Phys Chapter 22: Metabolic adaptations, energy, balance, and temperature regulation

Where does energy to form ATP come from?

• food we eat (carbs, fats, proteins)

• catabolism of our body tissues

The energy value in food is measured as what

kilocalories

1 kilocalorie (1 Calorie) is equal to how many calories

1000 calories

1 calorie is equal to the amount of energy to raise how many cm of water

to raise 1 cubic cm water 1 degree C

Energy requirements depend on what

physical activity

The typical rqange, average female, and average male energy requirements

• can range from 1,300 to 5,000 kcal/day

• average male= 2,900 kcal/day

• average female= 2,100 kcal/day

what molecules can be used for energy

glycogen and fat are good sources, body proteins can be used in emergencies

once fatty acids, glucoes, and amino acids are in the blood stream, what do they do?

they are ciculationg energy constructs

What is the brains preferred energy source

glucose

what is the skeletal muscles at rests preferred energy source?

fatty acids

What organs use ketone bodies

brain

what organ uses lactic acid

heart

what organ uses amino acids

liver

How is the metabolic rate measured

by the amount of heat generated or amounf ot O2 consumed per minute

what is the basal metabolic rate (BMR)

• measurement of the metabolic rate in quiet, resting, and fasting condition

• 1200-1800 kcal/day in adults

What hormone increased basal metabolic rate

T3/T4

What factors affect metabolic rate

hormones, exercise, nervous system, body temperature, ingestion of food, age, other factors

what hormones affect metabolic rate

• T3 and T4 are major regulators of BMR - calorigenic effect

• testosterone, insulin, and growth hormone

How does exercise affect metabolic rate

strenuous exercise increases metabolic rate 15x the basal rate

how does the nervous system affect metabolic rate

• sympathetic NS

• Epi/Norepi

How does body temperature affect metabolic rate

an increase in 1 degree Celsius increased the rate of reactions by 10%

How does ingestion of food affect metabolic rate

food induced thermogenesis- “cost” of digesting, absorbing, and storing nutrients

what other factors affect metabolic rate

age, gender, sleep, climate, malnutrition, etc.

what is the absorptive state

ingested nutrients enter the blood stream from GI tract to provide energy for the body 

the absorptive state has what readily available in blood

readily available glucose in blood

what is the post absorptive state

the GI tract lacks nutrients, and energy for the body is supplied by the breakdown of the body’s own nutrient store

the postabsorptive state does not have readily available ____ in blood

glucose

What does plasma concentration of glucose and amino acids regulate

regulates secretion of insulin and glucagon

What is the fasting plasma glucose range amount

65-105 mg/dl

what does the absorptive state range rise to 

rises to 140-150 mg/dl

What are the steps to supply energy needs/ synthesize proteins for absorptive state reactions?

1. catabolism of glucose

2. catabolism of amino acids

3. protein synthesis 

4. catabolism of few dietary lipds

What are the steps to convert into energy stores for absorptive state reactions?

5. glycogenesis

6. lipogenesis

7. transport of triglycerides from liver to adipose tissue

What is catabolism of glucose

• cellular respiration

• 50% of glucose from typical meal is used to produce ATP

What is catabolism of amino acids

• deaminated (removal of amine group)

  • enter krebs cycle

  • synthesize glucose or fatty acids

what is protein synthesis

in liver or skeletal muscle (plasma proteins)

what is catabolism of few dietary lipids

• only a few dietary lipids catabolized for ATP

• Most stored in adipose tissue

what is glycogenesis

• excess glucose converted to glycogen in liver and skeletal muscle 

• 10% of glucose stored as glycogen

What is lipogenesis

• liver converts excess glucose or amino acids to triglycerids to store

• adipocytes also take up excess glucose to convert to triglycerides

• ~40% of glucose converted to triglycerides

what is transport of most triglycerides from liver to adipose tissue

most triglycerides packed into very-low-density lipoproteins (VLDLs) and carried to adipose tissue for storage

What hormone promotes the absorptive reactions

insulin

After a meal insulin is released. what stimulates its release?

