Thermodynamics of the Human Body (Heat)

Question 1

Thermal Energy

Answer 1

• is the energy portion of a system that increases with its temperature
• in thermodynamics, thermal eneergy is the internal energy present in a system in a state of therodynamis equilibrium by virtue of its temperature

Question 2

Internal Energy U

Answer 2

• the sum of all microscopic forms of energy of a system
• related to the molecular structure & the degree of molecular activity & may be viewed as the sum of kinetic & potential energies of the molecules

Question 3

Heat

Answer 3

• a form of energy called thermal energy (energy of the inert molecules & the atomic interactions)
• the connection of the kinetic fractions energy with their potential energy
• symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature is a form of heat transfer called thermal energy( energy of the inert moelcules & the atomic interactions)

Question 4

Heat: Part 2

Answer 4

• heat can flow spontaneously from an object with a high temperature to an object with a lower temperature
• transfer of heat from an object, to another object with an equal or higher temperature, however, can happen only with the aid of a heat pump

Question 5

Body Heat

Answer 5

• is the byproduct of the metabolic processes of the body
• hormones thyroxine & epinephrine increase metabolism & consequently increase body heat
• muscular activity also produces body heat
• at complete rest (basal metabolism) the amount of heat produced from muscular activity may be as low as 25% of the total body heat
• during excersie or shivering the percentage may rise to 60%
• body temp. is regulated by the thermostatic center in the hypothalamus

Question 6

Thermoregulation

Answer 6

• body’s thermostat, hypothalamus receives messages about the body’s temp. from the blood circulating through it & from special receptors in the skin which send messages directly
• the group of physical & physiological factors which allow to maintain the constant temp. of the body
• temp. regulation is poorly developed in newborn babies & is especially lacking in premature babies
• warm & cold baths alter the temp. of a baby more than an adult
• temp. of elderly pople is usually below normal
• the body is less active, the circulation is not as strong, & they are less able to compensate for changes in external environment

Question 7

Heat Q can flow across the boundary of teh system & thus change its internal energy U

Answer 7

Question 8

First Law of Thermodynamics

Answer 8

• the chagne in internal energy U of a substance is equal to the amount of heat the substance minus the amount of work W done by the substance
• U= Q-W
• conservation of energy

Question 9

Basic Unit of Temperature

Answer 9

• Kelvin, Fahrenheit
• SI unit is Kelvin (K)
• Fahrenheit & Celsius scales are defined by 2 points: absolute zero, & the triple point of water

Question 10

Absolute Zero

Answer 10

• is defined as being preceisely 0 K & -273.15 °C
• is where all kinetic motion in the particles comprising matter ceases & they are at complete rest in the “classic” (non-quantum mechanical) sense
• at absolute zero, matter contains no thermal energy

Question 11

The Scales of Temperature

Answer 11

Question 12

The Temperature of the “Core” (Normal Body Temperatures)

Answer 12

• remains almost exactly constant, within + or - 1 degree F (+ or - 0.6 °C) - except when a person develops a febrile illness

Question 13

The Skin Temperature (Normal Body Temperature)

Answer 13

• (in contrast to the core temperature) rises & falls with the temperature of the surroundings

Question 14

Normal Body Temperatures

Answer 14

• the average normal temperature is generally considered to be between 98 °F & 98.6 °F (37 °C) when measured orally & about 1 degree F higher when measured rectally

Question 15

Basic Metabolic Rate

Answer 15

• a velocity of the organism metabolism, which remains in the physical and psychological comfort and also in the temperature, after at least 12 hours for the last physical effort and after 8 hours sleeping. It is an energy needed to survive and to protect the basal living functions

Question 16

Tha basal metabolic rate is intended for the systems work:

Answer 16

• 1/4 of all for the nervous system
• 1/5 of all for the liver
• 1/15 of all for the kidneys
• 1/15 of all for the heart
• the rest energy for the muscles work

