Physiology Lecture 23
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Questions and Answers

What are the three forms of energy storage in the body?

  • Triglycerides, protein, glucose
  • Glycogen, triglycerides, protein (correct)
  • Glycogen, starch, protein
  • Glycogen, triglycerides, minerals

Triglycerides are primarily stored in the liver.

False (B)

Where is glycogen stored in the body?

Liver and muscle

During the fasting phase, glucose is derived from the ______.

<p>liver</p> Signup and view all the answers

Match the hormones with their functions:

<p>Insulin = Promotes nutrient storage Glucagon = Releases glucose from storage Epinephrine = Stimulates glycogenolysis and lipolysis Cortisol = Promotes catabolism</p> Signup and view all the answers

How long can triglycerides provide energy?

<p>Several weeks (D)</p> Signup and view all the answers

The use of protein for energy is efficient and cost-effective.

<p>False (B)</p> Signup and view all the answers

What hormone primarily controls anabolic processes for nutrient metabolism?

<p>Insulin</p> Signup and view all the answers

Glucose is stored as ______ and/or triglycerides during the digestive phase.

<p>glycogen</p> Signup and view all the answers

Match the hormones with their classification;

<p>Insulin = Anabolic hormone Glucagon = Counter-regulatory hormone Epinephrine = Catabolic hormone Growth hormone (GH) = Counter-regulatory hormone</p> Signup and view all the answers

What effect does insulin have on skeletal muscle?

<p>Stimulates insulin independent glucose transport with muscle activity via GLUT4 (D)</p> Signup and view all the answers

Insulin decreases ketogenesis in the liver.

<p>True (A)</p> Signup and view all the answers

What is the main target of glucagon?

<p>Liver</p> Signup and view all the answers

Insulin increases the activity of ________ in adipose tissue.

<p>Lipoprotein Lipase (LPL)</p> Signup and view all the answers

Match the hormone with its action:

<p>Insulin = Increases FFA storage Glucagon = Promotes glucose synthesis FFA = Act as a glucose sparing effect LPL = Facilitates lipid storage</p> Signup and view all the answers

Which GLUT transporter is involved in glucose transport in the liver?

<p>GLUT2 (B)</p> Signup and view all the answers

FFA can be directly converted to glucose.

<p>False (B)</p> Signup and view all the answers

What happens during a marathon in terms of metabolic hormone activity?

<p>Nearly all metabolic hormones are active.</p> Signup and view all the answers

During a sprint, hormonal activity is too ________ for the body to respond effectively.

<p>quick</p> Signup and view all the answers

Match the activity with its phase:

<p>During sprint = Too quick for hormonal activity After sprint = Repletion from liver to muscle During marathon = Nearly all metabolic hormones active After marathon = Repletion by eating</p> Signup and view all the answers

What role do alpha cells in the pancreas play?

<p>Secretion of glucagon (B)</p> Signup and view all the answers

Carbo-loading guarantees improved performance.

<p>False (B)</p> Signup and view all the answers

What causes the closure of ATP-dependent K+-channels in pancreatic beta cells?

<p>Increase in ATP levels</p> Signup and view all the answers

The initial burst of insulin secretion represents the release of ________ insulin.

<p>pre-formed</p> Signup and view all the answers

Match the pancreatic mechanisms with their functions:

<p>Alpha cells = Secrete glucagon Beta cells = Secrete insulin Somatostatin = Inhibit glucagon and insulin C peptide = Diagnostic purposes for insulin production</p> Signup and view all the answers

Which of the following hormones inhibits insulin secretion?

<p>Somatostatin (B), Epinephrine (C)</p> Signup and view all the answers

Insulin secretion is controlled solely by hormones.

<p>False (B)</p> Signup and view all the answers

What is the main function of glucose entering pancreatic beta cells?

<p>To trigger insulin secretion</p> Signup and view all the answers

The ________ phase of insulin secretion involves the synthesis of new insulin.

<p>secondary</p> Signup and view all the answers

What is more efficient for insulin response, oral administration or intravenous?

<p>Oral administration (B)</p> Signup and view all the answers

What is one function of epinephrine during physical activity?

