Higher: B5 - Homeostasis Flashcards
What is kept the same in the human body?
- Water levels.
- Temperature.
- Glucose levels.
- Salt levels.
What is a stimulus?
A change in external environment.
What is a reflex?
An automatic and instantaneous nervous response which does not require conscious thought and helps prevent injury.
What is the name given to the part of the nervous system which contains only nerves?
The peripheral nervous system.
What is the hormone system called and what does it do?
The endocrine system - sends hormones around the body through the blood.
What are hormones produced by?
Endocrine glands.
What are hormones? (3 points)
Chemical messengers which control things that need constant adjustment in organs and cells. They have long lasting effects and act in a general way.
Why is homeostasis important for the body?
Cells need the right conditions to function properly, e.g. enzyme action.
What is negative feedback?
Receptors detect stimuli, like levels of a hormone being to high. The coordination centre organises a response and the effector produces a response which counteracts the change. The optimum level is restored.
Where is the pituitary gland?
At the base of the brain.
Where is the thyroid?
Along the front of the windpipe.
Where are the ovaries?
In the lower abdomen.
Where are the adrenal glands?
One above each kidney.
Where are the testes?
In the scrotum.
Where is the pancreas?
Behind the stomach.
What is the role of the pituitary gland?
Produces many hormones which regulate body conditions. Some of these hormones act on other glands, which produce other hormones.
What is the role of the thyroid?
Produces thyroxine, which regulates things like rate of metabolism, heart rate and temperature.
The pituitary gland produces TSH (thyroid-stimulating hormone), which regulates production of these hormones.
What is the role of the adrenal glands?
Produce adrenaline in stressful/scary situations, to prepare for a fight or flight response.
What is the role of the pancreas?
Monitors and control blood glucose levels: produces insulin and glucagon. Also produces enzymes.
How does a nervous response compare to an endocrine one?
Nervous: faster, short-lasting action on a precise area. Endocrine: slower, longer lasting response on a general area.
What are the food groups?
Carbohydrates, lipids and proteins.
What are lipids made of?
Glycerol and fatty acids.
What are the types of carbohydrates and what are they all made of?
All made of strings of glucose molecules:
In plants: fibre, starch, cellulose.
Animals: glycogen.
What are amino acids made of?
Glucose and nitrate.
What happens when blood glucose levels are too high?
Insulin is secreted by the pancreas and is carried by the blood to the liver. Here, the insulin triggers the liver to turn excess glucose into glycogen, which is stored in the liver and muscle cells.
What happens when blood glucose levels are too low?
Glucagon is secreted by the pancreas and is carried by the blood to the liver. Glucagon triggers the liver to convert stored glycogen into glucose, which is released back into the blood.
What is type 1 diabetes?
The pancreas produces little or no insulin, so glucose can rise to dangerous levels.
How is type 1 diabetes controlled and treated?
1) Regulation of simple carbohydrate consumption and regular exercise. 2) Insulin therapy used, involving several insulin injections per day, usually at mealtimes, to stop sugar levels getting too high. The amount of insulin needed depends on diet and activity.
What is type 2 diabetes?
Although insulin is produced, body cells don’t respond properly to, and become resistant to, the body’s own insulin. Causes blood glucose levels to rise dangerously.
How can type 2 diabetes be controlled?
Regulation of simple carbohydrate consumption and regular exercise.
If not enough, then tablets and sometimes even insulin.
What is the role of thyroxine?
Regulates basal metabolic rate, heart rate and temperature. Also stimulates protein synthesis for growth and development.
What happens at puberty?
The body starts releasing sex hormones which trigger secondary sexual characteristics and cause eggs to mature in women.
What are the primary sex hormones for males and females?
Males: testosterone.
Females: oestrogen and progesterone.
(Oestrogen and testosterone are produced by both sexes).
Give 2 examples of secondary sexual characteristics.
Development of facial hair in men and breasts in women.
What is the function of testosterone?
Controls puberty and sperm production in males.
What four hormones control the menstrual cycle?
FSH, LH, oestrogen and progesterone.
How many days long is the menstrual cycle (usually)?
28.
What happens in stage 1, day 1-4, of the menstrual cycle?
Menstruation: uterus lining breaks down.
What happens in stage 2, day 4-14, of the menstrual cycle?
Uterus lining builds up into a thick layer ready to receive a fertilised egg.
What happens in stage 3, day 14, of the menstrual cycle?
Ovulation: an egg is released from the ovary.
What happens in stage 4, day 14-28, of the menstrual cycle?
The uterus lining is maintained. If no fertilised egg lands on the uterus wall by day 28, the lining breaks down and the cycle repeats.
What do FSH and LH stand for?
- Follicule-stimulating hormone.
- Luteinising hormone.
