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1 a Hormone is any member of a class of signaling molecules produced by glands in multicellular organisms that are transported by the circulatory system to target distant organs to regulate physiology and behavior.
b Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct.
2 Coordination and control by hormones differs from coordination and control by the nervous system. Nervous control is very rapid and integral for immediate action, coordination and control, and receiving and interpreting messages from your environment. The rapid control is achieved via a network of neurons in the central and peripheral nervous systems (CNS and PNS).
To understand rapid control you must understand how the neurons function. The neurons connect onto each other and a rapid electrical impulse is transmitted from one to the other (the basis of which is ion channels opening and closing and changing the potential difference across the membrane of the neuron relative to its surroundings).
These events occur speedily and efficiently- going from sensory neurons in your skin (all part of the PNS) or sense organs straight to the CNS (brain and spinal cord). There the information is processed, and sent back along motor neurons (also in the PNS) to the effectors (usually muscles, but can be glands or organs) in order to elicit a response from them. This occurs in a matter of milliseconds.
On the other hand, the endocrine system controls functions which take much longer to come into effect. This includes growth and development, homeostasis (which is keeping the systems balanced in the body), and signalling for longer term responses. You do not grow all at once, or reach puberty in a millisecond.
The way in which the endocrine system controls functions over a long period pf time is via the release of specific hormones from specific glands and organs which target the cells or organs for which the effect is meant.
The types of functions controlled by the endocrine system include maturation of an individual during puberty, milk production and release in female mammals, blood glucose and sodium levels, and growth of all tissues approaching, during, and after puberty.
3 The pituitary gland is sometimes called the master gland of the endocrine system because it controls the function of most other endocrine glands and is therefore sometimes called the master gland. In turn, the pituitary is controlled in large part by the hypothalamus, a region of the brain that lies just above the pituitary. By detecting the levels of hormones produced by glands under the pituitary’s control (target glands), the hypothalamus or the pituitary can determine how much stimulation the target glands need.
4 a If pituitary gland doesn’t produce enough growth hormone, growth can slow. A lack of growth hormone causes growth hormone deficiency. This can cause a child to be very short to have very low bone density and muscle strength.
b If pituitary gland continued to produce lots of growth hormone in an adult. In adults, excessive growth hormone for a long period of time produces a condition known as acromegaly, in which patients have swelling of the hands and feet and altered facial features. These patients also have organ enlargement and serious functional disorders such as high blood pressure, diabetes and heart disease. Over 99% of cases are due to benign tumors of the pituitary gland, which produce growth hormone. This condition is more common after middle-age when growth is complete so affected individuals do not get any taller.
1 a Insulin is a hormone produced in the pancreas by the islets of Langerhans, which regulates the amount of glucose in the blood. The lack of insulin causes a form of diabetes.
b Diabetes is a disease in which the body’s ability to produce or respond to the hormone insulin is impaired, resulting in abnormal metabolism of carbohydrates and elevated levels of glucose in the blood
c glycogen , a polysaccharide that is the chief carbohydrate storage material in animals, being converted to glucose by depolymerization; it is formed by and largely stored in the liver, and to a lesser extent in muscles, and is liberated as needed.
2 a In response to an increase in blood glucose level above the normal level, the pancreas produces a hormone called insulin which is released into the bloodstream. Insulin causes glucose to move from the blood into cells, where it is either used for respiration or stored in liver and muscle cells as glycogen.
b When blood sugar drops too low, the level of insulin declines and other cells in the pancreas release glucagon, which causes the liver to turn stored glycogen back into glucose and release it into the blood.
c Many people who live with diabetes don’t feel any particular symptoms, unless they are experiencing hyperglycemia (glucose level is too high) or hypoglycemia (glucose level is too low). Hyperglycemia can cause significant damage to some organs, which then leads to complications of diabetes. These include:
To avoid the complications of diabetes, you must control your blood glucose very well to minimize the risk of hyperglycemia. This will allow you to prevent the complications of diabetes.
3
Differences between type 1 and type 2 diabetes | |
Type 1 Diabetes | Type 2 Diabetes |
Often diagnosed in childhood | Usually diagnosed in over 30 year olds |
Not associated with excess body weight | Often associated with excess body weight |
Often associated with higher than normal ketone levels at diagnosis | Often associated with high blood pressure and/or cholesterol levels at diagnosis |
Treated with insulin injections or insulin pump | Is usually treated initially without medication or with tablets |
Cannot be controlled without taking insulin | Sometimes possible to come off diabetes medication |
4 Insulin and glucagon have both similarities and differences. Both are hormones secreted by the pancreas but they are made from different types of cells in the pancreas. Both help manage the blood glucose levels in the body but they have opposite effects. Both respond to blood glucose levels but they have opposite effects.
During digestion, foods that contain carbohydrates are converted into glucose. Most of this glucose is sent into your bloodstream, causing a rise in blood glucose levels. This increase in blood glucose signals your pancreas to produce insulin.
