Fact Sheet B2.1 Homeostasis

Transcription

1 Fact Sheet B2.1 Homeostasis Homeostasis What is homeostasis? Why is homeostasis important? State the components that all control systems have. Describe the roles of the above components. Define negative feedback The nervous system and reflex reactions What does the nervous system enable humans to do? Give 2 key features of reflex reactions Why are reflex reactions important? What is the central nervous system (CNS)? What does the CNS do? The maintenance of a constant internal environment The regulation of the internal conditions of a cell or organism To maintain optimal conditions in response to internal and external changes Maintains optimal conditions for enzyme action and all cell functions 1. Receptor cells 2. Coordination centres (such as the brain, spinal cord and pancreas) 3. Effectors (muscles or glands) 1. Detect stimuli (changes in the environment) 2. Receive and process information from the receptors 3. Bring about responses which restore optimal levels The body will act to reverse any change in internal conditions To bring conditions back to their optimal levels React to their surroundings Coordinate their behaviour Fast and automatic (do not involve the conscious part of the brain) They enable us to rapidly move away from objects/ situations that would damage us To keep us safe/ avoid/ limit damage to body The brain and spinal cord Coordinates the action of effectors - Muscles contract - Glands secrete hormones Passes along sensory neurones as electrical impulses How does information from receptors reach the central nervous system (CNS)? How does information from the CNS reach the effectors? Passes along motor neurones as electrical impulses Name the neurones that are found in the CNS and are Relay neurones involved in reflex reactions. Name the junction between 2 neurones Synapse State how information crosses the synapse - A chemical (neurotransmitter) is released - It diffuses across the gap - And initiates (starts) an electrical impulse in the next neurone Name the stages in a reflex arc The brain What does the brain do? What is the brain made of? Stimulus receptor sensory neurone synapse coordination centre (relay neurone) synapse motor neurone effector response Controls complex behaviour Billions of interconnected neurones It has different regions that carry out different functions

2 Name the regions of the brain. 1. Cerebral cortex 2. Cerebellum 3. Medulla 4. Thermoregulatory centre Which brain region coordinates muscle activity to maintain balance? Which brain region is involved with memory, intelligence, learning and consciousness (milc)? Which brain region monitors and controls body temperature? Which brain region coordinates involuntary actions (breathing rate, heart rate, gut movements etc)? HT Why is it difficult to investigate brain function and to treat brain damage and disease? HT How have neuroscientists been able to map the regions of the brain to particular functions? Give a risk of carrying out a procedure on the brain, nervous system or eye. The eye What is the eye? (2) Label the structures on the diagram of the eye Cerebellum Cerebral cortex Thermoregulatory centre Medulla The brain is very complex and delicate 1. Studying patients with brain damage 2. Electrically stimulating different parts of the brain 3. MRI scanning May introduce a pathogen/ cause an infection that damages it A sense organ Containing receptors sensitive to light intensity and colour 1. Cornea 2. Suspensory ligaments 3. Lens 4. Iris 5. Ciliary muscles 6. Sclera 7. Retina 8. Optic nerve Describe the function of the above structures. 1. Protects the eye surface and focuses light as it enters the eye 2. Holds lens in place 3. Focuses light on the retina to produce a clear image 4. Regulates amount of light reaching the retina - to see in dim light and prevent damage in bright light 5. Changes lens shape to focus light on the retina 6. Protects the eye from damage 7. Detects light intensity and colour 8. Transmits impulses to the brain Explain how the structure of each part of the eye relates to its function Tough, transparent, curved to refract light 2. Attached to the ciliary muscles and the lens 3. Flexible so it can change shape to focus light rays 4. Muscles contract/ relax to change pupil size

3 5. Muscles contract/ relax 6. Tough material to protect 7. Contains light receptor cells to detect light 8. Made of sensory neurons to transmit impulses What is accommodation? The process of changing the shape of the lens To focus on near or distant objects What is the purpose of accommodation? To focus the light rays onto the retina So we can see in focus Describe how the eye focusses on near objects. Ciliary muscles contract Suspensory ligaments loosen Lens becomes thicker and refracts light rays strongly Describe how the eye focusses on distant objects. Ciliary muscles relax Suspensory ligaments pulled tight Lens is pulled thin and only slightly refracts light rays Describe how the eye adapts to dim light. Radial muscles in iris contract Pupil dilates More light rays can enter the eye Name this eye condition and describe the problem. Myopia (short sightedness) The rays of light do not focus on the retina (they focus at a point in front of it) Distant objects appear blurred Caused by a lens that is too thick/ curved or an eye that is too long State and describe how the above condition is corrected. Draw a ray diagram to illustrate this. Use a concave lens to refract the light rays so they focus on the retina (don t forget the arrows on the light rays) Name this eye condition and describe the problem. Hyperopia (long sightedness) The rays of light do not focus on the retina (they focus at a point behind it) Near objects appear blurred Caused by a lens that is too thin/ flat or an eye that is too short State and describe how the above condition is corrected. Draw a ray diagram to illustrate this. Use a convex lens to refract the light rays so they focus on the retina. State the new technologies that can be used to treat eye defects. 1. Hard and soft contact lenses 2. Laser surgery to change the shape of the cornea 3. Surgically replacing the lens in the eye

