homeostasis and response Flashcards
(215 cards)
1
Q
Define homeostasis
A
- The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
- This is needed for enzyme action and all cell functions.
2
Q
Why must the body regulate the core body temperature of 37ºC?
A
- Because this is the optimum temperature for enzyme action and all cell functions
3
Q
What happens if body temperature falls too high or above optimum?
A
- Enzymes will denature and metabolic processes can’t take place, so cells will die
4
Q
What does homeostasis control?
A
- Blood glucose concentration
- Body temperature
- Water levels
5
Q
What is involved in the automatic control systems?
A
- Nervous and hormonal communication is involved in the automatic control systems, which detect changes and respond to them.
6
Q
What two types of response can control systems have?
A
- Chemical or electrical
7
Q
What do all control systems include?
A
- Receptors
- Coordination centres
- Effectors (muscles or glands)
8
Q
What is the function of the receptors?
A
- Cells that detect stimuli (changes in the environment)
9
Q
What is the function of the coordination centre?
A
- They receive and process information from the receptors
e.g. brain, spinal cord and pancreas
10
Q
What is the function of the effectors?
A
- Bring about responses to bring the conditions in the body back to optimum levels
e.g. muscles or glands
11
Q
Define stimuli
A
- Changes in the environment
12
Q
What does the nervous system allow?
A
- The nervous system allows us to react to our surroundings, and coordinate actions in response to stimuli.
13
Q
Explain how a (normal) response is brought about
A
- Receptor cells convert a stimulus into an electrical impulse.
- This electrical impulse travels along cells called sensory neurons to the central nervous system (CNS).
- Here, the information is processed and the appropriate response is coordinated, resulting in an electrical impulse being sent along motor neurones to effectors.
- The effectors carry out the response (this may be muscles contracting or glands secreting hormones).
14
Q
How does information get from receptors to the CNS?
A
- Receptor cells convert a stimulus into an electrical impulse.
- This electrical impulse travels along cells called sensory neurons to the central nervous system (CNS).
15
Q
What happens when the CNS receives the information?
A
- Here, the information is processed and the appropriate response is coordinated, resulting in an electrical impulse being sent along motor neurones to effectors.
16
Q
What happens when the information gets to the effectors?
A
- The effectors carry out the response (this may be muscles contracting or glands secreting hormones).
17
Q
What is the CNS made up of?
A
- CNS is made up of our brain and spinal cord
18
Q
Name the order of stimulus to response
A
- stimulus -> receptor -> coordinator -> effector -> response
19
Q
Name examples of stimuli
A
- Temperature, light, position, sound, touch, etc.
20
Q
What is the function of a sensory neurone?
A
- They transmit messages from sense receptors
e.g. eye or nose, to the brain or spinal cord
21
Q
What is the function of a motor neurone?
A
- They transmit messages from the brain and spinal cord to the muscles and organs, which are effectors
22
Q
Define reflexes
A
- Automatic responses which take place before you have time to think are called reflexes.
23
Q
Why are reflex actions important?
A
- Reflex actions are automatic and rapid (do not involve the conscious part of the brain)
- This means they prevent the individual from getting hurt and protects are body from danger
24
Q
How is a reflex action different to a normal one?
A
- The information travels down a pathway called a reflex arc, allowing vital responses to take place quickly.
- This pathway is different from the usual response to stimuli because the impulse does not pass through the conscious areas of your brain.
25
Define a reflex arc
* The nervous pathway that a nerve impulse takes during a reflex action
26
What is the function of a relay neurone?
* They connect motor neurones to sensory neurones
27
What is a synapse?
* A synapse is a junction where two or more nerve cells meet. (a gap between two neurons)
28
What is the function of a synapse?
* Allows the nerve cells to pass on their electrical impulse to another cell
* Also controls the direction in which impulses travel, as they can only travel one way through a synapse.
29
What happens at the synapse?
* When the impulse reaches the end of the first neuron, a chemical is released into the synapse.
* This chemical diffuses across the synapse.
* When the chemical reaches the second neuron, it triggers the impulse to begin again in the next neuron.
30
Explain how a reflex response is brought about
1. A stimulus is detected by receptors.
2. Impulses are sent along a sensory neuron.
3. In the CNS the impulse passes to a relay neuron.
4. Impulses are sent along a motor neuron.
5. The impulse reaches an effector resulting in the appropriate response
31
Name example of reflex arcs
* Pupils getting smaller to avoid damage from bright lights
* Moving your hand from a hot surface to prevent damage
32
Define reaction time
* Your reaction time is how long it takes you to respond to a stimulus.
33
How can you measure reaction time?
* Ruler drop test
34
What is the function of neurotransmitters?
