General Senses Sensation: Sensation: An impression from the effective stimulation of sensory receptors Sensory Receptors Structures present in the body, which are responsible for responding to different stimuli Alias: Alias: Body Transducers Input: Input: Chemical; Output: Output: Electrical Convert the mechanical stimuli to an Action otential o Review: Action Potential is the Nervous System’s Language Every receptor is capable of generating an Action otential !st structure affected by a change inside and outside of the body "ery low threshold for a particular stimulus Adequate Stimulus: Stimulus: every receptor has its own ade#uate Stimulus Specificity: Specificity: specific change and specific receptor $t may be part of a neuron or a speciali%ed cell that initiates generation of Action otential in a neuron &ncommon: 'eceptors being part of a neuron acting as a receptor (E)* +ree erve ending such as -lfactory receptor. Common: 'eceptors are speciali%ed cells Capable of Adaptation
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$f the receptor e)posed to an ade#uate stimulus with a threshold intensity, the receptor continuously fires an Action otential* o The importance of repetitive firing of A** by an activated sensory receptor is to continuously be aware of the stimulus0sensation* o +re#uency of discharge is related to the stimulus1 strength
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What happens when a receptor is activated? Sensory arm of the reflex arc Activation of Sensory 'eceptors Activation of Sensory Afferent eurons Center (Brain. Awareness of the Sensation •
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Local Response Alias: /enerator potential or Subthreshold potential otential of a Sensory receptor • •
/ener /e neral al Senses Sen ses
What will happen if there is are anormalities? !may e pertaining to any part of the refle" refle" arc# $ncrease or 2ecrease Sensation Absence of Sensation o $f there is an Absence of Sensation, there will be no reaction • •
Sensory Threshold Capacity of the sensory arm to process a stimulus 2ependent on the Sensory Arm What can affect the $hreshold? o Sensory Capacity o revious E)posure to a stimulus, especially if the previous e)posure left an unpleasant e)perience o Attitude of the sub3ect towards the sensory e)perience Types of Sensation • • •
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Can be classified according to the location of the receptor and the structure of the receptor E)teroceptive: E)ternal, Superficial receptor; 'eceptor capable of responding to an e)ternal stimuli $nterocepive: $nternal Epicritic: 4ocali%ed (E)* Touch, ressure. rotopathic: oorly 4ocali%ed (E)* "isceral ain. Special: $nvolved receptors in specific body parts, utili%es the same structure with the general receptor (E)* "ision. /eneral: Somatic Sense, involves all receptors in the body (E)* +ats 5 ressure and ain. -TE: E#uilibriums can be special or general o Special because it is present in the inner ear as the vestibule apparatus and saccule o /eneral because balance re#uire proprioceptors of the muscles and eyes 'emember, if it re#uires the help of the proprioceptos it can be considered /eneral $mmediate0Acute: Sudden Sensation 2elay0Chronic: 4onger latency before the person can be aware o $mmediate and 2elay sensation is characteri%ed by the type of sensory neuron utili%ed by the sensation receptor since some neurons are fast conducting and slow conducting o +astest are Type A alpha; Type C is slow $nfluenced by the presence or absence of myelin and the diameter Classification •
/eneral Senses
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/roup $ a: 6uscle spindle, 6yelinated; +astest /roup $b: /olgi tendon organ 6yelinated /roup $$: +ine touch +ine pressure, 6uscle spindle and 6yelinated /roup $$$ crude touch crude ressure, pain and temp myelinated 7777 dual sensation 78 type A alpha /roup $" crude touch, crude pressure, itch, pain and temp unmyelinated 78 type C neurons 777 dual sensation
Dual sensation Affector ! Affector 9 Center &ses 9 eurons, Type A and Type C Thus there is a chronic and acute sense of pain E)ample: Ticle Sensation: Crude Touch and Crude ressure • • • •