4 Thermoregulation State how thermoregulation is an example of negative feedback. Where in the body are the receptor cells that detect temperature? How does information get from the receptor cells in the skin to the thermoregulatory centre? Name the coordination centre for body temperature. How does information get from the thermoregulatory centre to the effectors? Name the effectors for thermoregulation. Describe the responses that decrease body temperature when it is too high. HT explain the above responses. Describe the responses that increase body temperature when it is too low. HT explain the above responses. The human endocrine system What is the human endocrine system composed of? Name the endocrine glands 1 2 If body temperature drops too low, the body acts to reverse the change to bring temperature back to optimal levels (and vice versa). The thermoregulatory centre in the brain (cells are sensitive to blood temperature) The skin Via electrical impulses along sensory neurones The thermoregulatory centre Via electrical impulses along motor neurones Blood vessels, sweat glands, skeletal muscles 1. Blood vessels dilate (vasodilation) 2. Sweat glands secrete sweat 3. Both cause a transfer of heat energy from the skin to the environment, cooling the skin and body down 1. More blood flows to capillaries close to the surface of the skin. This increases the amount of heat lost by radiation. 2. Heat is transferred away from the skin by evaporative cooling. 1. Blood vessels constrict (vasoconstriction) 2. Sweat glands stop secreting sweat 3. Both reduce transfer of heat energy from the skin to the environment. 4. Skeletal muscles contract (shiver) 1. Less blood flows to capillaries close to the surface of the skin. This decreases the amount of heat lost by radiation. 2. Heat is not transferred away from the skin by evaporative cooling. 4. This increases the rate of respiration which generates heat and increases body temperature. Glands which secrete hormones directly into the bloodstream. 1. Pituitary gland 2. Thyroid gland 3. Adrenal gland 4. Pancreas 5. Ovary 6. Testes

5 Name the master gland and describe its function. Pituitary gland Secretes several hormones into the blood in response to body conditions These hormones act on other glands To stimulate the release of other hormones To bring about effects Describe the principles of hormonal coordination. Gland secretes hormones into bloodstream Blood carries hormone to target organs Where it produces an effect Compare the endocrine system to the nervous system. Effects of the endocrine system Are slower (than the nervous system) Blood glucose regulation Name the organ that monitors and controls blood glucose levels. Where are the receptors for blood glucose levels? Which hormone causes a decrease in blood glucose levels? Describe and explain how blood glucose levels are decreased when they rise too high. HT Which hormone causes an increase in blood glucose levels? HT - Describe and explain how blood glucose levels are increased when they fall too low. HT Explain how glucagon interacts with insulin in a negative feedback cycle. Name the disorder where sufferers are unable to regulate blood glucose levels. What causes Type 1 diabetes? What causes Type 2 diabetes? Which type is characterised by uncontrolled high blood glucose levels? How is Type 1 diabetes treated? Explain how Type 1 diabetes is treated. How is Type 2 diabetes treated? Explain how Type 2 diabetes is treated. Give a risk factor for Type 2 diabetes. The kidney Why does water move into or out of cells? What happens if cells lose or gain too much water by osmosis? HT What is produced when protein is digested? HT What happens if the person ate too much protein? HT What does the liver do with excess amino acids and what does it produce? Pancreas Act for longer (than the nervous system) Pancreas Insulin Pancreas produces and releases insulin into blood Insulin acts on liver/ muscle cells Causing them to take excess glucose in and convert it to glycogen for storage Glucagon (because the glucose is gone!) Pancreas produces and releases glucagon into blood Glucagon acts on liver cells Causing them to convert glycogen into glucose which is released into the blood If blood glucose level rises to high, insulin is released to cause levels to decrease to optimal levels. If blood glucose levels fall too low, glucagon is released to cause levels to increase to optimal levels. Diabetes Pancreas fails to produce sufficient insulin Body cells no longer respond to insulin Type 1 diabetes Insulin injections. Insulin acts on liver/muscle cells, causing them to remove excess glucose from the blood to store as glycogen. A carbohydrate controlled diet An exercise regime Diet reduces amount of glucose taken into body/ blood. Exercise increases use of glucose by cells. No point giving insulin as cells no longer respond. Obesity Water moves by osmosis, through the partially permeable membrane, towards the most concentrated solution. They do not function efficiently. Amino acids There would be an excess of amino acids that need to be excreted safely. Excess amino acids are deaminated to form ammonia.

