DOC PREVIEW
The PNS: Afferent Nervous System

This preview shows page 1-2-3-4-28-29-30-31-57-58-59-60 out of 60 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 60 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

The PNS: Afferent Nervous SystemPerception & SensationSensationSensationSensory PathwaysSlide 6Slide 7Slide 8Slide 9Primary Somatosensory areaPowerPoint PresentationSlide 12Proprioceptive SensationSlide 14Slide 15PainSlide 17Slide 18The Tongue & PapillaeSlide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Rods and ConesRetinal cellsSlide 43Slide 44Slide 45Dark vs. LightSlide 47Slide 48Slide 49Visual PathwaysSlide 51External EarMiddle Ear CavityCochlear AnatomySlide 55Physiology of HearingPhysiology of Equilibrium (Balance)Static equilibrium: Saccule & UtricleDynamic equilibrium: Semicircular DuctsHomeostatic Imbalances in Vision and HearingThe PNS: Afferent Nervous System•two kinds of pathways–1. Somatic: sensory/afferent information from skeletal muscle•receptors are scattered at the body surface•can become specialized = Special senses–2. Visceral: sensory information from the internal viscera•receptors are scattered throughout the viscera (organs located in a cavity)•e.g. blood pressure, body fluid concentration, respiratory gas concentration•never reaches a conscious level•although you can become aware of pain•this information is critical form determining the appropriate efferent output to maintain homeostasisPerception & Sensation•Sensation: response to environment via generation of nerve impulse•-sensation occurs upon arrival of nerve impulse at cerebral cortex•-before nerve impulse is generated - sensory receptors integrate or sum up the incoming signals• -several types of integration: one type is adaptation - decrease in response to a stimulus–role of the thalamus?? (gatekeeper??)•-nerve impulses sent via ascending tracts in spinal cord to the brain•Perception: our conscious interpretation of the external world–created by the brain based on information it receives from sensory receptors–interpretation of sensationSensation •each type of sensation = sensory modality•one type of neuron carries only one type of modality•modalities can be grouped into two classes–1. general senses – includes both the somatic and visceral senses•tactile (touch, pressure), thermal, pain and proprioception–2. special senses: sight, sound, hearing, tasteSensation•1. stimulation of the sensory receptor–alters the permeability of the neuron’s PM–usually does this through non-specific opening of small ion channels•2. transduction of the stimulus–increased influx of Na ions – depolarization – called a graded receptor potential–therefore the sensory receptor converts (transduces) the energy of the stimulus into a graded potential•3. generation of the nerve impulse–increase in graded receptor potential past threshold -> Action Potential–AP propagates toward the CNS•4. integration of the sensory input–receipt of sensory information by a particular region in the CNS–integration of sensation and perceptionSensory Pathways•these pathways consist of thousands of sets of neurons – grouped into threes–1. first order neurons – conduct sensory information from the receptor into the CNS•cranial nerves conduct information from the face, mouth, eyes, ears and teeth•spinal nerves conduct information from the neck, trunk and limbs–2. second order neurons – conduct information from the brain and SC into the thalamus•these neurons decussate (cross over) within the thalamus–3. third order neurons – conduct information from the thalamus to the primary somatosensory areas within the cerebral cortex•for integrationSensory PathwaysSensory Pathways•sensory pathways enter the SC and ascend to the cerebral cortex via:–1. the posterior column-medial lemniscus path•for conscious proprioception and most tactile sensations•two tracts of white matter: posterior column and the medial lemniscus•first order neurons from sensory receptors in the trunk and limbs form the posterior columns in the spinal cord•synapse with second order neurons in the medulla oblongata•these then cross to the opposite side of the medulla and enter the medial lemniscus in the thalamus – synapse with the third order neurons that travel to the cortex (primary somatosensory area)–fine touch–stereostegnosis – ability to recognize shapes, sizes and textures by feeling–proprioception–vibratory sensations–2. the anterolateral/spinothalmic path•first order neurons receive impulses from receptors in the neck, trunk or limbs•receptors end in dorsal root ganglion•synapse with the 1st order neurons are located in the dorsal root ganglion•synapse with second order neurons in the posterior gray horn•second order neurons than cross to the opposite side of the SC and pass to the primary somatosensory area in either the: •second order neurons pass through the brain stem as two possible tracts:–lateral spinothalmic tract: pain and temperature–anterior spinothalmic tract: information for tickle, itch, crude touch and pressureSensory Pathways•two tracts: posterior spinocerebellar and anterior spinocerebellar•major routes for proprioceptive impulses from lower limbs that reach the cerebellum•not consciously perceived•critical for posture, balance and coordination•posterior spinocerebellar routes are degraded upon advanced syphillis – severe uncoordination•first order neurons: muscle spindles and tendon organs•second order neurons: cell bodies in dorsal gray horn via thalamus to the cuneate nucleus of basal ganglia•third order neurons: thalamus to cerebellum (no decussation)Sensory PathwaysPrimary Somatosensory area•specific areas of the cerebral cortex receive somatic sensory input from various parts of the body•precise localization of these somatic sensations occurs when they arrive at the primary somatosensory area•some regions provide input to large regions of this area (e.g. cheeks, lips, face and tongue) while others only provide input to smaller areas (trunk and lower limbs)-sensory receptors: can either be a1) specialized ending of an afferent neuron2) a separate cells closely associated with an afferent neurons-can classify a sensory receptor based on:1. microscopic features:a. free nerve endings: bare dendrites associated with pain, heat, tickle, itch and some touchb. encapsulated nerve endings: dendrites enclosed in a connective tissue capsule - touche.g. Pacinian corpusclec.


The PNS: Afferent Nervous System

Download The PNS: Afferent Nervous System
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view The PNS: Afferent Nervous System and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view The PNS: Afferent Nervous System 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?