The insulin tells cells throughout your body to take in glucose from your bloodstream. As the glucose moves into your cells, your blood glucose levels go down. Some cells use the glucose as energy. Other cells, such as in your liver and muscles, store any excess glucose as a substance called glycogen. Your body uses glycogen for fuel between meals.
Glucagon works to counterbalance the actions of insulin.
About four to six hours after you eat, the glucose levels in your blood decrease, triggering your pancreas to produce glucagon. This hormone signals your liver and muscle cells to change the stored glycogen back into glucose. These cells then release the glucose into your bloodstream so your other cells can use it for energy.
This whole feedback loop with insulin and glucagon is constantly in motion. It keeps your blood sugar levels from dipping too low, ensuring that your body has a steady supply of energy.
Question:
1
Differences between type 1 and type 2 diabetes | |
Type 1 diabetes | Type 2 diabetes |
Symptoms usually start in childhood or young adulthood. People often seek medical help, because they are seriously ill from sudden symptoms of high blood sugar. | The person may not have symptoms before diagnosis. Usually the disease is discovered in adulthood, but an increasing number of children are being diagnosed with the disease. |
Episodes of low blood sugar level (hypoglycemia) are common. | There are no episodes of low blood sugar level, unless the person is taking insulin or certain diabetes medicines. |
It cannot be prevented. | It can be prevented or delayed with a healthy lifestyle, including maintaining a healthy weight, eating sensibly, and exercising regularly. |
2 a It is not always true for people with type 1 diabetes, because for type 1 diabetes, insulin has long been the essential treatment method. Blood glucose monitoring, frequent insulin injections, even insulin pumps are used to help diabetics control their glucose levels and avoid dangerous spikes and dips in their blood sugar. it is found that transplanting purified human pancreatic islet cells into type 1 diabetics can lead to nearly normal glycemic control and no longer being reliant on insulin.
b Treatment with insulin injections is relatively uncommon for people with type 2 diabetes. Because people with type 2 diabetes don’t respond normally to insulin anymore, so glucose stays in the bloodstream and doesn’t get into the cells. This causes blood glucose levels to go too high.
4 Different methods used to treat type 1 diabetes and type 2 diabetes, linking these methods to how the types of diabetes are caused. High blood sugar levels can make teens with type 2 diabetes feel sick, so their treatment plan involves keeping their blood sugar levels within a healthy range while making sure they grow and develop normally. To do that, they need to:
The good news is that sticking to the plan can help people feel healthy and avoid diabetes problems later.
B11.4 AQA GCSE Biology B11 The Role of Negative Feedback: Page No. 167
1 Negative feedback is a regulatory mechanism in which a ‘stimulus’ causes an opposite ‘output’ in order to maintain an ideal level of whatever is being regulated.
There are many negative feedback pathways in biological systems, including:
2 Thyroxine is the main hormone secreted into the bloodstream by the thyroid gland. Thyroid hormones play vital roles in regulating the body’s metabolic rate, heart and digestive functions, muscle control, brain development and maintenance of bones.
This hormone production system is regulated by a negative feedback loop so that when the levels of the thyroid hormones, thyroxine and triiodothyronine increase, they prevent the release of both thyrotropin-releasing hormone and thyroid stimulating hormone. This system allows the body to maintain a constant level of thyroid hormones in the body.
3 In Ethiopia up to 40% of the population, both adults and children, do not get enough iodine in their diet. Around 40% of the population also have non-communicable diseases caused by low thyroxine levels.
4 a Because lack of iodine make the body susceptible to non-communicable disease.
b Way to overcome the problems of diseases linked to low thyroxine levels. Adrenaline is a hormone released from the adrenal glands and its major action, together with noradrenaline, is to prepare the body for ‘fight or flight’.
Adrenaline is released mainly through the activation of nerves connected to the adrenal glands, which trigger the secretion of adrenaline and thus increase the levels of adrenaline in the blood. This process happens relatively quickly, within 2 to 3 minutes of the stressful event being encountered. When the stressful situation ends, the nerve impulses to the adrenal glands are lowered, meaning that the adrenal glands stop producing adrenaline.
1 Negative feedback is a regulatory mechanism in which a ‘stimulus’ causes an opposite ‘output’ in order to maintain an ideal level of whatever is being regulated.
There are many negative feedback pathways in biological systems, including:
2 Thyroxine is the main hormone secreted into the bloodstream by the thyroid gland. Thyroid hormones play vital roles in regulating the body’s metabolic rate, heart and digestive functions, muscle control, brain development and maintenance of bones.
This hormone production system is regulated by a negative feedback loop so that when the levels of the thyroid hormones, thyroxine and triiodothyronine increase, they prevent the release of both thyrotropin-releasing hormone and thyroid stimulating hormone. This system allows the body to maintain a constant level of thyroid hormones in the body.