6 State how water leaves the body. State how water, ions and urea are lost from the skin. State how excess water, ions and urea are removed from the body. Which of these can regulate the loss of water, ions and urea the skin, the lungs or the kidneys? State the 2 functions of the kidney. Describe the function of the kidneys in maintaining the water balance of the body. HT What is ADH? HT Which gland releases ADH? HT What is the target for ADH and what effect does it have? HT - Describe how the water level in the body is controlled when the blood becomes too concentrated. HT Explain how regulation of body water levels is an example of negative feedback. How can kidney failure be treated? How does kidney dialysis work? What are the advantages of a kidney transplant compared to dialysis? What are the advantages of dialysis (mechanical device) compared to a kidney transplant? The role of hormones in human reproduction Name the main male reproductive hormone, say where it is produced and give its function. Name the main female reproductive hormone and say where it is produced. What happens in the ovaries when a girl reaches puberty? Ammonia is toxic so is immediately converted to urea for safe excretion. Via the lungs during exhalation. In sweat Via the kidneys in the urine The kidneys To remove the urea and excess ions from the blood. To maintain the water balance of the body. 1. Filtration of the blood 2. Removes water, ions, glucose and urea 3. Selective reabsorption 4. returns useful substances (such as glucose, some ions and water) back into the blood 5. Urine is produced A hormone That controls water levels in the body The pituitary gland It acts on the kidney tubules To increase their permeability The pituitary gland releases ADH into the blood This acts on the kidney tubules To make them more permeable So that more water can be reabsorbed back into the blood If water levels drop too low, the body acts to reverse this (through the action of ADH). If water levels are too high, the body acts to reduce them. Organ transplant Kidney dialysis 1. Dialysis fluid contains the correct concentrations of substances found in the blood. 2. Fluid passes on one side of the partially permeable membrane and blood on the other. 3. Substances in excess (water, ions and urea) diffuse into dialysis fluid. 4. Concentrations of substances in the blood restored back to normal. Longer term solution that allows the person to live a normal life (travel etc). Don t need to spend hours each week on a dialysis machine. Can be done at home. No risk of a large operation (anaesthetic, infection etc) or risk of rejection. No need to take immunosuppressant drugs so the immune system can function normally. No very long waiting lists. Testosterone Produced by the testes Stimulate sperm production Oestrogen Produced in the ovaries Eggs begin to mature One is released every 28 days (called ovulation)

7 Name the 4 hormones that are involved with the menstrual cycle. Give the full name for FSH and give its function. Give the full name for LH and give its function. Give the function of oestrogen and progesterone What happens when levels of oestrogen and progesterone fall? HT describe the interactions of the different hormones in the control of the menstrual cycle HT - Define fertility drug HT - Which hormones do fertility drugs contain and why? HT - Describe IVF (In Vitro Fertilisation) FSH, LH, Oestrogen and Progesterone Follicle stimulating hormone Causes egg to mature in the ovary (maturation) Luteinising hormone Stimulates the release of the egg (ovulation) Involved in maintaining the uterus lining The uterus lining is shed in the monthly period 1. FSH released (from pituitary gland). 2. This stimulate the release of oestrogen (from ovary). 3. Oestrogen inhibits the release of FSH and stimulates the release of LH (from the pituitary gland). 4. Oestrogen and progesterone (produced by the ovary) together inhibit the release of FSH and LH. 5. When oestrogen and progesterone levels fall FSH can be released and the cycle continues. (See above for the functions of all of the hormones to add into this process!) A drug taken to help a woman to become pregnant in the normal way FSH and LH To stimulate the maturation and release of eggs If a woman does not produce enough FSH and LH of her own 1. Mother given FSH and LH to stimulate maturation of several eggs 2. Eggs collected from mother 3. Eggs fertilised by fathers sperm in the laboratory 4. They develop into embryos 5. One or two embryos inserted into the mother uterus The development of microscopy techniques HT - Which technological advancement has enabled IVF techniques to be development? HT - What is the advantage of fertility treatment? The woman has a chance to have a baby of her own HT - What are the issues involved with fertility treatment? Very emotionally and physically stressful Success rates are not high Can lead to multiple births (a risk to both babies and mother) Expensive for the NHS/ postcode lottery/ NHS only pays for some of treatment/ poorer women can t afford further treatment from private clinics Define contraceptive Describe the hormonal methods of contraception Describe the nonhormonal methods of contraception Which are the most reliable contraceptives (for preventing pregnancy)? Something that prevents pregnancy 1. Oral contraceptives (contain hormones to inhibit FSH production so no eggs mature) 2. Injection, implant or skin patch (slow release progesterone to inhibit maturation of and ovulation for months/ years) 3. Intrauterine devices (release a hormone) 1. Barrier methods (condoms and diaphragms which prevent sperm from reaching the egg) 2. Intrauterine devices (prevents embryo from implanting) 3. Spermicidal agents which kill or disable sperm 4. Abstaining from intercourse when an egg may be in the oviduct 5. Surgical methods of male and female sterilisation The hormonal methods, barrier methods and sterilisation

