Week 11 independant reading energy balance and thermoregulation

Metabolism

refers to all chemical reactions in the body to maintain life. These reactions are divided into two types anabolism and catabolism

Anabolism

building large complex molecules (proteins and fats) from smaller ones, this process requires energy

Catabolism

breaking down large molecules into smaller components to release energy

metabolic rate

the rate at which the body uses energy to perform vital functions like breathing

Basal Metabolic Rate

the body’s energy use under resting conditions, measured when a

person is awake but at rest, has fasted for at least 12 hours, and is in a thermoneutral environment (not

too hot or cold). BMR reflects the energy needed to keep the body’s basic systems running.

factors that affect metabolic rate

Body size and composition – muscle tissue increases metabolic rate more than fat tissue.

• Age and sex – BMR decreases with age and tends to be higher in males.

• Hormones – thyroid hormones and epinephrine can raise BMR.

• Body temperature and fever – increase metabolic rate.

• Nutritional status and activity level – affect daily energy expenditure.

Liver role in metabolism

• responsible for processing and distributing nutrients after they are absorbed from the digestive tract

• helps maintain blood glucose homeostasis by storing excess glucose as glycogen (glycogenesis)

• releases glucose during fasting through glycogenolysis and gluconeogenesis

livers role in fat metabolism

• converts excess carbohydrates and proteins into fatty acids and triglycerides

• produces ketone bodies during fasting

• synthesizes cholesterol and lipoproteins

Livers role in protein metabolism

• performs deamination of amino acids and converts toxic ammonia into urea for excretion

Adipose Tissue

• serves as body long term energy reserve

• In the fed state, adipocytes store excess energy as triglycerides, a process promoted by insulin through

  lipogenesis.

• During fasting, lipolysis releases fatty acids into the bloodstream for other tissues to use for energy.

• secretes leptin which regulates appetite and energy expenditure

• secretes adiponectin which enhances insulin sensitivity and fatty acid oxidation

Skeletal Muscle role in metabolism (fed state)

• major site of energy use and protein storage

• in fed state, muscles take up glucose and store it as glycogen

• during exercise muscle fibers oxidize glucose and fatty acids to generate atp for contraction

Skeletal muscle role in metabolism (fasted state)

• glucose availability decreases, muscle proteins are broken down into amino acids, which are sent to liver to support gluconeogenesis

Energy yields per gram of nutrient

Carbohydrates: 4 kcal/g

• Proteins: 4 kcal/g

• Fats: 9 kcal/g

Hypothalamus

serves as the primary control center for appetite, integrating signals about nutrient levels, hormone concentrations, and stomach stretch.

Ghrelin

• stimulates hunger when energy stores are low

Hormones involved in Satiety

Leptin, released by adipose tissue, reflects long-term energy stores and suppresses appetite when fat stores are adequate.

• Insulin, secreted after meals, promotes nutrient uptake and also signals the brain to decrease

hunger.

• Peptide YY and cholecystokinin (CCK), released from the small intestine, contribute to short-

term satiety after eating.

Thermoregulation

• hypothalamus acts as bodys thermostat

Circulatory System role in thermoregulation

distributes heat generated by active tissues throughout the body.

It adjusts blood flow to the skin to help regulate temperature, redirecting warm blood toward the surface when you’re hot and conserving heat by limiting blood flow to the skin when you’re cold.

It also transports nutrients, oxygen, and hormones that fuel and coordinate metabolism.

muscular system and thermoregulation

major contributor to both energy use and heat production. Skeletal

muscles generate heat during movement and through involuntary contractions such as shivering,

which increases body temperature during cold exposure.

endocrine system role in thermoregulation

regulates metabolism through hormones such as insulin, glucagon,

thyroid hormones, and cortisol, which control how nutrients are stored, released, or used for

energy. These hormones adjust energy balance in response to the body’s activity level, nutritional

state, and temperature requirements.

Integumentary system role in thermoregulation

acts as the body’s interface with the

environment. It helps control heat loss through sweating, vasodilation, and vasoconstriction,

while also providing insulation through subcutaneous fat and hair.

which type of reaction releases energy by breaking down complex molecules?

catabolism

what does metabolic rate measure

the rate at which the body uses energy

. Which of the following increases metabolic rate?

A. Low body temperature

B. Fasting and malnutrition

C. Thyroid hormones and fever

D. Sleep deprivation

C. thyroid hormones and fever

Which tissue type contributes most to metabolic rate?

A. Muscle tissue

B. Adipose tissue

C. Connective tissue

D. Cartilage

A. muscle tissue

Which organ acts as the body’s metabolic hub?

A. Pancreas

B. Liver

C. Kidney

D. Stomach

B. liver

Which process allows the liver to maintain blood glucose during fasting?

A. Lipogenesis

B. Glycogenolysis and gluconeogenesis

C. Glycolysis only

D. Ketogenesis inhibition

B. Glycogenolysis and gluconeogenesis

7. Which statement about adipose tissue is correct?

A. It stores energy as triglycerides and releases fatty acids when needed

B. It only provides insulation and cushioning

C. It produces bile and detoxifies toxins

D. It breaks down proteins during fasting

A

8. What is the major role of skeletal muscle in metabolism?

A. Uses and stores large amounts of energy; provides amino acids during fasting

B. Produces bile and stores glucose for other tissues

C. Secretes hormones that regulate body temperature

D. Converts fatty acids directly into glucose

A

9. During the fed state, skeletal muscle primarily:

A. Breaks down protein for gluconeogenesis

B. Takes up glucose and stores it as glycogen

C. Uses only fatty acids for energy

D. Produces ketone bodies

B

10. During fasting, skeletal muscle contributes to energy balance by:

A. Releasing amino acids for gluconeogenesis

B. Making glucose directly from glycogen

C. Increasing fat storage

D. Releasing insulin

A

11. The hypothalamus regulates appetite by integrating signals from:

A. Hormones, nutrient levels, and stomach stretch receptors

B. The liver and kidneys

C. Only blood glucose levels

D. The adrenal medulla

A

13. Which hormone signals long-term energy sufficiency and suppresses appetite?

A. Leptin

B. Insulin

C. Epinephrine

D. Thyroxine

A

12. Which hormone increases appetite before meals?

A. Leptin

B. Insulin

C. Ghrelin

D. CCK

C

14. When body temperature rises, the body responds by:

A. Vasodilation and increased sweating

B. Vasoconstriction and shivering

C. Increasing food intake

D. Reducing sweat production

A

15. When body temperature falls, the body responds by:

A. Vasodilation and sweating

B. Increasing heart rate and sweating

C. Vasoconstriction and shivering

D. Lowering metabolic rate

C

16. Which organ system distributes heat and adjusts blood flow to regulate temperature?

A. Endocrine system

B. Circulatory system

C. Digestive system

D. Lymphatic system

B

17. Which organ system produces most of the body’s heat during activity or shivering?

A. Endocrine

B. Muscular

C. Integumentary

D. Respiratory

B

18. Which organ system helps control heat loss through sweating and vasoconstriction?

A. Nervous system

B. Integumentary system

C. Digestive system

D. Immune system

B

19. Why is maintaining body temperature important for metabolism?

A. To keep heart rate steady

B. To prevent excessive sweating

C. Because enzymes function only within a narrow temperature range

D. To reduce oxygen use

C