B3.2 - The Endocrine System Flashcards
What are hormones? Where are they made, and how are they transported?
- They are chemical messengers
- Made in the endocrine glands and secreted into the plasma in the blood to be transported to the target organ to cause a response.
What is homeostasis?
Maintenance of a constant internal environment.
Examples of major endocrine glands and hormones they produce?
- Hypothalamus and pituitary gland: produce hormones that regulate the production of other hormones
- Thyroid gland: produce thyroxine
- Adrenal glands: produce adrenaline
- Pancreas: produce insulin
- Ovaries: oestrogen and progesterone
- Testes: testosterone
What are target cells?
- Hormones travel all over the body but only target organs respond.
- Hormones diffuse in the blood and bind to specific receptors for that hormone on the membrane or cytoplasm of cells, those are the target cells.
- This stimulates the target cells to respond.
What is thyroxine and its function?
Thyroxine is produced in the thyroid gland and regulates your body’s metabolic rate - speed that your body transfers energy from its chemical stores in order to perform functions.
What is negative feedback?
A system that detects a change in a condition, the system acts to return the conditions to a desired level.
Explain how thyroxine levels are controlled.
Hypothalamus detects cell needs more energy > pituitary releases TSH > thyroid secretes thyroxine > hypothalamus detects cells have enough energy > inhibits TSH via the pituitary > thyroid stops producing thyroxine.
What is adrenaline?
A hormone that is secreted in times of stress (via the adrenal glands).
Prepares the body for intensive action.
How does the body respond when you are threatened or scared?
- Heart rate and blood pressure increases as adrenaline binds to receptors in the heart stimulating this action of contracting more forcefully.
- Results in quicker respiration, producing more ATP.
- Binds to liver to help breakdown glucose in glycogen stores.
What are the 4 hormones that control the menstrual cycle and their roles?
All made in the ovaries
LH - Luteinising hormone - stimulates the release of an egg (ovulation)
FSH - follicle stimulating hormone - stimulates the maturing of an egg. (Stimulates ovaries to produce oestrogen)
Oestrogen - builds up the lining of the uterus wall. (Stimulates LH and inhibits FSH so only one egg is released per cycle)
Progesterone - maintains the lining of the uterus wall in case of receiving a fertilised egg. (Levels are high during pregnancy)
Stage 1 of the menstrual cycle
- Day 1-4 - uterus lining breaks down and is released (menstruation).
Stage 2 of the menstrual cycle
- Day 4-14, lining of the uterus builds up (oestrogen) again ready to receive a fertilised egg. (egg is maturing (FSH))
Stage 3 of the menstrual cycle
- Egg is released after maturing from an ovary at about Day 14 (LH)
Stage 4 of the menstrual cycle
- Day 14-28 the uterus lining is maintained in case a fertilised egg arrives, if one doesn’t, the lining will breakdown and the cycle starts again. (Progesterone)
Two classifications of contraception.
Hormonal - use hormones to disrupt females reproductive cycle.
Non-hormonal - physical barriers protecting the sperm from reaching the egg or spermicides to kill sperm.
Give an example of a way that hormones can be used to treat infertility.
In vitro fertilisation. (IVF).
Causes of infertility.
- Blocked sperm ducts
- Blocked fallopian tubes
- Lack of mature eggs produced in the ovaries
- Failure of egg release by the ovaries
How can some infertility be treated using hormones?
FSH can be used.
- Stimulates maturing of the egg and triggers oestrogen production.
- Increases chance of getting pregnant and increases likelihood of one or more eggs being released.
How doe IVF work?
- Fertility drugs make lots of eggs mature at the same time
- Eggs placed in a special solution in a Petri dish.
- Sample of semen placed in the Petri dish and the eggs are checked to see if they have been fertilised.
- When there are fertilised eggs, they are placed into the womb of the mother.
Ethical issues around IVF.
- Not natural
- Allows parents who can’t conceive naturally to conceive.
- Enables older parents to have kids
- IVF treatment results in multiple births, dangerous for mother and unborn kids
- Allows younger women to focus on career and have kids later
- Very expensive.
What is tropism and its two types?
Plants responding to stimuli and growing in a certain direction.
- Phototropism - growing towards light allowing plant to photosynthesise more.
- Gravitropism - growing in the same direction as gravity. Important for roots into soil to provide anchorage and access minerals and water.
What is the plant hormone that enables plant growth?
Auxin
- Made near tips of plant shoots or roots.
- Stimulate shoot cell growth but inhibits root cell growth.
How do shoots respond to light?
SHOOTS ARE POSITIVELY PHOTOTROPIC
- Light hits one side of the shoot tip
- The auxins concentrate themselves on the shaded side of the shoot and respond by elongating
- This causes the shoot to bend towards the light.
- Once the light falls the auxin evenly distributes itslef around the tip and all the auxins grow at the same rate, straight.
How do shoots respond to gravity?
SHOOTS ARE NEGATIVELY GRAVITROPIC
- The auxins distribute on the lower side of the shoot (if it’s horizontal)
- The cells elongate bending the shoot away from gravity and upwards.
How do roots respond to light?
ROOTS ARE NEGATIVELY PHOTOTROPIC
- Roots are sideways, if they are exposed to light the auxins will (as usual) go to the shaded (in this case lower) side of the root.
- Auxins inhibit cell elongation on the shaded side and they bend downwards.
How do roots respond to gravity?
ROOTS ARE POSITIVELY GRAVITROPIC
- Auxins end up on the lower side (“attracted to gravity”)
- Auxins inhibit growth so the cells on top elongate and the root bends towards the ground.
How do auxins affect roots and shoots?
The side with the least auxins in ROOTS grow more.
The side with most auxins in the SHOOTS grow more.
Give 3 examples of plant hormones and their functions.
Auxins - stimulate growth by cell elongation. Inhibit the shedding of leaves.
Ethene - Causes plant fruit to ripen by stimulating the conversion of starch into sugar. Only plant hormone that exists as a gas.
Gibberellins - promote growth via stem elongation. They can end the dormancy periods of seeds and buds forcing them to produce shoots and flowers.
Commercial uses of plant hormones.
Killing weeds Root growth Delayed ripening Ripening fruit Producing seedless fruit Controlling dormancy
Explain how weeds are killed.
Killing weeds - selective herbicides, they kill broad leaved plants not narrow leaved (grass), the auxins make the weed grow too fast and kill it.
Explain how to promote root growth.
Rooting powder has auxins, they are used to produce clones from cuttings of a plant, dip into rooting powder and plant.
Explain how ripening is delayed.
- Axuin sprayed on to delay ripening.
- Allows harvest to be collected at the same time and prevents fruit from dropping too early.
Explain how fruit is ripened.
- Ethene is sprayed onto fruit trees and plants so they ripen quicker, fruit can be ready early in the growing season.
How are seedless fruits produced?
- Use auxins, apply to unpollinated flowers and they won’t produce seeds.
