Lecture 11 pt 2: Body temp regulation

Question 1

True or false: Temperature extremes injure tissues.

Answer 1

True

Question 2

How do heat and cold damage tissues?

Answer 2

1) Heat: Denatures proteins
2) Cold: Ice crystals form

Question 3

Are increases in body temp necessary? Why or why not?

Answer 3

Some increases are necessary for specialized functions to increase reaction rate.

Question 4

1) Increasing temp by 10°C increases the reaction rate by a factor of ___ or ___
2) Ratio between these: ______

Answer 4

1) 2 or 3
2) Q10

Question 5

What are 5 sites for monitoring body temperature?

Answer 5

1) Oral
2) Axillary
3) Rectal
4) Tympanic membrane
5) Temporal scanner

Question 6

1) What two body temperatures are 98.6F?
2) What temperature is typically 1F warmer?

Answer 6

1) Oral and axillary
2) Rectal

Question 7

1) Devices can measure heat generated by tympanic membrane and convert to an _____ equivalent reading
2) How are temporal scanners used?

Answer 7

1) oral
2) Stroked across forehead to measure blood in temporal artery, which is near the surface

Question 8

1) All heat exchange must ultimately occur between the body and what?
2) What organ plays a major role in heat exchange
3) Heat moves _______ its thermal gradient from a ___________ to a ___________ region

Answer 8

1) external environment
2) Skin
3) down; warmer; cooler

Question 9

What 4 mechanisms allow for temperature balance?

Answer 9

1) Radiation
2) Conduction
3) Convection
4) Evaporation

Question 10

1) Define radiation
2) How much of heat loss does it make up?

Answer 10

1) Emission of thermal energy from body surface in the form of heat waves (electromagnetic waves). Incl. emission from the sun or a fire.
2) Half of heat loss

Question 11

1) Define conduction
2) What does the rate of heat transfer depend on?
3) Heat exchange occurs between skin and what?

Answer 11

1) Transfer of heat between objects that are in direct contact
2) Magnitude of temperature difference and the thermal conductivity of the substances
3) The air that directly contacts it

Question 12

1) Is a lot of heat exchanged via conduction? Why?
2) Why will water feel cooler than air of the same temperature?

Answer 12

1) Minimal heat is exchanged this way because air has poor thermal conductivity
2) Because water has higher thermal conductivity and heat is lost more rapidly from body surface

Question 13

1) Define convection
2) How is convection achieved?
3) What can enhance convection? Give 2 examples

Answer 13

1) Transfer of heat energy by currents (air or water)
2) Convection currents
3) Forced movement; like air from a fan, riding a bike

Question 14

How do convection currents work?

Answer 14

1) Skin in direct contact with cooler air will warm the air
2) Warm air rises and replaced by cooler air, which is also heated
3) Repeated process creates a current that carries heat away (otherwise the layer of air in contact with skin would immediately equilibrate with skin temperature)

Question 15

What would happen if the convection current process didn’t repeat?

Answer 15

The layer of air in contact with skin would immediately equilibrate with skin temperature

Question 16

1) Describe evaporation in the context of the human body
2) What does this do?
3) Evaporative heat is lost from what 2 places?

Answer 16

1) Heat required to transform water from liquid to a gas is absorbed from the skin
2) Cools the body
3) Respiratory linings and the skin surface

Question 17

1) How is water lost via evaporation in the airways?
2) What about via evaporation through the skin?
3) Can we control evaporation through the skin? What about in cold weather?

Answer 17

1) Air is humidified in airways
2) Skin is not perfectly waterproof, water molecules diffuse through and evaporate
3) Passive baseline diffusion not subject to physiologic control, even with very cold weather

Question 18

1) What is the body’s thermostat? What is it also called?
2) Does it receive or send afferent information about temperature?
3) Does it send efferent signals? If so, why?
4) How many centers for temperature regulation does it have?

Answer 18

1) Hypothalamus; Thermoregulatory integration center
2) Receives afferent information
3) Sends efferent signals to initiate counter-mechanisms
4) Two

Question 19

What are the two centers for temperature regulation within the hypothalamus?

Answer 19

1) Anterior: activated by warmth
2) Posterior: activated by cold

Question 20

What are the two ways the hypothalamus receives afferent information about temperature?

Answer 20

1) Peripheral thermoreceptors in skin
2) Central thermoreceptors in hypothalamus and organs

Question 21

1) Chronic cold exposure stimulates what?
2) What is this abundant in? (2 things) What does this do?
3) What idea is this relevant to?

Answer 21

1) Brown adipose tissue (“brown fat”)
2) In mitochondria and iron; gives red/brown appearance
3) Thermogenesis

Question 22

What is brown adipose tissue?

