Control of Growth and Metabolism Flashcards
What is metabolism?
Sum of all chemical and physical changes that occur in the body tissue
What are the three main components of metabolism?
- Basal metabolic rate
- Mobilization and delivery of nutrients to cells
- Anabolism and cell/tissue growth
What is basal metabolic rate?
Think CALORIES
Generation of ATP
- measure of energy
- how many nutrients are available
- how much ATP can be generated (some waste will be produced)
- how much ATP do we need to make to maintain basic processes/functions
- typically measured in CALORIES
- the number of calories your body needs to accomplish its most basic (basal) life-sustaining functions.
- an estimate of the energy intake the entire body requires to produce enough ATP to maintain all its basic functions at rest
What is mobilization and delivery of nutrients to cells?
- movement of nutrients and delivery of them to cell so that they can use that ATP for other processes
- hormones affect the ability to move nutrients
- mobilizing and distributing the nutrient pool to cells throughout the body
- nutrients are obtained through the digestive tract
What is anabolism and cell/tissue growth?
- small molecules building up larger molecules (building of macromolecules from smaller components)
- synthesis of complex molecules (from fatty acids, glucose, smaller molecules, etc.)
- requires use of ATP
- smaller components build up for cell growth/tissue growth
- involves cell division, growth and proliferation
Heat is a byproduct of using ATP: Explain its uses
- waste is produced as a result of using ATP
- heat is one of those waste products
- heat contributes to maintaining general body temperature
What is a nutrient pool of a cell?
All the nutrients that are immediately available for catabolism by its mitochondria
- may find stores of nutrients in cells
- will be available for certain cell types to generate ATP at any time
Briefly summarize what each effect is and an example of a hormone that regulates this aspect of metabolism:
Direct regulation of BMR
BMR - how much ATP is needed to maintain basic functions (calories)
Direct effect of THYROID hormones
Briefly summarize what each effect is and an example of a hormone that regulates this aspect of metabolism:
Regulating nutrient mobilization and uptake
Movement/delivery of nutrients to different cells (availability to produce ATP at a given time)
Thyroid hormones, epinephrine, cortisol, growth hormone, glucagon, insulin
Briefly summarize what each effect is and an example of a hormone that regulates this aspect of metabolism:
Regulating anabolism and cell/tissue growth
Building up of larger molecules from small molecules
Thyroid hormones, growth hormone, somatomedins, sex steroids, calcitriol
Recall: What are class 1 hormones?
Amino-acid derivatives
- hydrophobic
- epinephrine and thyroid hormones
- produced and stored in vesicles
- released as needed or when calcium levels rise
What are class 2 hormones?
Peptide hormones
- hydrophilic
- stored in large vesicles and released when calcium levels rise
What are class 3 hormones?
Lipid-derivative hormones
- hydrophobic
- travel through blood with a carrier protein because they are lipid-soluble and cannot travel through the fluid by themselves
- bind to intra-cellular receptors
How do thyroid hormones directly regulate BMR?
Regulate BMR by affecting mitochondrial function
- thyroid hormones are hydrophobic hormones that act through intracellular receptors
- bind to protein receptors on mitochondria and within nucleus
- directly changes the rate in which ATP is generated
- directly affects MBR because the hormone binds to receptor on mitochondria
- can increase ATP production in mitochondria = more waste = more heat (thermal regulation)
What does is mean for thyroid hormones to be hydrophobic?
They are class 1 - amino-acid derivative hormones
- they are hydrophobic
- have the ability to pass through the membrane on its own but cannot travel through the bloodstream by itself
- must bind to carrier proteins to reach target cells
- acts on intracellular proteins because they do not interact with the membrane
How do thyroid hormones indirectly affect metabolic processes?
Thyroid hormones indirectly affect metabolic processes by changing gene expression through nuclear receptors
- can affect nutrient mobilization and uptake
- can regulate anabolism and cell/tissue growth
Instead of acting on the mitochondria (direct effect), thyroid hormones act on intracellular receptors located in the nucleus to change the expression levels of specific genes in the target cells when activated
How do non-thyroid hormones affect metabolism? Which non-thyroid hormones do this?
