B5: Homeostasis Flashcards
(29 cards)
What do enzymes and cells need to function?
Stable and specific conditions
What is homeostasis?
The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
What are the features of an automatic control system? (3)
- Receptor cells
- Co-ordination centre
- effector
Receptor cells detect conditions in the environment, which is a stimulus. They pass info to a coordination centre eg. brain which processes it and sends instructions to the effector (muscle or gland) which carried out a response to restore the optimum level.
What are the two parts of the nervous system?
- CNS (brain, spinal chord)
- other nerves (running to and from the CNS)
Describe the stages of a reflex arch
- Stimulus (eg. heat) is detected by receptors (eg. skin)
- Electrical impulses pass from the receptor along the sensory neurone to the CNS)
- Synapse releases chemical with diffuses to relay neurone in central nervous system
- electrical impulse travels along the relay neurone to synapse
- Electrical impulse along motor neurone to effector (eg. muscle) which triggers response.
- No decision by the conscious part of the brain, so they are automatic and rapid)
What is the endocrine system?
Glands which release hormones to control the internal conditions of out body. Often slower than nervous system.
Where are the different endocrine glands in the body?
- Pancreas - mid belly, in between adrenal glands
- Ovaries - hips
- Testies - groin
- Thryoid Gland - throat
- Adrenal glands - mid belly, either side of pancreas
-Pituitary gland - in the brain
What is the role of the pituitary gland in the endocrine system?
Act on other glands, causing other hormones to be released. The master glands. Can trigger a range of different effects.
How is insulin used to control the blood glucose concentration?
Pancreas produces insulin. It travels in the blood, triggering body cells to take up glucose in the blood. Triggers liver and muscles to store excess glucose as glycogen. This causes the concentration to return to normal.
What is type 1 diabetes?
The pancreas does not produce enough insulin.
What is type 2 diabetes?
Body cells stop responding to insulin.
How do we treat type 1 diabetes?
Inject with insulin after a meal etc.
How do we treat type 2 diabetes?
A diet containing a controlled level of carbohydrates to stop the blood glucose concentration rising too high. Exercise.
What is the role of glucagon?
If the blood glucose concentration is too low, the pancreas releases glucagon into the blood stream. It triggers liver cells to convert glycogen stores back into glucose, which is released into the blood.
What is the role of the hormones in the menstrual cycle? (4)
- FSH causes an egg to mature in the ovary
- LH causes this egg to be released, ovulation
- Oestrogen and progesterone are involved in maintaining uterus lining.
Describe the menstrual cycle fully, including how the hormones interact
- FSH: released by the pituitary gland, travels to the ovaries and it causes an egg to mature. It triggers the ovaries to make…
- Oestrogen causes the lining of the uterus to thicken. Also stops FSH.
- LH: released by pituitary gland. Triggers ovulation. After, ovary produces…
- Progesterone: stops FSH and LH and keeps lining thick. If no fertilisation, levels of progesterone fall rapidly and this triggers a period.
Why can issues around contraception not be answered by science alone?
It’s also a ethical and religious argument.
Evaluate the oral contraceptives eg. The pill (hormonal)
- hormones to prevent FSH being released (so no eggs mature)
+ highly effective if taken correctly - must be taken every day
- side effects eg. Small increased risk of breast cancer
- Don’t protect against STI
Evaluate the use of an implant, skin patch or injection. (Hormonal)
- Contains progesterone which stops eggs from maturing
+ more convenient than a pill (eg. patch lasts a week) - Have side effects
- Don’t protect against STI
Evaluate barrier methods of contraception (condom, diaphragm)
- stop sperm reaching egg
+ effective if used correctly, especially if used with spermicide. (Which kill sperm)
+ no side effects as don’t use hormones - can break or slip off
+ protect against STI
Evaluate intrauterine device, IUD, coil
- prevent embryo implanting
- some also use hormones to reduce chances of fertilisation
+ highly effective, can prevent for up to ten years
+ have few side effects - no protection from STI
Evaluate surgical methods of contraception (sterilisation)
+ highly effective
- difficult to reverse
- no protection from STI
Evaluate natural contraception
- don’t have sex after ovulation
- difficult to tell when woman as ovulated
- no protection from STIs
How are hormones used to treat infertility? (fertility drug)
- Fertility drug: LH and FSH are injected into the woman. Causes her to ovulate more.
