9.3 - Thermoregulation

Question 1

Define endotherms

Answer 1

An animal that maintains its internal body temperature by internal mechanisms (humans)

Question 2

Define ectotherms

Answer 2

An animal that maintains its body temperature by absorbing thermal energy from the environment (behavioural!!)

Question 3

Define hypothalamus

Answer 3

A region of the brain that controls body temperature

Question 4

What are the 2 types of thermoreceptors (sensors)?

Answer 4

1. Peripheral receptors - in the skin monitoring skin temp.

2. Central receptors - in the arteries and organs monitoring core temperature

Question 5

Where does the hypothalamus receive information from?

Answer 5

The two thermoreceptors

Question 6

What is the difference between skin and internal temperature?

Answer 6

1 degree

Question 7

What are the two parts of the pituitary gland?

Answer 7

Anterior and posterior

Question 8

Where is change in skin temperature?

Answer 8

Peripheral thermoreceptors in skin

Question 9

Where is change in core (internal) temperature?

Answer 9

Central thermoreceptors in hypothalamus, abdominal organs, and elsewhere

Question 10

What is the body’s thermostat?

Answer 10

Hypothalamus

Question 11

List and explain the 4 types of controlling body temperature

Answer 11

1. Voluntary changes in behaviour (taking on/off clothing when hot/cold)
2. Motor neurons (when you feel cold) - send message to skeletal muscles to contract really fast (shivering) to warm body
3. Nerves: smooth muscle in arterioles in skin - arterioles smooth muscle vasoconstrict or vasodilate
4. 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)

Question 12

What is the adjustment in: voluntary changes in behaviour

Answer 12

In gain or loss of thermal energy

Question 13

What is the adjustment in: motor neurons

Answer 13

In muscle activity (in metabolic thermal energy output) -> when cold

Question 14

What is the adjustment in: smooth muscle in arterioles in skin

Answer 14

In loss or conservation of thermal energy

Question 15

What is the adjustment in: sweat glands

Answer 15

In loss of thermal energy -> when too hot

Question 16

When does shivering and vasoconstriction occur in fever?

Answer 16

When thermoregulation before fever is above set point

Question 17

When does sweating and vasodilation occur in fever?

Answer 17

When thermoregulation after fever is below set point

Question 18

Effects of fever

Answer 18

Regulation of body temperature is at elevated level during fever (new set point)

Question 19

What does fever do?

Answer 19

Hypothalamus informs body that fever is new set point -> to kill infection & virus

Question 20

List and explain steps in homeostasis of body temp. with hypothalamus

Answer 20

1. Thermoreceptors detect decrease in temperature, and send message to hypothalamus
2. Hypothalamus releases TRH (thyroid releasing hormone) into the blood
3. TRH is carried by blood to pituitary gland
4. Anterior pituitary releases TSH (thyroid stimulating hormone) into blood
5. TSH travels to thyroid gland, signals thyroid follicles to release hormone Thyroxine (T3 & T4) into blood
6. Thyroxine signals body cells to burn more glucose -> increased heat prod. -> increases body temp.

Question 21

What is the stimulus of body temperature/when is homeostasis DISTURBED?

Answer 21

Decreases T3, T4 in blood, or low body temperature

Question 22

When is homeostasis RESTORED?

Answer 22

Increased T3, T4 in blood

Question 23

What are the 2 negative feedbacks for hypothalamus?

Answer 23

1. Thermoreceptors tell thyroid to stop TRH prod. b/c temperature is normal (feedback is to high body temperature)
2. High levels of thyroxine prod. provides negative feedback to hypothalamus by stopping prod. of TRH

Question 24

Define hyperthyroidism

Answer 24

• too much thyroxine in the blood (negative feedback is not working -> hypothalamus does not detect increase of thyroxine)
• metabolism is too high
• more common

Question 25

Symptoms of hyperthyroidism

Answer 25

• 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)

Question 26

Causes of hyperthyroidism

Answer 26

• autoimmune (thyroid stimulating antibody) (Grave’s disease)
• > when your immune system sends antibodies to thyroid to overwork
• cancer
• thyroiditis (inflammation from infection STIMULATES thyroid)

Question 27

Treatment for hyperthyroidism

Answer 27

• anti thyroid drugs
• radioactive iodine (most common treatment)
• > pill goes to thyroid, uses iodine to kill part of thyroid with radiation
• surgery

Question 28

Define hypothyroidism

Answer 28

Levels of thyroxine in blood is too low

Question 29

Symptoms of hypothyroidism

Answer 29

• hair loss
• weight gain
• muscle weakness
• feeling cold
• fatigue
• goiter (swelling b/c thyroid is being attacked with lots of TSH)

Question 30

Causes of hypothyroidism

Answer 30

• 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)

Question 31

Treatment for hypothyroidism

Answer 31

• thyroxine supplements daily (when the thyroid can’t work to make thyroxine)
• iodine supplements (thyroid uses it to make thyroxine hormone)
• > in fish/seafood