L4 Metabolic Regulation

Question 1

Absorptive state

Answer 1

period when ingested nutrients are entering the blood from the GI tract, occurs DURING meal digestion

Question 2

Postabsorptive state

Answer 2

period when the GI tract is empty of nutrients, therefore energy must be supplied from catabolism of body stores

normal blood glucose concentration must be maintained

Question 3

True fasting

Answer 3

no food for 24 hours

Question 4

Digestion

Answer 4

not equivalent to absorption

breakdown of food into molecules small enough to be absorbed, accomplished by enzymes

Question 5

Absorption

Answer 5

movement of food molecules from the GI tract into the blood

digestion occurs before absorption

Question 6

Carb & Protein absorption

Answer 6

breakdown of these products are absorbed by the GI tract directly into the blood, circulates to the liver via the portal vein and then into systemic circulation

Question 7

Fat absorption

Answer 7

1. ingested fats are emulsified by bile salts
2. gut cells transform fats into chylomicrons
3. Travel to the blood via lymph system, end up in adipose and muscle
4. Broken down into FFA and chylomicron remnant

Question 8

Chylomicrons

Answer 8

enable fats to move within the aqueous environment of blood

travel through lymph vessels/lacteals to use lymph to enter the blood via the thoracic duct

chylomicron remnants become VLDLS to be resecreted into the blood

Question 9

What happens to absorbed glucose

Answer 9

Enters cells to become ATP if energy is needed

Energy not needed: make fat or make glycogen in muscle and liver

Question 10

What happens to glucose in the liver?

Answer 10

1. Made into glycogen
2. Processed to form triglycerides
3. MOST is packaged to form VLDLs, which are then stored as triglycerides

Question 11

VLDLs and Triglyceride storage

Answer 11

VLDL is made of cholesterol and triglycerides

Adipose tissue contains lots of lipoprotein lipase, which breaks down VLDL

VLDL becomes fatty acid and monoglyceride (remains in blood and are metabolized by liver)

Question 12

What happens to absorbed triglycerides?

Answer 12

absorbed fat becomes stored fat

Comes from the chylomicrons that transfer FFA to adipose tissue

lipoprotein lipase breaks down these into FFA, monoglycerides, chylomicron remnants.

absorbed fat from your food becomes stored as fat in adipose tissue

Question 13

What happens to absorbed amino acids?

Answer 13

1. Majority are taken up by cells for protein synthesis
2. Others enter the liver to make liver proteins, plasma proteins, or keto acids
3. Protein only replaces protein that was lost in postabsorptive state
4. Any excess becomes stored as fat

Question 14

Summary of absorptive state

Answer 14

1. most of cells energy needs are provided by absorbed glucose
2. Some glucose is stored as glycogen in liver and skeletal, most excess is stored as fat
3. There is a net uptake of glucose by the liver
4. Synthesis of body proteins, much of dietary protein is used for energy or converted to fat

Question 15

As the absorptive state ends…

Answer 15

net synthesis ceases
net catabolism begins

Question 16

Events that maintain normal blood glucose during postabsorptive state

Answer 16

1. Processes that provide sources of blood glucose (Glycogenolysis, Gluconeogenesis from fat or protein)
2. Increased fat utilization, which spares glucose

Question 17

Glycogenolysis

Answer 17

from liver directly
muscle only indirectly via cori cycle

Question 18

Gluconeogenesis

Answer 18

pyruvate, lactate, glycerol, amino acids

from fat = only glycerol

from protein = few hours into postabsorptive state, AA become source of blood glucose. large quantities of protein can be catabolized from muscles if needed

Question 19

Glucose sparing

Answer 19

Includes all processes that enable to utilize fat for energy vs glucose in postabsorptive state, accelerated lipolysis is necessary

Most tissues use GLUCOSE in absorptive state
Most tissues use FAT in post absorptive

Question 20

Summary of postabsorptive

Answer 20

1. Glycogen, fat, protein anabolism are curtailed, net catabolism begins
2. Glucose is formed by glycogenolysis and gluconeogenesis
3. Accelerated lipolysis releases FFA into blood, through beta oxidation, and ketones
4. Brain uses glucose and ketones

Question 21

Hormonal regulation of metabolsim

Answer 21

The most important regulators with respect are 2 peptide hormones, both produced and released from islets of langerhans in pancreas

insulin = beta
glucagon = alpha

Question 22

Insulin

Answer 22

anabolic hormone of absorptive state

Secretion INCREASES during absorptive
Secretion DECREASES during postabsorptive

has two actions, metabolic and growth-promoting effects

Question 23

Metabolic effects of insulin

Answer 23

effects on carbohydrates, lipid, and protein synthesis

Question 24

What occurs after a meal?

