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Biology yr11 > Topic 7 Animal Coordination, Control and Homeostasis > Flashcards

Topic 7 Animal Coordination, Control and Homeostasis Flashcards

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1
Q

What is the endocrine system?

A

A network of glands that produce and

secrete hormones into the bloodstream

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2
Q

What is a hormone?

A

● A cell signalling molecule produced by
endocrine glands and released into the blood
● Travels to a target organ and binds to
receptors on effectors initiating a response

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3
Q

Compare the endocrine and nervous systems (4)

Endocrine system Nervous system

A

Compare the endocrine and nervous systems (4)
Endocrine system Nervous system

Uses hormones
Uses nerve impulses

Hormones travel in the bloodstream to
the target organ
Nerve impulses travel via neurones to
the effectors

hormones have a Slower response
Nerves have a Faster response

Lasts until all hormones have broken
down which takes a long amount of time
Lasts until the nerve impulse stops which
takes a short amount of time

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4
Q

What is the pituitary gland?

A

Described as the ‘master gland’
Endocrine gland that produces hormones which
control other glands (e.g. adrenal glands)

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5
Q

What are the adrenal glands?

A

Endocrine glands that produce

adrenaline

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6
Q

Where are the adrenal glands located?

A

Above the kidneys

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7
Q

What is adrenaline?

A

A hormone produced by the adrenal glands
that is involved in the ‘fight or flight’
response (where the body prepares to
confront danger or flee from it)

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8
Q

State the effects of adrenaline on the body (4)

A

● Increases heart rate
● Increases blood pressure
● Increases blood flow to muscles
● Increases blood glucose levels

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9
Q

Describe how adrenaline increases heart rate and

blood pressure

A

● Secreted by the adrenal glands, travels in the blood to the heart
● Binds to specific receptors on cells in the heart
● Causes heart muscle to contract more forcefully and frequently
● ∴ heart rate increases, blood pressure increases

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10
Q

Describe how adrenaline increases respiration at

muscle tissues

A

● Adrenaline binds to specific receptors on cells in the liver
● Triggers breakdown of glycogen stores and release of glucose
∴ blood glucose levels increase
● Increased heart rate causes greater blood flow to muscles
● ∴ muscle cells receive more oxygen and glucose for respiration

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11
Q

What is negative feedback?

A

● A corrective mechanism that allows only small shifts
from a set point
● It reverses a change in conditions e.g. if the concentration
of a hormone increases, negative feedback systems work
to reduce the concentration back to normal level

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12
Q

What is the thyroid gland?

A

Endocrine gland that produces thyroxine

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13
Q

Where is the thyroid gland located?

A

In the neck

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14
Q

What is thyroxine?

A

A hormone secreted by the thyroid gland
that controls metabolic rate, heart rate
and temperature.

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15
Q

What is metabolic rate?

A

The rate at which biochemical reactions

occur in cells

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16
Q

Describe how thyroxine is released

A

● Hypothalamus secretes TRH
● TRH stimulates secretion of TSH from pituitary gland
● TSH stimulates the release of thyroxine from the
thyroid gland

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17
Q

What does TRH stand for?

A

Thyrotropin releasing hormone

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18
Q

What does TSH stand for?

A

Thyroid-stimulating hormone

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19
Q

Describe how a negative feedback system controls

blood thyroxine levels

A

● If blood thyroxine levels increase above a set point, TRH and TSH
secretion is inhibited. Less thyroxine is produced by the thyroid gland.
Thyroxine levels return to normal.
● If blood thyroxine levels decrease below a set point, TRH and TSH
secretion is increased. More thyroxine is produced by the thyroid
gland. Thyroxine levels return to normal.

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20
Q

How do the ovaries act as an endocrine gland?

A

They secrete oestrogen into the

bloodstream

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21
Q

How do the testes act as an endocrine gland?