Question 17

The local activity of the cold factor

Answer 17

• The first phase based on the blood vessels spasm situated in the skin(a paleness effect). Next is the second phase, which insists on openning the superficial blood vessels and in fact the hyperanemia reaction (Lewis waves)

Question 18

The local activity of the warm factor

Answer 18

• At the first moment the skin blood vessels are opened. After the arterial hyperanemia the skin issue begins to become a cyanotic reaction

Question 19

Circulatory cold factors

Answer 19

• A hypovolaemia(a decrease of the circulatory blood volume)
• a bradycardia (a decrease of the functional heart parameters: a cadiac output and ejection volume)
• a decrease of the peripheral vascular resistance
• a blood pressure rise

Question 20

Circulatory warm factors

Answer 20

• a hypervolemia(an increase of the circulatory blood volume)
• a tachycardia(an increase of the functional hear parameters: cardiac output and ejection volume)
• decrease of peripheral vascular resistance
• a blood pressure fall

Question 21

Respiratory system warm and cold factors

Answer 21

Cold factors

• an increase of the pulmonary minute ventilation
• a respiratory acidosis

Warm factors

• an increase(300-400%) of the pulmonary minute ventilation
• a hyperventilation
• a respiratory alkalosis

Question 22

Metabolism cold factors

Answer 22

• a gastric hypersecretion
• a hyperperistalsis in the alimentary tract

Question 23

Types of Diathermy

Answer 23

Shortwave Diathermy(SWD)

• More commonly used
• able to penetrate through subcutaneous fat better than MWD

Microwave Diathermy(MWD)

Question 24

Urinary system cold and warm factors

Answer 24

Cold factors

• a hyperuresis(if is a short -time impulse)
• an oliguresis(if is a long time impulse

Warm factors

• a hyperuresis

Question 25

Physiological responses to diathermy

Answer 25

• Increased tissue temperature
• Increased blood flow(vasodilation)
• Increased venous and lympatic flow
• Increased metabolsim
• Changes in physical properties of tissues
• Muscle relaxation

Question 26

Thermotherapy

Answer 26

• is one of many brances of the physical medicine, in which heatis used to treat, so it is the treatment of bodily structures by the application of heat
• distinguished by few thermal factors
  
  • IRR(infrared radiation)
  • a shortwave diathermy

Question 27

The electromagnetic spectrum is divided into:

Answer 27

• radio waves
• microwaves
• infrared radiation
• visible light
• ultraviolet light
• x-rays
• gamma rays

Question 28

IRR

Answer 28

According to the wavelength of infrared radiation we can divide this radiation into:

• Short wave duration, with a wavelength from 770 to 1500nm
• Medium Wave duration, with a wavelength from 1500 to 4000nm
• Long wave duration, the wavelength from 4000 to 15000 nm

Question 29

INFRA - Red Radiation IRR

Answer 29

• is an invisible radiation in the elctromagnetic spectrum between the red visible radiation and the microwaves(the wavelength 770 - 15000nm)

Question 30

IRR

Answer 30

• Natural source of infrared radiation is the Sun
• This radiation is also applied by special lamps(the Sollux for instance)
• The distance between the generator and the skin is about 40 -50cm
• The sources of infrared radiation are heated bodies. Accordig to the law of Viena, the wavelength of infrared radiation depends on the temperature of heated body
• The higher the temperature, the smaller the wavelength and vice versa

Question 31

Sollux Lamp

Answer 31

• Sollux lamp is equiped with a set of glass filters(red and blue)
• The red glass passes infrared radiation and red invisible radiation, while the blue glass passes mostly blue visible radiation

Question 32

Effect of infrared radiation

Answer 32

• enlargement of the blood vessels of the skin and therefore increases blood flow thorugh tissues
• Reduction in muscle tension. The reactions from deeper vessels
• A decrease of pain
• An increase of metabolism
• Thermal stimulation of skin receptors

Question 33

Diathermy

Answer 33

Application of high frequency electromagnetic energy:

• used to generate heat in body tissues
• heat is produced by resistance of tissues
• also used for non thermal effects

Question 34

Normal Body Temperatures: How is it measured?

