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Biology > B11 Hormonal Coordination > Flashcards

B11 Hormonal Coordination Flashcards

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1
Q

What is the name of the body’s coordination system which involves hormones?

A

The endocrine system

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2
Q

What is a hormone?

A

A hormone is a chemical messenger secreted by a gland. It travels in the blood to a target organ, where it causes a response

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3
Q

What type of organs secrete hormones?

A

Glands

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4
Q

Which gland controls many other glands in the body?

A

The pituitary gland

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5
Q

What are the important structures in the endocrine system?

A

Important structures in the endocrine system are:
- Pituitary gland: a ʻmaster glandʼ making hormones such as FSH and LH
- Pancreas: produces insulin which regulates the blood glucose level
- Thyroid: produces thyroxine which controls metabolic rate and affects growth
- Adrenal glands: produces adrenaline
- Ovaries (females): produce oestrogen
- Testes (males): produce testosterone
pg 161

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6
Q

Why is the pituitary gland considered a “master gland”?

A

The pituitary gland in the brain is a ʻmaster glandʼ because it secretes several hormones into the blood.
These hormones in turn act on other glands to stimulate other hormones to be released to bring about effects
For example, in certain conditions, the pituitary gland makes and secretes thyroid-stimulating hormone (TSH) which stimulates the thyroid to release thyroxine

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7
Q

What is the role of the pituitary gland in the endocrine system?

A
  • It secrets human growth hormone - controls human growth
  • Releases the hormone TSH that stimulates the thyroid gland to make thyroxine, a hormone that helps control the rate of your metabolism
  • Releases the hormone FSH (follicle stimulating hormone), which stimulates ovulation and the production of oestrogen in the ovaries
  • Stimulates the production of sperm and testosterone in the tests
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8
Q

What is the role of the thyroid gland in the endocrine system?

A

Secretes the hormone thyroxine - controls metabolism, heart rate and body temperature

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9
Q

What is the role of the pancreas in the endocrine system?

A

Secretes the hormone insulin - controls blood glucose levels

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10
Q

What is the role of the adrenal gland in the endocrine system?

A

Secretes adrenaline - controls the body’s fight or flight response

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11
Q

What is the role of the ovaries in the endocrine system?

A

Secrete oestrogen, which coordinates the menstrual cycle and the development of female secondary sexual characteristics

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12
Q

What is the role of the tests in the endocrine system?

A

Secrete testosterone which coordinates the production of sperm and the development of male secondary sexual characteristics

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13
Q

What controls blood glucose concentration?

A

Pancreas

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14
Q

What is the pancreas?

A

The pancreas is an endocrine gland (making and secreting hormones into the bloodstream) and it also plays a vital (but separate) role in digestion (making and secreting enzymes into the digestive system)

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15
Q

Why is blood glucose concentration an example of homeostasis (like temperature control)

A

Blood glucose concentration must be kept within a narrow range, so itʼs another example of homeostasis (like temperature control)

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16
Q

How does the pancreas respond when blood glucose levels are too high?

A

If the blood glucose concentration is too high, the pancreas produces the hormone insulin to bring it back down. Insulin binds to receptors on the liver and muscles, causing excess glucose to be converted into glycogen and stored.

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17
Q

Why is too high a level of glucose in the blood dangerous?

A

Too high a level of glucose in the blood can lead to cells of the body losing water by osmosis, which can be dangerous.

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18
Q

How does the pancreas respond when blood glucose levels are too low?

A

The pancreas secretes an hormone called Glucagon. Glucacon makes your liver break down glycongen, converting it back to glucose.

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19
Q

How is blood glucose concentration controlled using a negative feedback loop?

A

Glucagon and insulin interact as part of a negative feedback cycle to control blood glucose (sugar) levels in the body:
- Insulin is produced when blood glucose rises and stimulates liver and muscle cells to convert excess glucose into glycogen to be stored – this reduces the
blood glucose level
- Glucagon is produced when blood glucose falls too low and stimulates liver and muscle cells to convert stored glycogen into glucose to be released into
the bloodstream – this increases the blood glucose level

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20
Q

What is Type 1 Diabetes?

A

Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin to control blood glucose levels.
Scientists think this is a result of a personʼs own immune system destroying the cells of the pancreas that make insulin during development.
As a result, blood glucose levels are very high leading to excessive urination, tiredness and weight loss.

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21
Q

How can type 1 diabetes be treated?