A

They secrete testosterone into the

bloodstream

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22
Q

What is the menstrual cycle?

A

The cycle in women (typically lasting 28 days) that involves:
● Shedding of uterus lining (menstruation)
● Repair of uterus lining
● Release of an egg (ovulation)
● Maintenance of uterus lining

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23
Q

Describe the stages of the menstrual cycle

A

● Days 1-4: if fertilisation and implantation do not occur the uterus
lining sheds and the egg is expelled with it (menstruation)
● Days 4-14: uterus lining thickens and blood vessels grow in
preparation for the implantation of an egg
● Day 14: egg released from a follicle into the oviduct (ovulation)
● Days 14-28: uterus lining maintained so implantation can occur

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24
Q

Name the hormones that control the menstrual cycle

4

A

● Follicle stimulating hormone (FSH)
● Oestrogen
● Luteinising hormone (LH)
● Progesterone

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25
Describe the role of FSH in the menstrual cycle
● Secreted by the pituitary gland ● Transported in the bloodstream to the ovaries ● Triggers the development of a follicle in the ovaries which releases oestrogen
26
Describe the role oestrogen plays in the menstrual | cycle
● Secreted by the ovaries ● Repairs and thickens the uterus lining ● Inhibits secretion of FSH from the pituitary gland ● Stimulates secretion of LH from the pituitary gland
27
Describe the role of LH in the menstrual cycle
● Secreted by the pituitary gland ● Transported in the bloodstream to the ovaries ● Surge in LH triggers ovulation ● Stimulates follicle remains to develop into a corpus luteum which then secretes progesterone
28
What is a corpus luteum?
● Temporary endocrine structure ● Mass of cells that releases progesterone ● Degenerates after a few days
29
Describe the role of progesterone in the menstrual | cycle
● Secreted by the corpus luteum ● Stimulates the growth of blood vessels in the uterus lining (in preparation for implantation) ● Inhibits the release of FSH and LH ● If no implantation occurs, progesterone levels decrease and the uterus lining sheds. FSH increases and the cycle starts again.
30
What happens to progesterone levels if fertilisation | and implantation occur?
The placenta produces progesterone so levels remain high. This prevents further ovulation and maintains the uterus lining.
31
What are contraceptives?
A method or device utilised to prevent | pregnancy
32
Which hormones can be taken to prevent | pregnancy?
● Progesterone taken on its own | ● Progesterone combined with oestrogen
33
How does progesterone prevent pregnancy? (3)
● Sperm find it more difficult to enter the uterus as the cervical mucus is thickened ● Thins the uterine lining, reducing the likelihood of egg implantation ● Prevents ovulation in some women (but not all)
34
How does oestrogen prevent pregnancy?
Oestrogen inhibits FSH, preventing | ovulation
35
Outline how progesterone can be administered as a | contraceptive (2)
● Mini-pill taken daily | ● Injection
36
Outline how progesterone and oestrogen can be | administered as a contraceptive (2)
● Combined pill (taken continuously for 21 days then paused for 7 days) ● Skin patch (worn continuously for 3 weeks then without for 1 week)
37
What are the benefits of hormonal contraceptive | methods? (3)
● 99% effective when used properly ● Generally longer lasting than non-hormonal methods ● Used to treat other conditions e.g. painful/heavy periods
38
What are the risks of hormonal contraceptive | methods? (4)
● Side effects e.g. mood changes, acne, bloating ● Do not protect against STIs ● May involve uncomfortable medical procedures ● Not effective if used incorrectly
39
Describe the barrier methods of contraception
Prevent the sperm and egg meeting | e.g. condoms, diaphragms (fit over cervix)
40
What are the benefits of barrier methods of | contraception? (3)
● Condoms are simple and quick to use ● Condoms prevent the spread of STIs ● No side effects
41
What is the main risk of barrier methods of | contraception?
Less effective than hormonal methods | e.g. condom may split whilst in use.
42
What two methods (involving hormones) are used to | treat infertility?
