Bod Y temperatur REGULATION Body Temperature Two types

Bod. Y temperatur REGULATION

Body Temperature Two types Core temperature Shell temperature

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

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

Measurement of body temperature Usually measured at oral cavity – Oral temperature – Normal value – 37 o. C or 98. 6 o. F Arm pit – Axillary temperature (o. 55 ocor 1 o. F less than oral temperature) Anus –Rectal temperature --(0. 55 o. C or 1 o. F more than oral temperature)

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

Variation of body temperature Ø Diurnal variation –Fluctuation of 1. 5 o. C –low in early morning & highest in evening; lowest in sleep & high in awake and with activity increases proportionate Ø Age –In children, temperature regulation is less precise; in old age –subnormal Ø Sex –Female slightly less; during menstruation is at minimum; during ovulation increases by 0. 5 o. C a Ø Food –consumption body temperature

Conti-- Ø Exercise, emotion – Ø Piloerection – Ø Hyperthyrodism –

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

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

Factors affecting loss or gain of heat through the skin 1. Radiation system of body (Rate of blood flow through skin) 2. The presence of significant layer of hair or fur 3. Horripilation (erection of hair) 4. In human clothing

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

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

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 (3000 Kcals) In heavy exercise –Heat production may four times of BMR (6000 Kcals) In short bursts of extreme severe exercise –Heat production may 10 to 16 times of BMR

Factors affecting heat production through metabolic activities 1. BMR of all the cells of the body 2. Extra metabolism caused by muscle activity (exercise & shivering) 3. Extra metabolism caused by hormones (Thyroxine & adrenaline & noradrenal 4. Brown fat oxidation 5. SDA of food (for protein 30%, carbohydrate 6% and fat 4% energy used for assimilation)

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

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

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

Too cold Too hot D - Hair muscles relax. Hairs lie flat so heat can escape. E - Sweat secreted by sweat glands. Cools skin by evaporation. F - Blood flow in capillaries increases. 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. A - Hair muscles pull hairs on end. B - Erect hairs trap air. C - Blood flow in capillaries decreases.

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

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

Ø 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 Ø Signals are non-rhythmic; do not cause actual muscle contraction; only tone of muscles through out body Ø When tone of muscle above certain critical level, shivering begins Ø Maximum shivering heat production by 4 to 5 times

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

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

Brown fat mechanism Ø Brown fat contains large number of mitochondria & many small globules of fat Ø Mitochondria– lack of coupling enzymes Ø Stimulation of this cell cause ‘uncoupling oxidative phosphorylation’ Ø They are supplied by sympathetic nervessss Ø Sympathetic stimulation of brown fat heat production through β 3 adrenergic receptor

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

DISTURBANCE OF BODY TEMPERATURE 1. Fever 2. Hyperthermia 3. Hypothermia FEVER OR PYREXIA 1. Body temperature 98. 6 F But 104 F 2. Physiologic adaptation : Prevent bacreteal growth Enhances immunity

3. Cause of fever : Due to the action of bacterial toxins on macrophages Secrete cytokines and interleukins (IL 1, IL 6) Stimulate prostaglandins formation Raise the set point of hypothalamic thermostat

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. O 2 consumption of body HR, BP are all reduced. Induced hypothermia useful for surgery of heart and brain.

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