Temperature Regulation Dr Dileep Verma Associate Professor Deptt of Physiology KGMU.
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Transcript of Temperature Regulation Dr Dileep Verma Associate Professor Deptt of Physiology KGMU.
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Temperature RegulationTemperature Regulation
Dr Dileep Verma Associate Professor Deptt of Physiology KGMU
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Lecture-1 :TopicsLecture-1 :Topics
Core and Shell body temp.
Heat Balance
Factors promoting -
a) Heat gain
b) Heat loss
Temp. regulatory mechanisms
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Learning ObjectivesLearning Objectives
Normal Body Temperature
Ways of measuring Body Temp
List the mechanisms of heat
production & heat loss
Regulation of Body Temp.
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Body TemperatureBody TemperatureNormal Body Temperature (NBT) –
98.60F(370C)Range of NBT ----- (970F to 990F)Rectal Temp ----- (0.50F to 10F) above
the OralRectal Temp reflects the internal body
Temp (Core Body Temp)Core Body Temp remain almost constantSkin Temp (Shell Temp)-----Variable
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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.
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Heat BalanceHeat balance maintains the body
tempBalance between heat production
& heat loss (Heat Balance)Heat Balance
Heat production= Heat loss
Heat production is called thermogenesis
Heat loss is called as thermolysis
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Heat Production (Thermogenesis)
BMRSpecific Dynamic Action of foodActivity of skeletal muscle
Shivering Exercise
Chemical Thermogenesis Epinephrine &Norepinephrine ThyroxineBrown Fat- Source of considerable heat
production Abundant in infants
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Heat Loss (Thermolysis)
RadiationConductionConvectionEvaporationPerspirationRespirationLoss through urine & feces
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Role of SkinRole of Skin
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Heat Exchange in the SkinHeat Exchange in the Skin
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Vasoconstriction and Vasoconstriction and VasodilatationVasodilatation
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Thermoregulation
Temperature is regulated by nervous feedback mechanisms
Thermoregulatory center located in the Hypothalamus
Thermoregulatory regulatory responses include
AutonomicSomatic
Endocrine Behavioural changes
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Feedback systemFeedback 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
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Body Temperature Control System
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 These detect changes in blood temperatureblood temperature
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Thermoregulatory regulatory responses
Activated by Exposure to Cold
1. Shivering2. Increase voluntary activity3. Increase TSH secretion4. Increase Catecholamines5. Vasoconstriction6. Horripilation7. Curling up
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Thermoregulatory regulatory responses
Activated by Exposure to Heat
1. Vasodilatation2. Sweating3. Increase in Respiration4. Anorexia5. Apathy6. Decrease TSH secretion
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Thermoregulatory regulatory responses
Exposure to ColdShivering
Increase voluntary activity
Increase TSH secretion
Increase Catecholamines
Vasoconstriction
Horripilation
Curling up
Exposure to HeatVasodilatation
Sweating
Increase in Respiration
Anorexia
Apathy
Decrease TSH secretion
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1-A major source of heat production in infants isA. Increased muscular activityB. Brown fatC. Increased sympathetic activityD. Specific dynamic action of food
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2-At normal room temperature most body heat loss is by-
A.ConventionB.ConductionC. Radiation D.Sweating
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3-Constituents of secreted sweat are similar to plasma except for
A. ProteinsB. ChlorideC. BicarbonateD. Potassium
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4-The only available mechanism of heat transfer when the environmental temperature is greater than the body temperature is
A. RadiationB. ConductionC. ConvectionD. Evaporation
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5-Cause of thermogenesis in the body is
A. Skeletal muscle relaxationB. Assimilation of foodC. Decreased cardiac metabolismD. Hypothyroidism
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6-A major factor resulting in increase in body temperature during exercise is-
A. Heat dissipating mechanisms inefficient
B. Enormous thermogenesisC. Vasoconstriction on non-
working musclesD. Resetting of thermostat
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7-Site which reflects the true value of core temperature
A. Oesophagus and rectumB. Tympanic membraneC.VaginaD.All of the above
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8-BMR is dependent on
A. Body weight B. Surface areaC. Amount of lean body mass D. Height
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9-One feels hotter on a humid day because-
A. Rate of sweating increases B. Surrounding temperature is
moreC. Heat loss by the body via
process of radiation decreasesD. Rate of evaporation of water
from body decreases
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10-A major factor resulting in increase in body temperature during exercise is-
A. Heat dissipating mechanisms inefficient
B. Enormous thermogenesisC. Vasoconstriction on non-
working musclesD. Resetting of thermostat
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Temperature RegulationTemperature Regulation
Dr Dileep Verma Associate Professor Deptt of Physiology KGMU
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Lecture-2 :TopicsLecture-2 :Topics
Life in Hot environment -Effect of acute heatThermoregulatory responsesHeat syndrome -Heat cramps -Heat exhaustion -Heat stroke
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Contd…Contd…
Life in cold environment -effect of acute & long term cold exposure on bodyApplied -Hypothermia -Harmful effects of extreme cold
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Learning ObjectivesLearning Objectives
Effect of Hot & Cold environment on
the body.