A
  • insulin injections before meals - allows glucose to be converted into glycogen
  • Limiting carbs intake
  • pancreas transplant; This operation is risky. Only a few hundred pancreas operations take place in the UK in a year. Not enough donors are available. Also one medicine (insulin) is swapped for another (immunosuppressant)
  • pancreatic cells transplant: these cells coming from both living and dead donors but has had limited success so far.
  • Investigating into genetic engineering of pancreatic cells: scientists hope to be able to engineer faulty pancreatic cells so that they do work properly. Then they will be able to return them to the body of the patients with no rejection issues. Possibly this will use stem cells from embryos but this is not ethically accepted by everyone. So far (2008) scientists discovered a new technique where they turned mouse pancreas cells into insulin producing cells
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22
Q

What is Type 2 diabetes?

A

In Type 2 diabetes the body cells no longer respond to insulin produced by the pancreas - the person still makes insulin but their cells are resistant to it and donʼt respond as well as they should.
This can also lead to uncontrolled high blood glucose levels.

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23
Q

What are common treatments for Type 2 Diabetes?

A

A carbohydrate-controlled diet
an exercise regime
weight loss
If this does not work, there are drugs that:
help insulin work better
help the pancreas make more insulin
Reduce the amount of glucose you absorb from your gut

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24
Q

What is a risk factor for Type 2 diabetes?

A

Obesity is a big risk factor for Type 2 diabetes; probably because a person who is obese may consume a diet high in carbohydrates, and over-production of insulin results in resistance to it developing

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25
Q

Compare type 1 and 2 Diabetes

A

Causes: Type 1 Inability of Pancreas to produce insulin; Type 2: Cells of the body become resistant to insulin or insufficient insulin produced by the pancreas
Treatment: Type 1 Monitoring of blood glucose levels and injecting human insulin throughout the day (particularly after meals). Type 2: Maintain a low carbs diet and regular exercise to reduce need for insuline

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26
Q

What is Glycogen?

A

Glycogen is the polysaccharide glucose is stored as

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27
Q

Who is affected the most from Type 2 Diabetes?

A

Old people but now more and more young people very overweight are affacted

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28
Q

Functioning and importance of negative feedback systems

A

They work to maintain a stable state in the body.
If a factor in the internal environment increases, changes take place to reduce it and restore it to its original level. The opposite happens when a factor in the internal environment decreases.

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29
Q

What is thyroxine?

A

It is an hormone produced by the thyroid gland in your neck. To produce it, the thyroid gland uses iodine from your diet. This hormone controls metabolism, growth and development

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30
Q

How is the release of thyroxine controlled by negative feedback?

A
  • Levels of blood thyroxine falls - detected by receptors in the brain
  • Pituitary gland releases more TSH (Thyroid stimulating hormone)
  • As a result more thyroxine is produced and released by the thyroid gland
  • blood thyroxine levels return to normal
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31
Q

What is adrenaline?

A

It is an hormone produced by the adrenal glands in times of fear or stress. It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for “fight or Flight”

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32
Q

Where are adrenal glands located?

A

The adrenal glands are located just above the kidneys (they also make cortisol)

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33
Q

What does adrenaline cause?

A
  • Adrenaline increases the heart rate and breathing rate
  • boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for ʻflight or fightʼ
    Increased glucose and oxygen are needed by the cells for respiration to release energy; the delivery of more enables more energy to be released (to fuel the muscles to move/run away for example!)
  • pupils dilate to let in more light
  • mental awareness increases
  • blood is diverted from digestive system to the big muscles in your limbs
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34
Q

Is adrenaline controlled by negative feedback?

A

No

35
Q

What is puberty?

A

It is the time when the reproductive organs become active and the body takes its adult form

36
Q

What is the function of reproductive hormones during puberty?

A

They control the development of secondary sexual characteristics?

37
Q

What is the male main reproductive hormone?

A

It is testosterone which is produced by the testes and controls sperm production

38
Q

What happens when levels of testosterone increase?

A

Main changes include a growth spurt, pubic hair, underarm hair and facial hair growth, the larynx gets bigger and the voice breaks. The externa genitalia and the skin darkens, the testes grow and become active producing sperm. The shoulders and chest broadens and the brain matures. Boys usually go into the first stages of puberty between 9 and 15 yrs of age.

39
Q

What is the main female reproductive hormone?

A

It is Oestrogen, which is produced by the ovaries and is involved in the menstrual cycle, as well as causing physical changes to occur in the body (such as breast development)

40
Q

What happens when levels of oestrogen increase?