Parameters Immediately Knon !y a Person Affected "uality of #odality of sensation: Type of stimulus that is affecting the specific sense Stimulus intensity Location$Topo%nosis: 2etermine the body part stimulated; ability to recycle the body part being stimulated o Stereognosis: $dentify ob3ects by means of touch •
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9 oint 2iscrimination: Affected by 9 2ifferent stimuli at the same time Timing of Stimulus: Application and removal of stimulus
&hat affects the "uality or #odality of a Sensation Specificity of the 'eceptor La of specific 'er(e )ner%ies o Specificity is also observed in the sensory neuron and even up to teh center (E)* "ision 'ods and Cones<. -ptic Chiasm is part of the optic pathway -ptic nerve Converts -ptic Tract -ccipital 4obe -ccipital 4obe number != o 2escribed by 6uller1s 2octrine 5 euron 4abeled 4ine rinciple: Seen in the sensory afferent nerve, it follows a specific line to transmit the impulses to the center Codin% mechanism: $nvolved the manner of a)on transmission by the activated receptor dependent on the number of receptor activated
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Codin% mechanism Temporal pattern codin% o The center will immediately now that the stimulus affecting the body based on the manner of discharge Sensation depend on the pattern of neuronal activity Temp > ?@ euron firing in bursts •
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/eneral Senses
Temp 8 ?@ euron is continuous with high fre#uency A** is transmitted to the corte) Spatial Pattern Codin% o Sensation depends on teh number of neurons and receptors activated o 'eceptors of taste is due to simultaneous activation of ? neurons (? Taste 'eceptors. o Salty taste is due to the simultaneous activation of 9 neurons o Ability to determine color (Cones, ow many groups of color sensitive cones: ? '/B<. hite: All cones are stimulated in the same intensity •
Stimulus Intensity: +re#uency of A** Poer La: 2irect relationship of fre#uency and power of discharge o By 2r* Steven &e!er *echner La: 6agnitude of sensation felt o Sensation is dependent on the stimulus intensity o -bserved that the magnitude felt is related to the logarithm of stimulus intensity $t means we have to create a change that is at least e#ual to @D of the previous intensity E)* /uyton en F eight change not felt; /uyton 6oore F eight change felt 'um!er of Receptors o 'ecruitment of sensory units Sensory receptor and afferent nerve (!:!. •
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Every sensory unit in the body has its own sensory receptive field Sensory Receptor: Area in the body controlled by the receptor, superficial body parts and visceral tissue ending in the sensory areas of the high center Also note, other than the corte), thalamus also capable of analy%ing sensory stimulation Topo%nosis Ability to precise the locali%ation of the body part stimulated The accuracy of the identified position of stimulation is the same even if our eyes where opened or closed The sensation can be easily locali%e when the eyes are closed because it is not affected by any other sensory stimulation The law of pro3ection e)plains a very good topographic ability Sensory unit of the receptive field: the greater the number of receptor in the sensory unit, the bigger the receptive field, Surround Inhi!ition$Lateral Inhi!ition #echanism: Enhance topognotic ability o $f you stimulate a group of receptors, you cannot activate the ad3acent units, despite the wea stimulation it was sub3ected with* o The activated receptor field inactivates the ad3acent receptor* o Ad3acent region is stimulated, but the activity is less, so the center only receives the receptors greatly stimulated so the ad3acent neurons will now be inhibited* As a result the transmission of impulses will stop but the area of ma)imum stimulation will continue and that will enhance tropognotic ability
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resence of the sensory homunculus (rimary Sensory Area, Brodmann areas (!,9,?. post central gyrus, somesthetic corte), somatic sensory area !, post central areas ?*!*9 o 6ost represented is the face (Especially the lower lips., hand and foot o 4east represented: "isceral organs (Changes in the organs are protopathic.