Answer 34

• body temperature is usually measured by a thermometer placed in the mouth, rectum, or auditory canal, (for tympanic membrane temp)
• The tympanic membrane temp is a direct reflection of the body’s core temperature

Question 35

Normal Body Temperatures: How is it controlled?

Answer 35

• controlled by balancing heat production against heat loss

Question 36

Heat Production: Is a principle by?

Answer 36

• Heat production is a principle by - Product of Metabolism
• Most important factors that determine rate of heat production are:
  
  • Basal Rate of all the cells in the body?
  • Extra rate of metabolism caused by?

Question 37

Metabolic Rate

Answer 37

• it is the rate of heat production within the body, and includes all of the heat given off by all of the chemical reactions taking place in the body
• Unit: MET
  
  • Sleeping: 0.7 METS
  • Seated, Quiet: 1.0 METS
  • Walking (3mph): 2.6 METS
  • Tennis (singles): 4.6 METS

Question 38

Heat Loss: Where is most of the heat in the body produced?

Answer 38

• Most of the heat is produced in deep organs, such as the liver, brain, heart, and skeletal muscles during exercise.

Question 39

What 2 factors determine at what rate heat is lost?

Answer 39

1. How rapidly heat can be conducted from where it is produced in the core of the body to the skin
2. How rapidly heat can then be transferred from the skin to the surrondings

Question 40

Complete Energy Exchange Between Organism and Environment Formula

Answer 40

S = M + C_v + C_d + R - E

M- Metabolic Warmth Production

C_v- Energy taken under influence of convection(C_v)

C_d- Energy taken under influence of conduction(C_d)

R- Energy taken under influence of radiation(R)

E- Eliminated warmth under the influence of evaporation

Question 41

Why does a naked person at room temp lose energy? At what percentages?

Answer 41

• Radiation: 60%
• Evaporation: 25%
• Conduction: 8%
• Convection: 7%

Question 42

Image

Answer 42

Question 43

Radiation: Heat Loss

Answer 43

• Loss of heat by radiation means loss in the form of infrared radiation, a type of electromagnetic wave longer than light, but shorter than microwaves.
• infrared radiation has wavelengths between 700 nanometers to 1 millimeter

Question 44

Image

Answer 44

Question 45

Heat Rays

Answer 45

• All objects that are not at absolute zero temperature radiate infrared rays!!
• Human body radiates heat rays in all directions
• Heat rays are also being radiated from the walls and other objects towards the body
• If temp of body is greater than temp of surroundings, more heat from body is radiated than surroundings to body.

Question 46

What is heat conduction?

Answer 46

Heat Conduction is the spontaneous transfer of thermal energy through matter, from a region of higher temperature to a region of lower temperature, and hence acts to even out temperature differences.

Question 47

Conduction

Answer 47

• only one minute quantities of heat are normally lost from the body by direct conduction from the surface of the body to other objects
• on the other hand, loss of heat by conduction to air does represent a sizable proportion of the body’s heat loss even under normal conditions.

Question 48

What is convection?

Answer 48

• It is the transfer of heat in a gas or liquid by movement of currents. Heat moves with the fluid. It can also happen in some solids like sand.
• it is the transfer of heat by the actual movement of the warmed matter

Question 49

Image

Answer 49

Question 50

Evaporation in the Human Body

Answer 50

• evaporation of sweat has a cooling effect due to the latent heat of evaporation of water
• thus in hot weather, or when muscles heat up due to exertion, more sweat is produced
• at 37^o C (normal body temp), evaporation of 1 liter sweat loses about 2.4 MJ (about 580 kcal) from organism
• there is continual heat loss at a rate of about 22 to 16 cal per hour even with no sweating
• water evaporates at a rate of 450-600 ml per day