17.1 Energy Balance Flashcards
State the first law of thermodynamics
Energy cannot be created nor destroyed, only transformed from one form to another.
For body weight to remain constant, what must be the case?
the calorie value of food must equal to the total energy needs.
Energy that is not used up by the body is transformed into what type of energy?
Thermal energy
Why is it important that body temperature is regulated?
Because the cellular chemical reactions depend on temperature and overheating damages cellular proteins
What is the major integrating center for maintaining both body temperature and body balance?
The hypothalamus
compare external work and internal work
External work: contractions of skeletal muscles to perform external activities such as lifting objects.
Internal work: a) Skeletal muscle activity other than external work such as shivering when it is cold.
b) activities that require energy to sustain life such as breathing and blood pumping by the heart.
what is ATP( Adenosine triphosphate)?
it is an organic molecule that is the main energy carrier in cells.
Define metabolic rate
It is the rate at which energy is expended by the body during internal and external work.
what is the basic unit for heat energy?
calorie
name 4 factors that cause the metabolic rate and heat production to vary; HINT (SAFE)
- Exercise
- Anxiety
- shivering
- food intake
State which factor influences metabolic rate the most
Increased skeletal activity/ exercise
why is it important that we measure metabolic rate at standardised basal conditions?
So that we may control as many variables as possible that alter metabolic rate, in this way we will determine the metabolic activity necessary to maintain the body’s basic functions at rest.
what is basal metabolic rate(BMR)?
The metabolic rate of the body under standardised specific basal conditions
what are the four specific conditions that BMR is measured under?
- Physically at rest, refraining from exercise for at least 30 minutes
- At mental rest to minimise skeletal muscle tone
- At comfortable room temperature and no shivering
- To not have eaten for at least 12 hours and no caffeine.
What are the 3 factors that influence BMR?
Thyroid hormone, epinepherine amd sleep
what are the three states of energy balance?
- Neutral
- Positive
- Negative
explain neutral energy balance
Energy input is exactly equal to energy expenditure when performing external work, as well as basal internal energy expenditure
( body weight remains constant).
explain positive energy balance
When energy input is greater than energy expenditure. This excess energy in the body is not utilised but rather stored as adipose tissue causing weight gain
Explain negative energy balance
When energy input is less than energy expenditure. This causes the body to use stored energy thus causing weight loss
What is the most important factor (hint from SAFE) that maintains body weight and energy balance long term and what organ controls this factor?
Food intake controlled by the hypothalamus
what is the structure of the arcuate nucleus?
arc-shaped collection of neurons located adjacent to the floor of the third brain ventricle.
state the long term and short term roles of the arcuate nucleus of the hyphothalamus
Long term: Control of energy balance and body weight
short term: control of food intake from meal to meal
what is satiety?
the feeling of being full
what two hormones do the two subsets of neurons of the arcuate nucleus release?
one subset releases neuropeptide Y and the other releases melanocortins derived from pro-opiomelanocortins (POMC)
What is NPY?
it is one of the most potent appetite stimulators that increases food intake and thus increases body weight.
What are melanocortins
they are a group of hormones that suppress appetite to reduce food intake and promote weight loss ( most notably a-melanocyte-stimulating hormone) a-MSH
what type of melanocortin produced in the skin acts locally on melanocytes to cause tanning due to exposure to UV light from the sun?
a-melanoctye-stimulating hormone
what are the two regulatory input hormones that act on the arcuate nucleus in the long-term maintenance of energy balance?
Leptin and Insulin
what is the name of the collection of hormones that adipose tissue secretes that play important roles in energy balance and metabolism?
Adipokines
What is the largest hormone-secreting endocrine gland organ in the body
Adipose tissue
Finish the sentence, Leptin levels in the blood are an indication of………………..
the total amount of triglyceride fat stored in adipose tissue ( the greater the fat stores, the more leptin released)
Define metaflammation
the newly identified link between obese-induced inflammation and its metabolic consequences.
what is the function of adiponectin?
it increases sensitivity to insulin thus protecting the body against type 2 diabetes mellitus.
adiponectin is suppressed by which other adipokine?
resistin which is primarily released in obese people causing insulin resistance
What is the function of leptin?
Leptin suppresses appetite and thus decreases food intake and promotes weight loss by inhibiting NPY and stimulating melanocortins. and when fat stores are low the opposite happens.
What other hormone plays an important role in long-term control body weight
Insulin
what organ secretes insulin and what is its role?
the endocrine pancreas. It is released in response to the rise in the concentration of glucose and other nutrients in the blood after a meal. It also stimulates cellular uptake, use, and storage of these nutrients.
The increase of insulin secretion accompanied by nutrient abundance ……..
causes NPY to be inhibited thus decreasing appetite and suppressing further food intake
What are the two second order neuronsal areas of the hypothalamus that play a role in energy balance and food intake?
The lateral hyphothalmic area (LHA) and paraventricular nucleus (PVN)
What do the LHA and PVN release
they release hormones in response to input from the arcuate nucleus neurons. These released hormones act downstream from NPY and melanocortin signals to regulate appetite.
What hormone does LHA release and what is its function?
Orexins which are potent appetite stimulators
What hormone does the PVN release and what is its function?
corticotropin-releasing hormone, it is an appetite suppressor thus also decreasing food intake.
Why are leptin and insulin considered adiposity signals
because they are signals related to the size of fat stores in adipose tissue.
What are the two boold-borne peptides secreted by the digestive tract to regulate short term eating behaviour?
Ghrelin and PYY3-36
what produces gherlin and what regulates it?
it is produced by the stomach and is regulated by the feeding status
What is the function of Gherlin?
It is a hunger hormone meaning it stimulates appetite potently
How does gherlin go about increasing appetite?
Activating NPY secreting hormones
what is the function of PYY3-36 and what produces it?
It is an appetite suppressor by inhibiting NPY stimulating hormones and is an important mealtime terminator. It is produced by the small and large intestines
What is the name of the satiety center that processes signals important in the feeling of being full and thus contributing to short term eating behaviours?
Nucleus tractus solitarius (NTS)
where is the nucleus tractus solitarius located?
in the brain stem
What is another VERY important satiety signal ?
CCK-Cholecytokinin
where is CCK released from
the dudoenal mucosa
What stimulates CCK release
Nutrients in the duodenum
CCK facilitates _____ and _____ of nutrients in the duodenum
Digestion and Absorption
When does the influence of CCK being a satiety signal come in?
After you have eaten but before digestion and absorption
What other factors aftect food intake besides physiological ones?
environment and psychosocial factors
what is stomach distension
When the stomach expands due to the ingestion of food, gas and liquid activated by stretch receptors to indicate satiety to the brain. Thus it decreases appetite.
When does Obesity occur
When more kilocalories are consumed than burned ( energy input > energy output)
what are the four BMI categories
- Underweight
- heathy
- Overweight
- Obese
What does BMI stand for and define it
Body Mass Index- a mathematical means of accessing the proportion of body fat
What is the BMI boundary before you are considered overweight?
25kg/m^2 - 29,9kg/m^2
What BMI do you have to have to be considered obese?
from 30kg/m^2 and above
Name some causes of obesity?
- stress
- Heredity
- Overeating
- little sleep
- Lack of exercise
- Disturbances in the leptin-signaling pathway
What is anorexia Nervosa
A condition that causes the sufferer to have a pathological fear of gaining weight
Which group of individuals suffer from anorexia nervosa the most?
adolescent girls and young women.
what are the characteristics of anorexia nervosa?
severe weight loss
starvation (sometimes to death)
altered secretion of many hormones
absent menstrual cycle
low body temperature