Answer 24

1. Plasma glucose concentration rises, stimulates insulin secretion from beta pancreatic cells
2. Insulin is released into the blood and binds to muscle, fat, and liver cells, resulting in glucose being taken up
3. Insulin inhibits gluconeogenesis in the liver
4. Blood glucose level decreases, which serves as a negative feedback signal

Question 25

GLUT4 transporters

Answer 25

when insulin binds to its receptor, signal transduction pathway leads to movement of glucose transporters from inside of cell to surface of cell GLUT4 transporters move glucose from blood into the cell the more glucose transporters in the cell membrane, the more glucose that can be taken up by the cell

Question 26

What stimulates insulin release?

Answer 26

high blood glucose high blood amino acid activation of parasympathetic nerves to islets peptides secreted from GI tract due to eating

Question 27

What inhibits insulin secretion?

Answer 27

activation of sympathetic nerves to islets and/or increase in circulating epinephrine

Question 28

Glucagon

Answer 28

hormone of the postabsorptive state overall effect of glucagon is to increase plasma glucose concentration main target organ is the liver

Question 29

Main effects of glucagon

Answer 29

increases glycogen breakdown increases gluconeogenesis promotes ketone synthesis

Question 30

Plasma concentrations in the postabsorptive state

Answer 30

plasma glucose is low glucagon is high insulin is low

Question 31

Regulators of glucagon secretion

Answer 31

Low blood glucose concentration is the major stimulus sympathetic innervation to islets stimulates glucagon secretion circulating epinephrine stimulates glucagon secretion

Question 32

What's happening when you become hypoglycemic?

Answer 32

Glucagon secretion and activation of the SNS hormonal and neural responses insulin is low, glucagon is high hypothalamus mediates the response increased SNS causes increased glycogenolysis, gluconeogensis, lipolysis increase in plasma glucose, fatty acids, glycerol

Question 33

Additional hormones that regulate metabolism

Answer 33

Cortisol and Growth hormone their secretion is not strictly tied to transition between absorptive and postabsorptive states both produce actions that are opposite to insulin, they both increase blood glucose levels

Question 34

Cortisol

Answer 34

many metabolic reactions cannot occur unless a small amount of cortisol is present cortisol is necessary to maintain necessary concentrations of enzymes required for gluconeogensis and lipolysis cortisol also plays a role in counter regulatory mechanisms that protect against hypoglycemia

Question 35

What does cortisol do?

Answer 35

it is catabolic increases protein catabolism increases fat catabolism increases gluconeogenesis net result = increased plasma concentration of AA, glucose, FFA = fuel in the blood!

Question 36

Growth hormone

Answer 36

stimulate growth and protein synthesis has minor effects on metabolism, severe changes in amounts affects carb/lipid metabolism can increase gluconeogenesis, reduces isulins ability to promote glucose uptake

Question 37

Counter-regulatory hormones

Answer 37

hormones that have effects opposite to insulin glucagon, cortisol, growth hormone, epinephrine they are the ones that save your life during times of fasting, because they raise plasma glucose levels

Question 38

Similarities in Postabsorptive and Exercise state

Answer 38

Both have an increase in SNS, increased levels of glucagon, cortisol, GH, low plasma insulin

Question 39

Fuel during exercise

Answer 39

during exercise, large quantities of fuel must be mobilized to provide energy for muscle contraction major sources are plasma glucose and FFA, muscle glycogen

