Paper 2: Topic 5 Homeostasis & response - Hormonal coordination in humans (LV) Flashcards
1
Q
Describe the endocrine system (2)
A
- Glands which produce and secrete hormones directly into the plasma
- Hormones then travel in the plasma to reach their target organs where they stimulate a response
2
Q
Define the term hormone (3)
A
- A chemical messenger molecule
- that is produced and secreted by an endocrine gland and
- travels via the bloodstream to its target organ where it causes as response
3
Q
Define the term endocrine gland (2)
A
An organ that produces a hormone which it secretes directly into the plasma
4
Q
Define the term target organ
A
An organ made of cells that have specific receptors on their cell membranes that are complementary to specific hormones
5
Q
State 6 differences between the nervous system and endocrine system
A
- Nervous system uses nerve impulse, endocrine system uses hormones
- Nervous system causes a quicker response, endocrine system causes a slower response
- Effect of the nervous system is short-lived, effect of the endocrine system is longer-lasting
- Nervous system uses neurones, endocrine system involves glands and hormones
- Nervous system uses an electrical signal, endocrine system uses a chemical messenger
- Nervous system acts on a very precise area, endocrine system acts in a more general way
6
Q
Name the master gland and explain why it is called this
A
Pituitary gland
Reason: It produces hormones which act on other glands to make them produce different hormones
7
Q
Name 4 hormones produced and secreted by the pituitary gland
A
- Anti-diuretic hormone
- FSH (Follicle stimulating hormone)
- Luteinising hormone (LH)
- Thyroid Stimulating Hormone (TSH)
8
Q
Why is the pituitary gland called the ‘master gland’
A
It produces several different hormones which act on other glands to stimulate other hormones to be released and cause different effects in the body
9
Q
Describe the position of the pituitary gland
A
The pituitary gland is no larger than a pea, and is located at the base of the brain. The pituitary gland is attached to the hypothalamus.
10
Q
Describe the position of the pancreas
A
Part of the digestive system, located above the small intestine but below the stomach
11
Q
Describe the position of the thyroid gland
A
Located in the neck region
(Exam/test hint: be able to identify it’s position on a diagram)
12
Q
Describe the position of the adrenal glands
A
Located just above the kidneys (one adrenal gland per kidney)
(Exam/test hint: be able to identify it’s position on a diagram)
13
Q
Describe the position of the ovaries
A
Part of the reproductive system, located in the pelvic region
(Exam/test hint: be able to identify their position on a diagram)
14
Q
Describe the position of the testes
A
Part the reproductive system, located in the scrotum
15
Q
Describe the function (role) of the pituitary gland
A
- Produces and secretes several different hormones into the plasma
- e.g. TSH, LH, FSH and ADH
16
Q
Describe the function/role of the pancreas
A
Produces and secretes insulin and glucagon into the plasma
17
Q
Describe the function/role of the thyroid gland
A
- Produces and secretes thyroxine into the plasma
- To regulate the heart rate, core body temperature and metabolic rate
(Exam/test hint: be able to identify it’s position on a diagram)
18
Q
Describe the function/role of the adrenal glands
A
- Produces and secretes adrenaline into the plasma
- To increases the heart rate for ‘flight, fright and fight’
(Exam/test hint: be able to identify their position on a diagram: on top of the kidneys)
19
Q
Describe the function/role of the ovaries
A
- Produces and secretes oestrogen into the bloodstream
- To control puberty and the menstrual cycle
20
Q
Describe the function/role of the testes (3)
A
- Produces and secretes testosterone into the bloodstream
- To control puberty
- To control sperm production
21
Q
Name the two hormones involved in regulating blood glucose levels
A
Insulin and glucagon
Exam/test hint: you MUST be able to spell these correctly
22
Q
What is the difference between glucagon and glycogen?