• Glucose dependent insulinotropic peptide (GIP) from small intestine

  • intestinal incretin - feedforward control

• Increased glucose and certain amino acids

Glucose is transported into cells by what type of diffusion

facilitated diffusion

Glucose is transported into cells by facilitated diffusion via what 

GLUT

how does GLUT transport glucose into cells b y facilitated diffusion

• insulin inserts GLUT 4 into cells (especially muscles and adipocytes)

• GLUT 2 (hepatocytes) and GLUT 3 (neurons) are always present

what are hepatocytes

liver cells

What are the steps of the postabsorptive state and the maintenance of blood [glucose]

1. glycogenolysis in the liver

2. glycogenolysis in muscle

3. lipolysis

4. protein catabolism

5. gluconeogenesis

What are the steps of the postabsorptive state and glucose sparing

6. catabolism of fatty acids

7. catabolism of lactic acid 

8. catabolism of amino acids

9. catabolism of ketone bodies

what role does glycogenolysis in the liver play in postabsorptive state

• released glucose into blood

  • glucose-6-phosphate

• 4 hours supply of glucose

what role does glycogenolysis in muscle play in postabsorptive state

• lacks glucose-6-phosphate

  • muscle can only use glycogen itself

what role does lipolysisplay in postabsorptive state

glycerol is converted to glucose in the liver

what role does protein catabolism play in postabsorptive state

amino acids converted to glucose

what role does gluconeogenesis play in postabsorptive state

• glucose formed from noncarbohydrate sources

  • lactic acid, glycerol, or amino acids

what role does catabolism of fatty acids play in postabsorptive state

converted to AcetylCoA and used to make ATP

what role does catabolism of lactic acid play in postabsorptive state

cardica muscle can use lactic acid to make ATP

what role does catabolism of amino acids play in postabsorptive state

hepatocytes can use amino acids directly to make ATP

what role does catabolism of ketone bodies play in postabsorptive state

• hepatocytes convery fatty acids to ketone bodies which can be used to amke ATP

  • Acetoacteic acid

  • Beta-hyroxybutyric acid

  • Acetone

What 2 things is the postabsorptive state regulated by

hormones and sympathetic nervous system

What does decreased blood glucose in postabsorptive state stimulate

• release of glucose

• activation of sympathetic neurons

  • release neurotransmitter norepinephrine

  • adrenal medullae released epi/norepi

Stress stimulates the release of what 

cortisol

what does cortisol promote in postabsorptive state

gluconeogenesis, lipogenesis, and protein catabolism

What is fasting?

going without food for hours or days

what is starvation

weeks or months of food deprivision or inadequate food intake

what happens with an increase in ketogenesis

• formation of ketone bodies increases as fatty acid catabolism increases

• can be used for ATP production (cardiacand skeletal muscle fibers; Neurons)

what is the normal ketone level

0.01 mmol/liter

what happens when we fast for 2+ days

ketones increase 100-300 times higher (1-3 mmol/liter)

• supplies 1/3 of brains fuel for ATP production

what happens when a person goes through starvation for 40 days

• ketones provide 2/3 of brains energy

• presence od ketones reduces use of glucose for ATP production

  • decreases gluconeogenesis and catabolism of muscle

What happens when someone has ketoacidosis

low pH because of build-up of ketone bodies

what is food intake regulated by

• neural control

• endocrine control

• nutrient levels in blood

• GI tract signals

how does neural control regulate food intake

hypothalamus regulates satiety

• arcuate nucleus

• paraventricular nucleus

• neurotransmitter melanocortin inhibits food intake

what is leptin produced by

adipocytes

what does leptin regulate

the amount of adipose tissue present

what does leptin inhibit

hypothalamic pathways that increase eating and activated other pathways that increase energy expenditure

what does neuropeptide Y stimulate

food intake

what is ghrelin stimulated by

stomach

what does ghrelin increase

appetite

how do nutrient levels in blood regulate food intake

increases in blood glucose decreases appetite

how do GI tract signals regulate food intake

distention of stomach and duodenum inhibit food intake

How is body temperature regulated

despite wide fluctuations in environmental temp, homeostasis maintains constant internal body temp

• constant core temp around 37 degrees C (98.6 degrees F)

• shell temp (body surface) is typically 1-6 degrees lower than core temp

what is conduction

heat exchange between materials that are in direct contact with eachother

• example: coffee mug warms hands

what is convection

transfer of heat by the movement of air or water between areas of different temps

• example: convection oven moves air

what is radiation

transfer of heat in the form of infrared rays between a warmer object and a cooler one without physical contact

• example: sitting in the sun

what is evaporation

conversion of a liquid to a vapor

• example: sweat

where does the preoptic are receive input from

peripheral (in hypothalamus) and center thermoreceptors

what does the heat-losing center do

lowers body temp

• ex: sweating, face/ body turning red due to vasodilation, etc.

what dpes the heat-promoting center do

raises body temp

• vasoconstriction

• release of epi/norepi

• shivering

• release of thyroid hromones