* They carry chemical signals from one neuron (nerve cell) to the next target cell
* This can be another nerve cell, a muscle cell or a gland
35
What is the function of the brain?
* The brain is made up of many connected neurons and controls complex behaviour.
* It is a part of the central nervous system, along with the spinal cord.
* Different regions control different functions.
36
What are the (main) components of the brain?
* Cerebral cortex
* Cerebellum
* Medulla
37
What is the function of the cerebral cortex?
* Controls consciousness, intelligence, memory and language
* It is the outer part of the brain
38
What is the function of the cerebellum?
* Controls fine movement of muscles (balance, muscle coordination, movement)
* Rounded structure towards the bottom/back of brain
39
What is the function of the medulla?
* Controls unconscious actions such as breathing and heart rate
* Found in the brain stem in front of the cerebellum
40
Why is investigating brain function and treating brain damage and disease difficult?
* It is complex and delicate
* It is easily damaged
* Drugs given to treat diseases cannot always reach the brain because of the
membranes that surround it
* It is not fully understood which part of the brain does what
41
How can neuroscientists map out the regions of the brain to particular functions?
* Studying patients with brain damage
* Electrically stimulating different parts of the brain
* MRI scans
42
How can we use patients with brain damage to study the brain?
* Observing the changes in an individual following damage on a certain area of the brain can provide information on the role this area has.
43
How can we use electrical stimulations to study the brain?
* This can be done by pushing an electrode into the brain.
* The stimulation may result in a mental or physical change in the individual, providing information on the role this area of the brain has.
44
How can we use MRI scans to study the brain?
* A magnetic resonance imaging scanner can be used to create an image of the brain.
* This can be used to show which part of the brain is affected by a tumour, or which part is active during a specific task.
45
What are the pros and cons of electrically stimulating different parts of the brain?
PROS:
* Helps control your movement symptoms when your medications aren’t working as well as they used to
* Doesn’t damage brain tissue
CONS:
* Could cause stroke
* Temporary pain and swelling at the implantation site
46
What are the pros and cons of MRI scans?
PROS:
* Non-invasive and doesn’t use radiation
* No side-effects
CONS:
* Very expensive
* May cause peripheral muscle or nerve stimulation
47
What is the eye?
* The eye is a sense organ containing receptors sensitive to light intensity and colour.
* It has many different structures within it. They are adapted to allow the eye to change its shape in order to focus on near or distant objects (a process called accommodation), and to dim light.
48
Define accommodation
* The process of changing the shape of the lens to focus on near or distant objects
49
What is the function of the retina?
* Layer of light sensitive cells found at the back of the eye
* When light hits this, the cells are simulated
* Converts light that enters your eye into electrical signals (impulses) which the optic nerve sends to the brain which
interprets the information to create an image.
50
What is the function of the optic nerve?
* A nerve that leaves the eye and leads to the brain.
* Composed of many sensory neurones that carries the impulses from the retina to the brain to create an image
51
What is the function of the sclera?
* Tough white protective outer layer which supports the structures inside the eye.
* It is strong to prevent some damage to the eye
52
What is the function of the cornea?
* The see-through layer at the front of the eye.
* It allows light through
* The curved surface bends and focuses light (refracts) onto the retina
53
What is the function of the iris?
* Muscles that surround the pupil
* They contract or relax to alter the size of the pupil
54
How does the eye adjust in bright light?
* The circular muscles contract
* Radial muscles relax
* Makes the pupil smaller- avoiding damage to the retina.
55
How does the eye adjust in dim light?
* The circular muscles relax
* The radial muscles contract
* Makes the pupil larger- so more light can enter to create a better image
56
What is the function of the ciliary muscles?
* They control the thickness of the lens to allow focussing
57
What is the function of the suspensory ligaments?
* Attach the ciliary muscles to the lens and holds the lens in place
58
How does the eye focus on near objects?
* Ciliary muscles contract
* Suspensory ligaments loosen
* Therefore the lens is then thicker and more curved and refracts light rays strongly
59
How does the eye focus on distant objects?
* Ciliary muscles relax
* Suspensory ligaments are pulled tight
* Therefore the lens is then pulled thin and only slightly refracts light rays
60
How do eye defects occur?
* When rays of light do not focus on the retina
61
Describe myopia
* Short sightedness
* The lens is too curved, so distant objects appear blurry.
62
Describe hyperopia
* Long sightedness
*The lens is too flat, so it cannot refract light enough.
63
How can myopia be treated?