3 In Ethiopia up to 40% of the population, both adults and children, do not get enough iodine in their diet. Around 40% of the population also have non-communicable diseases caused by low thyroxine levels.
4 a Because lack of iodine make the body susceptible to non-communicable disease.
b Way to overcome the problems of diseases linked to low thyroxine levels. Adrenaline is a hormone released from the adrenal glands and its major action, together with noradrenaline, is to prepare the body for ‘fight or flight’.
Adrenaline is released mainly through the activation of nerves connected to the adrenal glands, which trigger the secretion of adrenaline and thus increase the levels of adrenaline in the blood. This process happens relatively quickly, within 2 to 3 minutes of the stressful event being encountered. When the stressful situation ends, the nerve impulses to the adrenal glands are lowered, meaning that the adrenal glands stop producing adrenaline.
1 Hormones are the drivers of human reproduction, responsible
For secondary sexual development (puberty)
controlling the menstrual cycle.
Oestrogen in female produced by ovary. Testosterone in male produced by testes and stimulates sperm production
2 Similarities between boys and girls at puberty
Differences between boys and girls at puberty
The physical changes for females during puberty experience are marked by the following features of growth:
The physical changes during puberty for males that occur are different in a number of ways. The developments that a boy undergoes during adolescence are:
3 a The role of hormones in the menstrual cycle. The menstrual cycle is an approximately 28-day cycle which results in the release of a mature egg from the ovary. This egg may then go on to become fertilized or may be released, unfertilized, along with the lining of the uterus. The latter may take place with monthly bleeding called menstruation — day 1 of the 28-day cycle. This delicate cycle results from a complicated interplay among several hormones.
Follicle-Stimulating Hormone (FSH)
This hormone stimulates the development of new follicles as well as the production of the hormone estrogen. During this phase, called the follicular phase of the menstrual cycle, an increase in FSH occurs. This increase stimulates the growth and development of new follicles, one of which will develop into the ovulated egg.
Estrogen
Estrogen is responsible for the continuing development of follicles within the ovaries. However, the effects of estrogen are not limited to within the ovaries. In the uterus, the rising levels of this hormone play an important role in thickening the endometrium — a layer of the uterus. It also causes the mucus within the cervix to become thicker. Finally, estrogen release acts as a suppressor of its own release — called a negative feedback loop. It also acts to suppress the production of LH, until just before ovulation. Afterward, estrogen actually stimulates the release of large amounts of LH in what is called the mid-cycle LH surge.
Luteinizing Hormone (LH)
LH peaks in the middle of the 28-day cycle. This is typically called the LH surge and serves as a signal that ovulation — the release of the mature egg from one of the two ovaries — is about to occur. During this peak of LH release, concentration of this hormone becomes ten times higher than usual. Ovulation generally occurs within 9 hours of the LH surge. The egg releases from the ovary, able to be fertilized for about 1-2 days after it releases. If it does not become fertilized, it begins to disintegrate or releases along with the inner lining of the uterus as part of the monthly menstruation cycle.
Progesterone
Once ovulation has occurred, the hormone progesterone releases from a structure called corpus luteum. Progesterone makes the mucus around the entrance of the uterus thick and sticky, preparing for a potential pregnancy. If the released egg becomes fertilized, it will become implanted in the wall of the uterus and the fetus will begin to grow.
b differences between the production of mature eggs in women and mature sperm in men.
Size
Egg: One of the largest cells in the female body.
Sperm: One of the smallest cells in the female body.
Produced in
Egg: Produced in the ovary of a female.
Sperm: Produced in the Testicles of a male.
Appearance
Egg: Round shaped and consists of a large amount of cytoplasm before conception.
Sperm: Oval head on the top and has a rigid middle with a slimly tail in the back to allow it to swim.
Amount
Egg: Only a single egg cell is produced during once menstruation cycle.
Sperm: Millions of cells are released during a single ejaculation.
Temperature
Egg: Requires warm body temperature for sustenance.
Sperm: Requires approximately two degrees lesser than body temperature.
Life-Span
Egg: Have a short life span 12-24 hours.
Sperm: Longer life span surviving for 3-5 days.
Storability
Egg: Cannot be stored.
Sperm: Can be frozen and stored.
B11.6 Hormones and the Menstrual Cycle AQA GCSE Biology B11 Hormonal Cordination Kerboodle Answers:Page No. 171
1 a The four hormone that control the menstrual cycle are:
FSH:
LH:
OESTROGEN:
PROGESTERONE:
b the lining of the uterus builds up each month because of the interaction of four hormones control the maturing and release of an egg from the ovary and the buildup of lining of the uterus in the menstrual cycle
2 a On 28th day women have menstrual cycle
b LH and FSH are the hormones that encourage ovulation. Both LH and FSH are secreted by the pituitary gland in the brain. At the beginning of the cycle, LH and FSH levels usually range between about 5-20 mlU/ml. Most women have about equal amounts of LH and FSH during the early part of their cycle. However, there is a LH surge in which the amount of LH increases to about 25-40 mlU/ml 24 hours before ovulation occurs. Once the egg is released by the ovary, the LH levels goes back down.
c Oestrogen hormone control the buildup of lining of uterus
3 The menstrual cycle is a recurring process which takes around 28 days. During the process, the lining of the uterus is prepared for pregnancy. If pregnancy does not happen, the lining is then shed. This is known as menstruation.