Thermo-receptors
Regulation of Body Temperature
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Life in Hot environment
Hot climates- These are two typesa) Hot-dryb) Warm-humid
Hot-dry climate- Found in deserts Temp >500 C Not humid Warm-humid climate –
Found in tropical forest Temp usually<350 CHumidity >75%
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Contd----Contd----
Effects of acute heat - Effects of acute exposure to heat
are divided into-
a) Thermoregulatory responses
b) Other effects
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Contd----Contd----
Thermoregulatory regulatory responses
VasodilatationSweatingIncrease in RespirationAnorexiaApathyDecrease TSH
secretion
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Contd----Contd----
Other effects of acute heat exposure on-
Cellular metabolism
Rate of respiration
Work of breathing
Pulse rate
Dehydration
Urinary volume
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Contd----Contd----
Heat Syndromes- adverse reaction to heat exposure
a) Heat Crampsb) Heat
Exhaustionc) Heat Stoke
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Life in cold environmentEffect of cold exposure on body-
a) Acute cold exposure b) Long term cold exposure
Applied -Hypothermia -Harmful effects of extreme cold
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Contd----Contd----
Effect of acute cold exposure on body
ShiveringIncrease voluntary activityIncrease TSH secretionIncrease CatecholaminesVasoconstrictionHorripilationCurling up
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Contd----Contd----
Effect of long term cold exposure
Metabolic Responses Insulative Responses Hypothermic Responses
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Contd----Contd----
Hypothermia –Body temp below the normal lower limit (<970F)
Thermoregulatory responses Greatly impaired at
(<940F)
Lost at body temp(<850F)
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Contd----Contd----Frostbite
Occurs at very low tempSurface area freezesIce crystals formed
Common sites- Lobes of the earsDigits of handsDigits of feet
Cold induced vasodilatation- Final protection against
frostbite
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Summary of Effector Mechanisms Summary of Effector Mechanisms in Temperature Regulationin Temperature Regulation
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1- Thermal sweating differs from non-thermal sweating in that
A. Eccrine glands are responsible for it
B. Occurs due to activation of sympathetic cholinergic nerves
C. Found mainly over palm, sole and axilla
D. All of the above
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Core temperature of 260C leads to death due to:
a) Brain damage b) Respiratory insufficiencyc) Cardiac failured) All of the above
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2- Which area of hypothalamus functions as thermostat?
A. PreopticB. ParaventricularC. Dorso medial D. Lateral
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3- Insensible water loss (perspiration) will be absent if humidity is
A. 50%B. 70%C. 90%D. 100%
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4- Pyrogens raises body temperature by
A. Setting the thermostat to higher level
B. Releasing interleukinsC. Decreasing peripheral heat
liberating mechanismD. Causing peripheral vasoconstriction
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5- Heat loss process of the body not directly under physiological control is
A. Radiation from body B. Conduction and convection to
surroundingsC. Vaporization of sweatD. Warming of inspired air
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6- Fever is usually caused by
A. Interleukin-1B. Substance- pC. EndorphinsD. Encephalin
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7- During exposure to cold, body temperature is raised by
A. Vasoconstriction in the skinB. HorripilationC. ThermogenesisD. All of the above
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8- Profound hypothermic signs include all except
A. Show breathingB. BradycardiaC. HypotensionD. Hyperactivity
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9- Aspirin decreases the body temperature by
A. Inhibiting interleukin-1B. Inhibiting pyrogens releaseC. Killing fever producing organisms D. Inhibiting prostaglandin synthesis
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10- When the core temperature of the body falls below the hypothalamic set-point temperature
A. The blood vssels of the skin constrict
B. Heat production increases within minutes
C. The basal metabolic rate increasesD. All of the above
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