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Biology > B3.2 Hormones > Flashcards

B3.2 Hormones Flashcards

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1
Q

What are hormones?

A

Hormones are chemical messengers that is transported in the bloodstream.

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2
Q

What is the difference between endocrine and nervous system?

A

Endocrine system uses a chemical hormone signal. It’s hormones are transmitters. It has a slow response and has a long duration of response. It is targeted at a larger area.

Nervous system uses a electrical hormone signal. It’s nerve cells are transmitters. It has a fast response and has a short duration of response. It is targeted at a very precise area.

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3
Q

What is thyroxine ?

A

Thyroxine is a hormone that is produced in the thyroid gland
It controls the metabolic rate of the body
It works by negative feedback

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4
Q

How are thyroxine levels controlled?

A
  • If levels of thyroxine are low it stimulates hypothalamus and pituitary gland to release TSH, which then stimulates tyroid to produce more thyroxine.
  • when the thyroxine levels return to normal, TSH is inhibited
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5
Q

What is adrenaline?

A

In times of stress, the hormone adrenaline is produced.

It is the fight or flight response

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6
Q

How are adrenaline levels controlled?

A 
When you feel frightened or scared, the brain signals the adrenal gland to secrete adrenaline.
The body:
– increases heart rate
– increases breathing rate
– respire is more quickly
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7
Q

What is testosterone?

A

Testosterone is produced by the testes

It causes production of sperms

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8
Q

What is ovulation?

A

Ovulation is the release of a mature egg from the ovary around 14 days.

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9
Q

What is FSH?

A

Follicle stimulating hormone
Causes the egg to mature in the ovary
Stimulates the ovaries to produce oestrogen

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10
Q

What is oestrogen?

A

Causes thickening of the uterus in preparation for the egg to be implanted

Inhibits production of FSH
Stimulates the pituitary gland to release luteinising hormone.

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11
Q

What is luteinising hormone?

A

Causes release of egg from ovaries around the middle of the cycle.

When levels of oestrogen decrease it stimulates in order to increase FSH and LH. This is usually ovulation.

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12
Q

What is progesterone?

A

Maintains a thick uterus lining
Levels of hormones remain high throughout pregnancy
Progesterone stops the release of FSH and LH.

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13
Q

What is a non-hormonal contraception?

A

Physical barrier that prevents a sperm contacting the egg.

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14
Q

What is a hormonal contraception?

A

Use hormones to disrupt the normal female reproductive cycle

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15
Q

What does a condom do?

A

It is placed over the p***s or inside the vagina.
It prevents sperm from entering the vagina.
It can also prevent the spread of sexually transmitted infections.

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16
Q

What is a cervical cap?

Non-hormonal

A

It is inserted into the vagina to cover the cervix
Prevents sperm cells from entering the uterus
Removed after six hours following sex
- not effective unless used in combination with spermicide.

17
Q

What is auxin?

A

Auxin is a plant hormone that enables a plant to grow towards, or a way from a stimulus.
It causes cell elongation and controls gravitropism and phototropism

18
Q

What is positive phototropism?

A

Plant will grow towards the light .

  1. Plant is exposed to light on one side
  2. Auxin moves to the shaded side of the shoot
  3. Auxin stimulates cell to grow on the shaded side
  4. Shoot bends towards light source
19
Q

Why might the shoot grow straight?

A

Phototropism and gravitropism is caused by an uneven distribution of auxin.
If auxin distribution is equal than the shoot or roots will grow straight and not bend.

20
Q

What is positive gravitropism?

A

More auxin and less cell growth.

  1. Auxin moves to the lower side
  2. Stimulates cells to grow on the upper side.
  3. Causing the root to bend down towards gravity.

Advantages - growing towards soil meaning more nutrients and water to absorb.
- provides stability

21
Q

What are the uses of auxin?

A

Weed killers - high amount of auxin causes cells to grow too quickly which causes weed death.
✅- killing weeds allows desirable plant to grow better.

Rooting powders – plants are cloned from cuttings, cutting is dipped into rooting powder and planted, this causes roots to grow allowing take up of minerals and water.

Tissue culture – auxin is added to a plant tissue and roots and shoots start to grow.

22
Q

What is Gibberellins?

A

It is a plant hormone that promotes growth

It stimulates seed germination and flowering.

23
Q

What are the uses of gibberellins?

A

– Ends seed dormancy

  • promoting flowering – allowed plant to flower and increase in size.
  • increase fruit size
24
Q

What is Ethene?

A

Ethan causes plants to ripen, control cell division, stimulates enzymes that result in fruit ripening.

25
Q

What is the use of Ethene?

A

– Ripening fruit – Ethene is sprayed on fruit trees and plants so that their fruit ripening quicker. This allows fruit to be ready earlier in the growing season.

26
Q

Explain how intrauterine devices prevent pregnancy?

A
  • prevent the sperm from surviving

- they alter the lining of the womb , so that fertilised eggs can’t implant

27
Q

Explain why a low level of FSH may be preventing the women from being pregnant?

A

Having low FSH levels can mean that eggs don’t mature

So ovulation doesn’t take place

28
Q

Explain why taking the mini pill may prevent ovulation?

A

Progesterone in the pill inhibits the production of FSH and LH
Which stimulate egg maturation and ovulation

29
Q

Explain how auxin causes shoots to be negatively gravitropic

A

Auxin promotes growth
When a shoot is growing sideways , more auxin will be present on the lower side of the growing tip
Causes the lower side to grow faster , bending the shoot upwards

30
Q

Describe how Ethene stimulates leaf loss

A

Ethene stimulates cells that connect the leaf to the rest of the plant to expand
This breaks cells walls
Causing the leaves to fall off

Biology (17 decks)

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