1. Cardiac Control Questions JUST complete Q2 and 3

2. 2. Cardiac Control Answers 1 pressure receptors / baroreceptors / stretch receptors; 2 in aorta / carotid arteries / carotid sinus; (reject carotid body) 3 send impulses; (reject signals / messages / electronic) 4 to cardiovascular centre / medulla / cardio-inhibitory centre; 5 send impulses; (once only) 6 parasympathetic nerves / vagus; (accept inhibitory nerve) 7 to SAN; 8 release of ACh / inhibits SAN / decreases impulses from SAN; 9 decreases impulses to AVN / decreased stimulation of AVN / decreases

3. 3. Cardiac Control Answers 1 inhibit impulses in sympathetic nerves / from cardio-acceleratory centre; 2 SAN not stimulated / noradrenaline not released / (accept inhibits / blocks synapses); 3 heart rate lowers / does not increase;

4. The Menstrual Cycle

5. Hormones Four hormones involved in controlling menstruation NameMade…Function FSHPituitaryStimulates one egg cell to develop (become follicle) OestrogenFollicle (ovary)Stimulates rebuilding of the uterus wall LHPituitaryStimulates follicle to burst and release the ovum ProgesteroneCorpus Luteum (ovary)Completes development of uterus wall, promotes glycogen storage

6. The Cycle During the first week of the cycle the pituitary gland stimulated, and releases follicle stimulating hormone (FSH)

8. FSH stimulates a potential egg cell in the ovary The cells around the ovum also develop. This is called a follicle. Follicle cells secrete oestrogen. Oestrogen stimulates rebuilding of uterus wall. An oocyte (pre-ovum) surrounded by follicle cells

9. False colour SEM of human uterus wall, approximately 13 days into cycle. Green cells are secretory, and orange cells are ciliated

11. Initial concentrations of oestrogen are low. The low concentration has a negative feedback effect on the secretion of FSH.

12. Negative feedback lowers FSH concentration

13. As follicle grows is produces larger concentrations of oestrogen. At a certain threshold, its effect reverses. It now has a positive feedback effect on secretion of FSH from pituitary. Also stimulates pituitary gland to release luteinising hormone (LH)

15. Positive feedback from increasing oestrogen concentration causes increase in FSH and LH from pituitary gland. Follicle gets bigger – releases more oestrogen

16. Peak of LH causes follicle to burst and release ovum This is ovulation (on day 14 of the cycle) Follicle reforms to become structure called corpus luteum (‘yellow body’) LH stimulates corpus luteum to produce progesterone.

17. Peak of LH causes ovulation (day 14) Oestrogen falls because follicle is gone, but corpus luteum still produces some. Ovulation – ovum released from follicle. Follicle become corpus luteum

18. Progesterone completes uterus wall. Increases blood supply and promotes glycogen storage. Rising concentrations of progesterone has negative feedback effect on FSH and LH. This prevents new follicles forming.

19. Fall in FSH and LH due to negative feedback with oestrogen and progesterone Progesterone produced by corpus luteum. Inhibits FSH and LH Corpus luteum – produces progesterone. Uterus wall fully completed.

20. Fertilisation must occur within 2 days of ovulation. Embryo takes 3 days to reach the uterus and implant. If no embryo implants within a week the corpus luteum starts to break down. Progesterone and oestrogen concentrations fall. Uterus wall begins to break down. FSH no longer inhibited, so begins to rise. Cycle begins again

21. FSH and LH totally inhibited Breakdown of corpus luteum causes fall in progesterone and oestrogen Corpus luteum begins to break down if no embryo has implanted a week after ovulation

22. FSH begins to rise since it’s not inhibited by oestrogen and progesterone Low levels of progesterone and oestrogen because there is no follicle or corpus luteum Uterus wall breaks down due to low levels of oestrogen and progesterone New egg cell stimulated by rising FSH levels