Question 40

Plasma glucose during exercise

Answer 40

SHORT TERM: remains unchanged for 50 min LONG TERM: falls about 25% 4 hrs

Question 41

Plasmas Concentrations during exercise

Answer 41

Glucagon--> increases with a trigger of low glucose Insulin--> preprogrammed actions, preparing for the changes in the body Lipolysis is increasing as this is happening

Question 42

Changes during exercise

Answer 42

1. All exercise intensities cause SNS activity increases and circulating epinephrine increases 2. These changes are independent of blood glucose levels, they are a part of preprogrammed response to exercise 3. During prolonged exercise, hypoglycemia stimulates glucagon secretion 4. Exercise inhibits insulin secretion

Question 43

What is the time course of fuel utilization during mild/moderate intensity exercise?

Answer 43

1. During a brief period of moderate exercise, energy is derived from carbs and lipids equally 2. As exercise continues, glycogen decreases, blood glucose becomes main source 3. With increasing time, glucose utilization may outpace gluconeogensis and glycogen stores are depleting. Hypoglycemia is what triggers glucaogn secretion 4. After 1 hr, gradual increase in utilization of lipid for energy

Question 44

Lipid utilization during exercise

Answer 44

increases as exercise duration increases during 1st 40-90 min = 40% of energy comes from FFA by 4th hour of exercise, lipid is 62% Very long exercise , FFA supplies 80%

Question 45

Hitting the wall

Answer 45

-glycogen depleted state -work capacity progressively decreases -due to a slower rate of energy released from lipid, compared to carb catabolism S/S: weakness, fatigue, dizziness

Question 46

Techniques to prevent hitting the wall

Answer 46

1. Consume carbs during exercise 2. Consume carbs before exercise 3. Decrease exercise intensity

Question 47

Consume carbs before exercise

Answer 47

Helps to maximize initial glycogen levels in muscles includes combo of increasing complex carb intake and decreasing training intensity during few days before event recommended for events that last more than 60-90min

Question 48

Decrease exercise intensity

Answer 48

Lowers total energy requirements also lowers the percentage of energy that comes from glycogen

Question 49

Lipid and exercise intensity

Answer 49

Lipid utilization increases as exercise intensity decreases -Mild exercise intensities have main source as lipids -

Question 50

Lipid and training

Answer 50

Lipid utilization increases as training increases more aerobically trained individuals use more plasma FFA and conserve glycogen stores Why? have increased # of enzymes involved in FFA use, improve transport of FFA through membrane, proliferation of capillaries in trained muscle

Question 51

Immediate energy...

Answer 51

ATP-CP system walking briskly for 1 min all out exercise for 6 sec uses Stored ATP

Question 52

Short term energy...

Answer 52

anaerobic glycolysis all out exercise for 1-2 minutes uses blood glucose

Question 53

Long-term energy...

Answer 53

aerobic metabolism prolonged exercise uses kreb cycle

Question 54

Short-term energy transfer system

Answer 54

Provided by anaerobic glycolysis and lactate production allows for rapid ATP formation, not as fast as ATP-CP has a power output of 45% of the immediate energy system

Question 55

Blood lactate accumulation

Answer 55

Most rapid and highest lactate levels are reached during 1-2 minutes of all out exercise lactate is formed continuously at rest and during exercise in aerobic, lactate production rate matches lactate removal rate blood lactate rises exponentially at 55% of healthy untrained VO2 max

Question 56

Aerobic conditioning and lactate levels

Answer 56

Lactate marks anaerobic system uses or the limit of aerobic production of ATP Aerobic conditioning causes: 1. production of less lactate 2. increased rate of lactate removal 3. increased capillarization 4. Increased mitochondrial density 5. Increased concentration of enzymes 6. Increased intramuscular glycogen stores

Question 57

Factors related to lactate threshold

Answer 57

low tissue O2 reliance on glycolysis activation of fast-twitch muscle fibers reduced lactate removal

Question 58

Long-term energy system

Answer 58

source is aerobic metabolism -O2 uptake rises exponentially during first minute of moderate exercise -plateaus to reach steady state -theoretically, you can continue indefinitely at this level

Question 59

Steady-state

Answer 59

balance between energy requirements and ATP production by aerobic metabolism lactate produced is oxidized