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La of Pro+ection 'eceptor Corte) 'eceptor 2ependent on the 4ocation o matter where the sensory neuron is stimulated along its course to the sensory corte), the conscious sensation produced is referred to the location of teh sensory receptors using the activated sensory neuron o E)* hantom 4imb • •
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Sensiti(ity %ow did they &now the face have greater sensitivity than the hands? %ow aout why the ventral surface of the hand is more sensitive than the dorsal? 9 oint 2iscrimination Test: performed by e)posing part of the body to 9 stimuli and determining the sensitivity* Before this is performed, the 9 point threshold is identified* 9 oint Threshold: $s the smallest distance where the 9 point stimuli are perceived as 9 o The lesser the 9 point threshold, the greater is the sensitivity, thus it is inversely proportional o The smaller the 9 point threshold the greater the sensitivity Stereognosis 2ermatographia •
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/eneral Senses
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Adaptation ,desensiti-ation. appens if there is a continuous e)posure to a non changing stimulus activity, you can observe that in the activated receptors will stop the firing of A**, thus there is no sensation Some receptors can adapt but most cannot, the adaptation can be fast or slow 'apidly adapting receptors, aa 'ate0hasic06ovement receptors o Adapting 'eceptors ow +astH $mmediately After a few seconds or a few minutes E)ample: 2ar and light adaptation involving the photoreceptors E)* acinian can adapt in less than a second o on Adapting 'eceptors ow SlowH ours or 2ays E)* ormali%ing Blood ressure, Baroreceptors E)* ain receptors: are capable of changing their threshold for stimulation 6echanism for Adaptation o 'ead3ustment in the shape of the structure of the sensory receptor, such as teh pacinian once the pacinian morph, it stops firing o Change in the chemical agent used (E)*: hotoreceptors. o Accommodation in the terminal nerve fiber ($nactivation of a Channels.: o more activation of the sensory nerve and neuron Adapted 'eceptor does not mean it is refracted (But to be stimulated again, it must change the intensity.
What is the important of this aility to adapt? To allow some areas of the brain to rest •
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/eneral Senses
Requirements for Adaptation to !e O!ser(ed E)posure should be continuous to its ade#uate stimulus Consistent Stimulus $ntensity Stimulus $ntensity should be low to moderate, we cannot observe adaptation to receptor using a high stimulus intensity •
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Types of %eneral senses #echanorecepti(e: Somatic sense, 6echanical Sensation 6eissner1s o on hairy body parts are sensitive o Can detect touch and low fre#uency vibration (?@ to I@ cps. o hasic: +ast Adapting acinian o 2etects touch pressure and vibration o igh fre#uency: ?@ to I@@ cps 6erel1s dis epithelial cells o ill group together that will form a dome o Alias: $ggo dome receptor o resent in hairy body parts, mechanoreceptors, tonic receptors and detect touch pressure Thermorecpti(e 'uffini End -rgan o arm sensitive receptors can also detect touch pressure, proprioception o Tonic 'eceptor Jrause and Bulb: Cold 'ocicepti(e (E)* Tissue 2amage. •
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*ree ner(e endin% "ery sensitive 2etect touch pressure, pain Tonic receptors
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#echanorecepti(e senses Touch: stimulative, non discrimatory ressure: stimulative, non discrimatory "ibration Ticle and $tch: non discrimatory osition o 9 types of proprioception Static: stationaryaa proprioception< 2ynamic: in motion aa inestheisa< • • • • •
Thermorecepti(e senses arm and cold stimuli Also capable of causing pain sensations Cold sensitive receptors o /reater in number o &se type A delta and type C neurons o Activity is greatest at 9 degree C arm sensitive thermoreceptors o +ewer in number, use type C neurons Tonic sense, lingering sensation< o Activity is greatest at GG degree C ain sensitive thermoreceptors o &tili%e type A and type C neurons o Stimulated at temp below !C and above GC • • •