* With spectacle lenses : concave lenses to spread out the light to treat myopia
* Laser eye surgery: lasers can be used to reduce the thickness of the cornea (so it refracts light less) to treat myopia
* Contact lenses: work in the same way as glasses but allow activities such
as sport to be carried out, hard or soft contact lenses last for different lengths of time
64
How can hyperopia be treated?
* With spectacle lenses: convex lenses to bring the rays together to treat
hyperopia
* Laser eye surgery- lasers can be used to change the curvature of the cornea (so it refracts light more strongly) to treat hyperopia
* Replacement lens- Hyperopia can be treated by replacing the lens with an
artificial one made of clear plastic (or adding the plastic on top of the natural
lens).
65
What are the risks of replacement lens?
* The risks include damage to retina or cataracts developing.
66
What does the thermoregulatory centre do?
* Monitors and controls body temperature
67
How does the thermoregulatory work?
* Has receptors that are sensitive to and monitor the temperature of the blood
* Send nervous impulses to the thermoregulatory centre
68
Where is the thermoregulatory centre found?
* It is found in the hypothalmus
69
What happens if body temperature becomes too high?
* Sweat is produced from sweat glands which evaporates from skin surface resulting in increased energy transfer from the body to the environment
* Vasodilation occurs (blood vessels dilate) means more blood flows closer to the surface of the skin, resulting in increased energy transfer from the body to the environment
70
What happens if body temperature becomes too low?
* Sweating stops
* Skeletal muscles contract rapidly (shivering) to generate heat from respiration
* Hairs stand on end to create an insulating layer, trapping warm air
* Vasoconstriction (blood vessels constrict) means blood does not flow so close to the surface, resulting in less heat lost
71
What can cool us down on a hot day?
1) Vasodilation - capillaries get wider so a larger amount of blood can flow near the skins surface, heat is lost to the environment
2) Hairs and hair erector muscles are relaxed
3) Evaporation of sweat from the sweat glands which takes heat energy away from the body
4) No shivering
72
What can heat us up on a cold day?
1) Vasoconstriction - capillaries get thinner so less blood can flow near the skin surface, heat is kept near to the body
2) No sweat is produced, which reduces the amount of heat energy taken away from the body
3) Body starts to shiver to produce heat for the body
4) Hairs and hair erector muscles stand on end to trap a layer of air
73
What are the two communication systems that the human body has?
* The nervous system
* The endocrine system.
74
What is the function of the endocrine system?
* It secrets hormones (chemical messengers) directly into the bloodstream
* The blood carries the hormone to a target organ/tissue where it produces an effect/response
75
What is the endocrine system made up of?
* It is made up of glands which secrete hormones directly into the bloodstream.
76
Name all the glands in the endocrine system
* Pituitary gland, pancreas, thyroid, adrenal gland, ovary, testes
77
What is the function of the pituitary gland?
* The master gland that is found in the brain
* Secretes several hormones into the blood in response to body conditions
* It can have an effect on the body or act on other glands to stimulate them to produce different hormones to bring about effects
78
What is the function of the pancreas?
* It secretes insulin and glucagon
* To regulate blood glucose concentration
79
What is the function of the thyroid?
* It secretes thyroxine (its release is stimulated by the thyroid stimulating hormone)
* Controls the metabolic rate, heart rate, and temperature
* And plays a role in growth and development
80
What is the function of the adrenal gland?
* It secretes adrenaline in times of stress or fear
* Increasing heart rate and boosting delivery of oxygen and glucose to the brain and muscles in order to activate "fight or flight" response
81
What is the function of the ovaries?
* It secretes oestrogen to control female reproduction
* It is also involved in the menstrual cycle and the development of female secondary sexual characteristics (different features that develop during puberty that distinguish a female from a male)
82
What is the function of the testes?
* It secretes testosterone to control male reproduction
* It is also involved in the production of sperm and the development of male secondary sexual characteristics
83
What are the differences between the endocrine system and the nervous system?
* The endocrine system relies on hormones while the nervous system relies on electrical impulses
* The hormones are transported by the blood whilst impulses are carried along hormones
* Endocrine system slower but acts for much longer
84
What are the similarities between the endocrine system and the nervous system?
* They both send information around the body in order to carry out homeostasis
85
Which sends information faster, the endocrine system and or nervous system?
* Compared to the nervous system, the endocrine system transports hormones slower than the nervous system sends electrical impulses, but hormones act for longer
86
Why must the concentration of glucose in our blood be kept within a certain limit/ at a constant level?
* Because glucose is needed by every cell to carry out respiration and release energy to stay alive
87
What is the concentration of glucose controlled by?
* It is controlled by the pancreas.
88
What can increase the glucose levels in the blood?
* Eating foods that contain carbohydrates increases the glucose levels in the blood.
89
What can decrease the glucose levels in the blood?
