Energy Balance and Temp Regulation

Question 1

What is the difference between external and internal work performed by the body?

Answer 1

External - contraction of skeletal muscles in order to move body or move object

Internal - skeletal muscle contractions (isometric contractions - posture, shivering) & life sustaining activities (heart beating, breathing, active transport, chemical reactions)

Question 2

Where does the energy used in internal work eventually go?

Answer 2

50% energy –> transferred to ATP

rest lost as heat (body heat)

• 100% of energy expended during isometric contractions converted to heat

Question 3

What is metabolic rate? Is it constant?

Answer 3

rate at which energy is expended by the body

• varies based on activity –> awake; more muscular tone (flaccid arms when asleep) when awake some level of contraction

Question 4

kilocalories

Answer 4

1 kcal = amount of thermal energy needed to raise the temperature of 1 kg H2O by 1°C

Question 5

Does muscular tone produce body heat? Or only active movement of skeletal muscles?

Question 6

What is basal metabolic rate (BMR)? What largely determines the BMR?

Answer 6

Minimal metabolic rate necessary to power life-sustaining activities while awake

Measure: Minimize skeletal muscle contractions (all internal work = body heat); BMI measured by body heat

Indirectly - measure O2 consuming
Direct - chamber full water, how much body warms surrounding water (measures energy expenditure)

Question 7

BMR largely determined by ___

Answer 7

thyroid hormone

Question 8

What is the difference between a positive, negative or neutral energy balance?

Answer 8

Neutral energy balance: input energy = energy expended -> no change in stored energy

Positive energy balance: input energy > energy expended –> increase in stored energy (weight gain)

Negative energy balance: input energy < energy expended –> decrease in stored energy (weight loss)

Question 9

Where is the arcuate nucleus and why is it important?

Answer 9

plays central role in long-term control of body weight and short-term control of food intake

Question 10

What are the general functions of neuropeptide Y and melanocortins?

Question 11

secreted by pancreas in response to rise in blood glucose following a meal

Answer 11

Insulin; inhibits cells in arcuate that release neuropeptide Y –> surpasses appetite

Question 12

Does neuropeptide Y suppress or increase appetite? How about melanocortins? How about insulin? How about leptin?

Answer 12

• neuropeptide Y: increases appetite
• melanocortins: appetite suppressing; Insulin

Question 13

What are adipokines?

Answer 13

hormones releases by fat cells (adipocytes)

Question 14

Leptin

Question 15

Ghrelin

Question 16

Why do we stop eating before the nutrients in a meal actually enter the bloodstream? How does our body know to stop?

Answer 16

Peptide YY: hormone released by small & large intestines; increases as meal progresses—signals satiety (feeling full)

= inhibits neuropeptide Y-secreting neurons (surpasses appetite)

Question 17

Fats/proteins ingested ___ released

Answer 17

Cholecystokinin (CCK): hormone released by duodenum when fat and protein-rich chyme enters small intestine –> feel full

Question 18

What is the body’s core temperature maintained at? Why is it important to maintain core temperature?

Answer 18

Internal core temperature (thoracic and abdominal cavities) maintained at 100°F

• tight range ~ 100 degrees; keep chemical rxns in body

Question 19

What are the various processes by which heat is exhanged between the body and environment? Could you explain each?

Answer 19

1) Radiation - emission or absorption of heat energy as electromagnetic waves (greater temp, greater radiation of electromagnetic infrared waves); much of body heat lost

2) Conduction - transfer of heat by direct contact

3) Convection - transfer of heat energy by moving currents (Shell of air body warmed –> rises and replaced by cooler air –>body heat lost at faster rate)

4) Evaporation - heat energy used as the water in sweat state change –> liquid to gas (cooling mechanism)

Question 20

Thermal conductivity

Answer 20

Water vs. Outside temperature

• water colder than even though same temperature

Question 21

What are sources of heat input to the body?

Answer 21

Cellular respirations –> chem rxn –> source of heat

Question 22

What detects changes in core temperature? How about changes in skin temperature? Where in the brain is this information sent?

Answer 22

Thermoregulatory centers in hypothalamus

Question 23

Could you describe what compensations the body might produce for an increase in core temperature? How about for a decrease in core temperature?

Question 24

What does the thermoneutral zone mean?

Question 25

What is hypothermia and hyperthermia?

Question 26

What is heat exhaustion? How does it differ from heat stroke?