A
- Glucagon is a hormone produced by the pancreas when blood glucose levels are low
- Glycogen is a complex, insoluble carbohydrate that is used to store energy in skeletal muscles and the liver
23
Q
Describe what happens to excess glucose that is absorbed into the plasma e.g. after a carbohydrate rich meal
A
- The glucose is absorbed into the cells of the skeletal muscles and liver
- And it’s then converted to glycogen for storage
- This reduces the blood glucose levels in the plasma and restores the glucose concentration back to normal
24
Q
Name the organ that monitors and controls the blood glucose levels
A
Pancreas
25
Name the target organ**_s_** for insulin
* Liver
* Skeletal muscles
26
Name the target organ for glucagon
* Liver
27
Describe what happens if the blood glucose level falls too low
* The pancreas detects the fall in the glucose levels in the plasma
* The pancreas produces and secretes glucagon into the plasma
* Glucagon travels in the plasma to its target organ, the liver
* The cells of the liver respond to the glucagon by breaking down stored glycogen into glucose
* The glucose is released from the liver into the plasma
* This raises the plasma glucose levels and restores the plasma glucose level to normal
28
Describe what happens if the blood glucose level becomes too high
* The pancreas detects the rise in the blood glucose concentration in the blood
* The pancreas produces and secretes insulin into the plasma
* Insulin travels in the plasma to its target organs, the liver and skeletal muscles
* The cells of the liver and skeletal muscles respond to the insulin by absorbing more glucose from the blood plasma
* The glucose converted into glycogen inside the liver and skeletal muscle cells
* The glycogen is stored in the liver and skeletal cells
* This removes glucose from the plasma
* This lowers the blood glucose concentration and restores the plasma glucose level to normal
* This is an example of negative feedback
29
Name the term that describes how blood glucose levels are regulated by the body
Negative feedback
30
Describe a negative feedback loop (also called a negative feedback cycle)
* An internal factor e.g. blood glucose levels is elevated
* The elevated factor is detected by receptors
* The co-ordination centre receives the information
* The co-ordination centre co-ordinates a response
* The body responds by casing internal changes that lower the internal factor
* The internal factor is returned to its normal level
## Footnote
*Remember the same happens when the internal factor is too low but the body responds causing internal changes that raise the internal factor*
31
Explain why the negative feedback loop/cycle is referred to as a loop/cycle
* The body constantly responds to fluctuations in the internal factors of the body
* The process of detecting, responding and altering the internal factors is a continual process
32
Explain why the negative feedback loop/cycle is referred to as a negative process
The response that occurs is opposite to the change in the body’s internal factor
For example
* if an internal factor becomes elevated the response is to lower it
* if an internal factor becomes too low the body’s response it to raise it
33
State the two different types of diabetes
* Type I
* Type II
34
What causes type I diabetes?
The person’s pancreas fails to produce sufficient insulin for them to regulate their blood glucose levels
35
State the characteristics of type I diabetes
AND
Describe the symptoms of type I diabetes
**Characteristic**
* Uncontrolled high blood glucose levels
** Symptoms:**
* Tiredness and fatigue
* Breathlessness
* Dizziness and fainitng
* Frequent urination
* Dry mouth
* Weight loss
* Nausea and vomiting
* Blurred vision (which can lead to blindness)
36
Name the treatment given to type I diabetics
Insulin therapy
37
Describe insulin therapy
* The type I diabetic is given insulin injections
* Usually at mealtimes
38
Explain how insulin therapy works
* Insulin is administered at meal times
* This makes sure the blood glucose is removed from the blood as soon as the food is digested and glucose is absorbed
* This prevents the glucose levels from becoming too high (spiking)
* This form of treatment is very effective
39
State and explain 2 pieces of lifestyle advice is usually given to type I diabetics
* To reduce their simple carbohydrate intake i.e. reduce their intake of sugars
* To take regular exercise which will remove the excess glucose from the blood
40
What causes type II diabetes?