* Rigorous activity, e.g. exercise, uses glucose for respiration and therefore there is less in the blood
90
What happens if blood glucose concentration becomes too high?
*Increase in blood glucose concentration is detected by pancreas cells
* The pancreas produces the hormone insulin, which binds to cell in target organs (muscle and liver)
* This causes glucose to move from the blood into the muscle cells for respiration
* And excess glucose to move into the liver where it is converted to glycogen for storage
* The blood glucose concentration is reduced
91
What happens if blood glucose concentration becomes too low?
* Decrease in blood glucose concentration is detected by the pancreas cells
* The pancreas produces the hormone glucagon which binds to liver and muscle cells
* In the liver and muscle cells, glycogen is converted back into glucose and released into the blood
* Blood glucose concentration is increased
92
Explain negative feedback loop in terms of blood glucose concentration
* Blood glucose concentration is kept constant through using these two
hormones, glucagon and insulin
* They work in a negative feedback loop.
* When blood glucose levels increase/decrease, a hormone is secreted to
oppose the change.
* The action of this hormone cannot occur continually because when the blood arrives at a certain glucose concentration the other hormone is produced, resulting in the opposite effect
93
What happens to cells if there is too little glucose?
* Too little glucose could cause cells to die due to a lack of respiration and energy
94
What happens to cells if there is too much glucose?
* Too much glucose will affect solute concentration outside cells, affecting osmosis,
* Causing too much water to be drawn out of cells; this causes them to shrivel up and die
95
What is type 1 diabetes?
* A disorder in which the pancreas fails to produce sufficient insulin
96
What is type 1 diabetes characterised by?
* Uncontrolled high blood glucose levels - can rise to a fatal amount
* Glucose is excreted with urine and lots of urine is produced leaving the
individual very thirsty
97
How is type 1 diabetes treated?
* It is treated with insulin injections at meal times, which results in glucose being taken up from the bloodstream - this means the blood glucose
* It is also advised to limit the intake of simple carbohydrates which contain
lots of glucose
98
How are doctors attempting to cure type 1 diabetes?
* Doctors are attempting to cure diabetes with pancreas and pancreatic cell
transplants so that they don't have to reject insulin (immune rejection & immunosuppressants)
* Genetically engineering pancreatic cells from mice to make insulin
* Stem cell research/ artificial pancreases
99
What is type 2 diabetes?
* Where the body cells no longer respond to insulin produced by the pancreas
100
What is type 2 diabetes characterised by?
* Uncontrolled high blood glucose levels - can rise to a fatal amount
101
why should you get injections in type 1 diabetes and not pills
* because insulin is a protein (like all hormones) that would be destroyed by enzymes
102
How is type 2 diabetes treated?
* A carbohydrate controlled diet by reducing the number of simple carbohydrates
* Increasing to keep blood glucose levels at a minimum
* Losing weight
* There are also drugs to make insulin more effective on body cells, help the
pancreas make more insulin or reduce the amount of glucose absorbed from
the gut
103
Why can people with type 2 diabetes not get insulin injections?
* Because the cells stop responding to the insulin
104
What are the risk factors for type 2 diabetes?
* Main risk factor: obesity; as obesity levels increase, more people are getting type 2 diabetes
* Age: people over 40
* Genetics: having a close relative with the condition
* Ethnicity: South Asian, Chinese, African-Caribbean or black African
105
Explain the negative feedback loop of blood glucose concentration
* Blood glucose concentration of a normal person rises slightly and falls slightly over the course of the day; this is because the blood glucose concentration is controlled by a balance between insulin and glucagon
* So, when blood glucose levels fall, glucagon is released and when the blood glucose levels are too high, insulin is released – forming a negative feedback loop
106
Define osmosis
* Osmosis is the process by which water molecules move from a place where they are in high concentration to a place where they are in low concentration.
107
What happens when the water concentration of the blood increases?
* If the water concentration of the blood increases then cells in the body take up water.
* This is because the concentration of water in the bloodstream is higher than the concentration of water in the cells, so water moves into the cells by osmosis.
* Cells then expand as they take up more water, and may eventually burst.
108
What happens when the water concentration of the blood decreases?
* If the water concentration of the blood decreases then cells in the body lose water.
* This is because the concentration of water in the bloodstream is lower than the concentration of water in the cells, so water moves out of the cells by osmosis.
* Cells shrink as they lose water and shrivel
109
Why is it important that the body keeps the blood water concentration relatively constant?
* If the blood becomes too dilute, water will move into cells by osmosis, causing them to burst
* And, if blood becomes too concentrated, water will move out of cells by osmosis, causing them to shrivel
* In both scenarios, if body cells gain or lose too much water by osmosis, they will not work efficiently
110
What are the three ways in which we lose water. state whether they’re controlled or uncontrolled?