Answer 22

Adipocyte specialized at converting energy to heat
-Used in non-shivering (chemical) thermogenesis

Question 23

Why do newborns have large deposits of brown fat?

Answer 23

Non-shivering (chemical) thermogenesis; they cannot shiver

Question 24

Each cell in the body needs ____________ to perform essential functions

Answer 24

energy

Question 25

List 4 essential body functions that require energy

Answer 25

1) Active transport
2) Cellular repair
3) Gland secretion
4) Muscle contraction

Question 26

Heat storage is a balance between net ____________________ and net ____________________

Answer 26

heat production; heat loss

Question 27

1) Large amounts of body heat can be dissipated through what?
2) What can lead to overheating? What can this also lead to?
3) What else augments heat loss?

Answer 27

1) Sweat evaporation
2) Sweat Gland “fatigue” ; depletion of glycogen
3) Increased vasodilation of the skin

Question 28

What are the two main types of sweat glands? Which is dominant?

Answer 28

1) Eccrine: Dominant.
2) Apocrine

Question 29

1) Sweat glands involve mostly what 2 ions?
2) What type of sweat gland appears in puberty?

Answer 29

1) Na+ and Cl-
2) Apoeccrine

Question 30

1) The sympathetic fibers of what type of gland release ACh?
2) Does this type of gland have an odor?
3) If so, what creates odor? If not, explain why.

Answer 30

1) Sweat
2) No, odorless
3) Mixes with flora on the skin and creates odor

Question 31

1) What type of glands are viscous and in smaller amounts?
2) What is a subtype of this type? When does it appear?

Answer 31

1) Apocrine
2) Apoeccrine; appears during puberty

Question 32

1) What are the nutritional needs of the skin?
2) How is blood flow to the skin controlled? What does this operate in tandem with?
3) What is dependent on sympathetic nerve signals?

Answer 32

1) Nutritional needs of the skin are low
2) Blood flow is controlled by reflexes or changes in temperature; in tandem with sweating
3) Vasodilation

Question 33

Give an example of sympathetic control of skin circulation. What fibers is this mostly through?

Answer 33

Reflex Vasoconstriction; adrenergic fibers

Question 34

What is your default body temperature called? What can affect it?

Answer 34

Set point; exercise

Question 35

Circadian Rhythm and temperature:
1) When does minimum temperature happen?
2) What about maximum temperature?

Answer 35

1) At night hours before waking
2) Late afternoon/evening

Question 36

Regarding the menstrual cycle and temperature, when does lowest temperature occur?

Answer 36

Just before ovulation

Question 37

1) What makes up energy input?
2) What type of energy is it? What is it released from?
3) What two things can happen with this energy?

Answer 37

1) Ingested food
2) Chemical energy; released from bonds of nutrient molecules
3) Used immediately to perform biological work or stored for later use

Question 38

Energy output falls into two categories; what are they? Define them.

Answer 38

1) External work: Energy used when skeletal muscles contract to move the body or objects
2) Internal work: All other forms of energy (two types; skeletal muscle non-movement work and everything else)

Question 39

1) What is internal work a type of?
2) What is skeletal muscle non-movement work a type of?

Answer 39

1) Energy output
2) Internal work

Question 40

What are the two types of internal work? Give examples of each

Answer 40

1) Skeletal muscle non-movement work: shivering, posture, etc.
2) Everything else: pumping blood, breathing, cell transport, metabolism, repair

Question 41

1) Chemical energy used by the body is converted into what?
2) 50% of the energy from nutrient molecules is captured as what? What happens to the rest?

Answer 41

1) Thermal energy (heat)
2) ATP; lost as heat

Question 42

1) What percent of total energy from nutrients is used? What percent is lost as heat?
2) When is more energy lost as heat?
3) Is heat entirely wasted?

Answer 42

1) About 25% is used, 75% lost as heat
2) When cells use ATP
3) No, used to maintain temperature.

Question 43

1) Define metabolic rate
2) Give the formula for metabolic rate
3) What is metabolic rate normally expressed in terms of?

Answer 43

1) The rate at which energy is expended by external and internal work
2) Energy expenditure / time
3) Heat

Question 44

1) The Basic unit of heat energy is what? Define this term.
2) What do we use for terms of human heat generation instead? Why?
3) 1 Calorie = _________ calories

Answer 44

1) a calorie: amount of energy required to raise temperature of 1g of H2O by 1°C
2) Too small to be useful in human heat gen; kilocalorie “Calorie”
3) 1000

Question 45

What causes you to shiver or sweat?