The length of menstrual cycle has been assumed to be 28 days (which is the average among women). The entire duration of a Menstrual cycle can be divided into four main phases:
Menstrual phase (day 1-5)
Menstrual phase begins on the first day of menstruation and lasts till the 5th day of the menstrual cycle. The following events occur during this phase:
Follicular phase (day 1-13)
This phase also begins on the first day of menstruation, but it lasts till the 13th day of the menstrual cycle. The following events occur during this phase:
On the 14th day of the cycle, the pituitary gland secretes a hormone that causes the ovary to release the matured egg cell. The released egg cell is swept into the fallopian tube by the cilia of the fimbriae. Fimbriae are finger like projections located at the end of the fallopian tube close to the ovaries and cilia are slender hair like projections on each Fimbria.
Luteal phase (day 15-28)
This phase begins on the 15th day and lasts till the end of the cycle. The following events occur during this phase:
Several hormones control this cycle – for example, they are involved in controlling the release of an egg each month from an ovary, and changing the thickness of the uterus lining.
Hormone | Produced | Role |
FSH (follicle stimulating hormone) | Pituitary gland | Causes an egg to mature in an ovary. Stimulates the ovaries to release oestrogen |
Oestrogen | Ovaries | Stops FSH being produced (so that only one egg matures in a cycle). Repairs and thickens the uterus lining. Stimulates the pituitary gland to release LH. |
LH (luteinising hormone) | Pituitary gland | Triggers ovulation (the release of a mature egg) |
Progesterone | Ovaries | Maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy. |
1 Contraception (birth control) prevents pregnancy by interfering with the normal process of ovulation, fertilization, and implantation. There are different kinds of birth control that act at different points in the process.
2 a one similarity between each contraceptive is that all the form of contraceptive uses the progesterone.
b The pill uses hormones to prevent pregnancy. The combination pill contains estrogen and progestin. Birth control pills prevent pregnancy by stopping your ovaries from releasing an egg each month. The hormones thicken the cervical mucus, which makes it harder for sperm to swim to the egg. The hormones also alter the lining of the uterus, so that if an egg does get fertilized, it will be unable to implant in the uterus.
Contraceptive
The patch contains the same hormones as the pill, estrogen and progestin. The patch works just like the pill. The hormones prevent an egg from being released and change both the cervical mucus and uterine lining..
The implant is made of medical plastic that is sterile and soft. This contraceptive rod is 40mm (1.5 inches) long and 2mm (0.08 inches) in diameter. The implant, once inserted, is effective for a maximum of three years. Once the birth control implant is inserted, it begins releasing small doses of the synthetic progesterone. it is released slowly and steadily over the course of the three year period.
c Contraceptive implant is most effective of all of these because the contraceptive implant can last up to three years. A tiny tube is inserted under the skin by the doctor and slowly release progesterone. This 99.95% effective
3 By comparing the effectiveness of the three main types of contraception – hormone-based contraception, barrier methods, and surgical methods we got as follows:
Birth Control Methods Comparison Charts
Barrier method:
Abstinence
Surgical method:
Surgical “irreversible” methods of contraception.
These include:
1 In vitro fertilisation (IVF) is a process of fertilisation where an egg is combined with sperm outside the body, in vitro (“in glass”). The process involves monitoring and stimulating a woman’s ovulatory process, removing an ovum or ova (egg or eggs) from the woman’s ovaries and letting sperm fertilise them in a liquid in a laboratory. The fertilised egg (zygote) undergoes embryo culture for 2–6 days, and is then transferred to the same or another woman’s uterus, with the intention of establishing a successful pregnancy.
2 a Artificial hormone can be used to help people overcome infertility and conceive naturally.artificial FSH can be used as a fertility drug . it stimulate the eggs in the ovary to mature and also triggers oestrogen production. An artificial LH can then be used to triggers ovulation. If women who is not ovulating as a result of a lack of her own FSH is treated in this way she may be able to get pregnant naturally.
b Fertility drugs are also used in IVF (In vitro fertilisation).
IVF is a form of fertility treatment used if the oviducts have been damaged or blocked by infection, if a donor egg has to be used, or if there is no obvious cause for long-term infertility.