The person’s liver cells and skeletal muscle cells no longer responds to insulin produced by the pancreas
41
State the characteristics of type II diabetes
Uncontrolled high blood glucose levels
42
Describe how type II diabetes is normally treated
Follow a carbohydrate controlled diet and follow an exercise regime
43
Which type of diabetes increases the risk of obesity?
Type II
44
State 3 organs involved in the removal of waste materials/products from the body
1. Skin
2. Kidney
3. Lungs
45
State 4 waste products that must be removed from the body
* Carbon dioxide
* ***Excess*** water
* Urea
* ***Excess*** ions
46
State 3 ways water is removed from the body
* During exhalation as water vapour
* As the solvent that forms urine via the kidneys
* As sweat from the skin
47
State 2 ways ions are lost from the body
From the skin as sweat In the urine via the kidneys
48
State 2 ways urea is lost from the body
* In the **urine** via the kidneys
* A small (uncontrolled) quantity is lost from the skin as **sweat**
49
Explain why the skin and lungs are less efficient as excretory organs than the kidneys
* The skin and lungs have no control over water, ion or urea lost
* The kidney has a high degree of control over how much water, ions and urea is removed from the body
50
Explain why it is important to regulate the internal water content of the body
* If animal cells contain too much water they will **rupture **(do NOT say 'explode')
* This is called cytolysis
* If animal cells contain too little water they will **crenate**
* In both case this will cause the cells to fail to function correctly
51
Explain how urea is formed
* **Excess** proteins in the diet are broken down during digestion
* By protease enzymes into amino acids
* The excess amino acids are then deaminated in the liver
* To form ammonia
* However, ammonia is highly soluble and very toxic
* So it is immediately converted to urea
* So that it can be safely excreted
52
Explain the term excretion
* The removal of waste products from the body that have been produced by cells during metabolism e.g.
* carbon dioxide (from respiration)
* urea (from deamination)
53
Explain the term egestion
* The removal of dead cells and undigested food from the body
* E.g. dead bacteria from the gut
54
State the two main processes that occur in the kidney to produce urine
1. Filtration
2. **Selective** reabsorption (*exam hint: do not just say reabsorption*)
55
State 5 molecules that are filtered out of the blood plasma into the filtrate in the kidneys
1. Water
2. Ions
3. Glucose
4. Amino acids
5. Urea
56
Explain why cells are not filtered out of the blood plasma into the filtrate during urine formation
The cells are too big to pass through the membrane that filters the blood
57
State 3 molecules that are selectively reabsorbed back into the blood in the kidney
* **All** the glucose
* The **required quantity** of ions
* The **required quantity** of water
58
State 3 molecules that are excreted in the urine
* **Excess** ions
* **Excess** water
* The **majority** of the urea
59
Explain why it is important to regulate the ion levels in the blood
* If the ion content of the blood changes it alters the water potential of the blood
* This causes the cells to become crenated or to rupture
* This then prevents the cells from functioning correctly
60
Name the hormone involved in regulating the water content of the blood
Anti-diuretic hormone (ADH)
61
Name the part of the body that monitors the water content of the blood plasma
The osmo-regulatory centre of the brain
62
Name the receptors in the brain that detect changes in the water level of the blood plasma
Osmoreceptors
63
Describe the events that occur if the water content of the blood plasma is too high
* Osmoreceptors in the osmo-regulatory centre of the brain detect the increased water level of the blood following through the brain
* The co-ordination centre in the brain receives the information and co-ordinates a response
* The pituitary gland releases less ADH
* This causes less water to be reabsorbed from the filtrate back into the blood
* This causes the water volume of the blood to decrease
* A greater volume of urine is produced
* The urine is more dilute
64
Describe the events that occur if the water content of the blood is too low
* Osmoreceptors in the osmo-regulatory centre of the brain detect the lower water level of the blood following through the brain
* The co-ordination centre in the brain receives the information and co-ordinates a response
* The pituitary gland releases **more ADH**
* This causes **more water to be reabsorbed** from the filtrate back into the blood
* This causes the **water volume** of the blood to **increase**
* A **smaller volume** of urine is produced
* The urine is **more concentrated**
65
Describe the effect ADH has on the kidney tubules (2)
* The more ADH the more permeable the kidney tubules are to water
* So more water is reabsorbed
66
Name the term that describes how blood water levels are regulated by the body
