons that relay sensory information from sensory receptors to the CNS
• What are sensory receptors?

  Specialized cells or neuron processes that monitor specific conditions in the body or the external environment
• What happens when a sensory receptor is stimulated?

  A receptor generates action potentials that are propagated along sensory pathways
• What does the afferent division of the nervous system include?

  Somatic and visceral sensory pathways
• Where does somatic sensory information go in the brain?

  To sensory processing centers in the cerebral cortex
• Where does visceral sensory information primarily go?

  To the brainstem and diencephalon
• What does the efferent division of the nervous system control?

  Somatic motor pathways that control peripheral effectors
• How do motor commands travel from the brain?

  Along somatic motor pathways
• How can motor commands be modified?

  By higher-order functions in the brain
• What are effectors in the context of the nervous system?

  Skeletal muscles
• What is sensation?

  Sensory information arriving in the CNS
• What is perception?

  Conscious awareness of a sensation
• What is transduction in sensory receptors?

  The conversion of an arriving stimulus into an action potential
• What are general senses?

  Temperature, pain, touch, pressure, vibration, proprioception
• What are special senses?

  Olfaction, gustation, vision, equilibrium, hearing
• Where are special sensory receptors located?

  In sense organs such as the eye or ear
• What is receptor specificity?

  Each receptor has a characteristic sensitivity
• What is a receptive field?

  The area monitored by a single receptor cell
• How does the size of the receptive field affect stimulus localization?

  The larger the receptive field, the more difficult it is to localize a stimulus
• What is the receptor potential?

  The stimulus changes the receptor membrane potential
• What can a receptor potential be?

  It can be depolarizing (generator potential) or hyperpolarizing
• What does the size of the receptor potential depend on?

  The strength of the stimulus
• How do receptors of the special senses communicate with sensory neurons?

  At synapses
• Where does the receptor potential occur?

  In the receptor cell
• Where does the generator potential occur?

  In the sensory neuron
• What are phasic receptors?

  Normally inactive and generate action potentials only for a short time in response to changes
• What are tonic receptors?

  Always active and generate action potentials at a frequency reflecting the background level of stimulation
• How do tonic receptors respond to changes in stimulation?

  They increase or decrease the frequency of action potentials
• How do phasic receptors provide information?

  About intensity and rate of change of a stimulus
• What is a labeled line in sensory pathways?

  Sensory neurons that link specific peripheral receptors to specific cortical neurons
• What does sensory coding determine?

  The strength, duration, and variation of the stimulus determines the frequency and pattern of action potentials
• How does perception of a stimulus depend on the labeled line?

  It depends on the specific labeled line it uses
• What is adaptation in sensory receptors?

  Reduction of receptor sensitivity in the presence of a constant stimulus
• How does peripheral adaptation occur?

  When the level of receptor activity changes
• What are fast-adapting receptors?

  Receptors that respond strongly at first but then decrease activity
• What are slow-adapting receptors?

  Receptors that show little peripheral adaptation
• What is central adaptation?

  Involves the inhibition of nuclei along a sensory pathway
• Where is most incoming sensory information processed?

  In centers along the spinal cord, brain stem, or thalamus
• What is proprioception?

  Information about the position of skeletal muscles and joints
• What are exteroceptors?

  Receptors that provide information about the external environment