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Dive into the intricate mechanisms of body temperature regulation with Dr. Dileep Verma's lectures. Learn about heat balance, regulatory responses, thermogenesis, and more while understanding the impacts of hot and cold environments on the body.
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Temperature Regulation Dr DileepVerma Associate Professor Deptt of Physiology KGMU
Lecture-1 :Topics • Core and Shell body temp. • Heat Balance • Factors promoting - a) Heat gain b) Heat loss • Temp. regulatory mechanisms
Learning Objectives • Normal Body Temperature • Ways of measuring Body Temp • List the mechanisms of heat production & heat loss • Regulation of Body Temp.
Body Temperature • Normal Body Temperature (NBT) – 98.60F(370C) • Range of NBT ----- (970F to 990F) • Rectal Temp ----- (0.50F to 10F) above the Oral • Rectal Temp reflects the internal body Temp (Core Body Temp) • Core Body Temp remain almost constant • Skin Temp (Shell Temp)-----Variable
Temperature Homeostasis • Keep the body temp within a very narrow range • Range of NBT (970F to 990F) • Temperatures above this: denature enzymes and block metabolic pathways • Temperatures below this: slow down metabolism and affect the brain.
Heat Balance • Heat balance maintains the body temp • Balance between heat production & heat loss (Heat Balance) • Heat Balance • Heat production= Heat loss • Heat production is called thermogenesis • Heat loss is called as thermolysis
Heat Production (Thermogenesis) BMR Specific Dynamic Action of food Activity of skeletal muscle Shivering Exercise Chemical Thermogenesis Epinephrine &Norepinephrine Thyroxine Brown Fat- Source of considerable heat production Abundant in infants
Heat Loss (Thermolysis) Radiation Conduction Convection Evaporation Perspiration Respiration Loss through urine & feces
Thermoregulation • Temperature is regulated by nervous feedback mechanisms • Thermoregulatory center located in the Hypothalamus • Thermoregulatory regulatory responses include Autonomic Somatic Endocrine Behavioural changes
Feedback system • 1) Receptor • Sensor that responds to changes (stimuli) • 2) Control Center • Sets range of values • Evaluates input and • Sends output • 3) Effector- • Receives output from control centre • Produces a response
Hypothalamus Acts as a thermostat Receives nerve impulses from cutaneous thermoreceptors Thermoreceptors Cold &Heat Hypothalamus- also has thermoreceptors called central thermoreceptors These detect changes in blood temperature Body Temperature Control System
Thermoregulatory regulatory responses Activated by Exposure to Cold Shivering Increase voluntary activity Increase TSH secretion Increase Catecholamines Vasoconstriction Horripilation Curling up
Thermoregulatory regulatory responses Activated by Exposure to Heat Vasodilatation Sweating Increase in Respiration Anorexia Apathy Decrease TSH secretion
Thermoregulatory regulatory responses Exposure to Cold Shivering Increase voluntary activity Increase TSH secretion Increase Catecholamines Vasoconstriction Horripilation Curling up Exposure to Heat Vasodilatation Sweating Increase in Respiration Anorexia Apathy Decrease TSH secretion
1-A major source of heat production in infants is Increased muscular activity Brown fat Increased sympathetic activity Specific dynamic action of food
2-At normal room temperature most body heat loss is by- Convention Conduction Radiation Sweating
3-Constituents of secreted sweat are similar to plasma except for Proteins Chloride Bicarbonate Potassium
4-The only available mechanism of heat transfer when the environmental temperature is greater than the body temperature is Radiation Conduction Convection Evaporation
5-Cause of thermogenesis in the body is Skeletal muscle relaxation Assimilation of food Decreased cardiac metabolism Hypothyroidism
6-A major factor resulting in increase in body temperature during exercise is- Heat dissipating mechanisms inefficient Enormous thermogenesis Vasoconstriction on non-working muscles Resetting of thermostat
7-Site which reflects the true value of core temperature Oesophagus and rectum Tympanic membrane Vagina All of the above
8-BMR is dependent on Body weight Surface area Amount of lean body mass Height
9-One feels hotter on a humid day because- Rate of sweating increases Surrounding temperature is more Heat loss by the body via process of radiation decreases Rate of evaporation of water from body decreases
10-A major factor resulting in increase in body temperature during exercise is- Heat dissipating mechanisms inefficient Enormous thermogenesis Vasoconstriction on non-working muscles Resetting of thermostat
Temperature Regulation Dr DileepVerma Associate Professor Deptt of Physiology KGMU
Lecture-2 :Topics • Life in Hot environment -Effect of acute heat • Thermoregulatory responses • Heat syndrome -Heat cramps -Heat exhaustion -Heat stroke
Contd… • Life in cold environment -effect of acute & long term cold exposure on body • Applied -Hypothermia -Harmful effects of extreme cold
Learning Objectives • Effect of Hot & Cold environment on the body. • Thermo-receptors • Regulation of Body Temperature
Life in Hot environment • Hot climates- These are two types a) Hot-dry b) Warm-humid • Hot-dry climate- Found in deserts Temp >500 C Not humid • Warm-humid climate – Found in tropical forest Temp usually<350 C Humidity >75%
Contd---- • Effects of acute heat - Effects of acute exposure to heat are divided into- a) Thermoregulatory responses b) Other effects
Contd---- • Thermoregulatory regulatory responses Vasodilatation Sweating Increase in Respiration Anorexia Apathy Decrease TSH secretion
Contd---- • Other effects of acute heat exposure on- Cellular metabolism Rate of respiration Work of breathing Pulse rate Dehydration Urinary volume
Contd---- • Heat Syndromes- adverse reaction to heat exposure a) Heat Cramps b) Heat Exhaustion c) Heat Stoke
Life in cold environment • Effect of cold exposure on body- a) Acute cold exposure b) Long term cold exposure • Applied -Hypothermia -Harmful effects of extreme cold
Contd---- • Effect of acute cold exposure on body • Shivering • Increase voluntary activity • Increase TSH secretion • Increase Catecholamines • Vasoconstriction • Horripilation • Curling up
Contd---- • Effect of long term cold exposure Metabolic Responses Insulative Responses Hypothermic Responses
Contd---- • Hypothermia–Body temp below the normal lower limit (<970F) • Thermoregulatory responses Greatly impaired at (<940F) Lost at body temp(<850F)
Contd---- • Frostbite Occurs at very low temp Surface area freezes Ice crystals formed • Common sites- Lobes of the ears Digits of hands Digits of feet • Cold induced vasodilatation- Final protection against frostbite
1- Thermal sweating differs from non-thermal sweating in that Eccrine glands are responsible for it Occurs due to activation of sympathetic cholinergic nerves Found mainly over palm, sole and axilla All of the above
Core temperature of 260C leads to death due to: Brain damage Respiratory insufficiency Cardiac failure All of the above
2- Which area of hypothalamus functions as thermostat? Preoptic Paraventricular Dorso medial Lateral
3- Insensible water loss (perspiration) will be absent if humidity is 50% 70% 90% 100%