A

They trigger the development of female secondary sex characteristics. It triggers growth spurt, pubic hair, underarm hair. The externa genitalia and the skin darkens, breasts develops. Female fat is deposited on tights, hips, buttocks, brain matures. Mature eggs start forming every month in the ovaries. The uterus grows, becomes active and menstruation begins. Between 8 and 14 yrs of age.

41
Q

What is the menstrual cycle?

A

It is the monthly cycle of physiological changes that occur in females, involving the shedding of the uterus lining (menstruation) and ovulation

42
Q

Describe the events in the menstrual cycle

A

During the menstrual cycle, the lining of the uterus (womb) thickens ready for pregnancy and eggs start maturing in the follicles of the ovaries.
About 14 days after the eggs start maturing, a mature egg is released from the ovaries. This is ovulation. If the egg is not fertilised, around 14 days later the lining of the uterus is shed together with the egg. This is the monthly period and also takes place at approx 28 days interval.
If the egg is fertilised by sperm, the pregnancy may take place.

43
Q

What are the hormones controlling the menstrual cycle?

A

Four hormones control the events that occur during the menstrual cycle:
- Two of these hormones are produced by the pituitary gland in the brain: Follicle-stimulating hormone (FSH) causes maturation of an egg in the ovary (the eggs grow surrounded by cells called follicle),
Luteinising hormone (LH) stimulates the release of the egg
- The other two hormones, oestrogen and progesterone are involved in maintaining the uterus lining with oestrogen being made by the ovaries and progesterone specifically by an empty egg follicle called the corpus luteum

44
Q

How do hormones work together to control the menstrual cycle?

A

The hormones produced by the pituitary gland and the ovary act together to control what happens in the menstrual cycle.
Oestrogen levels rise and by doing so they inhibit the production of FSH and encourage the production of LH by the pituitary gland. When LH levels reach a peak in the middle of the cycle, they stimulate the release of a mature egg.
FSH and LH are then suppressed and the body is kept ready for pregnancy until it becomes clear that the egg is not fertilised.
Then the hormones levels drop and the lining of the uterus pulls away and is lost from the body.
At this stage a new cycle begins and the levels of FSH and oestrogen start rising again.
See Biology book pg 171 for diagram

45
Q

What is ovulation?

A

It is the release of a mature egg from the ovaries. It occurs approx every 28 days

46
Q

What is the role of the FSH in the menstrual cycle?

A

FHS is secreted by the pituitary gland. It controls the maturation of eggs within the ovaries (inside a follicle) and triggers the production of oestrogen by the ovaries

47
Q

What is the role of oestrogen in the menstrual cycle?

A

Oestrogen is produced by the ovaries and released due to action of the FSH - it causes the regrowth of the uterus lining

48
Q

Luteinising hormone (LH) stimulates the release of the egg

A

Luteinising hormone (LH) is produced by the pituitary gland as a result of oestrogen. It stimulates the release of the egg

49
Q

Talk about female fertility

A
  • The ovaries of a baby girl contain all the eggs she will ever have.
  • After puberty the eggs mature and are released every month for an avg of 35/40 yrs except if she is pregnant
  • Eventually the eggs run out and the woman goes through menopause - she can no longer have children
  • If she gets pregnant there is a higher risk of having babies with genetic problems
50
Q

What is contraception?

A

It aim to prevent fertilisation and pregnancy, and include the use of hormones (oestrogen and progesterone) as well as non-hormonal methods (such as the use of barriers or surgery)

51
Q

What are the two types of oral contraceptives?

A

● Combined contraceptive pill (contains low doses of
oestrogen and progesterone).
● Mini pill (contains only progesterone).

52
Q

How does the contraceptive pill prevent
pregnancy?

A

● Inhibits FSH - eggs do not mature.
● Prevents the development of the uterus lining -
eggs cannot implant.
● Increases the thickness of cervical mucus -
immobilises sperm cells.

53
Q

Pros and Cons of the contraceptive pill

A

Pros:
Easy to use
Cons:
Side effects (raised blood pressure, thrombosis, breast cancer). Note: less side effects for progesterone only pill.
Needs to be taken regularly. Especially the progesterone only pill. If the do not, normal hormones take over quickly and there is pregnancy

54
Q

What is the contraceptive patch?

A
  • Contains both oestrogen and progesterone.
  • It is a patch that is placed onto the skin for 7 days at a time and then replaced. The hormones are absorbed directly in the blood stream
55
Q

What is the contraceptive implant?