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Thermal sensation re#uires the body to gain or lose heat, but if it is e)posed to an identical temperature, there is no heat transfer, thus no thermal sensation Adaptation possible at temp between 9@C to G@C Thermal sense will depend on the termperature o ! to 9 C : Cold o 9 to ?= C: Cold to arm o Above ?= C: ot o ?K to ?= C: E#ual stimulation of cold and warm sensitive thermoreceptors; indifferent, cannot determine if cold or warm o @ to !@ ain o !@ to ! Cold ain o ?= ot o 8 G ain
'ocicepti(e senses ,#ostly affected !y facilitation /enhance0 and inhi!it /decrease0. #echanosensiti(e nociceptors +ast pain: Type A 2elta neurons Thermosensiti(e nociceptors +ast and slow pain Thermal and ain receptors : 2ual Sense Type A delta and type C neurons Chemosensiti(e nociceptors Slow and lingering pain $nflammation of tissue0$n3ury o Cardinal signs of inflammation: 'edness, swelling, pain, loss of function Type C neurons Arterial alls (That is why 6ed Techs get blood from the "eins. Loints leura: Covering of 4ungs •
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Tissue ith numerous nociceptors Superficial 4ayers of the Sin eriosteum • •
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/eneral Senses
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Cranial "ault: +al) and tentorium Thus Pain receptors are found in Tissue co(erin%s
hen there is tissue in3ury, withdrawal and pain refle) (Aa nociceptive refle), fle)or refle). )xample of chemicals that can acti(ate the chemosensiti(e nociceptor1 factors0 ain causing factos o roduce by the in3ured tissue o Bradyinin: Can cause the most severe pain o Serotonin o istamine o Acid: 4actic acid; prolonged anaerobic activity; characteristics: pin pricing needles on the sin o Ach o roteases o ydrogen0otassium ions o rotaglandins: are pain causing factors but they are not capable of directly stimulating pain receptors* $nstead they are capable of changing the e)citability of the neurons of pain endings; 6ae the pain ending more sensitive to the other factors factors enhance the sensitive of mechanosensitive and thermosensitive nociceptors by decreasing their threshold for stimulation o As a result, slight movement to the in3ured body part can add additional pain •
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yperpathia: ain insensitive, inhibition of ain yperalgesia: ain sensitive o rimary: roblem is observed in teh region of the pain receptors, especially underneath the sin (E)* Sun Burn. /eneral Senses
Secondary: not in the region of pain receptors but at the center 5 spinal cordmost of the time< or brain* $t is an immediate attac o Allodynia: Supersensitive Pain is due to o ocious stimuli that can cause tissue damage Pain under%o facilitation due to1 o Psycholo%ical factors o Se): +emales are more sensitive o Age: Senior citi%ens are more sensitive o Cognitive 4evels o revious ains o +amily 4earning Culture o Situational *actors o E)pectation o Control relevance o )motional *actors o +ear: Enhance o Anger: $nhibit o +rustrations o
Pain pathays Acute$*ast pain pathay o 'eospinothalamic Pathay (Aa anterolateral pathway. o &se type A delta neurons o Transmit to the thalamus Cerebral Corte) Cortical 'egion is responsible for analy%ing teh acute pain impulses o Chronic$Slo Pain pathay (2elayed pain sensation. o Paleospinothalamic Pathay &ses type C neurons Thalamus analy%es slow pain pathway
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Transmit impulses only up to the thalamus
Acute$*ast Pain Pathay Characteristic o asses at 4amina ! and , but mostly 4amina ! o &ses mostly /lutamate, sometime substance Also a neurotransmitter< o $mpulses reaches the ventrobasal comple) and posterior nuclear group of the thalamus o Some fibers may reach the cerebral corte) o Associated with epicritic Sense: 'eaches the sensory homunculus, usually superficial tissue in3ury Chronic slo pain pathay o &ses mostly type C sometimes type A delta fibers o asses at 4amina 9 and ? (Enters at the 2orsal orn. o eurotransmitter: Substance sometimes /lutamate o $mpulses reach the reticular formation, some enter the intralaminar nuclei of the thalamus o Associated with protopathic sense: Thus purely locali%ed, thus it is mostly viscera in3uries Pain sensations o Classification according to location o sin0superficial0parietal pain o ro3ected ain o hantom limb pain o 2ue to the e)posed euron o -ccurs as a result to scheduled amputation of the limb, accidents o "isceral ain02eep ain: "isceral tissues o 'eferred ain: Actual in3ury is present in the visceral tissue, however the paintient wil complain of a pain distal from the actual site of in3ury o This is due to the same entry levels of the visceral nerve fibers and the sin nerve fibers* The corte) /eneral Senses
