Endocrine System

Question 1

Define homeostasis and explain its importance

Answer 1

Maintaining a stable environment
An organism is in homeostasis when conditions in the internal environment are maintained within physiological limits
When homeostasis is disturbed, illness may result, if body fluids and cells are not brought back into homeostasis death may occur

Question 2

Define ‘hormone’, and name the chemical classes of hormones

Answer 2

Hormones: they are chemical signals produced in endocrine glands or tissues that travel in the bloodstream to cause an effect on other tissues.
Classification of hormones:
-peptide/polypeptide, largest group, short chains of amino acids
-Glycoproteins, large protein molecules, often made of subunits
-amino acid derivatives (amines), synthesised from aromatic amino acids
-steroids, all derived from cholesterol

Question 3

Identify the major endocrine glands and the hormones they produce

Answer 3

-hypothalamus: 2 hormones are produced for release form posterior pituitary; OT (oxytocin) and ADH (antidiuretic hormone). 6 tropic hormones; TRH, PRH, PIH, CRH, GnRH, GHRH, GHIH
-anterior pituitary: TSH, ACTH, LH, FSH, PRL, GH
-adrenal glands release: mineralocorticoids, glucocorticoids, small amounts of androgens, adrenaline, noradrenaline
-thyroid glands: T3, T4, calcitonin
-parathyroid: PTH
-pancreatic islets: insulin, glucagon, somatostatin
-pineal gland: melatonin
-testes: testosterone
-ovaries: oestrogen, progesterone

Question 4

Understand the concept of negative and positive feedback

Answer 4

If response reverses original stimulus= -ive feedback (tends to restore to normal level)
If response changes original stimulus = +ive feedback (continues to reinforce the original stimulus—> increasing certain factors)
-ive is most common since it maintains consistency of internal environment
+ive is less as it tends to push things towards a climax or threshold e.g. childbirth and oxytocin

Question 5

Understand the relationship between the hypothalamus and pituitary gland (anterior and posterior)

Answer 5

The pituitary and the hypothalamus act as a unit, regulating the activity of most of the other endocrine glands, with a network of nerve fibres connecting them
The anterior is composed of hormone secreting glandular tissue because it is an upgrowth of glandular tissue form the pharynx
The posterior is a down-growth of nervous tissue from the brain