4 Advantage of artificial hormone to control the fertility:
Risks and disadvantages
1 a Phototropism: the orientation of a plant or other organism in response to light, either towards the source of light ( positive phototropism ) or away from it ( negative phototropism ).
b Gravitropism: Gravitropism (also known as geotropism) is a turning or growth movement by a plant or fungus in response to gravity. It is a general feature of all higher and many lower plants as well as other organisms
2 A ‘tropism’ is a growth in response to a stimulus. Plants grow towards sources of water and light, which they need to survive and grow.Auxin is a plant hormone produced in the stem tips and roots, which controls the direction of growth.
Tropisms are directional movement responses that occur in response to a directional stimulus. Plants are not able to relocated if they happen to start growing where conditions are suboptimal. However, plants can alter their growth so they can grow into more favorable conditions, To do so requires the ability to detect where the conditions are better and then alter their growth so they can “move” in the appropriate direction. One of the most commonly observed tropic responses in plants is phototropism, in which plant stems grow towards light. As anyone who has grown plants near a window knows, the plants tend to lean towards the window where the light is usually stronger than inside the room. Another commonly observed tropic responses is gravitropism, where a plant will grow so that it stays oriented relative to the source of gravity (the earth). Thus, if a plant is knocked down the shoot will grow faster on the lower side until the shoot is more-or-less standing up again.
Tropic responses result from differential growth. Phototropism is a blue-light-dependent response controlled by the action of specific blue light photoreceptors called phototropins. Gravitropism is dependent on the presence of starch-filled plastids (amyloplasts) in specialized cells. When the orientation of the cells changes, the mass of the starch-filled plastids causes them to sink to the lower end of the cell. The tumbling of the amyloplasts triggers, through unknown mechanisms, differential growth that causes curvature to develop.
1 a Plant hormones (also known as phytohormones) are chemicals that regulate plant growth. Plant hormones are signal molecules produced within the plant, and occur in extremely low concentrations. Hormones regulate cellular processes in targeted cells locally and, moved to other locations, in other functional parts of the plant
b Rooting hormone acts as a catalyst for the new roots and protects the cuttings from fungus and disease that may have been introduced during the cutting process. A rooting hormone is used in plant propagation to grow new roots on cuttings.
2 Auxin can be used to make effective weed killers. If auxin solution spray on to the leaves of plant, the hormone is absorbed. The extra auxin can send the plant into rapid uncontrolled growth, killing them. Selective weedkillers kill some plants but not others. This can be useful for getting rid of dandelions in a lawn without killing the grass, or getting rid of thistles in a field without killing the wheat plants. The selective weedkiller contains growth hormone that causes the weeds to grow too quickly. The weedkiller is absorbed in larger quantities by the weeds than the beneficial plants.
3 Plant hormones can be used to increase the food available to feed the world’s growing population. They can increase the productivity and reduce the hunger in a nation and also provides economic stability. As the population increases the resources must be there to feed the population.
1 a After eating, blood Glucose level rises for both the individuals
b 80-120 mg/l is the range of blood glucose concentration of the person without diabetes.
c 50-320 mg/l is the range of blood glucose concentration of the person with diabetes
d Insulin helps your body absorb glucose for energy. So Insulin injections are important to maintain the blood glucose level in Diabetes Patients.
e People with diabetes have to monitor the amount of carbohydrate in their diet. Because When people eat a food containing carbohydrates, the digestive system breaks down the digestible ones into sugar, which enters the blood. As blood sugar levels rise, the pancreas produces insulin, a hormone that prompts cells to absorb blood sugar for energy or storage. As cells absorb blood sugar, levels in the bloodstream begin to fall. When this happens, the pancreas start making glucagon, a hormone that signals the liver to start releasing stored sugar. This interplay of insulin and glucagon ensure that cells throughout the body, and especially in the brain, have a steady supply of blood sugar. Carbohydrate metabolism is important in the development of type 2 diabetes, which occurs when the body can’t make enough insulin or can’t properly use the insulin it makes.
Type 2 diabetes usually develops gradually over a number of years, beginning when muscle and other cells stop responding to insulin. This condition, known as insulin resistance, causes blood sugar and insulin levels to stay high long after eating. Over time, the heavy demands made on the insulin-making cells wears them out, and insulin production eventually stops.
2 a The main events of the menstrual cycle.
Phases of Menstrual cycle
The day count for menstrual cycle begins on the first day of menstruation when blood starts to come out of the vagina. In this section, the length of menstrual cycle has been assumed to be 28 days (which is the average among women). The entire duration of a Menstrual cycle can be divided into four main phases:
Menstrual phase (From day 1 to 5)
Follicular phase (From day 1 to 13)
Ovulation phase (Day 14)
Luteal phase (From day 15 to 28)
Menstrual phase (day 1-5)
Menstrual phase begins on the first day of menstruation and lasts till the 5th day of the menstrual cycle. The following events occur during this phase:
The uterus sheds its inner lining of soft tissue and blood vessels which exits the body from the vagina in the form of menstrual fluid.