Answer 45

Hypothalamus

Question 46

What hormone rises at night? What rises during the day?

Answer 46

Melatonin rises at night, cortisol rises during the day

Question 47

In the U.S. when we say “calories” we are referring to what?

Answer 47

Calories (kilocalories)

Question 48

1) Define metabolic rate
2) What are some of the many factors it depends on?

Answer 48

1) rate of heat production
2) Exercise, emotional state, shivering, food intake, etc and skeletal muscle activity

Question 49

What is able to raise metabolic rate to the greatest extent? What increases can affect metabolic rate?

Answer 49

Skeletal muscle activity ; even slight increases

Question 50

Define BMR (Basal metabolic rate)

Answer 50

1) Metabolic activity necessary to maintain basic body functions
2) Minimal waking rate of internal energy expenditure

Question 51

slide 40
1) What 3 factors does the metabolic rate need to be adjusted for?
2) Larger person has _____________ rate of heat production than a smaller person
3) _____________ hormone is the primary (but not sole) determinant of BMR

Answer 51

1) Size, age, sex
2) higher
3) Thyroid

Question 52

1) True or false: BMR is not the body’s lowest metabolic rate, it is the baseline waking rate
2) Sleep is __________ lower likely due to ________________

Answer 52

1) True
2) 10-15%; muscle relaxation

Question 53

1) Define neutral energy balance
2) Define positive energy balance
3) Define negative energy balance

Answer 53

1) Amount of energy input exactly equals energy output; energy from food intake exactly equals internal and external energy expenditure
2) Food intake energy exceeds energy expended. Body stores energy.
3) Energy expended exceeds food intake energy. Body uses stored energy.

Question 54

1) Food intake is primarily regulated by what?
2) Energy is balanced through what?

Answer 54

1) Hypothalamus
2) Molecular signals

Question 55

Energy is balanced through what 4 molecular signals?

Answer 55

1) How much fat is stored
2) Feeding status
3) Hunger
4) Circulating nutrients

Question 56

1) What part of the hypothalamus regulates hunger?
2) Define this structure

Answer 56

1) Arcuate nucleus of the hypothalamus
2) Two subsets of neurons functioning in opposition

Question 57

List, define, and give the functions of the two subsets of neurons (functioning in opposition) in the arcuate nucleus of the hypothalamus

Answer 57

1) One releases neuropeptide Y (NPY): Highly potent appetite stimulator. Promotes weight gain.
2) The other releases melanocortins: Suppress appetite in humans (allow camouflage in other animals)

Question 58

Two areas of the hypothalamus are richly supplied by axons from neurons of the arcuate nucleus; what are they? What does each do?

Answer 58

1) Lateral hypothalamic area (LHA): Produces orexins which are potent appetite stimulators
2) Paraventricular nucleus (PVN): Release chemical messengers that decrease appetite

Question 59

1) What stimulates the LHA?
2) What stimulates the PVN

Answer 59

1) LHA Stimulated by NPY, inhibited by melanocortins
2) Stimulated by melanocortins and inhibited by NPY

Question 60

1) What is leptin essential for?
2) What does serum leptin directly correlate to?
3) What does it suppress? What does it act on?
4) What is inhibited? What is stimulated?

Answer 60

1) Normal body-weight regulation
2) Stored triglycerides
3) Appetite; acts on arcuate nucleus
4) Inhibits NPY, stimulates melanocortins

Question 61

1) List the steps that allow decreased fat stores to increase appetite?
2) What is leptin the dominant factor of?

Answer 61

1) Decreased fat stores =
decreased triglycerides =
decreased leptin =
decreased inhibition of NPY and decreased stimulation of melanocortins =
increased appetite
2) Long term energy balance

Question 62

1) What is insulin?
2) What does it stimulate?
3) What is an increase in insulin secretion accompanied by?
4) What does it inhibit?

Answer 62

1) Hormone secreted by pancreas in response to glucose and other nutrients in the blood
2) Cellular uptake, use, and storage of nutrients
3) Increased use or storage
4) NPY-secreting cells of hypothalamus

Question 63

List two leptin-signaling disturbances and what causes each

Answer 63

1) Hypothalamic “set point” is set higher
-Receptors do not respond appropriately to high leptin levels
2) Defect in chemical messengers affecting blood-brain barrier
-Brain not responding to leptin appropriately

Question 64

1) There’s an Abundance of convenient, palatable, inexpensive, energy dense foods; why?
2) Companies invest a significant amount of research into engineering what and applying what principles?

Answer 64

1) Combination of fats, carbs, and salt is hyperpalatable
2) “Addictive” foods and applying psychosocial principles to their marketing of these foods