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Biology GCSE > B3.2 - The Endocrine System > Flashcards

B3.2 - The Endocrine System Flashcards

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1
Q

What are hormones? Where are they made, and how are they transported?

A
  • 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.
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2
Q

What is homeostasis?

A

Maintenance of a constant internal environment.

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3
Q

Examples of major endocrine glands and hormones they produce?

A
  • 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
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4
Q

What are target cells?

A
  • 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.
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5
Q

What is thyroxine and its function?

A

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.

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6
Q

What is negative feedback?

A

A system that detects a change in a condition, the system acts to return the conditions to a desired level.

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7
Q

Explain how thyroxine levels are controlled.

A

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.

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8
Q

What is adrenaline?

A

A hormone that is secreted in times of stress (via the adrenal glands).
Prepares the body for intensive action.

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9
Q

How does the body respond when you are threatened or scared?

A
  • 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.
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10
Q

What are the 4 hormones that control the menstrual cycle and their roles?

A

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)

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11
Q

Stage 1 of the menstrual cycle

A
  • Day 1-4 - uterus lining breaks down and is released (menstruation).
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12
Q

Stage 2 of the menstrual cycle

A
  • Day 4-14, lining of the uterus builds up (oestrogen) again ready to receive a fertilised egg. (egg is maturing (FSH))
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13
Q

Stage 3 of the menstrual cycle

A
  • Egg is released after maturing from an ovary at about Day 14 (LH)
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14
Q

Stage 4 of the menstrual cycle

A
  • 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)
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15
Q

Two classifications of contraception.

A

Hormonal - use hormones to disrupt females reproductive cycle.
Non-hormonal - physical barriers protecting the sperm from reaching the egg or spermicides to kill sperm.

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16
Q

Give an example of a way that hormones can be used to treat infertility.

A

In vitro fertilisation. (IVF).

17
Q

Causes of infertility.

A
  • Blocked sperm ducts
  • Blocked fallopian tubes
  • Lack of mature eggs produced in the ovaries
  • Failure of egg release by the ovaries
18
Q

How can some infertility be treated using hormones?

A

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.
19
Q

How doe IVF work?

A
  • 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.
20
Q

Ethical issues around IVF.

A
  • 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.
21
Q

What is tropism and its two types?

A

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.
22
Q

What is the plant hormone that enables plant growth?

A

Auxin

  • Made near tips of plant shoots or roots.
  • Stimulate shoot cell growth but inhibits root cell growth.
23
Q

How do shoots respond to light?

A

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.
24
Q

How do shoots respond to gravity?

A

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.
25
Q

How do roots respond to light?

A

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.
26
Q

How do roots respond to gravity?

A

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.
27
Q

How do auxins affect roots and shoots?

A

The side with the least auxins in ROOTS grow more.

The side with most auxins in the SHOOTS grow more.

28
Q

Give 3 examples of plant hormones and their functions.

A

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.

29
Q

Commercial uses of plant hormones.

A 
Killing weeds 
Root growth 
Delayed ripening
Ripening fruit 
Producing seedless fruit 
Controlling dormancy
30
Q

Explain how weeds are killed.

A

Killing weeds - selective herbicides, they kill broad leaved plants not narrow leaved (grass), the auxins make the weed grow too fast and kill it.

31
Q

Explain how to promote root growth.

A

Rooting powder has auxins, they are used to produce clones from cuttings of a plant, dip into rooting powder and plant.

32
Q

Explain how ripening is delayed.

A
  • Axuin sprayed on to delay ripening.

- Allows harvest to be collected at the same time and prevents fruit from dropping too early.

33
Q

Explain how fruit is ripened.

A
  • Ethene is sprayed onto fruit trees and plants so they ripen quicker, fruit can be ready early in the growing season.
34
Q

How are seedless fruits produced?

A
  • Use auxins, apply to unpollinated flowers and they won’t produce seeds.

Biology GCSE (6 decks)

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