Biology Psychology; Thermoregulation and eating behaviour Flashcards
______can regulate their body temperature via metabolic processes (‘warm blooded’ animals, including humans). Endothermic animals can stay active in cold weather, but they need more energy to heat their bodies and therefore need more food.
Endotherms
_______have a body temperature that is influenced by the external environment (incorrectly known as ‘cold blooded’). Ectothermic animals do not need energy to heat themselves but as a result they are inactive in cold weather.
Ectotherms
________do not need a fixed body temperature to survive, and most terrestrial ectotherms are poikilotherms (e.g. snakes & many lizards) but the naked mole rat is a mammal poikilotherm.
Poikilotherms
________are animals that need to maintain a constant body temperature to survive and are usually endotherms (some ectotherms, e.g. desert lizards, are homeotherms).
Homeotherms
- Insulation
- Metabolic heat production/physiological
thermoregulation - Countercurrent heat exchange
- Behaviour
THERMOREGULATION
Altering metabolic generation of heat to regulate
temperature
For example:
Metabolism increases to raise internal body
temperature in a colder environment
PHYSIOLOGICAL THERMOREGULATION
- Shivering
- Panting
- Evaporation of water
from respiration
and/or sweating
METABOLIC ACTIVITY
Warm and cold blood flow in opposite directions
to regulate the temperature (arteries & veins)
* Usually around the brain/head region
* e.g. Leatherback Turtle, Sea Gull
COUNTERCURRENT HEAT EXCHANGE
Using posture, orientation and/or microclimate selection
to regulate body temperature
e.g. lizard increases temperature by “spread eagle”
posture on top of a hot rock (microclimate) & turning its
back to the sun (orientation)
BEHAVIOURAL THERMOREGULATION
Reduced metabolic activity and body temperature for
less than a day (endotherm)- governed by circadian
rhythm
* Animals continue foraging
e.g. bats, hummingbirds, small Australian marsupials
(stripe-faced dunnarts
TORPOR (mini-hibernation)
Long-term torpor (can be 6 months) occurring in the
winter months (endotherms & ectotherms), to
conserve energy
* animals usually do not forage but rely on energy
stores (food caches or body energy reserves)
e.g. European ground squirrels, adders, some bears
HIBERNATION
Long-term torpor (can be 6 months) occurring in the
summer months (ectotherms)
* To avoid damage from high temperatures
(dessication- extreme dryness or drying out)
e.g. lungfish, salamanders, land snails, Australian
water-holding frog, cane toads
ESTIVATION
– active at night
e.g. owl, mice, koala
NOCTURNAL
– active during daytime
e.g. “grazers” – gazelles, elephants
DIURNAL
– active at dawn & dusk
e.g. deer, rabbits, most birds, red pandas, cats
CREPUSCULAR
– active at periods throughout 24-hours
e.g. some lemur
CATHEMERAL
Fever: pyrogens fight pathogens
Heat exhaustion (1020F/38.80C)
Heat stroke (1060F/410C) → death
Malignant hyperthermia – defective Ca++ release
HYPERTHERMIA: body temperature too high
Metabolism slows → loss of consciousness, death
Surgical applications: heart surgery
HYPOTHERMIA: body temperature too low
provides carbohydrates, proteins, & fats for
metabolism
Eating
___ is used for body heat & work: transport,
synthesis, storage
Energy
____ changes with age, sex, body fat,
activity & diet
Metabolic rate
___regulates anabolic cell activities & glucose
uptake in cells
Insulin
___takes 50% of our
energy
Maintaining homeothermy
What is the body’s main fuel?
Glucose
What is the function of the human digestive system?
Break food down into smaller molecules that cells can use.
Main signal to stop eating is distention of stomach: stomach
sends satiety messages to brain via___(info about
stretching stomach walls) &___(CCK) limits meal size
vagus nerve, cholecystokinin
- form of sugar that circulates in the blood
- provides major source of energy for body tissues
- Insulin (a hormone) levels go up, glucose goes down
- when level is low, we feel hunger
Glucose
- an individual’s natural level or “weight thermostat” for
weight regulation - when the body falls below this weight, an increase in
hunger & a lowered metabolic rate may act to restore the
lost weight
Set Point
- body’s base rate of energy expenditure
BASAL METABOLIC RATE
The _______controls eating & other body
maintenance functions
Hypothalamus
THE_________ CONTROLS:
* Insulin secretion
* Alters taste responsiveness
LATERAL HYPOTHALAMUS
What happens to hunger and the brain when there is damage to the lateral hypothalamus?
- Animal refuses food & water as if food distasteful
- Animal may starve to death if not force-fed
When electrical stimulation of the lateral hypothalamus occurs, what happens?
Animal increases eating & food-seeking
behaviours
What happens when there is damage to areas in or around the ventromedial hypothalamus?
- Animal has increased appetite, gains lot of
weight, then becomes ‘finicky’ eater - Eat normal meals more often (overeat)
What Factors other than biological ones influence
hunger & eating:?
- Memories of last meal
- Taste preferences: cultural
- Social eating; trends; food security
- Cravings as a result of mood?
Hormone secreted by pancreas: controls blood glucose
Insulin
Protein secreted by fat cells; when abundant, causes brain to increase metabolism and decrease hunger.
Leptin
Hunger-triggering hormone secreted by hypothalamus
Orexin
Hormone secreted by empty stomach; sends “I’m hungry” signals to the brain.
Ghrelin
Digestive tract hormone; sends “I’m not hungry dignals to the brain.
PYY
___monitors appetite hormone levels
Hypothalamus