Negative feedback
67
State 2 possible forms of treatment for a patient whose kidneys have stopped working
1. Kidney dialysis
2. Kidney transplant
68
Describe why kidney failure can be fatal
* The function of the kidneys is to remove waste products from the blood
* If they stop working (fully) the waste products accumulate
* The waste products can become toxic
* Causing cell damage and failure of the cells to work correctly
* This can then lead to multiple tissue and multiple organ failure potentially resulting in death
69
Describe the function of a dialysis machine
* To carry out the same function that would be carried out by healthy kidneys
* To remove waste products from the blood plasma
* This then maintains dissolved substances in the plasma at their normal levels
70
Describe the properties of the membrane used in a dialysis machine
Partially permeable
(this means it only allows certain molecules or ions to pass through it by diffusion)
71
What does the term ‘partially permeable membrane’ mean?
The membrane allows certain molecules to pass through but not others
72
Describe 3 dissolved substances that are removed from the blood plasma by a dialysis machine
* Excess ions
* Excess water
* All the urea
| Remember this is the same as the kidney would do
73
Describe how blood glucose levels are kept at the correct level when a patient has dialysis
* The dialysis fluid has glucose dissolved in it
* The concentration of the glucose in the dialysis fluid is the set at the level that the person requires
* This means only excess glucose is filtered out by dialysis
* As only the extra glucose will diffuse from the blood plasma into the dialysis fluid
74
How frequently must a patient have dialysis?
* 3 times a week
* Each session lasts 3-4 hours
75
State 2 risks of dialysis
1. Risk of infection
2. Risk of blood clots (thrombus) forming
76
State 4 advantages of dialysis compared to a kidney transplant
1. No risk of rejection
2. No need for immunosuppressant drugs for the rest of life
3. Readily available – new kidneys are rare
4. Can ‘buy time’ until a donor kidney becomes available
77
State 5 advantages of a kidney transplant compared to a dialysis
1. Lifestyle no longer restricted by dialysis
2. Life returns to completely normal
3. Diet is normal – no need for special food regime
4. Cheaper than long-term dialysis (although single one off operation is costly, the life-long cost of dialysis is much higher overall)
5. Recipient can return to a ‘normal’ lifestyle e.g. return to work
78
State 5 disadvantages of a kidney transplant
1. Lack of donor kidneys – so long waiting list
2. Risk associated with general surgery e.g. reacting to the anaesthetic
3. Risk of kidney rejection
4. Patient must take immune-suppressants for life
5. Operation itself is a high cost
79
State 3 disadvantages of dialysis
1. Very intrusive – lifestyle is seriously affected
2. Patient unlikely to be able to work (due to long and frequent trips to hospital)
3. Risk of infection is high It is not a ‘cure’ – can’t be used indefinitely
80
Describe the changes that occur to a female during puberty
* Menstrual cycle starts
* Breast tissue develops
* Hips widen i.e. change in body shape
* Pubic hair grows
81
Describe the changes that occur to a male during puberty
* Pubic hair grows
* Facial hair grows
* Shoulders broaden i.e. change in body shape
* Muscle development increases
82
Name the term that describes the physical changes that occur during puberty
Secondary sexual characteristics
83
Name the male hormone responsible for secondary sexual characteristics
Testosterone
84
Name the female hormone responsible for secondary sexual characteristics
Oestrogen
85
Name the organ that produces testosterone
Testes
86
Name the organ that produces oestrogen
Ovaries
87
State the 4 main stages that occur during a menstrual cycle
* Stage 1: menstruation occurs
* Stage 2: the uterus lining is rebuilt
* Stage 3 ovulation occurs
* Stage 4: implantation occurs if the woman has conceived OR the lining of the uterus begins to break down again
88
Describe the events that occur during stage 1 of the menstrual cycle, menstruation
* The lining of the uterus breaks down
* The blood is lost from the female body via the vagina
* This stage lasts ~4 days
89
Describe the events that occur during stage 2 of the menstrual cycle
* The uterus lining is rebuilt It becomes thick and full of blood vessels
* This stage lasts from day 4 to day 14
90
Describe the events that occur during stage 3 of the menstrual cycle, ovulation
* An ovum is released from an ovary
* The ovum is moved down the fallopian tubes towards the uterus
* This occurs on ~day 14
| Use the term ovum (not egg cell)
91
Describe the events that occur during stage 4 of the menstrual cycle
* If fertilisation occurs the zygote implants in the uterus lining
* If fertilisation has not occurred the spongy lining of the uterus breaks down
* The cycle repeats itself
92
What event marks the start of a menstrual cycle?