1) Water leaves the body via the lungs during exhalation (uncontrolled)
2) Sweating, as the sweat glands produce sweat on the skin and it evaporates (uncontrolled)
3) Through urine which is produced by the kidney. If blood is too dilute, kidney will remove this water and produce a greater volume of dilute urine (controlled)
111
What is the function of the kidneys and why is it important?
* The kidneys are very important in maintaining the balance of water and other substances in the body.
* As blood moves through the body, it makes urine by:
* Fltering out the waste products
* Selectively reabsorbing useful substances such as glucose, ions and water
112
Name examples of waste products that are processed at the kidney and removed in urine
* Water, ions, urea
113
How is else is water lost from our body?
* Can also leave the body at the lungs as a result of exhalation,
* From the skin in sweat (there is no control over the amount lost)
* Depending on the concentration of water in the blood, a certain amount of
water is lost as urine
114
How are ions taken into the body?
* Via food
115
What happens if the ion concentration is incorrect?
* If the ion concentration is incorrect, then too little or too much water may
enter body cells.
* This is because the water potential of the blood would be
altered
* In the kidneys, certain amounts of ions are reabsorbed into the blood after it has been filtered to ensure the concentration in the blood is maintained
116
How are ions lost?
* They are lost in sweat (there is no control over the amount lost)
117
How is urea removed from the body?
* It is lost in sweat (there is no control over the amount lost)
* In the kidneys, it is filtered out of the blood
118
What is removed via the sweat glands in sweat?
* Water, ions and urea
119
What does the digestion of protein from the diet cause?
* It results in excess amino acids which need to be excreted safely.
* In the liver, these amino acids are deaminated to form ammonia.
* Ammonia is toxic and so it is immediately converted to urea for safe excretion
120
What is the function of ADH?
* Anti-diuretic hormone is a hormone that is involved in the control the loss of water as urine by increase permeability of kidney tubule
121
Where is ADH released and where does it travel to?
* It is released into the pancreas by the pituitary gland when a receptor in the brain detects that the blood is too concentrated
* It travels in the bloodstream to the kidney tubule
122
What happens when there is a low blood water concentration?
1) The brain detects the low water levels and pituitary gland releases the hormone ADH as a result
2) ADH then travels through the blood and triggers kidney tubules to become more permeable
3) As the kidney tubules become more permeable, more water is reabsorbed back into the blood from the tubule during selective reabsorption
4) This increases blood water levels back to normal and produces a small volume of more concentrated (yellow) urine and the blood becoming less concentrated as more water moves into it
123
What happens when there is a high blood water concentration?
1) Pituitary gland detects high blood water levels and stops releasing ADH
2) This means that kidney tubules are less permeable so that less water is reabsorbed into the bloodstream during selective reabsorption
3) This decreases blood water levels back to normal because lots of dilute urine is produced that takes water away from the body
124
What is the regulation of blood water concentration an example of?
* This is an example of a negative feedback loop, because if the concentration of the blood increases/decreases, more/less ADH is secreted to reverse this change.
125
How do the kidneys produce urine?
* By filtration of the blood and selective reabsorption of useful substances such as glucose, some ions and water
126
Describe filtration
* As the blood enters the kidney, all small molecules are filtered out of the blood and into the kidney (filtration)
* These include water, urea, mineral ions, amino acids and glucose
127
Why can proteins and blood cells not be filtered?
* Proteins and blood cells are too large to diffuse through and remain in the capillaries
128
What does the release of more ADH cause?
* It causes more water to be reabsorbed back into the blood from the kidney tubules; this is controlled by negative feedback
129
What happens after filtration takes place?
* Selective reabsorption takes place
* This is where useful substances are reabsorbed back into the bloodstream
* i.e. all of the glucose (and all amino acids) some of the ions and some of the water is reabsorbed back into the blood through kidney tubules
130
What happens to the molecules not reabsorbed into the blood?
* They are released as urine and this includes urea, excess ions and excess water
131
Why do glucose levels not change after the kidney filters it?
* Because although it is filtered out of the blood, it is all reabsorbed
132
Why does the concentration of ions decrease after the kidney filters it?
* Because excess ions are not reabsorbed
133
Why is there no urea in the blood after the kidney filters it?
* Because urea is a waste product, none is reabsorbed back into the blood because we don’t need it
134
What happens when your kidney fails?
* Kidney failure is when your kidneys stop working.
* This means waste products build up which can be harmful to the body, and eventually results in death
135
How can kidney failure be treated?
