sistem sensoris kulit (dr.dini)
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Fisiologi Kulit dan Somatosensoris
Dr. Dini Sri Damayanti,M.Kes
Kulit
• Terdiri dari 2 lapis :
– Superfisial : epidermis yang terdiri dari jaringan epitel stratified squamous compleks
– Profunda : dermis yang terdiri dari jaringan ikat
Fungsi kulit
• Sebagai pelindung terhadap benturan, kimia, suhu, kuman , sinar matahari,dll
• Sebagai pengatur suhu tubuh• Sebagai tempat ekskresi sisa metabolisme• Mengandung reseptor yang berfungsi sebagai
penerima dan meneruskan rangsangan
Epidermis
• Terdiri dari epitel stratified squamous compleks dengan keratinisasi
• 4 tipe sel yaitu sel keratinosit, sel melanosit, sel Langerhans dan sel Merkel
• Sel keratinosit : penyusun utama dari epidermis, selalu mengalami mitosis,bila mengalami kematian akan terbentuk lapisan tanduk
Lapisan dari epidermis:1. Stratum basale
• lapisan paling dalam berbatasan dengan dermis
• Disebut juga stratum germinativum• Merupakan stem sel dari keratinosit dan aktif
bermitosis• Terdapat sel Merkel yang merupakan sensori
nerve ending• Terdapat sel melanosit yang berfungsi
membentuk pigmen melanin
2. Startum spinosum• Merupakan lapisan yang terdiri dari sel
keratinosit, mitosis lebih sedikit daripada sel basal.
• Terdapat Sel Langerhans yang merupakan sel macrofag yang berperan dalam sistem imun (fagositosis kuman).
3. Stratum granulosum• Mengandung sel keratinosit pipih,
menghasilkan glikolipid yang membuat kulit bersifat waterproof
• Sel sangat tebal sehingga merupakan lapisan pelindung
4. Stratum lucidumdisebut juga zona transisional
5. Stratum corneumTerdiri dari sel-sel kerotinosit yang mati
Dermis
• Terdiri dari jaringan ikat fibroblast, kolagen, elastik dan retikuler
• Mengandug sel-sel macrofag• Banyak terdapat ujung saraf dan pembuluh
darah 5% dari seluruh tubuh
Lapisan dermis
1. Lapisan papilaris- Lapisan superfisial - Terdapat dermal papilaris- Polanya diturunkan secara genetik dan unik untuk tiap individu
2. Lapisan retikuler- Terdiri dari jaringan kolagen dan elastik- Berfungsi sebagai penahan terhadap streching
Hipodermis
• Terdiri dari jaringan lemak• Merupakan depo lemak • Berfungsi segabai insulator
Bentukan yang ada di kulit
1. Folikel rambut• Terdistribusi diseluruh permukaan tubuh
kecuali, tepalak tangan+kaki , putting susu, sebagian dari genetalia eksterna (glan pennis)
• Pigmen rambut dihasilkan oleh melanosit.• Terdapat muskulus erector pili
2. Glandula sebacea• Bermuara di folikel rambut• Menghasilkan sebum• Berfungsi untuk melembabkan kulit, mengurangi
pengeluaran air, dan • membunuh bakteri3. Kelenjar keringat• Berfungsi untuk mengatur suhu tubuh• Terdiri dari 90% air dan garam• Berasal dari filtrasi pembuluh darah• Terdiri dari ekrine dan apokrine• Bermuara di folikel rambut
Kuku
1. Merupakan keratinisasi yang padat2. Warna merah muda pada kuku disebabkan
adanya kapiler darah dibawahnya3. Bagian yang aktif tumbuh disebut matriks kuku
• Stimulus– Internal– External
• Receptors– Sense organs– Transducer
• Afferent pathway• CNS integration
General Properties of Sensory Systems
Type of sensoris system
General sensoris• temperature• pain• touch• pressure• vibration• proprioception
Special sensoris
• smell• sight• taste• hearing
General Properties of Sensory Systems
Figure 10-4: Sensory pathways
Sensoris Receptor
interface between environment and the body
translate stimulus into an AP
receptors distributed throughout the body relatively simple
receptors send info to CNS :• arriving info is called sensation• our awareness of it is perception
• receptors have selective sensivity :
chemicalphysical touchlightheat transfer
Receptor Potential
• Membrane potential of the receptor• A change in the receptor potential is
associated with opening of ion (Na+) channels• Above threshold as the receptor potential
becomes less negative the frequency of AP into the CNS increases
Adaptation
• reduction in sensitivity in the presence of a constant stimulus
Pheriferal : change in receptor activityCentral : inhibition of nuclei in pathway
• adaptation reduces the amount of information reaching the cerebral cortex
about 1% of sensory information coming in reaches our awareness
Adaptation
• Slow-provide continuous information (tonic)-relatively non adapting-respond to sustained stimulus– joint capsul– muscle spindle– Merkel’s discs
• punctate receptive fields
– Ruffini end organ’s (corpusles)• activated by stretching the skin
Adaptation
• Rapid (Fast) or phasic• react strongly when a change is taking place• respond to vibration
– hair receptors 30-40 Hz– Pacinian corpuscles 250 Hz– Meissner’s corpuscles- 30-40 Hz– (Hz represents optimum stimulus rate)
• “Stimulation of a receptor produces action potentials along the axon of a sensory neuron. The frequency or pattern of action potentials contains information about the strength, duration, and variation of the stimulus. Your perception of the nature of that stimulus depends on the path it takes inside the CNS.”
