Lecture 4

Lecture 4 - NPB 101. Autumn 2008 The Nervous Systems: The...

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The Nervous Systems: The Peripheral Nervous System Afferent Division Chapter 6 NPB 101. Autumn 2008
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Brain Central nervous system (CNS) Spinal cord Peripheral nervous system (PNS) Afferent division Efferent division Sensory stimuli Visceral stimuli Somatic nervous system Autonomic nervous system Motor neurons Sympathetic nervous system Parasympathetic nervous system Skeletal muscle Smooth muscle Cardiac muscle Glands Effector organs (made up of muscle and gland tissue) (Input to CNS from periphery) (Output from CNS to periphery) Fig. 5-1, p. 132 Major sub-divisions of the nervous system
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Central nervous system (spinal cord) Peripheral nervous system Axon terminals Cell body Afferent neuron Central axon Peripheral axon (afferent fiber) Receptor Interneuron Efferent neuron* Effector organ (muscle or gland) Axon (efferent fiber) Axon terminals * Efferent autonomic nerve pathways consist of a two-neuron chain between the CNS and the effector organ. Cell body Fig. 5-2, p. 133
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Afferent division – carries signals to the Central Nervous System. Sensory afferents have two major sub-divisions: The visceral afferents The sensory afferents – special sensory and somatic sensory Special senses include vision, hearing, taste and smell Somatic sensory information comes from the body surface (touch, pain) and proprioception from the muscles, joints, skin and inner ear.
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Visceral afferents largely subconscious except for pain. Somatosensory and special senses – conscious awareness – perception.
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We do not perceive all signals – other vertebrates perceive electrical field, magnetic field, barometric pressure and perhaps others. What we do perceive does not cover the full range of possibilities. For example many animals can perceive sounds at higher frequencies than us, and some animals can see ultra violet light with dramatic differences in color patterns. Remember that some sensory input is filtered out whereas other inputs are accentuated. Then the cortex regions process input further combining it with memories, and visceral input. The result is remarkably complex assessment of environment within and without. E.g. recognizing the sound of a child or a friend in a crowd. Appreciation of the smells, sight, texture etc. of a banquet. Fight or flight response.
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Receptor “Sensor” Physiology Sensory modalities are the ways by which stimuli from the environment are perceived – specific to their energy forms (“their adequate stimulus”). These modalities include heat, light, sound, pressure and chemicals As we have seen, afferent neurons have sensors or receptors at the peripheral endings that respond environment (external and internal). Others may interact with a separate sensor cell. Transduction of the environmental signal is the conversion
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This note was uploaded on 01/06/2010 for the course NPB idk taught by Professor Wingfield during the Spring '09 term at UC Davis.

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Lecture 4 - NPB 101. Autumn 2008 The Nervous Systems: The...

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