LAB EXERCISE 18LAB EXERCISE 18GENERAL SENSESGENERAL SENSES
Sensory Information Afferent Division of the Nervous Afferent Division of the Nervous
SystemSystem
– ReceptorsReceptors
– Sensory neuronsSensory neurons
– Sensory pathwaysSensory pathways
Spinal cord to brainSpinal cord to brain
Deliver somatic and visceral Deliver somatic and visceral
sensory information to their sensory information to their
final destinations inside the final destinations inside the
CNS using:CNS using:
– NervesNerves
– NucleiNuclei
– Sensory tractsSensory tracts
Sensoryprocessingcenters in
brain
Sensorypathways
Generalsensory
receptors
Conscious andsubconsciousmotor centers
in brain
Higher-Order Functions
Memory, learning, andintelligence may
influence interpretationof sensory information
and nature of motoractivities
Sensory Information Somatic Motor Portion of the Efferent Somatic Motor Portion of the Efferent
DivisionDivision
– Controls peripheral effectorsControls peripheral effectors
Skeletal muscleSkeletal muscle
Somatic Motor CommandsSomatic Motor Commands
– Travel from motor centers in the Travel from motor centers in the
brain along brain along somatic motor somatic motor
pathwayspathways of: of:
Motor nucleiMotor nuclei
TractsTracts
NervesNerves
Motorpathways
SomaticNervous
System (SNS)
Skeletalmuscles
Sensory Receptors General Senses General Senses
– Describe our sensitivity to:Describe our sensitivity to:
TemperatureTemperature
PainPain
TouchTouch
PressurePressure
VibrationVibration
ProprioceptionProprioception
Sensory Receptors Special SensesSpecial Senses
The Special SensesThe Special Senses
– Are provided by special sensory receptorsAre provided by special sensory receptors
– OlfactionOlfaction (smell) (smell)
– VisionVision (sight) (sight)
– GustationGustation (taste) (taste)
– EquilibriumEquilibrium (balance) (balance)
– HearingHearing
SENSATION VS PERCEPTION SensationSensation
– Occurs when Occurs when nerve impulses arrive at nerve impulses arrive at the cerebral cortexthe cerebral cortex From sensory neurons created by an From sensory neurons created by an
action potential.action potential.–ChemoreceptorsChemoreceptors–ThermoreceptorsThermoreceptors–NociceptorsNociceptors–BaroreceptorsBaroreceptors
– What we are not aware ofWhat we are not aware of
SESNSATION VS PERCEPTION
PerceptionPerception–Perception is the conscious Perception is the conscious
awareness & interpretation of a awareness & interpretation of a sensationsensation
–Occurs when the cerebral cortex Occurs when the cerebral cortex interprets the meaning of interprets the meaning of sensations.sensations.
We have no perception of some information because it never reaches the cortex.
Blood pressure is received in the medulla
Sensory Integration Input comes fromInput comes from
– ExteroceptorsExteroceptors
– InteroceptorsInteroceptors
– ProprioceptorsProprioceptors
Input is relayed toward the Input is relayed toward the head, and is processed along head, and is processed along the waythe way
Sensory Receptors1.1. ExteroceptorsExteroceptors
– Respond to stimuli arising Respond to stimuli arising outside the bodyoutside the body
– Receptors in the skinReceptors in the skin TouchTouch PressurePressure PainPain TemperatureTemperature
– Most special sense organsMost special sense organs VisionVision HearingHearing EquilibriumEquilibrium TasteTaste SmellSmell
Sensory Receptors2.2. InteroceptorsInteroceptors
**Visceroceptors**Visceroceptors
– Respond to stimuli Respond to stimuli arising in internal arising in internal viscera and blood viscera and blood vesselsvessels
– Sensitive toSensitive to Chemical changesChemical changes Tissue stretchTissue stretch Temperature changesTemperature changes PainPain DiscomfortDiscomfort Hunger Hunger ThirstThirst
Sensory Receptors3.3. ProprioceptorsProprioceptors
– Provide a purely somatic sensationProvide a purely somatic sensation– Respond to stretch inRespond to stretch in
Skeletal musclesSkeletal muscles TendonsTendons JointsJoints LigamentsLigaments Connective tissue coverings of bones Connective tissue coverings of bones
and musclesand muscles
– Inform the brain of one’s body Inform the brain of one’s body movementsmovements
– No proprioceptors in the visceral organs of No proprioceptors in the visceral organs of
the thoracic and abdominopelvic cavitiesthe thoracic and abdominopelvic cavities
You cannot tell where your spleen, You cannot tell where your spleen,
appendix, or pancreas is at the appendix, or pancreas is at the
momentmoment
Processing at the Circuit Level This level consists of This level consists of
pathways of three pathways of three neurons conduct sensory neurons conduct sensory impulses upward to the impulses upward to the appropriate brain regionsappropriate brain regions
– First order neuronsFirst order neurons– Second order neuronsSecond order neurons– Third order neuronsThird order neurons
Processing at the Circuit Level First order First order
neuronsneurons– Conduct Conduct
impulses from impulses from the receptor the receptor level to the level to the second-order second-order neurons in the neurons in the brain stem or brain stem or spinal cordspinal cord