<p>Enhances oxygen transport to muscles (A)</p> Signup and view all the answers

Growth hormone decreases blood glucose levels by increasing insulin sensitivity.

<p>False (B)</p> Signup and view all the answers

What role does cortisol play during stress or fasting?

<p>It stimulates hepatic gluconeogenesis, promotes protein catabolism, and supports lipid metabolism.</p> Signup and view all the answers

During exercise, plasma glucose remains steady because the liver releases __________ to match increased skeletal muscle uptake.

<p>glucose</p> Signup and view all the answers

Match the hormone to its primary effect:

<p>Epinephrine = Increases cardiac output and oxygen transport Growth Hormone = Promotes protein anabolism and mobilizes energy Cortisol = Stimulates gluconeogenesis and supports metabolism Thyroid Hormone = Has permissive effects for other hormones</p> Signup and view all the answers

What happens to insulin levels during exercise?

<p>Insulin levels fall (D)</p> Signup and view all the answers

Fat oxidation can sustain high-intensity activities effectively.

<p>False (B)</p> Signup and view all the answers

What does prolonged exposure to growth hormone stimulate in the kidneys?

<p>Glucose production</p> Signup and view all the answers

Cortisol has permissive effects with hormones like __________ and glucagon.

<p>epinephrine</p> Signup and view all the answers

Which hormone is primarily responsible for regulating metabolism during stress?

<p>Cortisol (B)</p> Signup and view all the answers

Flashcards

What are the three main forms of energy storage?

Glycogen, triglycerides, and protein are the three main energy storage forms in the body.

Where is glycogen stored and how long does it last?

Glycogen is primarily stored in the liver and muscles, providing energy for a short duration, typically less than a day.

Where are triglycerides stored and how long can they provide energy?

Triglycerides are stored in adipose tissue, representing the largest energy reservoir in the body, lasting several weeks.

Where is protein stored and why is using it for energy costly?

Protein is stored in muscle tissue. Using protein for energy is considered costly since it involves breaking down functional muscle tissue.

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What happens to glucose during the digestive phase?

During the digestive phase, glucose is taken up by skeletal muscle, liver, and adipose tissue.

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How is glucose stored in the body during the digestive phase?

During the digestive phase, glucose is stored as glycogen or triglycerides (TG).

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What is the source of glucose, amino acids, and FFA during the fasting phase?

In the fasting phase, glucose is derived from the liver, amino acids are obtained from skeletal muscle, and free fatty acids are released from adipose tissue.

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Which hormone primarily controls anabolic processes for nutrient metabolism?

Insulin is the primary hormone regulating anabolic processes, promoting nutrient storage when levels are high.

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Which hormones are counter-regulatory and promote catabolism?

Glucagon, epinephrine, growth hormone (GH), cortisol, and thyroid hormone (TH) are counter-regulatory hormones that promote catabolism.

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Which hormone is the dominant regulator?

Insulin is the dominant hormone regulating glycolysis and anabolism while glucagon, epinephrine, and GH promote glycogenolysis and lipolysis.

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Epinephrine's role in energy

Epinephrine (adrenaline) increases the heart's pumping action, improving blood flow to muscles and vital organs, ensuring better oxygen and nutrient delivery.

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Growth hormone's role in energy

Growth hormone (GH) increases lean muscle mass by promoting protein synthesis, mobilizes energy through carbohydrate and fat breakdown, and regulates blood glucose levels.

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Cortisol's role in energy

Cortisol, a stress hormone, plays a crucial role in energy regulation by facilitating the actions of other hormones (like glucagon & epinephrine), promoting glucose production in the liver, breaking down protein for energy, and supporting fat breakdown.

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Thyroid hormone's role in energy

Thyroid hormone primarily acts as a facilitator for other hormones, allowing them to function effectively in energy regulation.

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Blood glucose during exercise

During physical activity, blood glucose levels remain stable as the liver releases glucose to match the increased uptake by working muscles.

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Insulin's role during exercise

Insulin levels decrease during exercise, minimizing energy storage and promoting the release of glucose and fats for energy.

