Homeostasis and Response Flashcards
what is homeostasis all about?
keeping internal conditions as constant as possible
what does homeostasis consist of?
automatic control systems
what are the three features of an automatic control system?
- receptors
- co-ordination centres
- effectors
what do receptors do?
- detect a change in the environment
- the ‘environment’ could either be the body’s internal conditions or the external conditions
what do co-ordination centres do?
- receive and process the information from the receptors
what do effectors do? (2)
- carries out the response to the change in environment
- restores optimum levels
what is the key role of the nervous system?
enables humans to react to their surroundings and co-ordinate their behaviour
what happens when you touch a hot object? (7)
- the stimulus is detected by a receptor
- electrical impulses pass from the receptor along the sensory neurone to the CNS
- at the end of the sensory neurone, there’s a synapse
- at the synapse, a chemical is release which diffuses across to a relay neurone in the CNS where it triggers an electrical impulse
- the electrical impulse passes across the relay neurone
- again, a chemical is released, triggering an electrical impulse in a motor neurone
- the electrical impulse now passes down the motor neurone to the effector, which responds to the change
what does the endocrine system do?
controls the body by chemicals called hormones
what does the endocrine system consist of?
a number of glands that secrete hormones directly into the bloodstream
what are the five specific target organs that the hormones act on?
- Pituitary Gland
- Thyroid Gland
- Pancreas
- Adrenal Glands
- Ovaries and Testes
Pituitary Gland (3)
- located in the brain
- also known as the ‘MASTER GLAND’
- releases a number of different hormones into the blood depending on the conditions
- pituitary hormones act on other glands and they cause other hormones to be released
- because of this, the pituitary glands can have a range of different effects on the body
Thyroid Gland (1)
- releases hormones to do with growth and how rapidly the body’s reactions take place
Pancreas (1)
- releases hormones (insulin) to help control the concentration of glucose in the blood
Adrenal Glands (1)
- release the hormone adrenaline which is produced during times of fear or stress
Ovaries and Testes (1)
- release hormones involved with puberty and reproduction
what does insulin do when there is a high concentration of glucose in the blood? (3)
- travels around the body through the blood stream
- triggers the body cells to take up glucose from the blood
- also triggers the liver and muscle cells to store excess glucose as a storage molecule called glycogen
define diabetes
where a person’s blood glucose control does not work effectively
Type 1 Diabetes (2)
- the pancreas does not produce enough insulin and therefore the body can not return its optimum
- people with type 1 diabetes inject themselves with insulin if their blood glucose levels raise too much
Type 2 Diabetes (2)
- the body cells stop responding to the insulin that the pancreas is producing
- people with type 2 diabetes often have a diet containing a controlled level of carbohydrates
what happens when the glucose concentration is too low? (3)
- the pancreas releases glucagon into the bloodstream
- glucagon triggers the liver and muscle cells to convert their glycogen stores back into glucose
- this glucose is released into the blood, restoring the normal level of blood glucose concentration
which hormone do the testes produce?
testosterone
what is the role of testosterone?
stimulates the testes to produce sperm
which hormone do the ovaries produce?
oestrogen
state the role of the follicle stimulating hormone (FSH)
causes an egg to mature in an ovary
state the role of the luteinising hormone (LH)
causes an egg to be released from an ovary
or
causes ovulation
state the role of oestrogen and progesterone
maintain the uterus lining in case the egg for that month has been fertilised and needs to implant
what are the four types of contraception?
- Oral Contraceptives
- Hormonal Contraceptives
- Barrier Method
- Sterilisation
an example of an oral contraceptive…
the pill
what does the pill do?
- contains hormones that stop FSH from being produced, which prevents an egg from being matured in an ovary
advantages (1) and disadvantages (1) of the pill?
ADVANTAGES
- highly effective if taken correctly
DISADVANTAGES
- must be taken every day; if the woman forgets to take it then there’s a risk of pregnancy
examples of hormonal contraception… (3)
- implant
- injection
- patch
what do the hormonal forms of contraception all do?
- all contain progesterone, which prevents FSH and LH from being released and in turn prevents an egg from both being matured and being released
advantages (1) and disadvantages (1) of hormonal contraception?
ADVANTAGES
- more convenient than taking a daily pill; implant lasts three years; the injection lasts thirteen weeks; the patch lasts around a week
DISADVANTAGES
- none of these protect against sexually transmitted diseases
examples of the barrier method include… (2)
- condom
- diaphragm
what do all the forms of the barrier method do?
prevent the sperm from reaching the egg
advantages (2) and disadvantages (1) of the barrier methods
ADVANTAGES
- don’t use hormones so they don’t have side effects
- can reduce the risk of STIs
DISADVANTAGES
- [condoms] can break or slip off
what does the coil do?
prevent an embryo from implanting
advantages (1) and disadvantages (1) of the coil?
ADVANTAGES
- highly effective and can prevent pregnancy for up to 10 years
DISADVANTAGES
- does not protect against STIs
what is sterilisation in females?
prevents the egg from reaching the uterus
what is sterilisation in males?
prevents the sperm from leaving the penis
advantages (1) and disadvantages (2) of sterilisation?
ADVANTAGES
- very effective in both genders
DISADVANTAGES
- very difficult for them to be reversed
- do not protect against STIs
two treatments for infertility
- women are given both FSH and LH (“a fertility drug”) which causes a woman to ovulate more than usual
- in-vitro fertilisation (IVF) where the fertilisation takes place outside of the body
what are the three possible problems with IVF
- success rates are not high
- emotionally very stressful for both parents
- can lead to multiple births
