UNIT 3: The Human Endocrine System

Question 1

an endocrine gland

Answer 1

an organ that secretes a hormone directly into the bloodstream

Question 2

hormone

Answer 2

a chemical messenger secreted by an endocrine gland directly into the bloodstream where it travels to a target organ / tissue where it exerts a specific effect

Question 3

exocrine gland vs endocrine

Answer 3

exocrine = an organ that secretes its product into a duct.
endocrine = gland that secretes its product directly into the bloodstream

Question 4

endocrine action vs nerve action

Answer 4

endocrine - slow, prolonged, and chemical in nature.

nerve - fast, short-lived and electrical in nature

Question 5

hypothalamus

Answer 5

secretes hormones that control the secretions of the pituitary e.g. growth hormone releasing hormone

Question 6

pineal gland

Answer 6

secretes melatonin - regulates biorhythms such as sleep and menstrual cycle.

Question 7

pituitary gland

Answer 7

(master gland) - controls all other glands: secretes many hormones - e.g. growth hormone (GH) stimulates protein synthesis and bone elongation

Question 8

thymus gland

Answer 8

secretes thymosin which helps white blood cells to mature into active immune cells

Question 9

pancreas endocrine gland

Answer 9

the islets of langerhans in the pancreas secrete insulin which stimulates all cells to absorb glucose.

• diabetes results if there is no insulin or lack on in the body.
• insulin is used as a hormone supplement to treat type 1 diabetes

Question 10

adrenal glands

Answer 10

secrete adrenaline which is secreted in times of stress or danger.

• increases blood flow to the brain and muscles.
• decreases blood flow to the skin and internal organs such as the intestines and kidneys.
• dilates the bronchioles allowing more air in.
• increases blood glucose levels.
• increases heart rate

Question 11

ovaries

Answer 11

secrete oestrogen (stimulates changes that occur at puberty in females) and progesterone which are both involved in the menstrual cycle and in preparing the female body for a possible conception.

Question 12

testes

Answer 12

secrete testosterone which stimulates the changes that occur in the male at puberty and also help to maintain these changes

Question 13

anabolic steroids

Answer 13

act in the same way as testosterone.

builds up muscle, therefore, anabolic steroids are used by bodybuilders.

Question 14

thyroid

Answer 14

secretes thyroxine which increases metabolism

Question 15

parathyroid

Answer 15

secretes parathormone which stimulates release of calcium from bone

Question 16

throxine deficiency leads to myxoedema

Answer 16

• goitre (swelling of the thyroid gland).
• low metabolic rate and mental retardation (cretinism in children).
• tiredness, fatigue.
• weight gain (fluid build-up - oedema)

Question 17

myxoedema treatment

Answer 17

• thyroxine is administered

- iodine is administered

Question 18

excess of thyroxine leads to

Answer 18

• bulging eyeballs
• goitre
• increased appetite
• irritability
• heat intolerance

Question 19

treatment of excess thryoxine

Answer 19

• surgical removal of part of the thyroid
• anti-thyroid drugs
• administration of radioactive iodine

Question 20

negative feedback mechanism of thyroxine

Answer 20

When thyroxine levels rise above normal:
- pituitary stops secreting thyroid-stimulating hormone (TSH) thereby causing the thyroid to reduce secretion of thyroxine.
When thyroxine levels fall below normal:
- pituitary starts secreting TSH causing the thyroid gland to secrete more thyroxine.
- when iodine is completely absent from diet thyroxine cannot be made - therefore, pituitary keeps secreting TSH which builds up to extreme levels in the thyroid causing goitre.