The first day of menstruation (period)
93
Name the 4 hormones that control the menstrual cycle
1. Follicle stimulating hormone (FSH)
2. Oestrogen
3. Progesterone
4. Luteinising hormone (LH)
94
Describe the role/function of FSH in the menstrual cycle
* Stimulates the growth and development of a follicle in an ovary
* Causes an ovum to mature in a follicle in one of the ovaries
* Stimulates the ovaries to produce and secrete oestrogen
95
Describe the role/function of oestrogen in the menstrual cycle
* Causes the lining of the uterus to thicken
* Stimulates the release of LH
* Inhibits the release of FSH
96
Describe the role/function of progesterone in the menstrual cycle
* Maintains the lining of the uterus during the 2nd half of the menstrual cycle
* Low levels of progesterone cause the uterus lining to break down
* Inhibits the release of LH
* Inhibits the release of FSH
97
Describe the role/function of LH in the menstrual cycle
Stimulates ovulation on day 14
Stimulates the production and secretion of progesterone
98
State where FSH is produced
Pituitary gland
99
State where oestrogen is produced
Ovaries
100
State where progesterone is produced
* Ovaries
* By the follicle cells left in the ovary after ovulation
101
State where LH is produced
Pituitary gland
102
Describe the term contraception
A method for reducing the chance of fertilisation (and hence pregnancy)
103
State the 2 main ways contraceptives work
* Reduce fertility
* Preventing fertilisation
104
Why is it incorrect to refer to surgical sterilisation as a contraception
* Surgical sterilisation is (generally) permanent
* When a woman has her fallopian tubes tied or a man has a vasectomy it is (very) rare for these operations to be reversed successfully
* Hence neither form of sterilisation can be used for a short period of time and then stopped
105
State the 2 hormones found in most combined oral contraceptive pills
1. Oestrogen
2. Progesterone
106
Describe how oestrogen can be used in a contraceptive pill to reduce fertility
* Oestrogen can be used to prevent ovulation
* Permanently high levels of oestrogen inhibits the release of FSH
* The absence of FSH stops the maturation of follicles and an ovum
* So no ovulation occurs
107
Describe how progesterone can be used in a contraceptive pill to reduce fertility
* Progesterone stimulates the production of thick mucus
* This thick mucus prevents the sperm travelling through the cervix to meet the ovum
* So no fertilisation can occur
108
State 4 disadvantages of taking combined oral-contraceptive pills to reduce fertility in females
* Risks of blood clots (thrombus)