● Clomifene therapy | ● IVF
43
Describe the role of hormones in IVF
1. FSH and LH given to a woman to stimulate egg production and ovulation 2. Eggs retrieved from the woman’s ovaries and fertilised in vitro 3. Resultant embryo transferred to the woman’s uterus
44
Outline clomifene therapy
● Prescription of clomifene drug to women who do not ovulate regularly ● Stimulates secretion of more FSH and LH which triggers egg production and ovulation
45
What is homeostasis?
The maintenance of a stable internal environment in the body despite fluctuations in internal and external conditions.
46
Why is homeostasis important?
To ensure optimum conditions for enzymes | and cellular processes in the body
47
State three conditions within the body that must be | controlled by homeostasis
● Temperature ● Blood glucose concentration ● Water levels
48
Which organ is responsible for the maintenance of | blood glucose concentrations?
Pancreas
49
How are blood glucose concentrations controlled?
Controlled by the hormones insulin and glucagon which are secreted by the pancreas
50
Insulin and glucagon are antagonistic hormones. | What does this mean?
They have opposite effects which | counteract one another.
51
Describe the role of insulin in the regulation of blood | sugar levels
● Causes liver and muscle cells to increase their uptake of glucose from the blood ● Glucose is converted into glycogen, a storage molecule
52
Describe the role of glucagon in the regulation of | blood sugar levels
● Causes the breakdown of glycogen to glucose in the liver ● Glucose is released into the blood
53
What is the control of blood glucose concentration | an example of?
Negative feedback
54
Describe what happens when blood glucose | concentrations become too high
● Blood glucose concentration increases above a set point ● Pancreas secretes insulin and stops producing glucagon ● Liver and muscle cells increase uptake of glucose ● Glucose is converted to glycogen and stored ● Some glucose may be stored as lipid in tissues ● Blood glucose concentration decreases, returning to normal level
55
Describe what happens when blood glucose | concentrations become too low
● Blood glucose concentration decreases below a set point ● Pancreas secretes glucagon and stops producing insulin ● Liver cells convert glycogen into glucose which is released into blood ● Blood glucose concentration increases, returning to normal level
56
What is diabetes?
A condition where the homeostatic control of blood glucose levels stops working.
57
What is the cause of type 1 diabetes?
Pancreas does not produce enough | insulin
58
How is type 1 diabetes treated? (3)
● Daily insulin injections at meal times ● Limiting intake of refined sugars ● Regular exercise
59
What is the cause of type 2 diabetes?
Person develops insulin resistance or doesn’t produce enough insulin (often due to obesity)
60
How is type 2 diabetes treated? (3)
● Balanced diet (eating fewer simple sugars and replacing them with more complex carbohydrates) ● Exercise ● Medication or insulin injections (however, these are less effective)
61
How does exercise help to control diabetes?
Exercise increases respiration in muscle cells. Excess glucose is removed from the blood to produce energy in the form of ATP.
62
Why are type 2 diabetics advised to replace simple
● Simple carbohydrates are broken down quickly so can raise blood glucose levels rapidly. ● Complex carbohydrates take longer to break down so have a reduced effect on blood glucose levels.
63
What is the Body Mass Index (BMI)?
A value based on height and mass used to categorise an individual as underweight, normal weight, overweight or obese.
64
How is BMI calculated?
Mass - ------------- (height) 2
65
What BMI values indicate obesity and an increased | risk of type 2 diabetes?
BMI value larger than 30
66
How is an individual’s waist-to-hip ratio calculated?
waist circumference ----------------------------- Hip circumference
67
What does a waist-to-hip ratio higher than 1.0 in | males or 0.85 in females indicate?
● Abdominal obesity | ● Increased risk of developing type 2 diabetes
68
What is osmoregulation?
The maintenance of constant water | levels in the body fluids of an organism

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