Non-thyroid hormones that affect metabolism alter the availability of nutrients in the bloodstream through effects on energy stores
- affect the mobilization and delivery of nutrients to cells
HORMONES: epinephrine, glucagon, growth hormone, glucocorticoids
Non-thyroid hormones: Epinephrine and glucagon
How do they affect metabolism in the liver and adipose tissue?
ACTS ON LIVER AND ADIPOSE TISSUES
- Epinephrine
- Glucagon
- release fatty acids (mobilize stored glucose and fatty acids)
- release fatty acids and mobilized stored glucose (increase blood glucose when it is low)
What is the glucose sparing effect and which non-thyroid hormone controls this?
The effects of glucocorticoids/GH include the stimulation of triglyceride breakdown (breakdown of lipids) and release into the blood by adipocytes
This results in a switch by most tissues from utilizing glucose as an energy source to utilizing fatty acids
This process is called a glucose-sparing effect
Allows for the body to reserve glucose for the brain and use fatty acids for the rest of the body to supply energy for basic functions
- tells other parts of the body to use fatty acids instead of glucose as energy
Non-thyroid hormones: Glucocorticoids and growth hormone
How do they affect metabolism in the liver and adipose tissue?
ACTS ON LIVER AND ADIPOSE TISSUES
- Glucocorticoids
- Growth hormone
- stores glucose and can synthesize glucose and fatty acids (glucose sparing effect)
- mobilize stored fatty acids and glucose AND promote lipid use AND stimulate gluconeogenesis
How do glucocorticoids and GH have the glucose sparing effect?
- liver
- muscle fibres
- adipose tissue
- brain/CNS
They promote the use of lipids for metabolism by most somatic cells to save glucose for the CNS/brain
- tells the liver to make glucose but tells the rest of the body to use fatty acids instead of glucose (stores glucose and can synthesize glucose, fatty acids, and ketones)
- if glucose stores run out, there are amino acid stores in muscle fibres that can be used if glucose levels become dangerously low
- both hormones release fatty acids but streamline glucose to the CNS to maintain the function of the brain
- hoards all the good stuff for the brain
- the rest of the tissues use fatty acids
Why do we need the glucose sparing effect?
To save up glucose for the CNS to use because the CNS cannot use fatty acids to generate ATP
- tells other tissue types to use fatty acids instead of glucose
- release stored glucose in the liver for the brain
What are the effects of synthesizing ketones for metabolism?
Production of ketone leads to the production of many toxins
- long-term: very harmful
- short-term: maintains brain
How does the pituitary growth hormone play a primary role in promoting growth?
- mobilization and delivery of nutrients to cells
- anabolism and cell/tissue growth
Release of GH causes:
- glucose-sparing effect
- growth effects
- increases uptake of amino acids from the blood
- enhances cellular proliferation and reduces apoptosis
- indirectly (somatomedins) acts on liver and stimulates liver to release hormones/release glucose/produce more glucose
- diabetogenic effect
- stimulates liver to break down glycogen into glucose, fueling growth effects
- can have a negative feedback effect on the inhibition of GH from the anterior pituitary
What are the four targets of the pituitary growth hormone?
- Bone cells
- Muscle cells
- Nervous system cells
- Immune system cells
At what life stage do reproductive hormones regulate growth?
Anabolism and cell/tissue growth
- role of different hormones at different stages of life
Puberty
- stimulate cell growth and differentiation in their target tissues
At what life stage do thyroid hormones regulate growth?
Anabolism and cell/tissue growth
- role of different hormones at different stages of life
Embryo & infancy
- required for normal growth and for NS development
At what life stage do parathyroid hormones and calcitriol regulate growth?
