9.1+9.2

Question 1

what is homeostasis?

Answer 1

maintenance of a state of dynamic equilibrium thru responses of body to external + internal stimuli

Question 2

why does pH need to be maintained?

Answer 2

• structures of protein molecules remain stable to maintain optimum activity

Question 3

why does water potential need to be maintained?

Answer 3

• avoid osmotic effects that could damage/destroy cells

Question 3

why does temp need to be maintained? 3

Answer 3

• for optimum activity of enzymes that control rates of cellular reactions
• maintain CSM
• affect metabolism

Question 4

what are -ve feedback systems

Answer 4

• help maintain condition within narrow range - change registered by recepters -> effectors stimulated to restore equilibrium

Question 5

what are +ve feedback systems

Answer 5

• effectors work to increase effect
  LESS COMMON
  eg contractions of uterus during labour

Question 6

where are mammalian hormones produced from

Answer 6

endocrine glands

Question 7

what are the 2 types of hormones give examples

Answer 7

1. peptide hormones eg adrenaline
2. steroid hormone based on cholesterol eg oestrogen

Question 8

what is the mode of action for peptide hormones

Answer 8

• they are water soluble so easily transported in blood plasma
• but CANT penetrate CSM as not soluble in phospholipid bilayer (polar)
• surface receptors for hormone on CSM
• binding brings abt response inside cell
• surface receptors = associated w enzyme (adenylate/adenyl cyclase)
• binding of hormone activates adenylate cyclase - converts ATP into cyclic AMP (cAMP)
• cAMP acts as 2nd messenger inside cell - triggers cascade effect on cytoplasmic enzymes (won’t be used up therefore cascade effect) which then bring abt effect

Question 9

what is the mode of action for steroid hormones?

Answer 9

• lipid soluble + water insoluble
• must have transport protein to transport them in blood plasma + tissue fluid to target cells
• once at target cells - receptor on cell - diffuse thru plasma membrane into cytoplasm
• bind to intracellular receptor - transfers hormone to nucleus - binds to chromatin - increase/decrease transcription + translation (direct effect on DNA)
• here steroid in nucleus acts as transcription factor!!

Question 10

how are hormones secreted 2 ways

Answer 10

1. via duct to outside = exocrine glands
2. directly into blood on inside = ductless gland = endocrine glands

Question 11

hormones travel to every cell in body but…

Answer 11

only have effect on particular cells/tissues
must combine w receptor that is specific for that hormone
only target cells/tissues/organs have the receptor

Question 12

which lobe of the pituitary gland releases ADH

Answer 12

posterior lobe (back)