-A hormone is a chemicalmessenger produced by a gland and carried by the blood, which alters the activity of one or more specific target organs i.e. they are chemicals which transmit information from one part of the organism to another and bring about a change.
-The glands that produce hormones in animals are known collectively as the endocrine system.
Endocrine glands have a good blood supply as when they make hormones they need to get them into the bloodstream (specifically the blood plasma) as soon as possible so they can travel around the body to the target organs to bring about the response.
Hormones only affect cells with target receptors that the hormone can bind to. These are either found on the cell membrane, or inside cells. Receptors have to be complementary to hormones for there to be an effect.
The liver regulates levels of hormones in the blood; transforming or breaking down any that are in excess.
Difference in nervous and endocrine system:
A) nerves, brain, spinal cord
B) glands
C) electrical impulse
D) chemical hormone
E) fast
F) slower
G) short- until nerve impulses stop
H) longer - until hormone is broken down
Thyroxine
-Thyroxine is a hormone that is released from the thyroidgland (which is located in the neck).
-It stimulates the metabolic rate; this is the speed at which chemical reactions occur in the body when it is at rest.
Thyroxine is an example of negativefeedback:
-Thyroxine levels are controlled by negative feedback; with levels of TSH (thyroid-stimulating hormone) released from the pituitary gland responsible for maintaining normal levels in the bloodstream.
-If the level of thyroxine is too high, the release of TSH is inhibited, so less thyroxine is released from the thyroid gland.
-If the level of thyroxine falls below a normal level, the release of TSH from the pituitary gland is increased, which stimulates the thyroid to release more thyroxine.
Adrenaline
The adrenaline glands lie near your kidneys. In times of stress they secrete the hormone adrenaline. Adrenaline immediately prepares the body for the fight or flight response.
-Negative feedback mechanisms in homeostasis helps to maintain conditions in the body within an optimal range; any movement away from ideal conditions results in changes occurring which bring them back.
-This involves detecting that the level of a substance or a condition has gone above or below normal levels, which triggers a response to bring the level back to normal again.
Testosterone
-main male sex hormone
-produced in the testes
-Stimulates sperm production
-Important for the development of the male reproductive system
Oestrogen
-Main female sex hormone
-produced in ovaries
-Involved in menstrual cycle
-Promotes female sexual characteristics e.g. breast development
Progesterone
-produced in ovaries
-Supports pregnancy
-Involved in menstrual cycle
FSH and LH
-released from pituitary gland
-Help control the menstrual cycle
the menstrual cycle
The average menstrual cycle is 28 days long and there are four main stages:
Day 1 is when menstruation starts. The uterus lining breaks down and is released.
Lining of the uterus builds up again (day 4 to 14), into a thick spongy layer full of blood vessels.
Ovulation (the release of an egg) occurs on around day 14, about halfway through the cycle, and the egg then travels down the oviduct to the uterus.
Maintenance of the uterus lining ready to accept a fertilised egg.
The menstrual cycle
A) menstruation
B) maintained
C) builds up
D) lining breaks down
Follicle-stimulating hormone (FSH)
Produced by the pituitary gland - causes an egg to mature in the ovary and stimulates the ovaries to produce oestrogen.
Luteinising hormone (LH)
Produced by the pituitary gland and stimulates ovulation (the release of the egg) and indirectly stimulates progesterone production.
Oestrogen
Produced by the ovaries - causes the lining of the uterus to thicken and grow and stimulates the production of LH and inhibits the production of FSH so that only one egg is released in each cycle.
Progesterone
-Produced specifically by an empty egg follicle called the corpus luteum and is required to maintain the lining of the uterus so when the level of progesterone falls and there's a low oestrogen level, the lining breaks down.
-Inhibits the production of FSH and LH
-A low progesterone level allows FSH to increase and then the whole cycle starts again.
Stages of the menstrual cycle
1. Pituitary gland produces FSH
2. FSH stimulates development of new follicle in ovary
3. Egg matures inside follicle
4. Follicle produces oestrogen
5. Oestrogen causes growth and repair of uterus lining
6. Oestrogen inhibits production of FSH
7. High oestrogen stimulates release of LH
8. LH causes ovulation
9. Follicle becomes corpus luteum
10. Corpus luteum produces progesterone
11. Progesterone maintains uteruslining
12. If egg not fertilised, corpus luteum breaks down, progesterone drops, menstruation occurs
13. If fertilisation occurs, corpus luteum continues producing progesterone, preventing uterus lining breakdown
14. Placenta develops, secretes progesterone to maintain lining throughout pregnancy
-Contain hormones to inhibitFSH production so that no eggs mature. There are two types:
The combined pill:
Contains oestrogen and progesterone, which is over 99% effective at preventing pregnancy.
High levels of oestrogen inhibit FSH production, preventing the maturation and release of eggs.
Progesterone also plays a role in inhibiting the release of mature eggs and stimulates the production of a thick mucus, which prevents sperm from reaching any eggs that are released.
The mini-pill:
A progesterone-only pill, which has fewer side effects.
Injection, implant, or skin patch:
-They slowly release progesterone to inhibit the maturation and release of eggs for a number of months or years.
-Benefits of implants reduce the chance of someone forgetting to take the pill.
Intrauterine devices (IUD):
-Inserted into the uterus to prevent the implantation of an embryo or release of a hormone.
-A plastic IUD produces progesterone, which stimulates the production of a thick mucuslining, preventing sperm from reaching any eggs.
-A copper IUD works by releasing low levels of copper ions, which disablesperm cells
Barrier methods:
Work by preventing sperm from reaching the egg:
Condom:
Latex sheath worn over the penis to prevents sperm from entering the vagina.
Female Condom:
Latex sheath worn inside the vagina and prevents entry of sperm
Diaphragm:
A rubber cap that fits over the entrance to the cervix
Prevents entry of sperm into the uterus
Natural methods:
Natural planning:
Avoiding sexual intercourse during the fertile period of the menstrual cycle when ovulation occurs.
Surgical methods:
Vasectomy:
The sperm ducts are cut, so prevents sperm from being ejaculated.
Very effective but difficult to reverse.
Female sterilisation (tubal ligation):
The oviducts are cut or tied off, preventing eggs from reaching the uterus or sperm from reaching the eggs.
Very effective but difficult to reverse.
Different Methods of Contraception Table:
A) 99
B) every day
C) fewer side effects
D) weeks or months
E) hormonal
F) STI's
G) medical professional
H) STI's
I) applied
J) break
K) combined pill and minipill
L) injection, implant or skin patch
M) condom, femidom and diaphram
N) natural planning
O) sterilisation and vasectomy
P) 99
Q) 98
R) 95
S) 94
T) chemical
U) control
V) menstrual cycle
W) illness
X) lifestyle
Y) 99
Z) permanent
[) surgery
\) STI's
]) 99
hormones to promote natural pregnancy:
Sometimes, women may have low levels of FSH so low numbers of eggs maturing in their ovaries or no eggs being released during ovulation. Hormones can be given to promote egg production:
FSH (Follicle-stimulating hormone) is given to stimulate eggs to mature.
LH (Luteinising hormone) is given to stimulate ovulation.
This method carries the risk that several eggs may be released at once, which would increase the chance of multiple births.
In Vitro Fertilisation (IVF)
A method of assisted reproduction where eggs are fertilised by sperm outside the body, in glass