A

A small rod inserted under the skin which continuously releases the hormone progesterone - lasts for 3 years.
This is 99.9% effective

56
Q

What is the contraceptive injection?

A

An injection containing the hormone progesterone - lasts for approximately 3 months.

57
Q

Exam tip on controlling fertility

A

Exam Tip
The use of hormones to control fertility is a pretty common exam question where you may be asked to evaluate the different methods of contraception
and to consider the benefits or problems associated with them. Benefits of contraception include preventing unwanted pregnancies or pregnancies that
may lead to risks to the mother’s health or pregnancies that have occurred as a result of rape. The counter-arguments involve ethical and religious
concerns about making decisions that may or may not lead to life. Issues around contraception cannot be answered by science alone – it’s important to remember that.

58
Q

What types of contraceptive methods exist?

A

Humans can use barrier, chemical, surgical and natural contraceptive methods to prevent a pregnancy

59
Q

What are Intrauterine devices (IUD)?

A

They are small devices inserted into the uterus by a doctor.
They last 3 to 5 yrs but can be removed at any time
A copper IUD works by releasing low levels of copper ions which disable sperm cells
A plastic IUD produces progesterone which stimulates the production of a thick mucus lining preventing sperm from reaching any eggs
PROS: very effective
CONS: they might cause infections or may cause period problems

60
Q

What are barrier contraceptive methods?

A

A barrier method of contraception involves a physical
separation between the sperm and the egg. They
include:
● Condoms - thin sheath worn on the penis - PROS They also protect from infections such as HIV and they do not have side effects CONS: may tear/break.
● Diaphragms - a thin cap placed over the cervix -
prevent entry of sperm. PROS they do not have side effects CONS: if cap is not positioned correctly, sperm might get past
These methods work best together with spermicides

61
Q

What is a spermicide?

A

A spermicide is a chemical that kills or immobilises sperm cells - however, they are not very effective, and work better when combined with barrier methods.

62
Q

What surgical methods of contraception are
available?

A

Sterilisation - in males, the sperm ducts are tied (vasectomy) and in females, the oviducts are tied.

63
Q

What is abstinence?

A

Abstinence is the practice of not having sex, which also avoids pregnancy. Some people abstain from sex around the time of ovulation - this is known as the rhythm method, but it is quite unreliable.

64
Q

How do fertility drugs increase the chance of
pregnancy?

A

Many fertility drugs contain FSH - which stimulates oestrogen production and the maturation of eggs in the ovary. They also contain LH which triggers ovulation.

65
Q

What is IVF and when is it used?

A

IVF (in vitro fertilisation) is type of fertility treatment
where eggs are fertilised by sperm outside of the body
(‘in vitro’ means ‘in glass’) – this is used particularly when there are issues with both male and female fertility (eg oviducts ae damaged or blocked by infection, if a donor egg has to be used or if there is no obvious cause for long term infertility.
● Mother is given FSH and LH - stimulates maturation
of eggs and ovulation.
● Eggs are fertilised using sperm in a laboratory. The fertilised eggs are kept in special solutions in a warm environment to help develop into embryos.
● 1 or 2 embryos are inserted into the mother’s womb. In this way they bypass the faulty tubes

CONS: very expensive, not always successful (the older the parents the less likely they are to have a baby; using donor egg or sperm from younger people can make it successful but then it is not the biological child)

This process rely on advance microscope techniques.

66
Q

What are the advantages of fertility treatment?

A

● Allows infertile couples to have children
● Can store a woman’s eggs for later

67
Q

What are the disadvantages of fertility treatment?

A

● It can be a very expensive process.
● It has a low success rate - especially for older couples.
● Increases chance of multiple pregnancies -
dangerous for mother and babies.
● Side effects of fertility drugs.

68
Q

What is infertility and when does it occur?

A

Infertility occurs when a couple find it difficult or are unable to conceive naturally. This can be a result of insufficient or too low levels of reproductive hormones
affecting the development of egg and sperm cells, or as a result of issues with the reproductive system of the female.
About 1/3 of cases are hard to explain, with partners being a bit less fertile than normal.
Common causes of infertility are obesity and eating disorders such as anorexia. One of the most common causes is age.

69
Q

Treating infertility with hormones - how?

