Biomedical Physiology (VTPP 427) Exam 3

what makes up energy output?

external work (working out) + internal work (posture, shivering, pumping blood, breathing)

how much nutrient energy is available for work?

25%

what does all energy from ingested food eventually become?

heat

what is the formula for basal metabolic rate (BMR)?

BMR = energy expenditure / unit of time at rest

what increases BMR?

increases in muscle tone (exercise)

what controls BMR?

thyroid hormone; increased TH increases BMR (so does epinephrine)

what is BMR affect by?

1) exercise (skeletal muscle contraction)

2) anxiety (epinephrine -> skeletal muscle contraction)

3) shivering

4) food intake (smooth muscle contraction; increased metabolic activity)

what are the mechanisms of heat loss?

1) radiation

2) conduction

3) convection

4) evaporation

what is radiation?

transfer of heat energy from a warmer object to a cooler object in the form of electromagnetic waves

what is conduction?

transfer of heat from a warmer to cooler object through direct contact; heat is transferred through the movement of thermal energy from molecule to adjacent molecule

what is convection?

transfer of heat energy by air currents; cool air warmed by the body through conduction rises and is replaced by more cool air

what is evaporation?

conversion of a liquid such as sweat into a gaseous vapor, a process that requires heat which is absorbed from the skin

what is the role of brown adipose tissue?

thermogenesis via UCP1 in mitochondria

what thermoreceptors detect change in skin temperature?

peripheral thermoreceptors in skin

what thermoreceptors detect change in core temperature?

central thermoreceptors in hypothalamus, abdominal organs, etc.

what do thermoreceptors signal?

hypothalamic centers (posterior activated by cold, anterior activated by heat)

what decreases heat loss?

skin vasoconstriction

what increases heat loss?

skin vasodilation, sweating

what increases heat production?

increased muscle tone, shivering, increased voluntary exercise, non shivering thermogenesis

what happens to core temperature during sustained exercise?

at the beginning, the rate of heat production initially exceeds the rate of heat loss so the core temperature rises but when heat loss mechanisms are increased, core temperature stabilizes slightly about resting point

what stimulates CCK release?

fat and protein after a meal, which stimulates the satiety center in brain stem to inhibit food intake

what is the function of neuropeptide Y in food intake?

inhibits paraventricular nucleus but stimulates lateral hypothalamus area to release oxreins which activates the appetite enhancing pathway and increases food intake

what is the function of melanocortins in food intake?

inhibits lateral hypothalamus area but stimulates paraventricular nucleus to activate the satiety center and CRH which activates the appetite surpassing pathway

what does activating the satiety center in the brain stem do?

signals satiety which decreases food intake

how does increasing leptin influence food intake?

inhibits NPY secreting neurons which release neuropeptide Y and stimulates POMC secreting neurons which release melanocortins

what are the major adipokines?

1) leptin

2) adiponectin

3) resistin

4) visfatin

5) TNF-alpha and IL-6

what is the source and effect of signal on appetite for neuropeptide Y?

arcuate nucleus of hypothalamus

and increases appetite

what is the source and effect of signal on appetite for melanocortins?

arcuate nucleus of hypothalamus

and decreases appetite

what is the source and effect of signal on appetite for leptin?

adipose tissue and decreases appetite

what is the source and effect of signal on appetite for insulin?

endocrine pancreas and decreases appetite

what is the source and effect of signal on appetite for orexins?

lateral hypothalamus and increases appetite

what is the source and effect of signal on appetite for CRH?

paraventricular nucleus of hypothalamus and decreases appetite

what is the source and effect of signal on appetite for ghrelin?

stomach and increases appetite

what is the source and effect of signal on appetite for peptide YY?

small + large intestines and decreases appetite

what is the source and effect of signal on appetite for stomach distention?

stomach and decreases appetite

what is the source and effect of signal on appetite for CCK?

small intestine and decreases appetite

what are the absorbable units of dietary protein?

amino acids

what are the absorbable units of dietary carbohydrates?

glucose

what are the absorbable units of dietary fat?

fatty acids and monoglycerides

what is anabolism?

buildup/synthesis of larger organic macromolecules from smaller ones

what is catabolism?

breakdown/degradation of large, energy rich organic molecules

what is the circulating form of carbohydrates?

glucose

what is the storage form and storage sites of carbohydrates?

glycogen and in liver + muscle

what is the circulating form of fat?

free fatty acids

what is the storage form and storage sites of fat?

triglycerides and adipose tissue

what is the storage form and storages sites of protein?

body proteins and muscle

what is the circulation form of protein?

amino acids

what are the exocrine portions of the pancreas?

acinar cells that secrete digestive enzymes and duct cells that secrete aqueous NaHCO3 solution

what are the endocrine portions of the pancreas?

islets of Langerhans that have beta cells that secrete insulin, alpha cells that secrete glucagon, and D cells that secrete somatostatin

how does glucose stimulate insulin secretion?

1) enters beta cells through GLUT-2 transporter

2) oxidizes into ATP and blocks K+ channel, increasing K+ in the cell and depolarizing it

3) depolarization opens voltage-gated calcium channels and calcium enters the beta cell

4) calcium in cell triggers insulin release from vesicle

what increases insulin secretion?

