Basic Principles Flashcards
What are Niko Tinbergen’s 4 levels of analyses?
Mechanisms
Development
Evolution
Adaptation
What is Krogh’s principle?
A Physiological problem of one species is likely to occur in another
What is the SENSOR in positive and negative feedback/
The hypothalamus
What happens when the physiological system of homeostasis fails?
Behaviour changes and behavioural homeostasis occurs
What does it mean to be POIKILOTHERMIC?
Cold-blooded
What % saline concentration does the body attempt to maintain? What does this equate to in g NaCl / L?
0.9% Saline Concentration
= ~8.5g NaCl / L
What stimulates the secretion of vasopressin?
Dehydration in osmoreceptors
Why does vasopressin target the kidney?
In order to gain maximal reclamation of H2O
What inhibits vasopressin?
Alcohol
What does PVN stand for?
Paraventricular Nuclei
What does SON stand for?
Supraoptic Nuclei
Where is vasopressin found?
Paraventricular Nuclei & Supraoptic Nuclei
What is ADH?
ADH = Antidiuretic Hormone = Vasopressin
What is thirst?
How many kinds of thirst are there?
What are they?
Thirst is the motivation to seek and ingest H2O;
There are two kinds;
Osmotic thirst & hypovolemic thirst.
What is the difference between osmotic thirst and hypovolemic thirst?
Osmotic thirst:
Increase in osmotic pressure of interstitial fluid relative to intracellular fluid (cellular dehydration)
Hypovolemic thirst:
A decrease in blood volume without a decrease in intracellular fluid
What are two reliable hormone indicators of body fat?
Insulin & Leptin
What does it mean to be OREXIGENIC?
To be hungry - an increase of food intake
Hormones associated: Neuropeptide Y & Agouti-Related Protein
What does it mean to be ANOREXIGENIC?
(Satiety) - a decrease in food intake
Hormones associated: Pro-opiomelanocortin (POMC) & Cocaine&hetamine regulated transcript (CART)
Which of the (5) nucleic acids are purines and which are pyrimidines?
Adenine & Guanine are PURINES
Cytosine, Thymine & Uracil are PYRIMIDINES
What is DNA?
A polynucleotide chain consisting of pentose residues linked with phosphodiester bonds
What facilitates the binding of polymerases in RNA?
An increased temperature (~92˚C) and or the addition of enzymes reduce the hydrogen bonds between nucleotides and facilitate the binding of polymerases
What is an example of a single-stranded RNA virus? (ssRNA)
Norovirus - causes vomiting and diarrhea
What is an example of a double-stranded RNA virus? (dsRNA)
Rotavirus - Severe diarrhea in infants and young children - immunity develops with each infection
What are two commonly studied epigenetic modifications?
DNA Methylation & Histone acetylation
Describe DNA Methylation
DNA methylation is an epigenetic modification that occurs at the promoters of DNA and silences transcription.
Around 1-5% of the cytosine residues are modified by the addition of a methyl group (-CH3) to the 5’ Carbon to form 5’-methyl-cytosine.
The action is catalysed by the enzyme DNA methyltransferase
It usually occurs in CpG sites, regions rich in CpG sites are called CpG islands and are abundant in promoters.
When the DNA is replicated, the new strand is unmethylated, maintenance methylase catalyses the methylation to create 5’-methyl-cytosine in the new strand.
Demethylase (TET) can reverse the methylation and once methylated, strands can be transcribed.
Heavily methylated strands tend to be inactive.
What is TET? What does it do?
Ten eleven translocation - Demethylases DNA
Describe histone acetylation
Histone acetylation is another form of epigenetic modification.
Each DNA histone has a tail at it’s N-terminus containing around 20 amino acids (mainly lysine), which is positively charged and sticks out.
Because of its positive charge and the negative charge of DNA, there is usually a strong ionic attraction between the tail and DNA.
However, histone acetylases add acetyl groups and change the charge of the amino acid tail. As a result of this, the compact nucleosome opens. Acetylated histones (COCH3) result in euchromatin.
Additional chromatin remodeling proteins, histone deacetylase can remove acetyl groups from histones and repress transcription. Deacetylated histones result in heterochromatin.
Histone deacetylases are being targeted as possible drugs for the treatment of some cancers.