Processing at the Circuit Level Second-order neuronsSecond-order neurons
– Transmit impulses to theTransmit impulses to the ThalamusThalamus
–Tracts cross overTracts cross over
Processing at the Circuit Level Third-order neuronsThird-order neurons
– Conduct impulses Conduct impulses fromfrom The thalamus to The thalamus to The The
somatosensory somatosensory cortexcortex–Perceptual Perceptual
levellevel
The axons of the third order The axons of the third order continue to ascend without continue to ascend without crossing over to the crossing over to the somatosensory area.somatosensory area.– As a resultAs a result
Left cerebral hemispheres Left cerebral hemispheres receive info from the right receive info from the right sideside
Right cerebral Right cerebral hemispheres receive info hemispheres receive info from the left sidefrom the left side
Processing at the Perceptual Level
Sensory Receptors
Learning OutcomesLearning Outcomes
15-3 15-3 Identify the receptors for theIdentify the receptors for the general senses, and describegeneral senses, and describe how they function.how they function.
Sensory Receptors General Sensory Receptors General Sensory Receptors
– Are divided into four types by the nature of the stimulus that excites Are divided into four types by the nature of the stimulus that excites
themthem
1.1. ChemoreceptorsChemoreceptors
**Chemical concentration**Chemical concentration
2.2. NociceptorsNociceptors
**P**Painain
3. Thermoreceptors3. Thermoreceptors
**Temperature**Temperature
4. Mechanoreceptors4. Mechanoreceptors
**Physical distortion**Physical distortion
Classifying Sensory Receptors Nociceptors Nociceptors (Pain Receptors)(Pain Receptors)
– MostMost concentrated in the superficial portions of the skin concentrated in the superficial portions of the skin
– In joint capsules In joint capsules
– Within the periostea of bones Within the periostea of bones
– Around the walls of blood vesselsAround the walls of blood vessels
Classifying Sensory Receptors Nociceptors Nociceptors
– Are free nerve endingsAre free nerve endings with large receptive fieldswith large receptive fields
– May be sensitive to:May be sensitive to:
1.1. Temperature extremes Temperature extremes
2.2. Mechanical damage Mechanical damage
3.3. Dissolved chemicals, such as chemicals Dissolved chemicals, such as chemicals
released by injured cellsreleased by injured cells
*Associated with tissue damage*Associated with tissue damage
Type A or Type CType A or Type C
Classifying Sensory Receptors
– Myelinated Type A Nociceptor fibersMyelinated Type A Nociceptor fibers
Carry sensations of Carry sensations of fast painfast pain, or , or prickling painprickling pain, ,
such as that caused by an injection or a deep cutsuch as that caused by an injection or a deep cut
Sensations reach the CNS quickly and often Sensations reach the CNS quickly and often
trigger somatic reflexestrigger somatic reflexes
Relayed to the primary sensory cortex and receive Relayed to the primary sensory cortex and receive
conscious attentionconscious attention
Classifying Sensory Receptors
– Type C Nociceptor fibersType C Nociceptor fibers
Carry sensations of Carry sensations of slow painslow pain, or , or burning and burning and
aching painaching pain
Cause a generalized activation of the reticular Cause a generalized activation of the reticular
formation and thalamusformation and thalamus
You become aware of the pain but only have a You become aware of the pain but only have a
general idea of the area affectedgeneral idea of the area affected
-Referred pain -Referred pain
“ “Incorrect" source perceivedIncorrect" source perceived
*Pain in the forehead when eating ice cream too quick*Pain in the forehead when eating ice cream too quick
*Heartburn*Heartburn
*Dentistry *Dentistry
*Angina *Angina
––Pain in the arm when the heart does not receive enough oxygenPain in the arm when the heart does not receive enough oxygen
Classifying Sensory Receptors
Classifying Sensory Receptors ThermoreceptorsThermoreceptors
– Also called temperature receptorsAlso called temperature receptors
– Are free nerve endings located in:Are free nerve endings located in:
The dermisThe dermis
Skeletal musclesSkeletal muscles
The liverThe liver
The hypothalamusThe hypothalamus
Classifying Sensory Receptors Mechanoreceptors Mechanoreceptors
– Sensitive to stimuli that distort their plasma Sensitive to stimuli that distort their plasma
membranesmembranes
– Contain Contain mechanically gated ion channelsmechanically gated ion channels
whose gates open or close in response to:whose gates open or close in response to: StretchingStretching
CompressionCompression
TwistingTwisting
Other distortions of the membraneOther distortions of the membrane
Classifying Sensory Receptors Three Classes of Mechanoreceptors Three Classes of Mechanoreceptors
1.1. Tactile receptorsTactile receptors Provide the sensations ofProvide the sensations of
– TouchTouch
» Shape & textureShape & texture
– PressurePressure
» Degree of distortionDegree of distortion
– VibrationVibration