1) increasing gastrointestinal hormones (incretins)

2) parasympathetic stimulation

3) increasing blood amino acid concentration

what inhibits insulin secretion?

sympathetic stimulation + epinephrine

what is the effect of increasing blood glucose on alpa and beta cells?

- stimulates beta cells which increases insulin release

- inhibits alpha cells which decreases glucagon release

- together, this decreases blood glucose to normal

what is the effect of decreasing blood glucose on alpha and beta cells?

- stimulates alpha cells which increases glucagon release

- inhibits beta cells which decreases insulin release

- together, this increases blood glucose to normal

what happens after a high protein meal in regards to glucagon and insulin?

- insulin release increases which increases glucose uptake by cells and decreases hepatic glucose output causing hypoglycemia

- glucagon release increases which increases hepatic glucose output causing hyperglycemia

- together, this allows blood glucose to remain normal

what is the effect of insulin on blood glucose?

decreases it by promoting glucose uptake and glycogenesis and inhibits glycogenolysis and gluconeogenesis

what is the effect of insulin on blood fatty acids?

decreases it by promoting triglyceride synthesis and inhibit lipolysis

what is the effect of insulin on blood amino acids?

decreases it by promoting amino acid uptake

what is the effect of insulin on muscle protein?

increases it by promoting protein synthesis and inhibiting protein degradation

what is the effect of glucagon on blood glucose?

increases it by promoting glycogenolysis and gluconeogenesis and inhibiting glycogenesis

what is the effect of glucagon on blood fatty acids?

increases it by promoting lipolysis and inhibiting triglyceride synthesis

what is the effect of glucagon on blood amino acids?

no effect

what is the effect of glucagon on muscle protein?

no effect

what is the effect of epinephrine on blood glucose?

increases it by promoting glycogenolysis, gluconeogenesis and glucagon secretion and inhibits insulin secretion

what is the effect of epinephrine on blood fatty acids?

increases it by promoting lipolysis

what is the effect of epinephrine on blood amino acids?

no effect

what is the effect of epinephrine on muscle protein?

no effect

what is the effect of cortisol on blood glucose?

increases it by promoting gluconeogenesis and inhibiting glucose uptakes by tissues other than the brain

what is the effect of cortisol on blood fatty acids?

increases it by promoting lipolysis

what is the effect of cortisol on blood amino acids?

increases it by promoting protein degradation

what is the effect of cortisol on muscle protein?

decreases it by promoting protein degradation

what is the major stimulant for insulin?

increased blood glucose and blood amino acids

what is the major stimulant for glucagon?

decreased blood glucose and increased blood amino acids

what is the major stimulant for epinephrine?

sympathetic stimulation during stress + exercise

what is the major stimulant for cortisol?

stress

what happens when insulin is over secreted?

hyperinsulinemia

what constitutes hyperinsulinemia?

- precursor to T2DM

- due to INSR not responding properly to insulin -> becomes insensitive

- occurs in old age or obesity

what constitutes under secretion?

- T1DM

- due to defect in beta islet cells to produce and secrete insulin

- typically considered juvenile onset but can occur even in young adults

what are treatment options for type 2 diabetes mellitus?

insulin therapy, insulin sensitizers, and diet + exercise (for obese patients)

what are treatment options for type 1 diabetes mellitus?

insulin therapy only

what are the acute effects of insulin deficiency?

1) increased hepatic glucose output

2) decreased glucose uptake by cells

3) decreased triglyceride synthesis

4) increased lipolysis

5) decreased amino acid uptake by cells

6) protein degradation

what can be determined from only BMI scores?

adipokines levels, NOT insulin

what regulates calcium absorption?

1,25 (OH)2 Vitamin D

where is calcium resorbed?

proximal tubules of kidneys

which area has 99% of the body's calcium and 85% of the body's phosphate?

bone

what is the biggest source of calcium and phsophate?

diet

what are the effects of PTH?

increases calcium, decreases phosphate

what are the effects of calcitonin?

blocks osteoclastic bone reabsorption, decreases calcium

what are the effects 1,25 (OH)2 Vitamin D?

increases calcium, increases phosphate

what does PTH activate osteoblastic cells and osteocytes to release?

RANKL

what causes PTH release?

decreases in calcium levels; acts on intestines, kidneys, and bone to bring calcium levels back up

what are activating disorders of the parathyroid?

hypoparathyroidism; overage of negative feedback loop on calcium sensor; "always firing"

what are inactivating disorders of the parathyroid?

hyperparathyroidism; lack of negative feedback loop on calcium sensors; "empty"

what stimulates the release of calcitonin and where is it produced?

increased levels of calcium in serum; parafollicular cells of thyroid gland

where is vitamin d hydroxylated (activated)?

liver

what controls the 1-alpha-hydroxylase in the kidney that activates vitamin d?

PTH

what is the active form of vitamin d?

1,25 (OH)2

what is the inactive form of vitamin d?

24,25 (OH)2

what are osteoblasts?

the builder cells of bone; line surface of bone; produces osteoid (matrix) and type one collage; releases ecm proteins osteoclatin and bone sialoprotein; expresses parathyroid hormone receptor (pthr)

what are osteocytes?

osteoblasts that have become trapped in bone matrix; connect by canaliculi; maintains localized bone instead of laying new bone