Metabolism

Question 1

Glucogon is stimulated by

Answer 1

Low blood glucose levels which stimulates glycogen breakdown in liver

Question 2

Insulin is stimulated by

Answer 2

High blood glucose levels which stimulates glycogen formation in lver and glucose uptake by tissue cells

Question 3

In absense of insuline signal (diabetes)

Answer 3

Body mobilizes fats, but no glucose can be made. Build up of ketone bodies in the blood (could lead to ketoacidosis as loss of acetyl-CoA acceptor molecules)

Question 4

3 P’s of diabetes mellitus

Answer 4

1. Polyuria (excess glucose in urine=inhibitation of water resorption by kidney)
2. Polydipsia (Dehydration stimulates hypothalamic thirst centers)
3. Polyphagia (Excessive hunger: starving due to inability to use ingested carbs)

Question 5

Type 1 diabetes

Answer 5

No insulin production–> due to autoiummune reaction (molecular mimicry - Bcells as intruders)

Question 6

Type 2 diabetes

Answer 6

Reduction in insulin secretion+/ target cell sensitivity. Ketoacidosis less of a problem for type 2

Question 7

Liver functions

Answer 7

1. Carb metabolism (glucose store…glycogenolysis- release glucose, gluconeogenesis- conv)
2. Fat metabolism (beta oxidativea
3. Protein metabolism (site of amino acid deamination (forms urea for removal of ammonia). Major site of generation of non-essential amino acids by transamination
4. Vitamin storage (1-2yr vit A, 1-4m, vit D,B12)
5. Biotransformation (“ionactivates” ethanol, drugs, actives some drugs)

Question 8

4 major types of lipoproteins (triglycerides and cholesterol)

Answer 8

1. Chylomicrons (mostly lipids= lowest density)
2. VLDL (triglycerides to adipose tissue. VLDL–>LDL)
3. LDL (Deliver cholesterol to tissues
4. HDL (cholesterol to liver)

Question 9

Trans fats

Answer 9

Unsaturated, stimulate an increaes in LDL, decrease HDL. REALLY BAD

Question 10

Unsaturated-Cis

Answer 10

Promote catabolism and excretion of chlosterol

Question 11

Saturated

Answer 11

“not that good” makes more chlosterol

Question 12

Anatomy of thyroid gland

Answer 12

Composed of follicles. Follicle cells produce thyroglobin. Iodinated thyroglobin serves as precursor for thyroid hormone. Parafolicular cells produce calcitonin.

Question 13

Thyroid hormone derived from:

Answer 13

1. Throxine (T4)- secreted by thyroid follicles. contains 4 iodine molecules
2. Triiodothyronine (T3) More active thyroid homrone. Derived from T4 at target cells

Question 14

6 steps of synthesis of thyroid hormone

Answer 14

1. Thryroglobin into follicle
   and Iodide transported from capillary in
2. Thyroglobin in through packaged exocytosis and iodide oxidized into iodine
3. Tyrosines (from thryoglobin) and iodine attache forming T1 and T2. We call out for this when we need it.
4. T1 and T2 are linked together to form T3 and T4
5. These are endocytosed and combined with a lysosome
6. Lysomsomal enzymes cleave T3 and T4 and hormones diffuse into bloodstream!

Question 15

Why is T3 so much more potent?

Answer 15

Active form. Higher affinity to receptors than T4

Question 16

Regulation of thyroid hormone.

Answer 16

Falling thyroid hormone levels lead to secretion of TSH (thryroid stimulating hormone) in the anterior pituitary. This released stored thyroid hormone (from follicules) and resynthesizes more.

Question 17

TH affects every cell in the brain except

Answer 17

adult brain, spleen, testes, uterus and thyroid gland

Question 18

Major function of TH

Answer 18

Regulate BMR, heat production (can do this in part by stimulating enzymes involved in glucose oxidation. Maintaining blood pressure, regulates tissue growth and dev.

Question 19

Nervous system. Hypo and hypersecretion of TH

Answer 19

Hypo: “slow stuff”. slowed brain dev. mental dulling, depression, memory impairment.