A combination of DNA Methylation and histone deacetylation means what for transcription?
Transcription is repressed
A combination of DNA un-methylation and histone acetylation means what for transcription?
Transcription is enhanced
DNA methylation and histone acetylation act during both embryonic and foetal stages with permanent effects. How is it transmitted?
Transmitted through maternal lineages and establishes in germline cells. Resulting in permanent effects on physiology can mean phenotypic variation despite identical genomes.
DNA methylation and histone acetylation are rhythmic, what does this mean?
They are reversible; both methylation and acetylation regulate a range of physiological processes that change throughout the day.
What is the basic structure of a protein?
Amino acid
amine, carboxylic acid, hydrogen and “R” group
What is the primary structure of a protein?
A linear sequence of amino acids
What is the secondary structure of a protein?
Alpha helices or Beta-pleated sheets
Briefly describe alpha helices
A right-handed coil. The R groups extend outward from the peptide backbone of the helix. Coiling is a result of hydrogen bonds forming between the hydrogen of N-H of one amino acid and the oxygen of C=O of another.
The coil is stabilised when this pattern is repeated over a segment of the protein.
Briefly describe beta-pleated sheet
Formed when two or more polypeptide chains are almost completely extended and aligned. The sheet is stabilised by hydrogen bonds between the N-H of one chain and the C=O groups of another.
A Beta-pleated sheet can form between separate polypeptide chains or between different regions of a single polypeptide chain that is bent back onto itself.
What is the tertiary structure of a protein?
Polypeptides fold, forming specific shapes. Folds are stabilised by bonds, including hydrogen bonds and disulfide bridges.
In many proteins, the polypeptide chain is bent at specific sites and then folded back and forth, resulting in the tertiary structure. Although alpha helices and beta-pleated sheets contribute to tertiary structure, usually only portions of the macromolecule have these secondary structures and large regions consist of tertiary structure unique to a particular protein.
Briefly describe how disulfide bridges are formed
Two cysteine molecules in a polypeptide chain can form a disulfide bridge (-S-S-) by oxidation (removal of hydrogen atoms).
What is the quaternary structure of a protein?
Many functional proteins contain two or more polypeptide chains, called subunits, each of them folded into its own unique tertiary structure. The protein’s quaternary structure results from the ways in which these subunits bind together and interact.
Quaternary structure can be dimers, trimers, tetramers etc.
What is the central DOGMA?
DNA –> RNA –> Proteins
What are some challenges to the central DOGMA?
Non-coding RNA (ncRNA) - They do not make proteins, but still have a function.
What are the two kinds of non-coding RNA?
What is the difference between them?
microRNA:
20-50 base pairs long; can function as ligands for proteins and mediate base-pairing interactions to specific RNA or DNA sites
long ncRNA:
>200 base pairs long; similar to microRNA; can fold into higher structures for versatility in proteins and target sequence recognition.
What is the structure of fatty acids?
A carboxyl head with a hydrocarbon tail (between 4-28 Carbons)
What is the difference between saturated and unsaturated fats?
Unsaturated fats have a double bond between two carbon molecules, meaning there is a “kink” in the hydrocarbon tail
Saturated fats do not have a double bond between two carbon molecules and therefore have a straight hydrocarbon tail.
Glycerides have what kind of molecule attached to a fatty acid?
Monoglycerides, diglycerides, and triglycerides are all dependent on what?
A Glycerol molecule.
The number of fatty acids attached to a single glycerol molecule
What would be the result if a phosphate group were to replace the glycerol molecule of a triglyceride?
A phospholipid
What is cholesterol?
How many types are there?
What are they?
What are their functions?
Cholesterol is a lipid sterol
There are two kinds,
Low-density lipoprotein: causes the formation of plaque
High-density lipoprotein: removes the build-up of low-density lipoprotein and takes it to the liver for degradation
What are monosaccharides?
Sugar molecules (either pentose or hexose) that are the building blocks for carbohydrates
What is a disaccharide?
Two monosaccharides joined together.
Most common examples are sucrose and lactose
Briefly describe sucrose
A glucose molecule with an alpha-glycosidic bond to a fructose molecule
Briefly describe lactose
A glucose molecule with a beta-glycosidic bond to a galactose molecule
What is a polysaccharide? Give examples
A polysaccharide is a linked number of monosaccharides.
