9.3 - Thermoregulation Flashcards
Define endotherms
An animal that maintains its internal body temperature by internal mechanisms (humans)
Define ectotherms
An animal that maintains its body temperature by absorbing thermal energy from the environment (behavioural!!)
Define hypothalamus
A region of the brain that controls body temperature
What are the 2 types of thermoreceptors (sensors)?
- Peripheral receptors - in the skin monitoring skin temp.
2. Central receptors - in the arteries and organs monitoring core temperature
Where does the hypothalamus receive information from?
The two thermoreceptors
What is the difference between skin and internal temperature?
1 degree
What are the two parts of the pituitary gland?
Anterior and posterior
Where is change in skin temperature?
Peripheral thermoreceptors in skin
Where is change in core (internal) temperature?
Central thermoreceptors in hypothalamus, abdominal organs, and elsewhere
What is the body’s thermostat?
Hypothalamus
List and explain the 4 types of controlling body temperature
- Voluntary changes in behaviour (taking on/off clothing when hot/cold)
- Motor neurons (when you feel cold) - send message to skeletal muscles to contract really fast (shivering) to warm body
- Nerves: smooth muscle in arterioles in skin - arterioles smooth muscle vasoconstrict or vasodilate
- Nerves: sweat glands - (when too hot), initially blood vessels dilate to heat skin as much as possible, then constrict when the organs begin losing too much heat (sacrificing skin to keep organs warm)
What is the adjustment in: voluntary changes in behaviour
In gain or loss of thermal energy
What is the adjustment in: motor neurons
In muscle activity (in metabolic thermal energy output) -> when cold
What is the adjustment in: smooth muscle in arterioles in skin
In loss or conservation of thermal energy
What is the adjustment in: sweat glands
In loss of thermal energy -> when too hot
When does shivering and vasoconstriction occur in fever?
When thermoregulation before fever is above set point
When does sweating and vasodilation occur in fever?
When thermoregulation after fever is below set point
Effects of fever
Regulation of body temperature is at elevated level during fever (new set point)
What does fever do?
Hypothalamus informs body that fever is new set point -> to kill infection & virus
List and explain steps in homeostasis of body temp. with hypothalamus
- Thermoreceptors detect decrease in temperature, and send message to hypothalamus
- Hypothalamus releases TRH (thyroid releasing hormone) into the blood
- TRH is carried by blood to pituitary gland
- Anterior pituitary releases TSH (thyroid stimulating hormone) into blood
- TSH travels to thyroid gland, signals thyroid follicles to release hormone Thyroxine (T3 & T4) into blood
- Thyroxine signals body cells to burn more glucose -> increased heat prod. -> increases body temp.
What is the stimulus of body temperature/when is homeostasis DISTURBED?
Decreases T3, T4 in blood, or low body temperature
When is homeostasis RESTORED?
Increased T3, T4 in blood
What are the 2 negative feedbacks for hypothalamus?
- Thermoreceptors tell thyroid to stop TRH prod. b/c temperature is normal (feedback is to high body temperature)
- High levels of thyroxine prod. provides negative feedback to hypothalamus by stopping prod. of TRH
Define hyperthyroidism
- too much thyroxine in the blood (negative feedback is not working -> hypothalamus does not detect increase of thyroxine)
- metabolism is too high
- more common
Symptoms of hyperthyroidism
- loss of weight (b/c high metabolism)
- irritability (burning food quickly)
- excessive sweating (temp in body increase)
- bulging eyes (Graves disease)
- skin problems (eczema, rashes)
- goiter (swelling of thyroid -> lump)
Causes of hyperthyroidism
- autoimmune (thyroid stimulating antibody) (Grave’s disease)
- > when your immune system sends antibodies to thyroid to overwork
- cancer
- thyroiditis (inflammation from infection STIMULATES thyroid)
Treatment for hyperthyroidism
- anti thyroid drugs
- radioactive iodine (most common treatment)
- > pill goes to thyroid, uses iodine to kill part of thyroid with radiation
- surgery
Define hypothyroidism
Levels of thyroxine in blood is too low
Symptoms of hypothyroidism
- hair loss
- weight gain
- muscle weakness
- feeling cold
- fatigue
- goiter (swelling b/c thyroid is being attacked with lots of TSH)
Causes of hypothyroidism
- autoimmune (Hashimoto’s) (Primary)
- > immune system kills thyroid
- treatment for hyperthyroidism (radioactive iodine kills too much of thyroid)
- pituitary disorder (not enough TSH) (Secondary) -> nothing is telling thyroid to produce thyroxine
- iodine deficiency (Primary)
Treatment for hypothyroidism
- thyroxine supplements daily (when the thyroid can’t work to make thyroxine)
- iodine supplements (thyroid uses it to make thyroxine hormone)
- > in fish/seafood