Blood loss of 10 ml to 80 ml is considered normal.
You may experience abdominal cramps. These cramps are caused by the contraction of the uterine and the abdominal muscles to expel the menstrual fluid.
Follicular phase (day 1-13)
This phase also begins on the first day of menstruation, but it lasts till the 13th day of the menstrual cycle. The following events occur during this phase:
The pituitary gland secretes a hormone that stimulates the egg cells in the ovaries to grow.
One of these egg cells begins to mature in a sac-like-structure called follicle. It takes 13 days for the egg cell to reach maturity.
While the egg cell matures, its follicle secretes a hormone that stimulates the uterus to develop a lining of blood vessels and soft tissue called endometrium.
Ovulation phase (day 14)
On the 14th day of the cycle, the pituitary gland secretes a hormone that causes the ovary to release the matured egg cell. The released egg cell is swept into the fallopian tube by the cilia of the fimbriae. Fimbriae are finger like projections located at the end of the fallopian tube close to the ovaries and cilia are slender hair like projections on each Fimbria.
Luteal phase (day 15-28)
This phase begins on the 15th day and lasts till the end of the cycle. The following events occur during this phase:
The egg cell released during the ovulation phase stays in the fallopian tube for 24 hours.
If a sperm cell does not impregnate the egg cell within that time, the egg cell disintegrates.
The hormone that causes the uterus to retain its endometrium gets used up by the end of the menstrual cycle. This causes the menstrual phase of the next cycle to begin.
b I Role of FSH in menstrual cycle
Follicle-Stimulating Hormone (FSH)
This hormone stimulates the development of new follicles as well as the production of the hormone estrogen. During this phase, called the follicular phase of the menstrual cycle, an increase in FSH occurs. This increase stimulates the growth and development of new follicles, one of which will develop into the ovulated egg.
ii Role of oestrogen in menstrual cycles.
Estrogen is responsible for the continuing development of follicles within the ovaries. However, the effects of estrogen are not limited to within the ovaries. In the uterus, the rising levels of this hormone play an important role in thickening the endometrium — a layer of the uterus. It also causes the mucus within the cervix to become thicker. Finally, estrogen release acts as a suppressor of its own release — called a negative feedback loop. It also acts to suppress the production of LH, until just before ovulation. Afterward, estrogen actually stimulates the release of large amounts of LH in what is called the mid-cycle LH surge.
Ill Role of LH
LH peaks in the middle of the 28-day cycle. This is typically called the LH surge and serves as a signal that ovulation — the release of the mature egg from one of the two ovaries — is about to occur. During this peak of LH release, concentration of this hormone becomes ten times higher than usual. Ovulation generally occurs within 9 hours of the LH surge. The egg releases from the ovary, able to be fertilized for about 1-2 days after it releases. If it does not become fertilized, it begins to disintegrate or releases along with the inner lining of the uterus as part of the monthly menstruation cycle.
iv Role of progesterone. Once ovulation has occurred, the hormone progesterone releases from a structure called corpus luteum. Progesterone makes the mucus around the entrance of the uterus thick and sticky, preparing for a potential pregnancy. If the released egg becomes fertilized, it will become implanted in the wall of the uterus and the fetus will begin to grow.
3 a In experiment 1 there is no bending of shoot towards the light as the tip is removed. In experiment 2 the tip is removed and replaced on impermeable block then there is no bending because the hormones that show phototropism cannot diffuse through the shoot. In experiment 3 the tip is replaced on agar block which is permeable and does not prevents the hormone. As a result of it the shoot bends.
B It demonstrates that phototropism is a hormonal process.
4 a Oral contraceptives protect against pregnancy by the combined actions of the hormones estrogens and progestin. The hormones prevent ovulation. The pills have to be taken every day as directed and do not work after vomiting or diarrhoea. Side effects of the pill can be nausea, headache, breast tenderness, weight gain, irregular bleeding, and depression.
b The other ways in which contraceptive hormones can be given are by injections which have an effect for 12 weeks in line. They can also be given by Hormonal implants which is having a longer life span of 3 years. It can be given by patches.
c The most common causes of infertility in women are ovulation disorder, blocked fallopian tubes, and age factor. The infertility in women is treated by administering clomiphene injections which will allow them to ovulate after a menstrual period, if this does not work even with increased concentrations ( up to a certain level), they go for Follicle stimulating hormone (FSH) injections coupled with Intra uterine inseminatin (IUI) . This results in hyperstimulation of ovaries leading to multiple ovulation and hence increases the chance of twins or triplets.
d In contraception oestrogen and progesterone are used.
To suppress pregnancy FSH and LH are used and for treatment infirtilitu artificial FS and LH are used to stimulate egg maturation.
5 a Negative feedback is a regulatory mechanism in which a ‘stimulus’ causes an opposite ‘output’ in order to maintain an ideal level of whatever is being regulated.