becomes confused* But if the viscera is more damaged, the visceral receptors will be more stimulated* Pain Sensations o Always associated with the changes in teh activity of the autonomic nervous system o ain perception decreases whenever there i simultaneous activation of other somatic receptors The reason !ehind hy massa%e the alle(iates pain 6echanoreceptor inhibitory interneuron Spinothalamic euron $nhibit ain< Pain Suppression o M/ating neuronN o resent in the dorsal horn, at lamina 9 called substantia gelatinosa o Analgesia System (Brainstem. o eria#ueductal /ray Area (6idbrains and &pper pons. o 'aphe 6agnus nucleus (4ower pons and upper 6edulla. o ain inhibitory comple) (2orsal horn of the spinal cord. Anal%esia System o Enephalin neurons (2orsal horn. sorotonergic neurons ('aphe nuclei. eria#ueductal /ray Area o The enephalin are morphine lie Agents that can suppress the activity of the pain fibers of type A and type C o The serotonin don1t suppress, but rather enhance the activity of the enephalin neurons, causing more pain suppression I
This is achieved by reducing the impulses to the corte) By Continuously e)posing the body to a painful stimuli, an active analgesia system is achieved o
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Su!stancia 2elatinosa o 2oes not need development, but can immediately convert a pain sensitive person to a hyperpathic person o Can happen in a sudden increase in a cortical neuron o Corte) can suppress the activity of pain fibers Purpose of Pain o arning of a threat o +orces the person to rest o Basis of 4earning 3ell #a%endie La: "entral roots 5 6otor, Sensory roots 5 2orsal Sensory Ascendin% Pathays 45 Dorsal Column$#edial Lemniscal Pathay o 4imited to mechanoreceptive senses: 4imited to discriminative mechanical sensation o 2ecussation occurs in the medulla o 4arge myelinated neurons: ?@ to !@@ m0s o &ses /roup 9 neurons (type A Beta neurons. o igher degree of spatial orientation (Brain. o +ine gradation of stimulus intensity o Smaller receptive field o -ne neuron carries one sensation o -nly 9 or ? synapses going to the corte) o &ses the gracilis and cuneatus nuclei: 2ivide the body into 9, division from teh symphysis pubis o Associated with epicritic senses /eneral Senses
Tests: Stereognosis, 2ermatographica, "ibration, ressure, 9 oint 2iscrimination, roprioception o !st order neurons are longer o 2oes not use the central region of the spinal cord 65 Anterolateral$Spinothalamic Pathay o Capable of transmitting many impulses, not limited to mechanical sensation o Broad spectrum of sensory modalities mechanical (non discrimitive sensation, e)emplified by a ticle and itch., thermal sensation, pain sensation o $mmediate decussation in the spinal cord o Small, myelinated neurons F> ?@ m0s o &ses /roup ? and /roup G neurons (Type A and Type C. o 4esser degree of spatial orientation (brain. o 4acs the fine gradation of stimulus intensity o Bigger receptive fields o #ultimodal1 Several sensations carried into one neuron (! ** O. o #ultisynaptic1 ? synapses going to the corte) o Associated with protopathic senses o 2oes not use /racilis and Cuneatus uclei o Shorter !st order neuron o $mpulses entring the dorsal horn immediately crosses the center of the spinal cord o Cornered with Se)ual Sensation o
Remem!er your neurons: o !st order: spinal cord o 9nd order: decussation o ?rd order: thalamus to corte) P
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La!eled line principle: the receptor present the a particular part of the body uses a certain nerve to transmit impulses, thus the dermatomes are conceptuali%ed Sensory A!normalities: Brown Se#uard, emisection of the spinal cord, Tabes 2orsalis, Syringomyelia, -cclusion of cord anterior and posterior arteries
/eneral Senses
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