Lecture 6

Lecture 6 - NPB 101. Autumn 2008 The Nervous Systems: The...

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The Nervous Systems: The Peripheral Nervous System Afferent Division Special Senses 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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Sensory afferents have two major sub-divisions: The visceral afferents The sensory afferents – special sensory and somatic sensory Hearing, equilibrium, smell and taste
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Special Senses The ear – hearing and equilibrium The ear has three major parts: The external and middle portions of the ear transmit and amplify sound waves to the inner ear – a fluid-filled organ containing sensory systems with receptors (sensors) that detect sound waves or balance and convert them into action potentials. Hearing involves neural perception of sound – what and where. Balance and equilibrium involves detection of position and motion of the head in relation to environment and the rest of the body.
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Inner ear Pinna of external ear Tympanic membrane (eardrum) Middle ear External ear Auditory ossicles Semicircular canals Utricle and saccule Oval window Vestibulocochlear nerve Cochlea Round window Eustachian tube To pharynx External auditory meatus (ear canal) Fig. 6-30, p. 210
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Fig. 6-31a, p. 210
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Normal density of air molecules when tuning fork is at rest Region of rarefaction Region of compression Fig. 6-31, p. 210
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Fig. 6-31, p. 210 Sound waves dissipate with distance traveled (attentuation). Can travel through water but higher density requires more pressure. In air, attentuation of sound can be affected by wind, topography of the ground, trees, buildings etc.
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Fig. 6-32, p. 211 Humans can hear sounds in the range 20 -20,000 cycles per second, but best at 1,000-4,000 cycles per second. Loudness is measured on a logarithmic scale of decibels (dB). Every 10 dB is a ten fold increase.
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Table 6-5, p. 211
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The pinna of the external ear captures sound waves and channels them into the external auditory meatus or ear canal. The pinna also partially shields the ear from sounds coming from behind allowing location of sound – distinguishing if the source of the sound is from behind or in front. The timing of when sounds waves reach the right and left pinnae allows further location of the source. Intensity is reduced in sound waves reaching the farthest pinna allowing further integration of position of the source. This is integrated by the auditory cortex using
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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 6 - NPB 101. Autumn 2008 The Nervous Systems: The...

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