* Can cause headaches
* Can cause nausea
* It does not protect against sexually transmitted diseases
109
State the advantage of using a progesterone-only contraceptive pill
****It has fewer side effects than the combined pill (and it still just as effective!)
110
Other than pills, state 4 other hormonal (chemical) contraception methods
1. Contraceptive patch
2. Contraceptive implant
3. Contraceptive injection
4. Intrauterine device (IUD) and intrauterine system (IUS)
111
Describe how the contraceptive patch works
* A small (5cm x 5cm) patch is stick to the female’s arm
* The patch contains both oestrogen and progesterone
* The hormones are slowly released into the plasma (and then travel to thier target organs)
* Each patch lasts one week
112
Describe how the contraceptive implant works
* A small implant is inserted under the skin in the female’s arm
* It releases a continual quantity of progesterone into the plasma
* The progesterone prevents ovulation and makes it harder for the sperm to pass through the cervix to reach the ovum
* So fertilisation is prevented
* Each implant can last ~3 years
113
Describe how the contraceptive injection works
* The injection contains progesterone
* The progesterone prevents ovulation and makes it harder for the sperm to pass through the cervix to reach the ovum
* So fertilisation is prevented
* Each does lasts 2-3 months
114
Describe how an intrauterine device (IUD or IUS) works
* These can be made from plastic or copper
* The t-shaped device is inserted into the uterus
* Plastic IUD/IUS release progesterone
* Copper IUD/IUS prevent the sperm surviving in the uterus
* They prevent the embryo from implanting in the uterus
115
State 4 examples of barrier contraceptives
Condoms
Femidoms
Diaphragm
Spermicide
116
Describe how barrier contraceptives work
Non-hormonal contraceptives that prevent the sperm from reaching the ovum
117
Describe how condoms are used to prevent fertilisation/pregnancy
* Condoms are worn over the penis during sexual intercourse
* The condom collects the sperm that are ejaculated
* This prevents the sperm from entering the vagina
118
Describe how femidoms are used to prevent fertilisation/pregnancy
* Femidoms are worn inside the vagina
* They prevent the sperm moving through the vagina and the cervix to the fallopian tubes
* This prevents the sperm from reaching an ovum
119
Describe how diaphragms are used to prevent fertilisation/pregnancy
* A diaphragm is a plastic cup that sits over the cervix
* This must be used with a spermicide
* They prevent the sperm moving through the vagina and the cervix to the fallopian tubes
* This prevents the sperm from reaching an ovum and the spermicide kills or disable any sperm that reaches the diaphragm
120
Describe how spermicides are used to prevent fertilisation/pregnancy
* A spermicide can be used on its own but it is NOT very effective (~70%)
* The spermicide kills or disables the sperm
121
Describe the two forms of surgical sterilisation
* Tubal ligation (females)
* Vasectomy (males)
122
Explain how tubal ligation can be used as a form of preventing pregnancy
* Cutting or tying the fallopian tubes will prevent the ovum from passing to the uterus
* So no fertilisation and implantation can occur
123
Explain how a vasectomy can be used as a form of preventing pregnancy
* Cutting or tying the sperm ducts will prevent the sperm passing into the urethra and being ejaculated
* So no fertilisation and implantation can occur
124
Explain the ‘natural’ method of contraception
* This is when a couple avoid sexual intercourse during the most fertile days of the menstrual cycle
## Footnote
*Please note: this is **NOT** a reliable or effective form of contraception*
125
State the most effective way to avoid pregnancy
Abstinence – avoid having sexual intercourse!