* Kidney transplants or dialysis
136
What does dialysis do?
* Performs the function of the kidneys which is carried out using an artificial membrane
* It acts as an artificial kidney and keeps people alive while they wait for a
transplant
137
What happens during dialysis?
* During dialysis, the patient’s ‘impure’ blood with excess water, mineral ions and urea is passed through a dialysis machine which contains a semi-permeable membrane surrounded by dialysis fluid that separates the blood and the dialysis fluid
* This membrane will only allow smaller molecules like water, ions and urea through but will not allow larger molecules like blood cells and proteins through
* Useful ions and glucose are not lost from the blood but urea, excess ions and water diffuse across the membrane.
138
Why are useful ions and glucose not lost from the blood during dialysis?
* Dialysis has the same concentrations of ions and glucose as healthy blood, so it does not diffuse across the partially permeable membrane
139
What does dialysis fluid contain?
* It contains the concentrations of water, ions and urea of healthy blood – meaning it contains no urea, some water and some ions
140
Why does the dialysis fluid need to have specific amounts of each substance?
* Because it forms a concentration gradient between the patient’s blood and the dialysis fluid, causing all the urea to diffuse from patient’s blood into fluid, some ions to diffuse from blood to fluid and some water to move by osmosis into the fluid across the semi-permeable membrane
141
Why are both the dialysis fluid and the blood of the patient constantly replenished and replaced?
* To maintain a steep concentration gradient for urea, ions and water to diffuse across
* This causes the patient’s blood to contain no urea and to contain normal levels of ions and water
142
How often does a patient have to have dialysis?
* It has to be done three times a week, with the process itself taking three to
four hours.
143
What are the pros of dialysis?
* No need to wait for donor
* No risk of immune rejection
* No immunosuppressants
144
What are the cons of dialysis?
* It is expensive
* You have to eat a controlled diet (to not produce too much urea)
* Inconvenient and time consuming; need to visit a hospital several times a week for several hours
* There is a risk that excess ions, water and urea will build up between sessions which can be dangerous, leaving patients feeling ill
* Possibility of blood clots forming, the
145
What are the pros of kidney transplants?
* Allows patient to lead normal life with little inconvenience, don't have to visit the hospital as regularly
* Cheaper than dialysis in the long-run
146
What are the cons of kidney transplants?
* Risk of immune rejection as a result of the immune system recognising the antigens on the donor organ as foreign - the chance of this happening can be reduced by using immunosuppressant drugs.
* Immunosuppressants; could forget to take and increases risk of other infections
* Shortage of kidney donors, so long waiting list; some could die before even getting a transplant
* Kidneys do not last forever
147
Name problems with the kidneys that require dialysis or transplants
* Damaged due to injury
* Polycystic kidneys (genetic)
* Bacterial infections
* Kidney failure
148
What happens during puberty?
* Reproductive hormones begin to be released.
* These causes secondary sexual characteristics to develop in men and women and eggs to mature in women.
149
What is the main male reproductive hormone?
* Testosterone produced by the testes
* It stimulates sperm production
150
What is the main female reproductive hormone?
* Oestrogen produced in the ovary
* Produces physical changes and is involved in the menstrual cycle
151
What is the menstrual cycle?
* The menstrual cycle is the process the body undergoes each month to prepare for
potential pregnancy.
152
What happens during the menstrual cycle?
* It begins with the lining of the uterus breaking down, and the woman has her period.
* The layer then builds up again, until ovulation (day 14) occurs- an egg is released from the ovary and moves to the uterus via the fallopian tube.
* If a fertilised egg has not been embedded in the lining after 28 days, it begins to break down and the cycle continues.
153
What is ovulation?
* Eggs beginning to mature and one being released approximately every 28 days
154
What four hormones control the menstrual cycle?
* FSH
* LH
* Oestrogen
* Progesterone
155
What is FSH secreted by and what does it cause?
* Secreted by the pituitary gland
* Causes maturation of an egg in the ovary within a structure called a follicle
* Stimulates ovaries to produce oestrogen
156
What is LH secreted by and what does it cause?
* Secreted by the pituitary gland
* Produced as a result of the hormone oestrogen
* Stimulates the release of the egg from the ovary, triggering ovulation
157
What is oestrogen secreted by and what does it cause?
* Produced in the ovaries, secreted as a result of FSH
* Causes the lining of the uterus to grow again after menstruation
* Stimulates the production of LH and inhibits the secretion of more
FSH
158
What is progesterone secreted by and what does it cause?
* Produced in the ovaries and secreted from the empty egg follicle.