Where is FSH produced?
In the pituitary gland.
What is the function of FSH?
- Causes the maturation of an egg in an ovary, in a structure called a follicle.
- Stimulates the ovaries to produce oestrogen.
Where is oestrogen produced?
In the ovaries.
What is the function of oestrogen?
- Involved in the repairing and thickening of the uterus lining.
- Stimulates release of LH.
- Inhibits release of FSH.
Where is LH produced?
In the pituitary gland.
What is the function of LH?
Stimulates ovulation (the release of an egg) at day 14.
Where and how is progesterone produced?
In the ovaries, after ovulation, by the remains of the follicle.
What is the function of progesterone?
- Maintains the lining of the uterus (during 2nd half of cycle).
- When progesterone levels fall, lining breaks down.
- Inhibits release of both LH and FSH.
Why is oestrogen used in hormonal contraception?
It inhibits production of FSH, so egg development and production is stopped.
How is progesterone useful in hormonal contraception?
- Stimulates the production of thick mucus, which prevents sperm reaching an egg.
- Inhibits release of FSH and LH (so eggs are not matured and released).
- Stops a fertilised egg being implanted in the uterus
List six hormonal methods of contraception.
- Combined oral pill
- Progesterone pill
- Patch
- Implant
- Injection
- The IUD (intrauterine device, or the coil)
What does the combined oral contraceptive pill contain?
Oestrogen and progesterone.
Describe the contraceptive patch.
- Small patch stuck to the skin.
- Contains oestrogen and progesterone.
- Lasts one week.
How does the contraceptive implant work?
- Inserted under the skin of the arm.
- Lasts up to 3 years.
- Releases a continuous amount of progesterone.
What does the contraceptive injection contain? How long does one dose last?
- Progesterone.
- 2-3 months
What is the intrauterine device? There are 2 main types; describe how each works.
T-shaped device which is inserted into the uterus.
2 main types:
- plastic IUDs release progesterone, preventing implantation of a fertilised egg.
- copper IUDs prevent sperm surviving in the uterus.
What are the two categories of non-hormonal contraceptives?
- Barriers
- More drastic methods
List 3 barrier methods of contraception.
- Condoms/femidoms
- Diaphragms
- Spermicides
__ are the only form of contraception that protect against STIs.
Condoms.
How do diaphragms work?
- Shallow plastic cups that fit over the cervix (entrance to the uterus) to form a barrier.
- Have to be used with spermicides.
How do spermicides work? How effective are they?
- Substances which disable/kill sperm.
- Only 70-80% effective.
List 3 more drastic non-hormonal methods of contraception.
- Sterilisation
- Natural method
- Abstinence
What does sterilisation involve?
The falllopian tubes (which connect the ovaries to the uterus) or the sperm duct (the tube between the testes and penis) are cut or tied.
This is permanent procedure, but there is a very small chance that the tubes can rejoin.
What is the natural method of contraception?
Pregnancy may be avoided by avoiding sexual intercourse on the days a woman is most fertile in the menstrual cycle. The method is not very effective.
Why can’t some women get pregnant?
They have FSH levels too low to cause their eggs to mature. No eggs are released - they cannot be fertilised.
Name two options that help a woman get pregnant if she has fertility problems.
- LH and FSH can be taken in a fertility drug to stimulate ovulation.
- If that doesn’t work, IVF.
What are the cons of the fertility drug containing LH and FSH?
- Doesn’t always work - repeating it gets expensive.
- Too many eggs can be fertilised, resulting in unexpected multiple pregnancies.
Describe the process of IVF treatment.
- A woman takes FSH and LH, so that several eggs mature in her ovaries.
- The eggs are collected and fertilised with a man’s sperm.
- Alternatively, if the man has a low sperm count, ICSI (intracytoplasmic sperm injection) is used: the sperm is directly injected into the egg.
- The fertilised eggs are grown into embryos in a laboratory incubator.
- Once the embryos become tiny balls of cells, 1 or 2 are transferred to the woman’s uterus, to hopefully impregnate her.
Give 3 cons of IVF treatment.
1) Multiple births are possible, which risk miscarriages or stillbirths.
2) Success rate is low.
3) Some women react strongly to the hormones, e.g. abdominal pain, vomiting or dehydration.
How have advances in technology improved the techniques of IVF treatment?
1) There have been advances in microscope techniques and micro tools, used for genetic testing (checking an embryo is healthy).
2) Time lapse imaging has been invented. The growth of embryos is monitored to determine those that are more likely to result in a successful pregnancy.
Why are some people against IVF treatment?
1) It often results in unused embryos being destroyed - this is considered unethical because they are potential human lives.
2) The genetic testing of embryos before implantation raises ethical issues, as it risks leading to the selection of preferred characteristics.