• Simple receptors• Complex neural• Special senses• Chemoreceptors• Mechanoreceptors• Thermoreceptors• Photoreceptors
Sensory Receptor Types
Sensory Receptor Types
Figure 10-1: Sensory receptors
• Receptor– Threshold– Action potential
• Sensory neurons– Primary – medulla – Secondary – thalamus– Tertiary – cortex
• Integration– Receptive field– Multiple levels
Somatic Pathways
Somatic Pathways
Figure 10-9: Sensory pathways cross the body’s midline
• Location– Lateral inhibition– Receptive field
• Intensity• Duration• Tonic receptors• Phasic receptors• Adaptation
Sensory Modality
Sensory Modality
Figure 10-3: Two-point discrimination
Sensory Modality
Figure 10-6: Lateral inhibition
Type sensoris receptor based on nature stimulus
• Nociceptors : pain
• Thermoreceptors : heat flow
• Mechanoreceptors : physical distortion
• Chemoreceptors : chemical consentration
Nocireseptor
• common in:– skin– joint capsules– coverings of bones– around blood vessel walls
•free nerve endings
•large receptive fields
• sensitive to:–extreme temperature –mechanical damage–dissolved chemicals
• (like those release by damaged cells)
• two fiber types convey info• type A
– fast pain (cut, etc.,)– easy to localize
• type C– slow pain (“burning, aching”)– difficult to localize
• tonic receptorsno significant peripheral adaptation as long as the stimulus is present, it will hurt
• but central adaptation can occur (perception of pain may decrease)
• sensory neurons bringing in pain info use glutamate and/or substance P as their neurotransmitter
• these nts can cause facilitation (?)pain may be disproportional (feels worse than it should)
• pain can be reduced by endorphins and enkephalins (inhibit activity in pathway)
Pain vs. Nociception
• Nociception-reception of signals in CNS evoked by stimulation of specialized sensory receptors (nociceptors) that provide information about tissue damage from external or internal sources– Activated by mechanical, thermal, chemical
• Pain-perception of adversive or unpleasant sensation that originates from a specific region of the body– Sensations of pain
• Pricking, burning, aching stinging soreness
Sensitization of Nociceptors
• Potassium from damaged cells-activation• Serotonin from platelets- activation• Bradykinin from plasma kininogen-activate• Histamine from mast cells-activation• Prostaglandins & leukotriens from arachidonic
acid-damaged cells-sensitize• Substance P from the 1o afferent-sensitize
Nociceptive pathways
• Spinothalamic-major – neo- fast (A delta)– paleo- slow (C fibers)
• Spinoreticular• Spinomesencephalic• Spinocervical (mostly tactile)• Dorsal columns- (mostly tactile)
Pain and Itching
Figure 10-12: The gate control theory of pain modulation
Thermoreceptor
free nerve endings in the dermis, skeletal muscle, hypothalamus and liver
warm receptors or cold receptors
phasic receptors active when temperature is changing, quickly adapting to stable temperature
detect transfer of heatheat loss from skin :coolheat gain to skin : warm
Mechanoreceptor
• contain mechanically regulated ion channels
3 type of mechanoreceptor:•Tactil receptor :touch, pressure, vibration•Baroreceptor : pressure changes(gut, genitourinary)•Propioreceptor : position of joints/muscles
Touch (pressure)
Figure 10-11: Touch-pressure receptors
Mechanoreceptors in the Skin
• Rapidly adapting cutaneous– Meissner’s corpuscles in glabrous (non hairy) skin-
(more superficial)• signals edges
– Hair follicle receptors in hairy skin – Pacinian corpuscles in subcutaneous tissue
(deeper)
Mechanoreceptors in the Skin
• Slowly adapting cutaneous– Merkel’s discs have punctate receptive fields
(superficial)• senses curvature of an object’s surface
– Ruffini end organs activated by stretching the skin (deep)
• even at some distance away from receptor
Baroreceptor
• free nerve endings in the walls of organs that stretch–e.g., blood vessels
when pressure changes they expand or contract
Proprioreceptor
1. Type of proprioreceptor:• Muscle spinde: stretch reflex• Golgi tendon organ : monitor tendon
tension• Receptor in joints capsule : free nerve endings in joints2. no adaptation3. continuously send info to CNS4. most processed at subconscious level
Somatosensory Cortex
• Two major pathways– Dorsal column-medial lemniscal system
• Most aspects of touch, proprioception
– Anterolateral system• Sensations of pain (nociception) and temperature• Sexual sensations, tickle and itch• Crude touch and pressure• Conduction velocity 1/3 – ½ that of dorsal columns
Somatosensory Cortex (SSC)• Inputs to SSC are organized into columns by
submodality– cortical neurons defined by receptive field &
modality– most nerve cells are responsive to only one
modality e.g. superficial tactile, deep pressure, temperature, nociception
• some columns activated by rapidly adapting Messiner’s, others by slowly adapting Merkel’s, still others by Paccinian corp.
Somatosensory cortex• Brodman area 3, 1, 2 (dominate input)
– 3a-from muscle stretch receptors (spindles)– 3b-from cutaneous receptors– 2-from deep pressure receptors– 1-rapidly adapting cutaneous receptors
• These 4 areas are extensively interconnected (serial & parallel processing)
• Each of the 4 regions contains a complete map of the body surface “homonculus”
Other Somatosensory Cortical Areas• Posterior parietal cortex (BM 5 & 7)
– BM 5 integrates tactile information from mechanoreceptors in skin with proprioceptive inputs from underlying muscles & joints
– BM 7 receives visual, tactile, proprioceptive inputs • intergrates stereognostic and visual information
– Projects to motor areas of frontal lobe– sensory initiation & guidance of movement
Secondary SSC (S-II)
• Secondary somatic sensory cortex (S-II)– located in superior bank of the lateral fissure– projections from S-1 are required for function of
S-II– projects to the insular cortex, which innervates
regions of temporal lobe believed to be important in tactile memory
Somatomotor area
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