Hyper: “fast stuff”. Irritarbility, restlessness, insomnia

Question 20

Muscular system: Hypo and Hyper

Answer 20

Hypo- “slow stuff”, sluggish, muscle cramps

Hyper- Muscle atrophy and weakness

Question 21

Sketelal system: Hypo and hyer

Answer 21

Hypo- Growth redardation, skeletal stunting, in adults- joint pain

Hyper- Child- excessive growth at first, then short stature and early epiphyseal closure. Adults- demineralization of skeleton

Question 22

Hypothyrodism

Answer 22

If inadequate dietary iodine, the follicle cells try to make colloid but annot iodinate it, TSH increases to try to induce it but leads to an enlarged and protruding thyroid gland (endemic goiter)

Question 23

Hyperthyroidism

Answer 23

Grave’s disease- autoimmune (antibodies that mimic TSH). Elevated BMR, sweating, raphid heatbeat…

Question 24

Calcitonin

Answer 24

Lowers calcium, inhibits bone resorption, stimulates Ca2+, uptake and incorportation into bone.

Increase blood levels of calcium

Question 25

BMR is influenced by

Answer 25

1. Body surface area (greater SA= more heat loss) 2. Age (decreases with age, loss of muscle mass) 3. Higher BMR in males (more muscle, less fat) Stress can also increase metabolic rate (norepinephrine and epinephrine increase fat catabolism, generate heat as a byproduct) Increases oxygen consumption by accelerating metabolic rate.

Question 26

Total metabolic rate (TMR) definition

Answer 26

BMR is most of this. Work done by skeletal muscle produce the largest increases

Question 27

4 Mechanisms of heat exchange

Answer 27

1. Radiation (50% ie cool room with warm people) 2. Conduction (Transfer of heat between direct contact, heat to body from warm tub) 3. Convection (warm air rises, ie fan) 4. Evaportation (regulate body temp. perspiration to shed heat)

Question 28

Role of hypothalamus

Answer 28

2 thermoregulatory centers - heat loss - heat promoting Receives input from peripheral thermoreceptors (just under skin) and central thermoreceptors (in core- blood temp) Perserve core temp!!

Question 29

Heat conservation mechanisms

Answer 29

1. Vasoconstriction of cutaneous vessels (supply skin)- frostbite if prolonged 2. Shivering (stimulate stretch receptors- involuntary shuttering) 3. Increase in metabolic rate (cold stimulus) 4. Enhanced thyroxine release (lowering of external temp. increased secretion of TSH) 5. Behavioural modifications (warmer clothing, drinking warm fluids)

Question 30

Heat-loss mechanisms

Answer 30

1. Vasodilation of cutaneous blood vessels (increased blood flow) 2. Enhanced sweating (activated by sympathetic nervous system) 3. Behavioral modifications

Question 31

Hyperthermia

Answer 31

Increased temp, increased metabolic rate, incrased heat production

Question 32

Fever

Answer 32

Pyrogens (body secretes this to increase body temp) released by macrophages. Vasoconstriction

Question 33

Short term regulation of appetite

Answer 33

Neural signals- Stretch receptors in GI tract inhibits appetite. Protein and carbohydrates stimulate vagal afferents to inhib appetite: protein stimulates longer response 1. During eating- plasma glucose levels rise, activate glucose receptors in brain- then eating is depressed 2. Elevated plasma AAs depress and low plasma AAs stimulate eating 3. Blood concentrations of FFA and glycerol play a simialr role.

Question 33

Mechanisms of appetite regulation

Answer 33

Arcuate nucleus in hypothalamus! Neuropeptide Y/ agouti-related Peptide (NPY/AGRP) secretion stimulates appetite Proopiomelanocortin/cocaine and amphetamine-regulated transcript (POMC/CART) neurons release melanocortins- sippress appetite via corticotropin releasing hormone by the VMH

Question 34

Short term reg. of appetite HORMONES

Answer 34

Insulin- in response to food intake, known to depress hunger Cholecystokinin- released by small intestine during food digestion, depreses hunger Glucagon- levels rise during fasting and stimulates hunger Ghrelin- released from stomach, potent stimulator of hunger

Question 35

Long term regulation of appetite (ie months and years)

Answer 35

Leptin- peptide hormone secreted by adipose tissue (more=more) - serves as a sensor for adipose stores, binds to receptors in the ACR nuceleaus (inhibs NPY secretion and increases CART expression). Leads to inhibirtion of appetite until adipose stores decrease