Glycogen is the primary form in animals and starch is the primary form in plants. Polysaccharides are stored in the liver and muscle cells of animals.
What is the 1st law of thermodynamics?
Energy can neither be created or destroyed, only changed from one form to another
What are the functions of calories?
- Maintain vital organs
- Build, maintain and repair cells and body tissues
- Drive metabolic processes
- Maintain body temperature
- Support external activites
What is a calorie?
The amount of heat required to raise the temperature of 1g of water by 1˚C
How many Joules of energy in 1 calorie?
1Kcal = 4.18J
How many calories in 1 Joule?
1 J = 0.239Kcal
What is digestive efficiency?
How do we calculate it?
The amount of ingested energy absorbed
DE = (GEI-(Loss/GEI))x100%
What is GEI?
How do we calculate it?
GEI = Gross Energy Intake
GEI = Food intake x Energy content in food
How do we calculate energy loss?
Loss = Faeces weight x Energy content in faeces
What is MEI?
How do we calculate it?
MEI = Metabolisable Energy Intake
MEI = GEI - Loss
What is BMR?
What does it stand for?
BMR = Basal Metabolic Rate
BMR is the minimum amount of energy required to sustain waking life under optimal conditions
What is the term used to describe energy costs above BMR?
Physical activity
What is NEAT?
What does it stand for?
NEAT = Non-Exercise Activity Thermogenesis
NEAT = everything but sleeping, eating and sport-like activity
What is TEF? What is DIT?
What do they stand for?
TEF = Thermic Effect of Food DIT = Diet Induced Thermogenesis
Increase in metabolic rate above BMR as a consequence of food intake
What is the relationship of BMR with:
a) age
b) sex
c) body mass
a) BMR decreases with age
b) Males tend to have higher BMR
c) Higher the body mass, higher the BMR
What is Kleiber’s Law?
What is the equation for it?
Kleiber’s Law (1932): Metabolism increases with Body Mass ^3/4
If q0 = MR & M = animal’s mass
then
q0 = ~M^3/4
Larger animals have a smaller area-volume ratio, what does this mean in regards to energy balance and thermal regulation?
Larger animals have a smaller area-volume ration and therefore retain more heat and need less energy
Effect of diet: What happened to the BMR of mice when they were exposed to calorie restriction?
The BMR lowered when the mice were exposed to dieting
What is considered extraordinary about pandas with regards to their daily energy expenditure?
Giant panda, carnivore turned vegetarian.
Average weight ~92kg - They have an extremely low DEE and have a daily calorie intake of ~1250kcal
For a human of 90kg, guided daily calorie intake is ~3000kcal
The cost of locomotion in mammals is dependent upon what?
- Body size
- Velocity
There is a linear increase in metabolic rate with speed
Larger mammals spend less energy over larger distances
What is regulatory DIT?
The increase in heat following a meal
What is obligatory DIT?
The cost of obtaining and processing food (including food breakdown, gut motility, excretion)
What are the three techniques for measuring metabolic rate?
- Direct calorimetry
- Indirect calorimetry
- Double-labeled Water
Briefly describe the disadvantages of using direct calorimetry
- Assumes all energy becomes heat
- Not very practical
- Imprecise at low levels
- Constrained
Briefly describe indirect calorimetry
Indirect calorimetry = Respirometry - Only used in labs
Briefly describe respirometry BMR & RMR
BMR: Rate of energy expended while fasting and at rest
- Post-adsorptive state
- TNZ = Thermoneutral Zone
- Eliminate exertion
- Minimal stress
- Awake
RMR: Combination of BMR & resting/sleeping
What is RQ?
What does it stand for?
How do we calculate it?
What do the results mean?
RQ = Respiratory Quotient
RQ = estimate of the proportion of carbohydrates/proteins/fats metabolised
RQ = rate of CO2 productions/rate of O2 consumption
RQ = 1 - Mainly carbohydrates utilised RQ = 0.7 - Mainly fats utilised RQ = 0.8 - Mainly proteins utilised RQ = 0.85 - Mixture of macromolecules utilised
What is the Double-Labeled Water technique?
(DLW) Double-Labeled Water measures energy expenditure of un-restrained, free-living animals.