* Maintains the lining of the uterus (in the second half of the cycle) so it's ready to receive a developing embryo, and supports a pregnancy if the egg is fertilised
* Inhibits the release of both FSH and LH
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Describe the trend in blood oestrogen level
* It increases to prepare for ovulation and decreases when ovulation begins
160
Name oral contraceptives
* Mixed pill (contains oestrogen and progesterone)
* Progesterone pill
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Why must contraceptive pills be taken regularly?
* The contraceptive pill must be taken regularly or the bodies own hormones will be
released, leading to an egg maturing.
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How do contraceptive pills prevent pregnancies?
* Oestrogen levels are constantly high, inhibiting FSH so no eggs mature.
* The lining also stops developing and the mucus in the cervix becomes thick
so sperm cannot move through
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What are the cons of the mixed pill?
* Some possible side effects include changes in mood, mood swings,
depression, breast pain or tenderness, breast enlargement, increased blood
pressure
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How does the progesterone pill differ to the mixed pill?
* This has less side effects in comparison to the mixed pill.
165
Describe the use of contraceptive patches and how long does it last?
* The contraceptive patch contains oestrogen and progesterone.
* It is small and is stuck on the skin
* Lasts for one week
166
How long do contraceptive implants last?
* Lasts for three years
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How long does the contraceptive injection last?
* Lasts for 2 to 3 months
168
What is an IUD?
* The plastic intrauterine device (IUD) is T shaped and is inserted into the uterus that releases progesterone
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How do contraceptive implants, injections and IUD prevent pregnancies?
* They release a continuous amount of progesterone which inhibit the maturation and release of eggs
* This prevents the ovaries from releasing the egg, thickens the mucus in cervix so sperm cannot swim and stops fertilised eggs from embedding in the uterus
170
What do non-hormonal methods of contraception do?
* These stop sperm fertilising the egg.
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Name non-hormonal methods of contraception
* Spermicides
* Condoms/ Diaphragm
* Sterilisation
* Copper intrauterine devices
* Abstinence
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Name barrier methods
* Condoms
* Diaphragms
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How are condoms used and what are they used for?
* Condoms are either worn over the penis or are inside the vagina and prevents the sperm from reaching the egg
* They also prevent the individual from contracting sexually transmitted diseases.
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What is the problem with condoms?
* A problem is that it can tear and therefore let sperm through.
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How are diaphragms used?
* A diaphragm is a plastic cup which is positioned over the cervix
* It is used with spermicide
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How do copper intrauterine devices prevent pregnancies?
* Works by killing sperm in the uterus and stopping any fertilised embryos from implanting in the uterus lining.
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How do spermicidal agents work?
* A chemical method that kill or disable sperm
* But are only 70% to 80% effective
178
When would you abstain from intercourse (as a method of contraception)?
* When an egg may be in the oviduct (during ovulation)
179
What is the surgical process for males and females as a contraceptive?
* Sterilisation which involves cutting and tying the fallopian
tubes or sperm duct.
* This lasts forever.
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What are fertility drugs used for?
* Fertility drugs are used to increase the chance of pregnancy.
* The main hormones used are FSH and LH because they stimulate the
maturation and release of the egg.
* The woman can then become pregnant normally.
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What is IVF?
* IVF is a treatment that involves giving a mother FSH and LH to stimulate the maturation of several eggs
182
How does IVF work?
1) Mother is given FSH and LH to stimulate maturation of several eggs
2) The eggs are collected from the mother and fertilised by sperm from the father in the laboratory
3) The fertilised eggs develop into embryos
4) At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus (womb)
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What are the cons of IVF?
* It is physically stressful as women may have reactions to the hormones, such
as feeling sick.
* It is emotionally stressful because it may not work- success rate for IVF is 26%
* It can lead to multiple births - unexpected and may be a risk to the babies and the mother.
* Can be expensive if the process needs to be repeated
184
What are the pros of IVF?
* Provides a way for an infertile couple to have a child.
185
What is negative feedback?
* Negative feedback is when the body responds to an increase or decrease in a factor by returning it back to its original level.
186
Explain how thyroxine regulates metabolic rates in terms of negative feedback
* The levels of thyroxine are controlled by negative feedback.
* When the levels increase, it is detected by receptors in the brain
* This inhibits the release of TSH
* This inhibits the release of thyroxine, so levels fall
187
What happens when adrenaline is produced in times of stress?
* Increased heart rate and breathing rate to deliver more oxygen and glucose to the brain and muscles for respiration
* Glycogen stored in liver is converted to glucose for respiration
* Pupils dilate to let in more light
* Blood flow to muscles is increased
* Blood flow to digestive system is decreased
188
Why do plants need hormones?
* Plants need hormones to coordinate and control growth.