A

Artificial hormones are used as part of modern reproductive technologies to treat infertility, particularly when the female is not producing enough eggs, usually as a result of the pituitary gland not producing sufficient FSH to cause egg maturation.
The hormones FSH and LH are given as a ‘fertility drug’ to stimulate egg production.
An important issue to consider with this is that several eggs can be released at once so this increases the chance of multiple births (twins or triplets etc).
It also doesn’t have a particularly high success rate and can be expensive

70
Q

Success rate of IVF

A

The success rate of IVF is low (~30%) but there have been many improvements and advancements in medical technologies which are helping to increase the success rate.
These advancements include improvements in microscope techniques and micro- tools that enable single cells to be removed from an embryo for genetic testing to identify if the embryo is healthy or has genetic defaults the couple might want to
consider

71
Q

Potential issues with fertility treatments

A
  • As several embryos are implanted, the risk of multiple births is quite high (which increases the risk of miscarriage or stillbirths as well as risks for the mother)
  • The success rate is not very high (although it is increasing);
  • IVF treatment failures can be very emotionally upsetting and physically stressful for couples
  • Some women use IVF to get pregnant at a later age than they would be able to conceive naturally
  • Some people are against IVF as more embryos can be produced than are used; the issue of who owns these embryos and whether they are used in research
    before eventually being destroyed is contentious (as embryos are a potential life)
  • The use of genetic testing is controversial as there is potential it could be misused in choosing characteristics of offspring (this is not allowed)

Exam Tip
You may have to evaluate methods used to treat infertility from the perspective of patients and doctors – they may have different views.

72
Q

What is a tropism?

A

A tropism is the response of a plant to a specific stimulus (light or gravity).

73
Q

What is phototropism?

A

Phototropism is the response of a plant to light. The shoots must grow upwards, away from gravity and towards light, so that leaves are able to absorb sunlight – shoots show a positive phototropic response and a negative gravitropic response

74
Q

What is gravitropism (or geotropism)?

A

Gravitropism is the response of a plant’s shoot or root to gravity. Roots need to grow downwards into the soil, away from light and towards gravity, in order to anchor the plant and absorb water and minerals from the soil particles so roots show a negative phototropic response and a positive gravitropic response.

75
Q

What is auxin?

A

Plants produce plant hormones called auxins to coordinate and control growth.
Auxins are produced in the tips of the shoots and the roots; the response of roots and shoots to stimuli of light and gravity are the result of unequal distribution of auxin. Shoots grow towards light and against the force of gravity. Roots grow in the direction of the force of gravity.
See picture on pg 177 of Biology book

76
Q

How do plant shoots show positive phototropism?

A

● One side of the shoot is in the light, causing auxin
to move to the shaded side.
● At the shaded side, the cells are stimulated to
grow - the shoot bends towards the light.
● As a result, photosynthesis can occur at a faster
rate.

77
Q

How do plant shoots show negative gravitropism?

A

In a horizontal shoot, auxin accumulates in the
lower side due to gravity.
● Cells on the lower side of shoot grow more, causing
the shoot to bend away from the direction of gravity.
● As a result, more light is usually available for
photosynthesis.

78
Q

How do plant roots show positive gravitropism?

A

● In a horizontal root, auxin accumulates in the
lower side, causing cells to grow less.
● The root bends in the direction of gravity
● As a result, more water and nutrients are available to the plant roots.

79
Q

What are gibberellins?

A

Gibberellins are a type of plant hormone involved in seed germination.

80
Q

What is ethene?

A

Ethene is a type of plant hormone involved in cell division and ripening.

81
Q

What are the uses of auxins?

A

● Weedkillers - auxin causes cells to grow at a rapid rate, causing plant death.
● Rooting powder - auxin causes new plant to grow very quickly. Gardeners dip the cut end of a cutting into rooting powder to increase the chances of success of the cutting growing into a plant
● Tissue culture - auxin promotes growth and cell division helping to produce many identical plants.

82
Q

What are the uses of ethene?

A

Control of food ripening in the food industry - allows fruit to be picked when not ripe (if they are not ripe the risk of them getting damaged during transport decreases) and ripened just before they are sold.

83
Q

What are the uses of gibberellins?

A

● Termination of seed dormancy (eg barley seeds)
● Promotion of flowering throughout the year
● Increase of fruit size

84
Q

Why when used as weedkiller auxin does not also kill the crops?

A

Many cereal crops and grasses are narrow leaved plants. Most weeds are broad leaved. The amount of hormone weedkiller Absorbed by a plant largely depends on its surface area. , so broad leaved weeds absorbed much more and go into uncontrolled growth and die.

Biology (16 decks)

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