It was invented in the 1950s and J.R.Speakman published the technique in 1997.
Dose the animal with DLW (^2H2^18O), to equilibrium with total body H2O and eliminate.
Deuterium ^2H leaves as H2O; ^18O leaves as H2O and CO2.
CO2 = ^2H - ^18O
Disadvantages:
- Expensive
- Numerus assumptions require validation for each experimental setting
What is FMR?
What does it stand for?
FMR = Field Metabolic Rate
FMR = Metabolic rate of an animal in its natural state
Show a positive energy balance of Einput and Eexpenditure.
Weight gain = Einput > Eexpenditure
Show a negative energy balance of Einput and Eexpenditure
Weight loss = Einput < Eexpenditure
What is the neuroendocrine system?
Interactions between the nervous system and the endocrine system
What is the endocrine system?
A system of glands which secrete hormones into the bloodstream to reach and act on target cells and organs
What are hormones?
Synthesised by specialist tissues/glands to change the activities of their targets
What are the functions of adipose tissue?
Energy store & endocrine organ:
- Nutrient transport
- Appetite and energy balance
- Blood pressure regulation
- Angiogenesis
- Vascular haemostasis
- Inflammation & immunity
- Lipid metabolism
- Insulin sensitivity & glucose homeostasis
What is angiogenesis?
The physiological process through which new blood vessels form from pre-existing vessels
What is the function of Leptin?
Leptin is an adiposity signal - it informs the brain about available body reserves
What is the function of Ghrelin?
- Regulates appetite & energy homeostasis
- Regulates insulin secretion
- Regulates glucose metabolism
- Regulates gastric secretion & emptying
- Regulates energy expenditure
- Influences on gonadal axis
- Inhibition of apoptosis and regulates cell proliferation & differentiation
What is the function of the hypothalamus?
Regulation of:
- hunger
- thirst
- body temperature
- fatigue
- sleep
- circadian cycles
What is thermoregulation?
The ability of an organism to keep its body temperature (Tb) within certain boundaries, even when ambient temperature (Ta) is very different.
Why thermoregulate?
The sun heats the Earth unevenly, but it is the Earth’s heat engine, causing:
- Evaporation of surface water
- Ocean circulation
- Convection
- Rainfall
- Wind
Heat is also redistributed back into space
Briefly describe a minimum of 5 temperature niches
- Hot desert (daily variation)
- Hot springs (high Ta)
- Alpine (extreme cold)
- Temperate (seasonal variations)
- Lakes (thermal stratification, winter freezing)
- Subterranean refuges (moderate & stable Ta)
- Intertidal (rapid variation in Ta)
- Epipelagic (variable Ta)
- Mesopelagic (stable Ta)
- Bathypelagic (cold, stable Ta)
What would happen if body temperature fluctuated with ambient temperature?
Why?
Death
Chemical reactions are temperature dependent.
Protein stress - Proteins are inactive at low temperatures and denature at high temperatures, forcing them to lose their catalytic abilities.
What does Q10 stand for?
What is it?
How do we calculate it?
What do the results mean?
Q10 = Temperature coefficient
Q10 = How the reaction rate changes with a 10˚C change in temperature
Q10 = Reaction rate at temperature (T) / reaction rate at T-10˚C
Q10 = 1 - reaction rate not affected by temperature
Q10 = 2 - reaction rate doubles with each 10˚C increase
Q10 < 1 - reaction rate decreases with increase in temperature
Cell membranes are made of fatty acids. Weak bonds between these fatty acids means the membrane is flexible. What happens when they are exposed to temperature change?
Temperature decrease - the membrane becomes too rigid
Temperature increase - the membrane becomes too fluid
In temperatures below 0˚C, ice crystals form and puncture the cell membranes
How do arctic fish not freeze?
They produce their own antifreeze proteins
Briefly describe what happens to a human with increasing body temperature
37˚C - Normal temperature 38˚C - Sweating 39˚C - Pyrexia (fever) 40˚C - Profuse sweating 41˚C - Medical emergency 42˚C - Possible comatose 43˚C - Probable death 44˚C + - Certain death
Briefly describe what happens to a human with decreasing body temperature
37˚C - Normal temperature 36˚C - Shivering 35˚C - Hypothermia 34˚C - Severe shivering 33˚C - Confusion 32˚C - Medical emergency 31˚C - Comatose 28˚C - Change in heart rhythm, breathing could stop at any minute 26˚C - Probable death
What is ALBEDO?