» Pulsing or oscillating pressurePulsing or oscillating pressure
Classifying Sensory Receptors Three Classes of Mechanoreceptors Three Classes of Mechanoreceptors
2.2. Baroreceptors Baroreceptors
Detect pressure changes in Detect pressure changes in
– Walls of blood vessels Walls of blood vessels
– Portions of the digestivePortions of the digestive
– Portions of the reproductivePortions of the reproductive
– Portions of the urinary tractsPortions of the urinary tracts
Classifying Sensory Receptors
Three Classes of Mechanoreceptors Three Classes of Mechanoreceptors
3.3. Proprioceptors Proprioceptors
Monitor the positions of joints and musclesMonitor the positions of joints and muscles
The most structurally and functionally complex of The most structurally and functionally complex of
general sensory receptorsgeneral sensory receptors
Classifying Sensory Receptors Tactile ReceptorsTactile Receptors
– Fine touch Fine touch andand pressure receptors pressure receptors
Are extremely sensitiveAre extremely sensitive
Have a relatively narrow receptive fieldHave a relatively narrow receptive field
Provide detailed information about a source of Provide detailed information about a source of
stimulation stimulation
– Including its exact location, shape, size, texture, Including its exact location, shape, size, texture,
movementmovement
Classifying Sensory Receptors Tactile ReceptorsTactile Receptors
– Fine touch Fine touch andand pressure receptors pressure receptors
Are extremely sensitiveAre extremely sensitive
Have a relatively narrow receptive fieldHave a relatively narrow receptive field
Provide detailed information about a source of Provide detailed information about a source of
stimulation stimulation
– Including its exact location, shape, size, texture, Including its exact location, shape, size, texture,
movementmovement
Classifying Sensory Receptors
Tactile ReceptorsTactile Receptors
– Crude touch Crude touch andand pressure receptors pressure receptors
Have relatively large receptive fieldsHave relatively large receptive fields
Provide poor localizationProvide poor localization
Give little information about the stimulusGive little information about the stimulus
Classifying Sensory Receptors Six Types of Tactile Receptors in the SkinSix Types of Tactile Receptors in the Skin
1.1. Free Nerve Endings Free Nerve Endings
Sensitive to touch and pressureSensitive to touch and pressure
Situated between epidermal cellsSituated between epidermal cells
Free nerve endings providing Free nerve endings providing touch sensations are tonic touch sensations are tonic
receptors with small receptive fieldsreceptors with small receptive fields
Classifying Sensory Receptors Six Types of Tactile Receptors in the Skin Six Types of Tactile Receptors in the Skin
2.2. Root hair plexus Root hair plexus nerve endingsnerve endings
Monitor distortions and movements across the body surface Monitor distortions and movements across the body surface
wherever hairs are locatedwherever hairs are located
Adapt rapidly, so are best at detecting initial contact and Adapt rapidly, so are best at detecting initial contact and
subsequent movementssubsequent movements
Classifying Sensory Receptors Six Types of Tactile Receptors in the Skin Six Types of Tactile Receptors in the Skin
3.3. Tactile discsTactile discs
Also called Also called Merkel discsMerkel discs
Fine touch and pressure receptorsFine touch and pressure receptors
Extremely sensitive to tonic receptors Extremely sensitive to tonic receptors
Have very small receptive fieldsHave very small receptive fields
Classifying Sensory Receptors Six Types of Tactile Receptors in the SkinSix Types of Tactile Receptors in the Skin
4.4. Tactile corpusclesTactile corpuscles
Also called Also called Meissner’s corpusclesMeissner’s corpuscles
Perceive sensations of fine touch, pressure, and low-Perceive sensations of fine touch, pressure, and low-
frequency vibrationfrequency vibration
Adapt to stimulation within 1 second after contactAdapt to stimulation within 1 second after contact
Fairly large structuresFairly large structures
Most abundant in the eyelids, lips, fingertips, nipples, Most abundant in the eyelids, lips, fingertips, nipples,
and external genitaliaand external genitalia
Classifying Sensory Receptors Six Types of Tactile Receptors in the Skin Six Types of Tactile Receptors in the Skin
5.5. Lamellated corpuscles Lamellated corpuscles
Also called Also called Pacinian corpusclesPacinian corpuscles
Sensitive to deep pressureSensitive to deep pressure
Fast-adapting receptorsFast-adapting receptors
Most sensitive to pulsing or high-frequency vibrating stimuliMost sensitive to pulsing or high-frequency vibrating stimuli
Meissner’s vs Pacinian If you close your eyes and have a friend place an object in the open If you close your eyes and have a friend place an object in the open
palm of your hand, chances are good you will be able to detect the palm of your hand, chances are good you will be able to detect the object but you will not be able to identify it. object but you will not be able to identify it.