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Body's energy adaptation during exercise

The body adapts to varying energy demands during exercise by regulating energy expenditure and mobilizing different fuel sources, such as glycogen and fat.

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Fat oxidation vs. glycogen for energy

Fat oxidation (burning fat) cannot sustain high-intensity activities, which rely on glycogen (stored carbohydrate) for energy.

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Cortisol's effect on blood sugar

Cortisol enhances the effects of other hormones, such as glucagon and epinephrine, on blood sugar levels.

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Liver's role in maintaining blood glucose during exercise

The liver releases glucose into the bloodstream to compensate for the increased uptake by skeletal muscles during exercise.

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Glucose Metabolism in Beta Cells

The process where glucose is converted into ATP, a molecule that supplies energy for cellular functions. This process occurs inside pancreatic beta cells.

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GLUT2 Transporter

A protein transporter found on the surface of pancreatic beta cells responsible for transporting glucose from the bloodstream into the cell.

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ATP-sensitive Potassium Channels

A type of potassium channel in pancreatic beta cells that is sensitive to ATP levels. When ATP levels rise, these channels close, leading to membrane depolarization.

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Membrane Depolarization

A key event in insulin secretion triggered by the closure of ATP-sensitive potassium channels, leading to the opening of voltage-gated calcium channels.

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Calcium Influx

A mineral essential for insulin secretion. It enters the beta cell through voltage-gated calcium channels and triggers the release of insulin.

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Pancreatic Beta Cells

These cells in the pancreas produce insulin, a hormone that regulates blood sugar levels.

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Insulin

A hormone released from the pancreas that lowers blood glucose levels by promoting glucose uptake by cells.

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Biphasic Insulin Secretion

The initial rapid release of pre-formed insulin stored within beta cells, followed by a slower, sustained secretion of newly synthesized insulin.

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Glucagon

A hormone produced by the pancreas that increases blood glucose levels by stimulating the breakdown of glycogen in the liver.

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Somatostatin

A hormone that inhibits both insulin and glucagon release, contributing to the regulation of blood glucose levels.

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Insulin Independent Glucose Transport in Muscle

Insulin's action on muscle cells is independent of insulin transport. Muscle activity brings GLUT4 transporters to the cell membrane, allowing glucose uptake.

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Insulin Independent Glucose Transport in Liver

Unlike muscle, liver cells utilize GLUT2, which is always present on the membrane, enabling insulin-independent glucose uptake.

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Long-term Insulin Deficiency

When insulin levels decrease significantly and for a long period, it triggers a cascade of events, primarily affecting the liver and ultimately leading to increased glucagon activity.

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Glucagon Action on Liver

Glucagon, released when blood sugar is low, stimulates the liver to produce glucose from stored glycogen and other sources, directly impacting glucose synthesis.

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FFA Indirect Effect on Glucose Synthesis

Free fatty acids (FFA) released from fat stores can indirectly trigger glucose synthesis in the liver.

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FFA Glucose Sparing Effect

FFAs released from fat stores act as a 'glucose sparing' effect, meaning they can provide energy without using glucose, thus conserving it for vital organs.

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Ketone Production

Ketones, produced from FFA breakdown, require increased FFA levels in the blood to be formed.

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GLP1 and Glucagon Interaction

GLP1 and glucagon both help regulate blood sugar by influencing glucagon secretion. GLP1 inhibits glucagon release, while glucagon promotes it.

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Metabolic Activity During Sprint

During intense, short bursts of activity like sprinting, hormonal responses are too slow to be significant. Muscle relies on stored glycogen.

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Metabolic Activity After Marathon

Following a marathon, the primary focus is on replenishing glycogen stores in muscles using glucose from the liver.

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Study Notes

Energy Storage Forms

  • The three energy storage forms in the body are glycogen, triglycerides, and protein.

Glycogen Storage

  • Glycogen is stored in the liver and muscle.
  • The liver's glycogen stores can supply energy for less than a day, while the muscles' stores are smaller.
  • Only the liver can supply glycogen to other tissues.

Triglyceride Storage

  • Triglycerides are stored in adipose tissue.
  • Adipose tissue is the largest energy reservoir, lasting several weeks.