What does black represent?
What does white represent?
The proportion of incident radiation that is reflected.
Black = Low ALBEDO, high absorption
White = high ALBEDO, low absorption
Heat is conducted from the core of our bodies to the periphery. The rate of heat flow dependent on conductance along the pathway, how is this compensated?
Compensated with the thickness of the peripheral layer.
Briefly explain how external and internal insulation works. Give examples.
External insulation:
Fur/feathers
Works by trapping a layer of air
Internal insulation:
Blubber
Lipid layer disrupts heat flow to the periphery
Why do animals moult?
Thick coats become a thermoregulatory burden in hotter months.
The cost of rebuilding the thick coat < The cost of keeping cool
What is convection?
The heat loss that occurs by movement of fluids.
What is free convection?
No gross movement of the medium, heat loss occurs over the boundary layer
What is forced convection?
Fluid flow over the surface, increasing heat loss
Briefly describe evaporation
The only way to lose heat against the temperature gradient.
If body temperature is less than or equal to the ambient temperature - there is a risk of hyperthermia.
Evaporation doesn’t depend on the ambient temperature gradient but how much water there is already in the atmosphere (i.e. humidity)
What is a homeotherm?
Constant body temperature within the range of ambient temperature
What is a poikilotherm?
Body temperature varies with the ambient temperature
What is a heterotherm?
Specific periods where the body temperature can change.
Exhibits characteristics of both homeotherms and poikilotherms.
What is an endotherm?
Has an internal source for body temperature. Physiology changes to regulate body temperature.
What is an ectotherm?
Has to seek an external source for body temperature. Behaviour changes to regulate body temperature.
Give advantages and disadvantages of ectothermy.
Disadvantages:
- Restricted hours of activity
- Sluggish until warm - increased predation risk
Advantages:
- Low metabolic rate means less food required
- Can endure shortages of water & oxygen
Briefly describe ways in which endotherms retain heat.
- Insulation
- Huddling
- Decrease surface area
- Vasoconstriction
- Countercurrent exchange
- ectothermic behaviour (seen in cats & birds)
- Anatomical changes i.e. darker patches of fur in extremities
Briefly describe ways in which endotherms cool down.
- Avoidance behaviour
- Reduce insulation
- Cutaneous loss
- Sweating
- Panting
- Increase surface area
- Vasodilation
Briefly describe the advantages and disadvantages of endothermy.
Disadvantages:
- High daily energy cost
- Less resistant to starvation
Advantages:
- Day-to-night activities
- Environmental independence
- Sustained activity
- Can inhabit a wider range of climates
Give examples of thermoregulatory organs
- Hypothalamus
- Skeletal muscle
- Adipose tissue
- Sweat glands
- Skin arterioles
- Thyroid gland
- Heart
What does TRH stand for?
TRH = Thyrotropin-Releasing Hormone
What does TSH stand for?
TSH = Thyroid-Stimulating Hormone
What is T4?
T4 = Thyroxine
What is T3?
What does an increase in this mean?
What does a decrease in this mean?
T3 = Triiodothryonine
An increase in T3 = Hyperthyroidism (HOT)
A decrease in T3 = Hypothyroidism (COLD)
What is TRP?
TRP = Transient Receptor Potential (ion channel superfamily)
What are nociceptors?
Sensory neurons that respond to potentially damaging stimuli
What nociceptors are associated with pain?
TRPA1 TRPV1 TRPV2 MS ASICs
What nociceptors are associated with high temperatures?
TRPV3
TRPV4
What nociceptors are associated with low temperatures?
TRPM8
What does POA stand for?
POA = Preoptic area
What does DMH stand for?
DMH = Dorsal Medial Hypothalamus
What does LHA stand for?
LHA = Lateral Hypothalamic Area
What does ARC stand for?
ARC = Arcuate nucleus
What does VMH stand for?
VMH = Ventral Medial Hypothalamus
What does IO stand for?
IO = Inferior Olive
What does Rpa stand for?
Rpa = Raphe pallidus
Which neuropeptides regulate calorie intake and energy expenditure by altering the core body temperature?
