HUMAN SYSTEMS QUESTION 1989:               L. PETERSON/AP BIOLOGY

	Describe negative and positive feedback loops, and discuss how feedback 
	mechanisms regulate each of the following:
		a.   The menstrual cycle in a nonpregnant human female
		b.   Blood glucose levels in humans

  
  
  STANDARDS:
  
  Introduction: (describe -/+ feedback loops)
  1 pt         1.  Definition as an overview of the process: Control mechanism which is              regulated through the effect it brings about.
  1 + 1 pts    2.  Negative feedback: Endproduct acts as an inhibitor of pathway 
                      (stimulatory-inhibitory).
                Seek terms such as inhibit/turn off. Examples: ACTH -> cortisol -> 
                feedback; Lac operon; thermostat metaphor; CO2 respiration, etc.
  1 + 1 pts    3.  Positive feedback: change in variable amplifies the pathway 
               (stimulatory-stimulatory).
                Seek terms such as turn on/stimulate/induce. Examples: 
                Oxytocin/birth; LH surge; trypsinogen/trypsin; neural membrane 
                permeability; mating process; sound amplification metaphor; etc.
     [one point for definition and one point for example] 
     Note: these points might be embedded in Parts A and B. 
  Total of 3 points maximum for introduction out of 5 points possible.
  
  Part A: Menstrual Cycle
  1 pt         1.  Primary function of the cycle as an overall concept: production of 
                gamete and preparation of the uterus. A borad interpretation OK.
  1 + 1 + 1 pts     2.  Hormones and interactions: look for information that suggests cause 
                and effect and a pathway. Items a-c are complete examples. To earn a 
                point, three targets, hormones, and sources must be given in a logical 
                sequence.
               Wrong information will void a string of three. The goal is to find 
               physiological relationships and not just terms.
         a.  GnRH (hypothalamus) -> FSH (pituitary) -> estrogen (ovary) -> 
              endometrium
         b.  GnRH (hypothalamus) -> LH (pituitary) -> progesterone (corpus luteum) 
              -> endometrium
         c.  estrogen -> LH surge -> ovulation
       Research on the regulation of the menstrual cycle is rapidly evolving and textbooks 
       can reflect different philosophies or progress of research.
  1 or 2 pts   3.  Negative feedback results on hypothalamus/pituitary.
               Estrogen/progesterone inhibits FSH and LH production at the GnRH 
               (hypothalamus) and pituitary level. If no choriogonadotropic hormone 
                -> estrogen/progesterone levels drop and endometrium stimulus no 
                longer supported - > endometrium lost as cycle begins again and FSH 
                and LH released from inhibition. [2 points for completeness]
  1 pt         4.  Positive feedback: estrogen -> LH surge. Note: estrogen can be both 
                inhibitory and stimulatory on the hypothalamus/pituitary.
  
  Total of 5 points maximum for Part A out of 7 points possible.
  
  Part B: Blood Sugar
  1 pt         1.  Concept of homeostasis, equilibrium, and/or maintenance of glucose 
                level.
  1 pts        2.  Concept of antagonistic relationship of glucagon and insulin.
  1 + 1 pts    3a. Low blood glucose -> glucagon release -> glycogen converted to 
                glucose/ glucose mobilized from liver to blood or alpha cells in 
                pancreas release glucagon
  1 + 1 pts    3b. High blood glucose -> insulin release - glucose mobilized into cells ->
                lower blood levels/glucose mobilized into liver or muscle or beta 
                cells of pancreas release insulin
  1 pt         4.  Alternate loops of blood glucose levels (only one point possible here):
                a.  adrenalin, noradrenalin
                b.  ACTH, cortisol
                c.  somatostatin
  
  Total of 5 points maximum for Part B out of 7 points possible.