Anabolism and cell/tissue growth
- role of different hormones at different stages of life
Childhood
- promote absorption of calcium salts for later deposition in bone
True or False: Correct all false statements
Thyroid hormones (T3 and T4) act through intracellular receptors found in both the nucleus and mitochondria
TRUE
True or False: Correct all false statements
Thyroid hormones can directly affect the amount of energy used by an organism to generate ATP when it is at rest
TRUE
- describing the direct effect of thyroid hormones on BMR
- maintaining/generating ATP
True or False: Correct all false statements
Hypersecretion of thyroid hormones is associated with increased fatigue and intolerance to cold
FALSE
- thyroid hormones promote metabolism and increase ATP production
- oversecretion of thyroid hormones = binds to mitochondria = activates ATP generation = more ATP = more energy = more waste = more heat
- more intolerant to HEAT
True or False: Correct all false statements
Epinephrine and cortisol both lead to a release of glucose and fatty acids into the bloodstream, but only cortisol also enhances the uptake of fatty acids by somatic organs for use in aerobic metabolism
TRUE
- epinephrine acts on the adipose tissue and liver to simulate the release of glucose and fatty acids into the bloodstream
- cortisol (glucocorticoids) and growth hormones are the only two that participate in the glucose-sparing effect
True or False: Correct all false statements
Thyroid stimulating hormone (TSH) increases the release of thyroid hormones from the thyroid, and the growth-releasing hormone (GHRH) increases the release of growth hormone from the liver
FALSE
- second half is False
- GHRH comes from the hypothalamus, acts on the anterior pituitary and then releases GH that CAN act on the thyroid (?)
True or False: Correct all false statements
All hormones that affect growth at different life stages are trophic hormones (What are trophic hormones?)
Trophic hormones - hormones that increase cell proliferation/division
FALSE
Why
What causes metabolic endocrine disorders?
- Overproduction or underproduction of hormones
- Reduced sensitivity of hormone receptors
What are some symptoms of over-secretion (hypersecretion) of thyroid hormones and why do these symptoms happen?
Over-active
Bulging eyes
Sweaty/skinny
Weight loss
Thyroid hormones stimulate the production/metabolism of ATP so when there is an oversecretion of thyroid hormones, this can cause the body to be over-active and experience symptoms of over-active metabolism
What are some symptoms of over-secretion (hyposecretion) of thyroid hormones and why do these symptoms happen?
Under-active
Heavier
Chilly/chubby
Weight gain
Thyroid hormones stimulate the production/metabolism of ATP so when there is an undersecretion of thyroid hormones, this can cause the body to be under-active and not experience the metabolism that they are supposed to in order to maintain healthy body conditions
Thyroid hormones have pleiotropic effects, but what does that mean?
Thyroid hormones have receptors on many different organs and organ systems which allows them to cause many different effects that are usually unrelated
List some of the effects of thyroid hormones
- Regulating nutrient and homeostasis in the liver
- Alter adipocyte development and regulation -> weight loss/weight gain
- Influences skeletal muscle growth and repair and directly increases muscle energy expenditure
- Influences feeding behaviour and energy expenditure through non-endocrine hypothalamic neurons (appetite)
- Increase cardiovascular output, increase sensitivity to sympathetic stimulation (elevated heart rate/blood pressure)
- Enhance blood production by bone marrow and mineral turnover by bone
Match the following symptom of thyroid disorder to the most likely target organ/system responsible for that symptom:
Sweating and facial flushing
Responsiveness to sympathetic ANS stimulation
Match the following symptom of thyroid disorder to the most likely target organ/system responsible for that symptom:
Increased blood pressure and heart rate
Responsiveness to sympathetic ANS stimulation
Match the following symptom of thyroid disorder to the most likely target organ/system responsible for that symptom:
Weight loss/muscle wasting
Changes to nutrient mobilization
Changes to skeletal muscle aerobic metabolism
Match the following symptom of thyroid disorder to the most likely target organ/system responsible for that symptom:
Intolerance to heat/cold
Changes to skeletal muscle aerobic metabolism
- cannot generate heat or generates too much heat from ATP metabolism
- how much or how little ATP is being generated as a waste product
Match the following symptom of thyroid disorder to the most likely target organ/system responsible for that symptom:
Anorexia (lack of appetite)
Changes to hypothalamic neural circuit activity
Match the following symptom of thyroid disorder to the most likely target organ/system responsible for that symptom:
Apathy/lethargy
What are pancreatic islets
Clusters of cells in the pancreas
What are the two peptide hormones secreted by pancreatic islets and what are their functions
- Glucagon
- Insulin
Is the pancreas an exocrine or endocrine organ? What is the difference between exocrine and endocrine?