126
Describe how hormones can be used to increase fertility
* FSH and LH can be prescribed to a woman who has low fertility
* These hormones will stimulate ovulation
127
State an advantage of prescribing a woman fertility drugs
It helps a lot of women who have naturally low levels of FSH to become pregnant
128
State 4 disadvantages of prescribing a woman fertility drugs
1. It is not always successful
2. It may have to be repeated several times
3. It is costly
4. Too many ova may be stimulated which can cause unexpected multiple pregnancies
129
State what IVF stands for
In-vitro fertilisation
130
Describe the 5 key stages in IVF
1. The woman is prescribed FSH and LH to stimulate several ova to mature
2. Ova are collected from the woman’s ovaries
3. The ovum is fertilised in a lab using a man’s sperm OR a sperm can be injected directly into an ovum using a technique called ICSI
4. The zygote is grown into an embryo in a lab incubator
5. The embryo is transferred into the woman’s uterus
131
State what ICSI stands for
Intra-cytoplasmic sperm injection
132
Describe a situation where a couple may be advised to consider using ICSI
When the male has a low/no sperm count
133
State an advantage of IVF
It enables infertile couples to conceive and have their own biological children
134
State 6 disadvantages of IVF
1. Multiple births can happen
2. Multiple births are risky for the unborn babies and the mother e.g. higher risk of miscarriage, higher risk of the babies being still born
3. The success rate of IVF is low
4. The procedure is very emotionally stressful and upsetting for the couple as it often ends with multiple failures
5. The procedure is physically stressful for the woman
6. Some women have side effects to the hormones e.g. vomiting, abdominal pain, dehydration
135
Give 3 reasons why some people object to IVF
1. IVF often produces several embryos that are unused which just get destroyed
2. People object to unused embryos being destroyed as they think it is unethical to destroy a potential human life
3. It is possible that through genetic testing of embryos certain characteristics could be selected e.g. hair colour which is unethical
136
State where adrenaline is produced
Adrenal glands
137
State 3 situations where adrenaline secretion is increased
When the body is preparing for
* Flight
* Fright
* Fight situations
138
State 3 effects of the increased secretion of adrenaline
1. Increased heart rate
2. Increased supply of oxygen to the brain and skeletal muscles
3. Increased supply of glucose to the brain and skeletal muscles
139
Name the hormone that regulates metabolism
Thyroxine
140
State where thyroxine is produced
Thyroid gland in the neck
141
State 2 effects of increased thyroxine secretion
1. Increasing metabolic rate
2. Stimulating protein synthesis
142
Name the hormone that stimulates the production and secretion of thyroxine
Thyroid stimulating hormone
143
Name the term that describes how thyroxine levels are regulated by the body
Negative feedback
144
Label the endocrine glands
145
Complete the table to compare the endocrine system and the nervous system
146
Distinguish between these three terms:
* Glucose
* Glycogen
* Glucagon
147
Describe the role of thyroxine (2)
* Thyroxine controls cell metabolism
* Thyroxine ensures metabolism occurs at the correct pace
148
What is thyroxine? How is it transported around the body?
What is thyroxine?
* Thyroxine is a **hormone** (chemical messenger)
* It is **produced by the thyroid gla**nd (an endocrine gland) located in the neck
How is it trasnported?
* Like all hormones, thyroxine is transported around the body in the **blood plasma**
149
Explain how thyroxine levels are regulated (controlled) in the body
* **Negative feedback** controls the levels of thyroxine
* Negative feedback en**sures that any changes are reversed and returned back to the normal level**
* As levels of thyroxine increase in the bloodstream **TSH is inhibited**
* This st**ops the thyroid gland producing thyroxin**e
150
What is adrenaline and when is it produced?
* Adrenaline is produced by the adrenal glands
* It is produced in times of fear or stress.
151
Describe the body's responses to adrenaline
It causes the following responses:
* increases the heart rate
* increases breathing rate
* stimulate the liver to break down glycogen to glucose
* increases the delivery of oxygen and glucose to the brain
* increases the delivery of oxygen and glucose to the muscles
* causes the pupils to dilate
* increases the person's mental awareness i.e. increased sensitivity
i.e. this prepares the body for 'flight or fight'.
152
Label frontal view of the female reproductive system
153
Label the side view of the female reproductive system
154
Label the frontal view of the male reproductive system
155
Label the side view of the male reproductive system
156
Label the 4 different stages of the menstrual cycle
157
Label the 4 different hormones involved in the menstrual cycle and identify the point of ovulation
