Hormonal control part 2 Flashcards
Define thyroxine and state what it does
Thyroxine is a hormone made by the thyroid gland.
It controls the body’s metabolic rate – how fast reactions happen in the body.
Define adrenaline and state what it does
Adrenaline is a hormone made by the adrenal glands in response to stress.
It prepares the body for “fight or flight” by increasing heart rate and blood flow to muscles. Adrenaline increases heart rate, triggers glucagon to convert glycogen to glucose, dilates the eyes, increases blood flow to the muscles.
State the steps of thyroxine action in a negative feedback loop
The pituitary gland releases TSH (thyroid-stimulating hormone).
TSH makes the thyroid gland release thyroxine.
Thyroxine levels rise in the blood.
High thyroxine levels stop the pituitary from releasing more TSH.
(This keeps thyroxine levels stable.)
Describe how a negative feedback system works
A change in the body is detected.
A response is triggered to counteract the change.
When normal levels are restored, the response is reduced.
This keeps conditions in the body stable.
Compare the role of thyroxine and the way it is controlled with adrenaline
Thyroxine controls metabolism and is controlled by a negative feedback loop.
Adrenaline prepares the body for action and is released quickly in response to stress.
Thyroxine levels stay steady through ongoing control.
Adrenaline acts fast and is not controlled by negative feedback.
What are primary versus secondary sex characteristics?
Primary sex characteristics:
These are the sexual organs a person is born with.
They are directly involved in reproduction.
Examples:
Males: penis, testes
Females: vagina, ovaries
Secondary sex characteristics:
These develop during puberty and are not directly involved in reproduction.
They show physical differences between males and females.
Examples:
Males: voice deepens, facial hair grows
Females: breasts develop, hips widen
What is oestrogen? What does it do?
Oestrogen = main female hormone, it’s released by the ovary. Once puberty starts, it helps mature egg cells in the ovary to be released every 28 days at ovulation.
What is testosterone? What does it do?
Testosterone is the main male reproductive hormone produced by the testes and stimulates sperm production.
Which hormones are involved in the menstrual cycle?
Follicle stimulating hormone (FSH), Luteinising hormone (LH), oestrogen and progesterone.
Describe the process of the menstrual cycle
Day 1–4: The cycle starts with menstruation – the uterus lining breaks down. Hormone levels are low.
Day 4–14: The pituitary gland releases FSH (Follicle Stimulating Hormone), which causes an egg to mature in the ovaries.
FSH also makes the ovaries produce oestrogen.
Oestrogen causes the uterus lining to thicken and stops further FSH release. It also triggers a rise in LH.
Day 14 (Ovulation): A sharp rise in LH (Luteinising Hormone) causes ovulation – the egg is released from the ovary.
Day 14–28: The empty egg follicle produces progesterone.
Progesterone keeps the uterus lining thick in case the egg is fertilised.
It also stops FSH and LH to prevent another egg from being released.
If the egg is not fertilised, progesterone levels fall, the uterus lining breaks down, and the cycle restarts.
What are the changes caused by testosterone at puberty?
Voice deepens
Facial and body hair grows
Muscles develop
Sperm production starts
Penis and testes grow
Roles of the hormones in t he menstrual cycle
FSH (Follicle Stimulating Hormone)
Job: Helps eggs in the ovaries mature and stimulates ovary to produce oestrogen.
When: Early in the cycle.
LH (Luteinizing Hormone)
Job: Triggers ovulation (the release of an egg).
When: Around the middle of the cycle.
Oestrogen
Job: Builds up the uterine lining (makes it thick and ready for a baby), stops the production of FSH, stimulate LH.
When: Rises before ovulation.
Progesterone
Job: Maintains the uterine lining (keeps it ready for a baby), stops production of LH and FSH.
When: After ovulation.
If no pregnancy happens:
Oestrogen and progesterone levels drop → the lining sheds → period starts.
