BILD 2: Multicellular Life - Reproduction and Hormonal Cycles

This set of flashcards covers reproduction learning objectives including the HPG axis, the roles of testosterone, FSH, LH, estrogen, and progesterone, and the phases of the ovarian and uterine cycles.

Why is the Surface Area to Volume Ratio ($SA/V$) relevant to why babies have more brown fat than adults?

Babies are smaller and have a higher $SA/V$, which means they lose heat more easily, and brown fat helps maintain the homeostatic set point for body temperature.

What are two specific effects of taking estrogen and progesterone (the pill) or progesterone alone?

It increases the thickness of the cervical mucus and prevents ovulation.

How do high levels of testosterone typically affect sperm production in individuals with typical testosterone levels?

Injections of high levels of testosterone generally suppress sperm production.

Which cells in the testes are stimulated by LH to produce testosterone?

Leydig cells.

Which cells in the testes support and nurture developing sperm, and what stimuli do they require?

Sertoli cells, which require both FSH and testosterone.

What is the primary difference between the ovarian cycle and the uterine cycle?

The ovarian cycle involves events at the ovaries (ovulation and hormone secretion), while the uterine cycle involves events at the uterus (thickening and shedding of the endometrium).

According to the HPG axis, what hormone is released by the Hypothalamus to stimulate the Anterior Pituitary?

GnRH.

What are the oocytes contained within in the ovaries?

Small sacs called follicles.

What is the response of a follicle to FSH in the ovarian cycle?

The follicle grows and matures.

What specific hormonal event triggers ovulation?

An LH surge (a sudden increase in LH levels).

Why would someone with constantly high levels of LH be less likely to ovulate?

Ovulation requires an LH surge; if LH levels are high all the time, they cannot surge (increase quickly).

What type of feedback is stimulated by high levels of estradiol in the HPG axis?

Positive feedback on the hypothalamus and anterior pituitary.

If both high estrogen and progesterone levels are present, which hormone's effects dominate?

Progesterone.

Which structure secretes progesterone and estrogen during the luteal phase of the ovarian cycle?

The corpus luteum.

What causes the 'Big Drop' in progesterone and estrogen levels around Day $28$ of the cycle?

The corpus luteum degenerates, so it no longer produces those hormones.

How does the uterine lining respond to a drop in progesterone and/or estrogen levels?

The uterine lining is shed, a process known as menstruation.

How would the uterine cycle be affected if an oocyte accidentally stuck to the follicle and died during ovulation?

It would not be affected as long as hormone levels are normal, because the uterus responds to hormones rather than the presence of the egg.