Ghrelin
Glucose
Insulin
Leptin
What does BAT stand for?
BAT = Brown Adipose Tissue
What does WAT stand for?
WAT = White Adipose Tissue
Briefly describe BAT
- Prevalent in small mammals and the young of larger mammals
- Not found in birds
- Before 2002, thought not to be in adult humans
- In rodents, found in the interscapular area
- In humans, found in the supraclavicular area and the neck
- Crucial in non-shivering thermogenesis, daily torpor, hibernation and diet-induced thermogenesis
- Cold-inducible
- Induced by thyroid hormone & energy balance
What does FDG PET stand for?
FDG PET = Fluorodeoxyglucose positron emmision tomography
Name a minimum of three properties of BAT
- Affected by age and obesity
- Multi-locular
- Small lipid droplets
- Low-fat content
- Large blood supply
- Mitochondrial packed
Name a minimum of three properties of WAT
- Uni-locular
- Almost completely fat
- Reduced blood flow
- Few mitochondria
- Energy storage
What is the pathway for the formation of either BAT or WAT?
Stem cell (multipotent) –> Pre-adipocytes (pluripotent) –> Committed pre-adipocytes (BAT or WAT) –> Adipocytes (BAT or WAT)
What is UCP-1?
What is its function?
UCP-1 = Uncoupling protein = Thermogenin
- Channels for protons H+
- Uncouples protons from electron transport chain
- Converts available energy in lipids to produce heat
Give examples of how heterotherms deal with long-term cold &/or food scarcity
- Torpor
- Hibernation
- Migration
- Food storage
Torpor is a regulated hypothermia. But what happens?
Metabolic rate is dropped below necessary in order to maintain body temperature.
Torpor coincides with sleep and is terminated by arousal.
Summarise torpor
- Metabolic rate drops below basal metabolic rate with correspondence to drop in body temperature
- More common in smaller animals
- Controlled
- Torpor body temperature < 31˚C
- Defined by short bouts
- Terminated by arousal
- Coincides with sleep
- Can be induced by food scarcity/dieting
Briefly describe hibernation
Very widespread within species includes:
- Carnivora
- Bats
- Insectivora
- Rodentia
- Primates
- Tenrecs
- Not down to a specific gene, more different regulation of common genes
What are the 4 stages of hibernation?
- Pre-hibernation fattening
- Energy stored as fat
- BAT fat stores increase - Entry into hibernation
- Cease heat production
- Drop in body temperature set point - Hibernation bout
- BAT inactive - Arousal
- Resetting of body temperature setpoint
- BAT activated due to depletion of fat stores
Periodic arousal is expensive. Give a minimum of three reasons why periodic arousal occurs.
- Reflects endogenous activity cycle
- To feed
- Drinking hypothesis
- Waste elimination hypothesis
- Sleep hypothesis
Briefly describe the different kinds of sleep
Awake:
- Low voltage, high-frequency beta waves
Drowsy:
- Alpha waves prominent
Stage 1 sleep:
- Omega waves prominent
Stage 2 sleep:
- Sleep spindles with electroencephalography (EEG) activity
Slow wave sleep (stage 3/4):
- Progressively more delta waves
REM sleep:
- Low voltage, high frequency waves
What three characters can be found in Alzheimer’s patients?
What is the problem with one of these characters?
- Neurofibrillary tangles
- Beta-amyloid plaques
- Tau protein
- Phosphorylation of tau protein is critical, progressive and irreversible
Why are ground squirrels a species of interest to scientists looking at Alzheimer’s?
After a 12-day torpor, a ground squirrels, brain looks much like that of an Alzheimer’s patient. The tau protein is completely phosphorylysed.
However, three hours after arousal, tau protein has been completely dephosphorylated and the brain function is returned to normal.
Large mammals benefit less from hibernation and some have special adaptations to lower their metabolic rate. Briefly describe the black bear (Ursus americanus).
Usually between 30 - 200kg, body temperature between 37 & 38˚C.
Hibernate for between 5 & 7 months.
During hibernation, they lose 15-20% of their body mass without loss of lean mass.
They are easily aroused into a mobile, reactive state and are alert and aware of their surroundings. Females birth and nurse during this hibernation period.
Reductions in body temperature are independent to metabolic suppression.