Thyroxine is the main hormone secreted into the bloodstream by the thyroid gland. Thyroid hormones play vital roles in regulating the body’s metabolic rate, heart and digestive functions, muscle control, brain development and maintenance of bones.
This hormone production system is regulated by a negative feedback loop so that when the levels of the thyroid hormones, thyroxine and triiodothyronine increase, they prevent the release of both thyrotropin-releasing hormone and thyroid stimulating hormone. This system allows the body to maintain a constant level of thyroid hormones in the body.
b Negative feedback control is so important in maintaining homeostasis because homeostasis involves monitoring internal variables and correcting changes by negative feedback mechanisms. Negative feedback mechanisms keep the body within safe limits. In negative feedback, the body’s response cancels the original stimulus. Body temperature, blood glucose, and water balance are controlled by negative feedback mechanisms. Three components – sensors, the brain and effectors – interact to maintain homeostasis Sensors are cells that can detect a specific change in the environment. The brain receives information from the sensors and compares it to a set point. If conditions are different from the set point, the brain sends a message to the effectors. Effectors respond to counteract internal changes.
c Adrenaline is part of the so-called “fight-flight” response to stress that protects you from harm. Adrenaline normally helps to maintain your body’s basic functions (homeostasis) and affects every organ in the body. Increased production and release of adrenaline in response to acute stress enhances its protective functions but may also be detrimental to those at risk.
In response to acute stress, increased adrenaline mostly speeds things up and leads to:
Heightened awareness and alertness to deal with the stressful situation
Increased energy to fight or run
Increased heart rate and force of contraction of the heart, which in a person with heart disease could trigger a heart attack
Increase blood pressure which could also trigger a stroke or heart attack in a susceptible person
Increased breathing to provide more oxygen to your tissues
Mobilizes glycogen (starch) from your liver to convert it to glucose for energy
Increased perspiration
Decreased response to pain
Decrease in bowel function
d Adrenaline is a hormone released from the adrenal glands and its major action, together with noradrenaline, is to prepare the body for ‘fight or flight’.
Adrenaline is released mainly through the activation of nerves connected to the adrenal glands, which trigger the secretion of adrenaline and thus increase the levels of adrenaline in the blood. This process happens relatively quickly, within 2 to 3 minutes of the stressful event being encountered. When the stressful situation ends, the nerve impulses to the adrenal glands are lowered, meaning that the adrenal glands stop producing adrenaline.
Practice questions: Page no. 181
01.1 By plotting the data in Table 1 as a line graph
01.2
01.3 the difference in the blood glucose concentrations of someone with type 1 diabetes compared TO someone who does not have type 1 diabetes. person with diabetes does not produce (enough) insulin (so) glucose / sugar is not absorbed by cells
02.1 How the methods work:
condoms act as a barrier
condoms prevent the sperm entering the female / vagina
IUD prevents implantation
IUD hormone inhibits maturation / release of eggs
Advantages of condoms:
protect against STIs
easy to use / buy
can be used by anyone
very effective if used perfectly
do not affect fertility
Disadvantages of condoms:
can split
not very effective if not used perfectly
may not always have one when needed
Advantages of hormone IUD:
very / more effective
effectiveness does not depend on the person
Disadvantages of hormone IUD:
needs a professional to insert / remove it
can be painful
may cause infection
not suitable for women who have not had a baby
some women may not want to use hormones
some women may not want to have something permanently inside them
3.1 Thyroxine is produced by the thyroid gland. B gland in Figure 1 is the thyroid gland?
3.2 Thyroxine stimulates basal metabolic rate and controls growth and development
3.3 (if) thyroxine level falls
pituitary gland stimulated
to release TSH
(increased TSH) stimulates thyroid to release thyroxine
level increases to normal
(if) level of thyroxine too high
TSH release stops
(so) no more thyroxine released from thyroid
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References:
BBC Bitesize
AQA GCSE Science Kerboodle textbook
Wikipedia
Wikimedia Commons
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This page contains the detailed and easy notes for AQA GCSE Biology Cell Biology for revision and understanding Cell Biology.
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Homeostasis is important for the enzymes as the enzymes control all the reactions of the body and they need optimum condition to work.
Motor Neurone
Sensory Neurone
Relay Neurone
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Example: Knee Jerk Reflexes,
|
| Sensory neurones |
Motor neurones
CEREBRUM (Cerebral Hemisphere) – It is nearly 80% part of the brain
CEREBELLUM – It lies behind the cerebrum and above the medulla oblongata. It is the second largest part of brain and is highly convoluted area which accommodates many neurons.
MEDULLA OBLONGATA or oblong marrow is oblong cylindrical part of the brain. It forms the hindermost part of the brain.
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Magnetic Resonance Imaging (MRI) helps to take the Images of different parts of the brain and relating it with loss of functions of the individual
Problems
For distant vision, ciliary muscle relax making the suspensory ligaments tensed which inturn make the lens thin so that the image is focussed on the retina.