By moving the object to your finger tips where Meissner's corpuscles are By moving the object to your finger tips where Meissner's corpuscles are abundant, you gather information about its shape, texture, and density, abundant, you gather information about its shape, texture, and density, information your brain uses to identify the object. information your brain uses to identify the object.
– The Pacinian corpuscles enable you to detect the object due to its The Pacinian corpuscles enable you to detect the object due to its
weight. weight. – Meisner’s enable you to define it by fine touchMeisner’s enable you to define it by fine touch
Classifying Sensory Receptors Six Types of Tactile Receptors in the SkinSix Types of Tactile Receptors in the Skin
6.6. Ruffini corpusclesRuffini corpuscles
Also sensitive to pressure and distortion of the skinAlso sensitive to pressure and distortion of the skin
Located in the reticular (deep) dermisLocated in the reticular (deep) dermis
Tonic receptors that show little if any adaptationTonic receptors that show little if any adaptation
Classifying Sensory Receptors BaroreceptorsBaroreceptors
– Monitor change in pressureMonitor change in pressure
– Consist of free nerve endings that branch Consist of free nerve endings that branch
within elastic tissues within elastic tissues
In wall of distensible organ (such as a blood In wall of distensible organ (such as a blood
vessel)vessel)
– Respond immediately to a change in Respond immediately to a change in
pressure, but adapt rapidlypressure, but adapt rapidly
Classifying Sensory Receptors
ProprioceptorsProprioceptors
– Monitor:Monitor:
Position of jointsPosition of joints
Tension in tendons and ligamentsTension in tendons and ligaments
State of muscular contractionState of muscular contraction
Classifying Sensory Receptors
Three Major Groups of Proprioceptors Three Major Groups of Proprioceptors
1.1. Muscle spindles Muscle spindles
2.2. Golgi tendon organsGolgi tendon organs
3.3. Receptors in joint capsules Receptors in joint capsules
Classifying Sensory Receptors
Muscle Spindles Muscle Spindles
– Monitor skeletal Monitor skeletal
muscle length muscle length
– Trigger stretch Trigger stretch
reflexesreflexes
Classifying Sensory Receptors Golgi Tendon OrgansGolgi Tendon Organs
– Located at the junction between skeletal muscle and its tendon Located at the junction between skeletal muscle and its tendon
– Stimulated by tension in tendonStimulated by tension in tendon
– Monitor external tension developed during muscle contractionMonitor external tension developed during muscle contraction
Classifying Sensory Receptors Receptors in Joint Capsules Receptors in Joint Capsules
– Free nerve endings detect pressure, tension, Free nerve endings detect pressure, tension,
movement at the jointmovement at the joint
ChemoreceptorsChemoreceptors
Respond to small concentration Respond to small concentration changes of specific molecules changes of specific molecules (chemicals)(chemicals)
Internal chemoreceptors monitor Internal chemoreceptors monitor blood composition (e.g. Nablood composition (e.g. Na++, pH, , pH, pCOpCO2 2 ))
Found within aortic and carotid Found within aortic and carotid bodiesbodies
Very important for homeostasisVery important for homeostasis
ChemoreceptorsChemoreceptors
Respond to small concentration Respond to small concentration changes of specific molecules changes of specific molecules (chemicals)(chemicals)
Internal chemoreceptors monitor Internal chemoreceptors monitor blood composition (e.g. Nablood composition (e.g. Na++, pH, , pH, pCOpCO2 2 ))
Found within aortic and carotid Found within aortic and carotid bodiesbodies
Very important for homeostasisVery important for homeostasis
IN REVIEW
IN REVIEW