BodY temperatur REGULATION

1. BodYtemperaturREGULATION

2. Body Temperature Two types Core temperature Shell temperature

3. Core Temperature Body temperature means core temperature It is the temperature of deep or central organ temperature It should always kept constant—in homoeothermic

4. Shell temperature It is the skin temperature or surface body temperature It varies with environment temperature skin temperature in help to maintain the core temperature (body temperature) constant

5. Measurement of body temperature Usually measured at oral cavity – Oral temperature – Normal value –37oC or 98.6oF Arm pit – Axillary temperature(o.55ocor 1oF less than oral temperature) Anus –Rectal temperature --(0.55oC or 1oF more than oral temperature)

6. Significance of different area temperature Rectal temperature is the accurate index of (core) body temperature Mouth temperature varies with rapid changes of blood temperature But the rectal temperature gives poor reflection of rapid changes in blood temperature During fever –both oral & rectal temperature are same

7. Variation of body temperature Diurnal variation –Fluctuation of 1.5oC –low in early morning & highest in evening; lowest in sleep & high in awake and with activity increases proportionate Age –In children, temperature regulation is less precise; in old age –subnormal Sex–Female slightly less; during menstruation is at minimum; during ovulation increases by 0.5oC a Food –consumption body temperature

8. Conti-- Exercise, emotion – Piloerection– Hyperthyrodism–

9. Role of skin in temperature regulation Skin –as Insular system of body

10. Insular system of body Skin, subcutaneous tissue & fat forms the insular system Skin temperature reflects environmental temperature Less than core temperature in cold climate & more in hot climate Provides a temperature gradient from surface to deep tissue Leads to transfer of heat –tissue conductance Tissue conductance –is by vasodilation & by vasoconstriction

11. Factors affecting loss or gain of heat through the skin Radiation system of body (Rate of blood flow through skin) The presence of significant layer of hair or fur Horripilation (erection of hair) In human clothing

13. Temperature regulating mechanism In cold climate –Body tend to lose heat to environment & body’s temperature tend to decrease Heat gain mechanism of the body is activated In hot climate –Body tend to gain heat from environment & body’s temperature tend to increase Heat loss mechanism is activated

14. Heat gain of the body By Heat produced in the body (Thermo genesis) By Heat taken up from the environment (in hot climate) By Heat conserving mechanism

15. Thermo genesis by Metabolic activity of body BMR—Heat production --1700 Kcal/day in male & 1500 Kcal/day in female Moderate physical activity -- Heat production twice over BMR (3000Kcals) In heavy exercise –Heat production may four times of BMR (6000Kcals) In short bursts of extreme severe exercise –Heat production may 10 to 16 times of BMR

16. Factors affecting heat production through metabolic activities BMR of all the cells of the body Extra metabolism caused by muscle activity (exercise & shivering) Extra metabolism caused by hormones (Thyroxine & adrenaline & noradrenal Brown fat oxidation SDA of food (for protein 30%, carbohydrate 6% and fat 4% energy used for assimilation)

17. Heat gain from environment Radiation –by direct radiation from sun & heated ground & by reflected radiation from sky Convection—When air temp. exceeds that of skin, the body surface takes up heat Conduction—Heat gain by the body due to contact of hot area

18. Heat conserving & producing mechanisms by increasing sympathetic stimulation Heat conserving mechanism– when cold – Cutaneous vasoconstriction – Heat loss by radiation system Piloerection –(Horripilation; Goose pimples)— Heat loss by convection

19. Arrector Pillorum Smooth muscle attached to hair follicle & epidermis Supplied by sympathetic fibers Stimulation of sympathetic nerve –cause contraction of arrectorpillorum muscle –Resulting in the hair stand out (Horriplication or Goose pimples)

20. Controlling temperature Remember: Capillaries do not move up and down inside the skin. Temperature is regulated by controlling the amount of blood which flows through the capillaries.

21. Shivering Sympathetic excitation Increased catecholaminne & thyroxine secretion Brown fat metabolism Non-shivering thermo genesis means chemical thermo genesis except shivering Increased Heat Production mechanism – Chemical thermogenesis

22. Shivering Primary motor center for shivering (PMCS) –Located in dorsomedial portion of posterior hypothalamus near wall of 3rd ventricle Anterior hypothalamic pre-optic center (Heat loss center) –inhibit PMCS Cold signals from skin & spinal cord excite PMCS PMCS becomes activated when body temp. fall even a fraction of a degree below critical temp. level

24. Signal from PMCS transmit through bilateral tracts down the brain stem, into the lateral column of sp.cord to ant.horn cells which gives motor innervation to muscles Signals are non-rhythmic; do not cause actual muscle contraction; only tone of muscles through out body When tone of muscle above certain critical level, shivering begins Maximum shivering heat production by 4 to 5 times

25. Sympathetic stimulation By direct stimulatory effect on cells – increasing rate of cellular metabolism & By increasing circulatory catecholamines –by cellular activity & also on muscle & liver cells causing glycogenolysis Also nor-adrenaline & adrenaline uncouple oxidative phosphorylation (oxidation of food stuffs without ATP formation) & energy is released in the form of heat

26. Role of Thyroxin in thermo genesis Thyroxin increase BMR Need several weeks exposure to cold –require thyroid gland to hypertrophy (by 20 to 40%) Mechanism –Cooling of anterior hypothalamus (pre-optic area) TRH secretion  TSH secretion  Thyroxin

27. Brown fat mechanism Brown fat contains large number of mitochondria & many small globules of fat Mitochondria– lack of coupling enzymes Stimulation of this cell cause ‘uncoupling oxidative phosphorylation’ They are supplied by sympathetic nervessss Sympathetic stimulation of brown fat heat production through β3 adrenergic receptor

28. Brown fat mechanism is Important in animals of cold climate –can heat production by 2 to 5 times Infants have some what more abundant of brown fat in the interscapular space, at the nape of neck, along great vessels of thorax & abdomen . So, infants can tolerate cold climate better than adult. Infants, with maximum sympathetic stimulation, heat production can by 100% Adult human have almost no brown fat

29. DISTURBANCE OF BODY TEMPERATURE Fever Hyperthermia Hypothermia FEVER OR PYREXIA 1. Body temperature 98.6 F But 104 F 2. Physiologic adaptation : Prevent bacreteal growth Enhances immunity

30. 3. Cause of fever : Due to the action of bacterial toxins on macrophages Secrete cytokines and interleukins (IL1, IL6) Stimulate prostaglandins formation Raise the set point of hypothalamic thermostat

31. HYPERTHERMIA : Body temperature 102 F Heat stroke. Dehydration and electrolyte loss, Failure of temperature regulation, Death of neurons, Circulatory shock Death HYPOTHERMIA: Fall in body temperature between 30 – 25 c. O2 consumption of body HR, BP are all reduced. Induced hypothermia useful for surgery of heart and brain.

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