For near vision, ciliary muscle contract making the suspensory ligaments to slack which inturn make the lens thick so that the image is focussed on the retina.
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MYOPIA
HYPERMETROPIA
Contact Lenses
Laser Surgery
Replacement Lens
Hormones
Nervous System
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EXAMPLES
| GLAND | HORMONE | TARGET ORGAN | EFFECT |
| Pituitary | Follicle stimulating hormone (FSH) Thyroid stimulating hormone (TSH) Anti-diuretic hormone (ADH) | Ovaries Thyroid Gland Kidneys | make the female sex hormones estrogen stimulate the gland to release thyroxine which control metabolism controls the water level by causing reabsorption of water |
| Thyroid Gland | Thyroxine | Liver and Kidneys | Controls the metabolism |
| Adrenal Gland | Adrenaline | Liver and Heart | prepares for fight and flight |
| Testes | Testosterone | Male reproductive organs | Developes secondary sexual characterstics |
| Pancreas- | Insulin Glucagon | Liver Liver | Decreases blood glucose levels Increases blood glucose levels |
| Ovaries | Oestrogen Progesterones | Female reproductive organs | Controls the development of egg, menstural cycle and develop secondary sexual characteristics. |
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Glucagon ‘is the hormone
Glycogen is the stored carbohydrate
| TYPE 1 | TYPE 2 |
| Insulin dependent | Insuline independent |
| Body does not produce insulin | Body is resistance to insulin |
| Caused by damage to pancreas | Caused by poor lifestyle and diet |
| Treated with insulin injections | Treated with lifestyle changes |
| Most common in young age | Common in obese people |
| It can be genetic. | It is mostly environmental. |
| Drugs might not be required | Drugs are given to make body to respond to insulin |
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TYPE 1
TYPE 2
FIGHT OR FLIGHT HORMONE
Emergency Hormones
HUMAN REPRODUCTIVE SYSTEM
Male hormone responsible for secondary sexual characters
Female hormone responsible for secondary sexual characters
| Days | Phase | Development |
| Day 1- Day 4 | Mensturation | Shedding of the uterus linning along with the egg. Progesterone falls |
| Day 5- Day 14 | Follicular Phase | Egg is matured in the ovary. Increase in FSH |
| Day 14 | Ovulation | Egg is released. Caused by Lutenizing Hormone |
| Day 14-Day 28 | Luteal Phase | Increase in progesterone and oestrogen which maintains the uterus linning and wait for eggs to fertilize. If not fertilize in next 14 days linning breaks. |
HORMONES OF MENSTURATION
| Hormone | Gland | Effective Days | Effect |
| Follicle Stimulating Hormone (FSH) | Pituitary | Day I-Day 14 | Maturation of egg in the follicle. Stimulate the production of Oestrogen |
| Lutenizing Hormone (LH) | Pituitary | Day 14 | Cause Ovulation |
| Oestrogen | Ovaries | Day 14-Day 28 | Develops uterus lining. Stimulates LH and inhibit FSH |
| Progesterone | Empty egg follicle in the ovaries | Day 14- Day 28 | Maintains linning of uterus and prepare for pregnancy. Inhibits both LH and FSH So no mensturatlon happen during pregnancy. |
Preventing Sperms to reach the egg. Preventing the implantation of the zygote in the uterus.
Barrier Methods: Prevent the sperm to meet the eggs
Hormonal Methods: Prevents the eggs to mature or prevent the implantation of eggs in the uterus.
Chemical Methods: Kills the sperm
Intrauterine Device: Prevent embryo from implanting
Surgical Method: It is permanent contraception
Contraceptive Pills
Contraceptive Pills
Intra Uterine Device
Surgical Methods
VASECTOMY: Male Sterlization
TUBECTOMY: Femal Sterlization
OVULATION PROBLEM
FAULTY TUBES
IMPLANTATION
PREGNANCY DEVELOPMENT
IN VITRO FERTILIZATION
Fertility drugs to stimulate ovulation
Ovary and sperm are collected to perform fertilization.
Fertilized egg is developed in the laboratory giving suitable conditions to develop into an embryo.
Embryo is inserted into the uterus
Develops into a baby.
Plant Hormones
Auxin is produced in the shoot tip. When light falls on auxin it is displaced to the shader side promoting growth of the shader region resulting in growth of shoot towards light.
Gravitropism – The movement of roots towards gravity.
AUXINS
GIBBERLINS
ETHENE
Cytokinin
Caused Cell Division
Abscicic acid
Stress hormone prepared the plant for stress conditions
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The products produced during metabolic reactions like respiration, digestion etc.
Carbon Dioxide
Water
Urea
ULTRAFILTRATION
SELECTIVE REABSORPTION
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Advantages
Disadvantages
Advantages
Disadvantages
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Make sure you have watched the above videos and are familiar with the key definitions before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.