8 Which are the least reliable contraceptives (for preventing pregnancy)? Give a religious issue with the use of contraceptives Give an issue with using oral contraception Give an extra benefit of using condoms Give a disadvantage of condoms Adrenaline and thyroxine HT - State where and when adrenaline is produced HT - Explain the role of adrenaline in the body HT - State where thyroxine is produced HT - Explain the role of thyroxine in the body HT - State how levels of thyroxine are kept relatively stable in adults HT - Describe how levels of thyroxine are kept relatively stable in adults Spermicidal agents (alone) and abstaining whilst egg may be in oviduct Eg The Roman catholic church only allows for abstinence the other methods are banned. Slight risk of side effects such as raised blood pressure, blood clots (thrombosis) and breast cancer. They offer some protection against sexually transmitted diseases eg HIV. They can get damaged quite easily and allow sperm through. Produced in the adrenal glands In times of stress and fear 1. Prepares the body for fight or flight 2. By increasing the heart rate 3. And boosting the delivery of oxygen and glucose to the brain and muscles In the thyroid gland Stimulates the basal metabolic rate Plays an important role in growth and development (eg of developing brains in children) By negative feedback 1. When low levels are detected in the blood by sensors in the brain 2. The thyroid glands are stimulated to release more thyroxine into the blood 3. When high levels are detected in the blood 4. Less thyroxine is released into the blood

9 Plant responses 1. State three effects of plant hormones Coordinate and control growth Cause plants to respond to light Cause plants to respond to gravity 2. A response to light is called a Phototropism 3. A response to gravity is called Gravitropism/geotropism 4. Explain how auxin causes roots and shoots to responds to gravity and light An uneven distribution of the hormone in the plant causes an unequal growth rate 5. Describe how auxin causes shoots to respond to Shoots grow towards light (positive phototropism) light 6. Describe how auxin causes roots to respond to gravity Roots grow downwards in the direction of gravity (positive geotropism) 7. State the effect of a high concentration of auxin Makes them elongate faster than other cells in shoot cells 8. State the effect of a high concentration of auxin Makes them elongate slower than other cells in root cells 9. Explain how auxin causes shoots to grow There is an uneven distribution of auxin towards light (3) Concentration of auxin higher in cells on the shaded side Cells here elongate faster causing the shoot to bend 10. Explain how auxin causes new shoots to respond to gravity (3) Auxin concentration higher in cells on lower side of shoot Cells elongate faster on the side with more auxin Shoot bends and grows up away from the force of gravity 11. Explain how auxin causes new roots to grow downwards in response to gravity (3) Auxin concentration higher in cells on the lower side of root These cells elongate slower than cells on the other side Root bends down towards the direction of gravity 12. HT: State the plant hormone involved in Gibberellins initiating seed germination 13. HT: State the plant hormone that controls cell Ethene division and ripening of fruits 14. HT: Define germination The process by which a plant grows from a seed. 15. HT: Give three uses of auxin in agriculture (3) As weed killers As rooting powders To promoting growth in tissue cultures 16. HT: Give three uses (with examples) of ethene in the food industry To end seed dormancy e.g. barley seeds used in brewing To promote flowering e.g. pot plants such as chrysanthemums To increase fruit size e.g. seedless grapes 17. HT: Suggest why auxins are used in agriculture (2) To control plant growth for more profit e.g. increase growth of crops and decrease growth of weeds 18. HT: Suggest why ethene is used in food production (2) To control ripening of fruit so it can be stored for long periods and transported for long distances without going 19. HT: Give the name for chemicals that affect one type of plant and not another over ripe Selective Herbicides