* They are also needed for tropisms
* Hormones move from the place they are made to where they are needed in order to produce the appropriate response
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What are the two tropisms?
* Phototropism, the response to light, and gravitropism or
* Geotropism/ gravitropism, the response to gravity.
190
Where do hormones move to and from?
* Hormones move from the place they are made to where they are needed in order to produce the appropriate response
191
What do most plants show in terms of phototropism?
* Most plants show positive phototropism because they grow towards the light source.
192
Explain what happens when the plant is exposed to light on one side
* The plant is exposed to light on one side
* Auxin, a hormone, moves to the shaded side of the shoot.
* Auxin stimulates cells to grow more here.
* This means the shoot bends towards the light.
* The plant receives more light, meaning photosynthesis can occur at a faster rat
193
What do most shoots show in terms in gravitropism?
* Most shoots show negative gravitropism as they grow away from gravity.
194
Explain what happens when a shoot is horizontal
* Auxin moves to the lower side.
* The cells of the shoot grow more on the side with most auxin, so it stimulates cells to grow more here.
* This makes the shoot bend and grow away from the ground.
* This is beneficial as light levels are likely to be higher further away from the ground.
195
What do most roots show in terms of gravitropism?
* Most roots show positive gravitropism as they grow towards gravity.
196
Explain what happens if a root is horizontal
* Auxin moves to the lower side.
* The cells of the root grow more on the side with less auxin, so it stimulates cells to grow on the upper side.
* This makes the root bend and grow downwards.
* This is beneficial as there are more likely to be increased levels of water and nutrients lower down, and it provides stability for the plant.
197
What happens to a plant when there are unequal distributions of auxin?
* This causes unequal growth rates in plant roots and shoots
198
What happens to a plant when there are equal distributions of auxin?
* When the auxin distribution becomes equal on both sides it grows straight in that directions.
199
How can you investigate the effect of light or gravity on newly germinated seedlings?
* You can investigate the effect of light or gravity on newly germinated seedlings by varying conditions.
* Placing in cardboard box and shining light from one side
* Attaching a petri dish containing the seedlings to a wall (effects of gravity)
200
Why are gibberellins important?
* They stimulate seed germination
201
Why is ethene important?
* They are involved in cell division and ripening of fruits
202
How do negative feedback systems work?
* They work to maintain a steady state; if a factor in the internal environment increases, changes take place to reduce it and restore the original level; if a factor in the internal environment decreases, changes take place to increase it and restore the original level
203
What are plant growth hormones used in?
* Agriculture and horticulture
204
How can humans use plant growth hormones?
* To alter plant growth.
205
Why do humans use plant growth hormones?
* To increase yield, obtain desirable features and to lower costs.
206
What are auxins used as?
* Weed killers
* Rooting powders
* Promoting growth in tissue culture
207
Why are auxins used as weed killers?
* Many weeds are broad-leaved
* Weedkillers, containing auxin, have been synthesised so they only
affect broad-leaved plants
* The increased amount of auxin causes the cells to grow too rapidly
* This results in the weed dying
208
Why are auxins used as rooting powders?
* Plants with desirable features are cloned to make more plants with the
same feature
* One way to clone a plant is to take a cutting from the original plant
* Rooting powder containing auxin is applied to it and it is placed in the
ground
* Roots grow and the new plant begins to grow very quickly
209
Why are auxins used to promote growth in tissue culture?
* Another way to clone a plant is to use tissue culture
* Cells from the plant are taken are placed in a growth medium containing lots of nutrients
* Hormones such as auxins are added
* The cells begin to form roots and shoots
210
What are ethenes used for?
* They’re used in the food industry to control ripening of fruit during storage and transport
211
Why is ethene used in the food industry?
* Fruit is picked when it is not ripe
* It is firm which means that during transport it gets less bruised and damaged
* When it is needed to be sold, it is exposed to ethene and warmer
temperatures
* Ethene is involved in controlling cell division and stimulates enzymes that
result in fruit ripening.
* This reduces wastage as more fruit is suitable to be sold and it does not ripen
too early
212
What is gibberellins be used for?
* End seed dormancy, promote flowering, increase fruit siz
213
How are gibberellins used in the brewing industry?
* In the brewing industry, the germination rate of barley seeds is
increased to make malt
214
How can gibberellins be used to promote flowering?
* Instead of requiring certain conditions such as longer days and low
temperatures to flower, applying this hormone allows it to flower in any
conditions and with bigger flowers.
215
How can be gibberellins be used to increase fruit size?
* The seeds in fruit produce gibberellins to increase fruit size.
* This means that seedless fruit is generally smaller.
* Seedless fruit can be sprayed with gibberellins to increase their size.