Pancreas is both an exocrine and endocrine organ
Exocrine = secretes substances into a ductal system
Endocrine = secretes substances directly into the bloodstream
What kind of pancreatic cell secretes glucagon
Alpha cells
What kind of pancreatic cell secretes insulin
Beta cells
Differentiate the function of glucagon and/or insulin
Glucagon and insulin interact with each other in a negative feedback loop
Glucagon = secreted when blood glucose is low and acts to raise blood glucose
Insulin = secreted when blood glucose is high and acts to lower blood glucose
Describe the direct feedback regulation of glucagon and insulin
When blood glucose levels are detected to be HIGH, insulin is released from the pancreas to lower blood glucose levels
- does so by synthesizing glycogen from glucose
- increases glucose uptake in cells to get rid of glucose in the bloodstream
- allow cells tot ake glucose up from bloodstream
Once blood glucose levels fall back to normal, the secretion of insulin is shut off
When blood glucose levels are detected to be LOW, glucagon is released from the pancreas to raise blood glucose levels
- does so by breaking down glycogen into useable glucose
Once blood glucose levels fall back to normal, the secretion of glucagon is shut off
HOMEOSTASIS OR ALLOSTASIS??
What stimulates insulin secretion
The production of ATP from glycolysis (breakdown of glucose) directly affects the membrane potential of pancreatic beta cells and causes insulin secretion
- Insulin would’ve been stored in vesicles
- When blood glucose increases, the pancreatic beta cells become depolarized
- Insulin is released from the pancreatic beta cells
What is the role of insulin in the liver
In the liver, insulin helps to reduce blood glucose by enhancing storage of glucose through glycogen synthesis
- acts on hepatocytes (liver cells)
What is Type I Diabetes Mellitus
- an endocrine disorder caused by destruction of insulin-secreting pancreatic beta cells
THROUGH THE DESTRUCTION OF INSULIN-SECRETING PANCREATIC BETA CELLS, INSULIN CANNOT BE SECRETED INTO THE BLOODSTREAM TO LEVEL BLOOD GLUCOSE WHEN IT ABNORMALLY HIGH
- causes hyposecretion of insulin
- high glucose in blood and urine
- wasting of glucose(?)
- frequent urination and increased thirst
- drowsiness and lethargy
- can be caused by viral infection (usually in childhood)
- fatal within months if not treated
What is Type II Diabetes Mellitus
- endocrine disorder caused by insulin resistance (Acquired receptor insensitivity)
WHEN THE INSULIN RECEPTORS ON CELLS FAIL TO RESPOND TO INSULIN PROPERLY, THIS DECREASES THE UPTAKE OF GLUCOSE INTO THE CELLS AND OUT OF THE BLOODSTREAM = CAUSES BLOOD GLUCOSE TO REMAIN HIGH
- high glucose in blood and urine
- secondary complications of high glucose
- risks increase with age, genetics, body mass, and inactivity
- much more common than Type I diabetes
What are some secondary complications of high glucose caused by Type II Diabetes Mellitus
- affects epithelial cells
- elevated blood glucose damages blood tissues
- damaged blood tissues can lead to increased cardiovascular issues
- leads to many health effects
Differentiate Type I from Type II diabetes
Type I = DESTRUCTION OF INSULIN-SECRETING PANCREATIC BETA CELLS
Type II = CAUSED BY INSULIN RESISTANCE IN RECEPTOR CELLS
Which of the following treatments would be directly helpful for treating Type I DM? Type II DM?
A. A low carb, high fat/protein diet
B. Regular insulin injection
C. Medications to reduce gluconeogenesis and liver glucose release
D. Losing weight and increasing physical activity
Type I DM
- A, B, D
- if you lose the cells that make insulin, the strategy is to replace insulin = replacing what is lost (losing the hormone = replace what is lost) = insulin injection
Type II DM
- A, C, D
- decrease the load on receptors = treat type II DM
How can type II DM be treated
- with insulin injections, pump, inhalers
- home glucose meters
- oral medications
- improved diet, exercise, and lifestyle overall
