Topic 7

Created by

Naomi A

Cards (100)

What is the endocrine system?
A network of glands throughout the body that manufacture and secrete hormones into the bloodstream.
What is a hormone?
chemical messenger that travels through the bloodstream to specific target organs. It binds to receptors on effectors initiating a response
compare the endocrine system to the nervous system
Endocrine system: uses hormones
Hormones travel in the bloodstream to the target organ
Slower response
Lasts until all hormones have broken down which takes a long amount of time.

Nervous system: uses nerve impulses
Nerve impulses travel via neurones to the effectors
Faster response
Lasts until the nerve impulse stops which takes a short amount of time.
What is the pituitary gland?
Described as the 'master gland'
Endocrine gland that produces hormones which control other glands (e.g. adrenal glands)
What are the adrenal glands?
Endocrine glands that produce adrenaline
Where are the adrenal glands located?
on top of the kidneys
What is adrenaline 
A hormone produced by the adrenal glands that is involved in the 'fight or flight' response (where the body prepares to confront danger or flee from it)
State the effects of adrenaline on the body
● Increases heart rate
● Increases blood pressure
● Increases blood flow to muscles
● Increases blood glucose levels
Describe how adrenaline increases heart rate and blood pressure
● Secreted by the adrenal glands, travels in the blood to the heart
● Binds to specific receptors on cells in the heart
● Causes heart muscle to contract more forcefully and frequently
● ∴ heart rate increases, blood pressure increases
Describe how adrenaline increases respiration at muscle tissues
● Adrenaline binds to specific receptors on cells in the liver
● Triggers breakdown of glycogen stores and release of glucose ∴ blood glucose levels increase
● Increased heart rate causes greater blood flow to muscles
● ∴ muscle cells receive more oxygen and glucose for respiration
What is negative feedback 
● A corrective mechanism that allows only small shifts from a set point
● It reverses a change in conditions e.g. if the concentration of a hormone increases, negative feedback systems work to reduce the concentration back to normal level
What is the thyroid gland
endocrine gland found in the neck that regulates metabolism and produces thyroxine
Where is the thyroid gland located?
neck
What is thyroxine? 
A hormone secreted by the thyroid gland that controls metabolic rate, heart rate and temperature.
What is metabolic rate? 
The rate at which all the chemical reactions in the cells of the body are carried out
Describe how thyroxine is released
- Hypothalamus secretes TRH
- TRH stimulates secretion of TSH from pituitary gland
- TSH stimulates the release of thyroxine from the thyroid gland
What does TRH stand for?
thyrotropin releasing hormone
What does TSH stand for?
thyroid stimulating hormone
Describe how a negative feedback system controls blood thyroxine levels
● If blood thyroxine levels increase above a set point, TRH and TSH secretion is inhibited. Less thyroxine is produced by the thyroid gland. Thyroxine levels return to normal.
● If blood thyroxine levels decrease below a set point, TRH and TSH secretion is increased. More thyroxine is produced by the thyroid gland. Thyroxine levels return to normal.
How do the ovaries act as an endocrine gland? 
They secrete oestrogen into the bloodstream
How do the testes act as an endocrine gland? 
They secrete testosterone into the bloodstream
What is the menstrual cycle?
The cycle in women (typically lasting 28 days) that involves:
● Shedding of uterus lining (menstruation)
● Repair of uterus lining
● Release of an egg (ovulation)
● Maintenance of uterus lining
Describe the stages of the menstrual cycle
- Days 1-4: if fertilisation and implantation do not occur the uterus lining sheds and the egg is expelled with it (menstruation)
- Days 4-14: uterus lining thickens and blood vessels grow in preparation for the implantation of an egg
- Day 14: egg released from a follicle into the oviduct (ovulation)
- Days 14-28: uterus lining maintained so implantation can occur
Name the hormones that control the menstrual cycle
Follicle Stimulating Hormone (FSH)
Oestrogen
Luteinising Hormone (LH)
Progesterone
Describe the role of FSH in the menstrual cycle
● Secreted by the pituitary gland
● Transported in the bloodstream to the ovaries
● Triggers the development of a follicle in the ovaries which releases oestrogen
Describe the role oestrogen plays in the menstrual cycle
● Secreted by the ovaries
● Repairs and thickens the uterus lining
● Inhibits secretion of FSH from the pituitary gland
● Stimulates secretion of LH from the pituitary gland
Describe the role of LH in the menstrual cycle
- Secreted by the pituitary gland
- Transported in the bloodstream to the ovaries
- Surge in LH triggers ovulation
- Stimulates follicle remains to develop into a corpus luteum which then secretes progesterone
What is the corpus luteum?
- Temporary endocrine structure
- Mass of cells that releases progesterone
- Degenerates after a few days
Describe the role of progesterone in the menstrual cycle
- Secreted by the corpus luteum after ovulation
- Stimulates the growth of blood vessels in the uterus lining (in preparation for implantation)
- Inhibits the release of FSH and LH
- If no implantation occurs, progesterone levels decrease and the uterus lining sheds. FSH increases and the cycle starts again.
- highest levels around days 20-25
What happens to progesterone levels if fertilisation and implantation occur 
The placenta produces progesterone so levels remain high. This prevents further ovulation and maintains the uterus lining
What are contraceptives 
A method or device utilised to prevent pregnancy
Which hormones can be taken to prevent pregnancy
● Progesterone taken on its own
● Progesterone combined with oestrogen
How does progesterone prevent pregnancy?
- Sperm find it more difficult to enter the uterus as the cervical mucus is thickened
- Thins the uterine lining, reducing the likelihood of egg implantation
- Prevents ovulation in some women (but not all)
How does oestrogen prevent pregnancy?
Oestrogen inhibits FSH, preventing ovulation
Outline how progesterone can be administered as a contraceptive
Mini-pill taken daily
Injection
Outline how progesterone and oestrogen can be administered as a contraceptive
- combined pill( taken continuously for 21 days then paused for 7 days)
- Skin patch ( worn continuously for 3 weeks then without for 1 week)
What are the benefits of hormonal contraceptive methods
● 99% effective when used properly
● Generally longer lasting than non-hormonal methods
● Used to treat other conditions e.g. painful/heavy periods
What are the risks of hormonal contraceptive methods 
● Side effects e.g. mood changes, acne, bloating
● Do not protect against STIs
● May involve uncomfortable medical procedures
● Not effective if used incorrectly
Describe the barrier methods of contraception
Prevent the sperm and egg meeting
e.g. condoms, diaphragms (fit over cervix)
What are the benefits of barrier methods of contraception
Condoms are simple and quick to use
Condoms prevent the spread of STIs
No side effects