SUHU TUBUH (ST) (Pengaturan Homeostatis Suhu Tubuh)dr. Halinda Sari Lubis, MKKKFakultas Kesehatan Masyarakat USUMedan, Indonesia

Kenapa menjaga keseimbangan Suhu Tubuh menjadi PENTING ? Laju aktifitas ENZIM dipengaruhi oleh Temperatur/Suhu

SUHU TUBUH & METABOLISMESuhu mempengaruhi metabolisme organisme dgn mempengaruhi kecepatan reaksi kimia dan efektifitas kerja enzim.

Tanpa pengaturan SUHU TUBUH saat olahraga, suhu tubuh akan meningkat melebihi batas yang mengakibatkan kematian. Beberapa atlit mati karena heat stress karena alasan ini. Penting untuk dipahami, bagaimana tubuh mengatur keseimbangan suhunya.

Manusia adalah homeothermic.SuhuTubuh internal (core) : 36.1 - 37.80C.

keseimbangan Suhu Tubuh menyerupai keseimbangan ENERGY Heat Gain (HG) = Pembentukan PanasHeat Loss (HL) = Pembuangan Panas

HG >> HL = + ST meningkat HG

Faktor yg mempengaruhi HG/pembentukan panasBMR, aktifitas otot, hormon, efek panas makanan, dan lingkungan. (Total laju metabolisme dpt meningkat 3-5 kali karena menggigil dan 20-25 kali selama olahraga berat.Panas dipertahankan ketika darah lebih banyak di rongga kranial, thoracic dan abdominal .

Faktor yg mempengaruhi HL/pengeluaran panasRadiasi, Konduksi, Konveksi, Evaporasi,

Mekanisme pemindahan panasRadiasi:Pemindahan panas melalui Pancaran Gelombang (Infrared radiation).Konduksi:Pemindahan panas langsung melalui kontak fisik.Konveksi:Pemindahan ke udara sekitar tubuh.Evaporasi:Penggunaan panas utk mengubah molekul air dari cair menjadi uap.

HypothalamusThermostat (pusat pengatur Suhu Tubuh)Peningkatan Suhu Tubuh internal (core temperature)hypothalamus AnteriorberkeringatVasodilatasi (peningkatan aliran darah di kulit)

Pemaparan dinginhypothalamus PosteriorPeningkatan produksi panasmenggigilMenurunkan pembuangan panasVasokonstriksi

Pengaturan Hypothalamic terhadapSuhu Tubuh inti (Core Temperature)Hypothalamus memiliki pusat pengaturan ST. Yang bertanggungjawab menjaga tubuh dari overheating atau overcoolingMekanisme pengaturan panas di aktifkan oleh :Reseptor suhu di kulit atauPerubahan suhu darahFree nerve endings pada kulit yang merespon panas dan dingin selnjutnya meneruskan ke hypothalamus dan cerebral cortex.

Major subdivisions of the hypothalamus and pituitary

ST: Inti dan KulitCOLDHOTSkin temperature tends to be colder than core temperature at a normal stateNormal33-34o C27o C47o C37o C27o C47o C37o CNormal37o CCore TemperatureSkin Temperature

Jika suhu kulit menjadi Panas:Then body will lose heat:1. Behavior - e.g. turn on a fan2. Increase skin circulation3. Etc...27o C47o C37o CHot 38o C27o C47o C37o CNormalCore temperatureSkin temperature

Then body will gain heat:1. Behavior - e.g. put on more clothes2. Decrease skin circulation3. Etc...27o C47o C37o CCold 30o C27o C47o C37o CNormalCore temperatureSkin temperatureJika suhu kulit menjadi dingin:

Range of SKIN TemperatureSensation of coldSensation of warmSensation of heatPainThreshold of burning painRapid tissue damageTemp** in degrees CelciusNo sensationComfort ZoneOUCH!!!AHHH!OH-OH!

Respon terhadap rangsang Panas

Respon terhadap rangsang Dingin

Beberapa tempat untuk mengukur ST

Alat untuk mengukur ST:ElectronikMembran timpanikacaSekali pakaiTemperature-sensitive patch or tapeAutomated monitoring devices

Definitions Fever elevation of body temperature due to a resetting of the hypothalamic thermoregulatory centerHyperthermia elevation of body temperature due to inadequate compensation by normal heat-loss mechanisms

Definitions (cont.)Hyperpyrexia elevation of temperature to unusually high levels, 105.8oF (41 oC) or higher Fever Without a Focus fever with no clear cause determined by history and/or physical exam Fever of Unknown Origin (FUO) prolonged fever lasting over 7 10 days without identified cause

Definitions (cont.)What is a normal temperature?Nothing magic about 98.6oF (37oC)Upper limit of normal extends to 100.2oF (37.9oC) in childrenPerson-to-person variations of normalCircadian variations of normal100.4oF (38.0oC) or above is considered a fever

Pathophysiology of Fever Cytokines called endogenous pyrogens are released in response to various inciting agents:Common:Viruses, bacteriaLess common:Immune complexes i.e. autoimmune disease Tumor cells malignancyCytokines reset the hypothalamic thermostat to a higher set-point.

Pathophysiology of FeverAnalogy to the thermostat on your homes heater In a normal equilibrium, the thermostat is set to an ideal or normal temperature

Pathophysiology of FeverWhen someone turns the thermostat up, the furnace comes on, and the temperature begins to rise:

Pathophysiology of FeverShivering

Goose bumps

Cutaneous vasoconstriction

Sensation of feeling coldSimilarly, in the human, when a pyrogen resets the hypothalamic thermostat, the bodys furnace comes on, and the temperature rises:

Pathophysiology of FeverThe symptoms of shivering, goose bumps, cutaneous vasoconstriction (cold, pale hands and feet), and a sensation of feeling cold are collectively known as chills

Chills occur when the fever is rising

Pathophysiology of FeverContinuing the analogy to your home thermostat:When the thermostat is reset to normal, the furnace goes off and the house cools

Pathophysiology of FeverSweating

Cutaneous vasodilitation

Sensation of feeling hot

When the hypothalamic thermostat is reset to normal (such as when antipyretic medication is given, or the illness ends), the body begins to cool and the temperature returns to normal:

Pathophysiology of FeverThe symptoms of sweating, cutaneous vasodilitation (warm, red skin), and a sensation of feeling hot are collectively called sweats

Sweats occur when the fever is breaking