post absorptive mechanisms & energy balance Flashcards
why are amino acids, triglyceride & glucose transported to the liver
for conversion into storage molecules
where are fats stored
adipose tissue
where is glycogen stored
muscle
where are proteins stored
proteins are not stored
they are converted to fats
and used as energy supplies
BMI calculation
Weight (Kg)/ Height2 (m)
what BMI is obese
above 30
what BMI is normal
between 18.5 and 25
what BMI is overweight
between 25 and 30
what BMI is underweight
below 25
how long are glycogen stores sufficient for an adult male
roughly 12 hoursn
how long are lipid stores sufficient for
3 months
when does tissue protein as a source of energy supply become significant
only in times of prolonged starvation
energy requirement of brain and liver
the brain & liver represent about 4.6% of body weight yet consume around 40% of energy
requirement at rest
which fuels does brain use
glucose
ketone bodies
which fuels do muscle use
glucose
ketone bodies (in starvation), triacyglycerol
branched-chain amino acids
which fuels does liver use
amino acids, fatty acids (including short chain acids), glucose & alcohol
ketone bodies are not used by the liver, although they are produced here
they are then sent to extrahepatic tissue to buy used there, the liver cannot use ketone bodies for fuel due to the fact they do not have the enzyme thiolase
which fuels does kidney use
glucose & ketone bodies (cortex)
only glucose (medulla)
which fuels does small intestine use
ketone bodies (mainly in starvation), glutamine (amino acid)
which fuels does large intestine use
short-chain fatty acids, glutamine
what is basal metabolic rate
minimum amount of energy required to keep the body alive
how is BMR measured
by O2 consumption in a person who is awake, restful and faster
for 12 hours
impact of age on BMR
BMR decrease with age
units of BMR
kcal expended/hr/m2
functions of vitamin A (7)
- Cellular growth & differentiation
- Process of vision (retinal pigments)
- Healthy skin
- Reproduction
- Embryonic development
- Maintenance of bodies mucus membranes
- Used in lymphocyte production - immune system
sources of vitamin A
- Liver
- Dairy products
- Oily fish
- Margarine
what does vitamin A deficiency cause
- night blindness
- Xerophthalmia (eye fails to produce tears)
- Growth retardation
- Keratinisation of epithelia
- Impaired hearing, taste & smell
- Increased susceptibility to infection
functions of vitamin C
- Synthesis of; collagen, neurotransmitters & carnitine (used in beta-oxidation)
- Antioxidant ability - can donate electrons to radical O2 compounds
- Absorption of non-haem (plant based) iron
sources of vitamin C
- Citrus fruits
- Green leafy vegetables
- Potatoes
- Kidney
what does vitamin C deficiency cause
Initial signs are non-specific
* Weakness
* Bleeding gums
* Hyperkeratosis (thickening of outer layer of skin)
* 50 - 100 days without Vitamin C = signs of scurvy
function of B vitamins
important in cell metabolism & energy production
where is the main B vitamin found
vitamin B 12
found in fish, poultry, meat & eggs
what does B12 deficiency cause
results in less erythrocyte formation - pernicious anaemia
where is B12 absorbed
in the terminal ileum
intrinsic factor is required which is produced by the parietal cells of
the stomach
what does the term vitamin D refer to
denotes a group of closely related compounds
- Liver storage prevent deficiency for 3-4 months
what forms vitamin D3
(cholecalciferol) is formed by the action of ultra-violet (UV) radiation
from sunlight on a cholesterol derivative in the skin
how is vitamin D metabolised
by the addition of hydroxyl groups, first in the liver and then in
certain kidney cells, the end result of these changes is 1,25-dihydroxyvitamin D
(1,25-(OH)2D) - the active hormonal form of vitamin D
where is vitamin D2 derived from
plants
function of the active hormonal form of vitamin D
to stimulate intestinal absorption of Ca 2+ and phosphate
consequence of vitamin D deficiency
decreased intestinal Ca2+ absorption resulting in a
decreased plasma Ca2+
* This decrease in detected via a plasma membrane Ca2+ receptor in the
parathyroid glands (embedded in the posterior surface of the thyroid gland)
* Resulting in the parathyroid glands releasing PARATHYROID HORMONE (PTH)
which exerts multiple actions that increase extracellular Ca2+ concentration
main function of vitamin E
as an antioxidant
main function of vitamin K
is essential for the production of clotting factors (10,9,7 & 2) in the liver
what is malabsorption
The inadequate absorption of nutrients from the intestines
- Failure to absorb certain vitamins, minerals, carbohydrate, proteins or fats
what is giardiasis
infection which causes the villi to atrophy thus reducing absorption
capacity
what is celiac disease
an auto-immune condition whereby gluten is partially degraded triggering an immune response whereby the system attacks the villi & microvilli resulting in a loss of intestinal brush border surface area resulting in decreased absorption of
many nutrients
-
Can prevent the absorption of vitamin D which ultimately results in the decrease in calcium absorption in the GI tract - resulting is osteoporosis
which is the only anabolic hormone that controls metabolism
insulin
the rest are catabolic
what determines weight
a balance of energy intake and expenditure
influenced by genetics, environment and energy regulation
where is the appetite control centre
hypothalamus
Within in hypothalamus lies the arcuate nucleus, which plays a key role in the control of appetite.
what do primary neurones in the appetite centre do
process external signals, be it neuronal, hormonal or nutritional.
are either excitatory or inhibitory.
what do secondary neurones in the appetite centre do
responsible for co-ordinating the inputs received via the primary neurone.
what do excitatory neurotransmiiters do
promote hunger
what do inhibitory neurotransmitters do
supress hunger
what is ghrelin
a peptide hormone produced in the pancreas and released from the stomach wall when the stomach is empty.
it stimulates the excitatory primary neurones, and therefore stimulates appetite.
when the stomach is full, ghrelin release is inhibited, thus the appetite stimulus is also inhibited.
what is PYY
a short peptide hormone released by cells in the ileum and colon in response to feeding.
It inhibits the excitatory primary neurones of the arcuate nucleus.
This causes appetite suppression.
what is leptin
a peptide hormone released into the blood by adipocytes (fat cells).
Leptin stimulates the inhibitory neurones and inhibits the excitatory neurones in the arcuate nucleus to cause suppression of appetite.
what is insulin
a hormone released from beta cells in the islets of Langerhans of the pancreas.
This suppresses appetite in a similar way to leptin.
factors influencing BMR
- genetics
- gender
- age
- body SA
- weight
- body fat %
- diet
-body temperature - external temperature
-excercise
factors that increase BMR
Being overweight, Fever, being male, pregnancy, caffeine, hyperthyroidism, exercise, low temperature
factors that decrease BMR
Increase in Age, being female, malnutrition/starvation, hypothyroidism
