Year 9 Response to Stimuli Part 2

Study Notes

Composed of various glands releasing hormones into the bloodstream, influencing target cells.
Functions primarily through a key and lock system: only specific cells have receptors for certain hormones.
Hormones can be water-soluble (faster action, shorter effect) or lipid-soluble (slower action, longer effect).
Major endocrine glands include the hypothalamus, pituitary, thyroid, parathyroids, adrenal glands, pancreas, ovaries, and testes.

Stimulus response model consists of: stimulus, receptor, modulator, effector, response, essential for homeostasis.
Negative feedback loops are crucial; they help maintain balance by modifying responses to stimuli.
- Example: Thermoregulation and blood glucose management.

A monthly series of physiological changes in preparation for potential pregnancy.
Duration typically ranges from 21 to 35 days, varying by individual.

Ovaries: Produce eggs (ova) and hormones (progesterone and estrogen), regulating the cycle and supporting pregnancy.
Fallopian Tubes: Transport eggs to the uterus; fertilization typically occurs here.
Uterus: Pear-shaped organ housing developing fetus; thickens and sheds its lining (endometrium) during the cycle.

Menstruation (Days 1-5): Shedding of the uterine lining occurs; commonly referred to as a period. Symptoms may include cramps, fatigue, and mood changes.
Follicular Phase (Days 1-13): Following menstruation, hormones prepare a new egg for release, while the uterine lining thickens. Individuals often feel energetic during this phase.
Ovulation: Release of the mature egg from the ovary.
Luteal Phase: Prepares the body for a potential pregnancy after ovulation.

Progesterone and estrogen are vital for regulating the menstrual cycle.
Feedback mechanisms ensure the cycle progresses smoothly, adapting to potential pregnancy needs or initiating menstruation when pregnancy does not occur.