Protein Storage

  • Protein is stored in muscle tissue.
  • Protein use for energy is costly as it involves breaking down functional muscle tissue.

Glucose during Digestive Phase

  • During digestion, glucose is absorbed and enters skeletal muscle, liver, and adipose tissue.
  • Glucose is stored as glycogen or triglycerides (TG).

Glucose, Amino Acids, and FFA during Fasting Phase

  • Glucose is derived from the liver.
  • Amino acids are obtained from skeletal muscle.
  • Free fatty acids are released from adipose tissue.

Anabolic Hormone

  • Insulin primarily controls anabolic processes.
  • Increased insulin levels promote nutrient storage.

Counter-Regulatory Hormones

  • Glucagon, epinephrine, growth hormone, and cortisol are counter-regulatory hormones which promote catabolism.

Epinephrine

  • Epinephrine is a hormone crucial in exercise and stress situations.
  • It encourages glycogenolysis in muscle and adipose tissue, and lipolysis to release fatty acids.
  • It also increases blood flow and oxygen to muscles and vital organs.

Growth Hormone (GH)

  • GH increases lean body mass promoting protein anabolism in muscles.
  • It mobilizes energy from carbohydrates and lipids.
  • GH reduces peripheral tissues' insulin sensitivity, leading to higher blood glucose levels.
  • GH also plays a role in regulating acidosis and ammonia production during metabolic stress.

Cortisol

  • Cortisol is essential for life and energy regulation.
  • It has permissive effects on glucagon and epinephrine, enabling them to function efficiently.
  • Cortisol stimulates hepatic gluconeogenesis to maintain blood glucose.
  • Cortisol promotes protein catabolism to supply amino acids for energy.
  • Cortisol supports lipid metabolism.

Thyroid Hormone

  • Thyroid hormone primarily has a permissive effect in metabolic processes.

Blood glucose during Exercise

  • During exercise, plasma glucose remains stable because the liver releases glucose to match the increased muscle uptake.
  • Insulin levels decrease during exercise, reducing storage processes and promoting the release of glucose and fats for energy.

Metabolism during Exercise

  • The body adapts to energy demands during exercise by regulating energy expenditure; mobilizing different fuel sources, such as glycogen.
  • Fat oxidation cannot sustain high-intensity activities relying on glycogen.
  • Glucose intake must be controlled during exercise to prevent disruptions in free fatty acid availibility or redirection of glucose to non-working tissues.
  • Muscle fatigue is linked to glycogen depletion, though other factors like carbohydrate intake may contribute.

Insulin Secretion

  • Insulin secretion is controlled by nutrients, hormones, and nerves.
  • Glucose metabolism within beta cells triggers insulin release through a sequence of steps involving ATP-sensitive K+ channels.

Additional Control of Insulin Secretion

  • GLP-1 is an important stimulator of insulin secretion.
  • Amino acids and oral administration trigger a more potent insulin response compared to intravenous administration.
  • Insulin secretion is biphasic—consisting of an initial burst and a secondary phase—with pre-formed insulin released initially and new insulin synthesized and released afterward.

Insulin's Acute Effects

  • Insulin's actions on skeletal muscle, liver, and adipose tissue involve glucose transport differently—independent of insulin.
  • Insulin's action on tissues includes decreased ketogenesis in the liver and increased FFA storage in adipose tissue.
  • Insulin's role includes increased activity of lipoprotein lipase and decreased activity of hormone-sensitive lipase.

Prolonged Insulin Deficiency

  • Prolonged insulin deficiency leads to various metabolic disturbances.
  • Elevated free fatty acids, hyperglycemia, oxidative stress, and potentially further damage may occur.
  • Insulin resistance can be a result of elevated oxidative stress, contributing to diabetic complications.

Glucagon's Role

  • Fatty acids indirectly increase glucose synthesis, but cannot be directly converted to glucose.
  • Glucagon acts as a glucose-sparing factor, increasing plasma ketones.
  • Glucagon plays a role in lipid and protein actions.
  • Regulation of glucagon and GLP-1 involves a multitude of factors and metabolic processes during exercise and recovery.

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