Lecture 18 - Control of Growth and Metabolism

Question 1

What is metabolism and what are the 3 components

Answer 1

It’s the sum of all chemical and physical changes that occur in body tissues

1. Basal metabolic rate
2. Mobilization and delivery of nutrients to cells
3. Anabolism and cell/tissue growth

Question 2

What is basal metabolic rate (BMR)?

Answer 2

An estimate of the energy intake the entire body requires to produce enough ATP to maintain all its basic functions at rest

Question 3

Describe the mobilization and delivery of nutrients to cells in the body

Answer 3

Each cell contains a nutrient pool that has nutrients that are immediately available for catabolism by its mitochondria

Question 4

What is anabolism and cell/tissue growth?

Answer 4

Anabolism is the building of macromolecules from smaller components

Growth in the body involves a combination of anabolism, individual cell growth, cell proliferation (growth and proliferation), and cell survival

Question 5

How do thyroid hormones regulate BMR and where are thyroid hormone receptors located?

Answer 5

Thyroid hormone signalling can directly regulate BMR by affecting mitochondrial function

Thyroid hormone receptors are located in the mitochondria and upregulate aerobic metabolic activity when activated

Question 6

How do thyroid hormones affect metabolic processes (ie. regulating nutrient mobilization and uptake, and regulating anabolism and cell/tissue growth)

Answer 6

They indirectly affect these metabolic processes through nuclear receptors

Thyroid hormone receptors located in the nucleus change the expression levels of specific genes in the target cells when activated

Question 7

How do non-thyroid hormones affect metabolism?

Answer 7

They alter the availability of nutrients in the bloodstream through effects on energy stores

Ex. Epinephrine and glucagon mobilize stored glucose and fatty acids. Glucocorticoids and growth hormones mobilize stored fatty acids and glucose, promote lipid use, and stimulate gluconeogenesis

Question 8

Describe the “glucose-sparing effect”. What metabolism category does this lie under?

Answer 8

Glucocorticoids and GH show this effect to promote the use of lipids for metabolism by most somatic cells, saving glucose for the CNS. The adipose cells are stimulated to break down stored fat, fuelling growth effects

*The CNS cannot use fatty acids to generate ATP

Mobilization and delivery of nutrients to cells category

Question 9

How does growth hormone play a primary role in promoting growth? What metabolism cateogry/ies does this fall under?

Answer 9

Growth effects increases uptake of amino acids from the blood and enhances cellular proliferation and reduces apoptosis. They also influence the glucose-sparing effect

Mobilization and delivery of nutrients to cells, anabolism and cell/tissue growth categories

Question 10

True or false? Only metabolic hormones regulate growth at different life stages

Answer 10

False - metabolic and non-metabolic hormones regulate growth at different life stages

Question 11

Name 7 symptoms of hyperthyoidism

Answer 11

1. Intolerance to heat
2. Bulging eyes
3. Facial flushing
4. Tachycardia
5. Increase in systolic blood pressure
6. Weight loss
7. Muscle wasting

Question 12

Name 8 symptoms of hypothyroidism

Answer 12

1. Intolerance to cold
2. Facial and eyelid edema
3. Extreme fatigue
4. Apathy
5. Lethargy
6. Anorexia
7. Muscle aches and weakness
8. Weight gain

Question 13

What are 6 ways thyroid hormone receptors influence the body?

Answer 13

1. Feeding behaviour and activity level - non-endocrine hypothalamic neurons
2. Increase cardiovascular output by increasing sensitivity to sympathetic stimulation
3. Skeletal muscle growth and repair - directly increase muscle energy expenditure
4. Enhance blood production by bone marrow and mineral turnover by bone
5. Regulates nutrient homeostasis roles of the liver
6. Modulate adipocyte development and regulation

Question 14

What is the function of the pancreas?

Answer 14

It secretes 2 peptide hormones, glucagon and insulin, that directly regulate blood glucose and glucose use

Question 15

How does glucagon and insulin work together to maintain blood glucose level?

Answer 15

They use opposing negative feedback loops to help maintain a normal blood glucose level (4-7 mmol/L)

Insulin stimulates glucose uptake by cells

Glucagon stimulates gluconeogenesis and glyconeogenesis in liver and release of glucose to plasma

Question 16

How is insulin secretion directly regulated by blood glucose at a cellular level?

Answer 16

ATP production via glycolysis directly affects the Vm of pancreatic beta cells and thus stimulates insulin secretion

At a resting Vm, ATP is down, and K_ATP channels are open and the voltage-gated Ca2+ channel is closed, so insulin remains in the secretory vesicles (no secretion)

If blood glucose increases, ATP is produced, closing K_ATP channels causing the cell the depolarize -> Ca2+ channels open and the Ca2+ entry triggers exocytosis and insulin is secreted

Question 17

State 2 functions of insulin

Answer 17

1. Allows cells to take glucose up from the bloodstream (in somatic cells ie. myofibre or adipocyte)
2. In the liver, insulin helps to reduce blood glucose by enhancing storage through glycogen synthesis

Question 18

What is Type I Diabetes Mellitus and name 4 symptoms

Answer 18

An endocrine disorder that’s caused by destruction of insulin-secreting pancreatic beta cells

Symptoms:
1. High glucose in blood and urine
2. Wasting
3. Frequent urination and increased thirst
4. Drowsiness and lethargy

Question 19

What is Type II Diabetes Mellitus and name 2 symptoms

Answer 19

An endocrine disorder caused by insulin resistance (acquired receptor insensitivity; no uptake of glucose)

Symptoms:
1. High glucose in blood and urine
2. Secondary complications of high glucose

Risks increase with age, genetics, body mass, and inactivity