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| Question | Answer |
|---|---|
| What is the normal body temperature? | 37 degrees centigrade |
| Why must the human body be kept around 37 degrees? | because this is the temperature at which work best |
| Which organ can cope with widely varying temperature? | the skin |
| What part of the body needs to be kept at a very stable temperature? | the core i.e. deep inside the body |
| How flexible is body about temperature? | it can cope with a few degrees fluctuation either side for short periods of time, but no more, so for example, a body temperature of only 39 degrees is dangerous to life |
| What can affect the internal body temperature? |
• heat from muscles during exercise • fever caused by disease • large swings in external temperature |
| What can a person do to regulate their temperature? |
• turn on heating • a change of clothing • go for a swim • build a fire |
| What controls the body temperature? | the thermoregulatory centre in the hypothalamus in the brain |
| How does the thermoregulatory centre measure the inner core temperature? | it contains receptors that are sensitive to the temperature of the blood |
| How is the skin in maintaining a stable body temperature? | receptors in the skin send information to the thermoregulatory centre |
| How sensitive are temperature receptors in the skin? | they are extremely sensitive able to detect a temperature difference as small as 0.5 °rees; C |
| What does the body try to do when the core body temperature begins to rise? | to transfer energy from the body to the surroundings to bring the body temperature down |
| Name the two main techniques for reducing body temperature. |
• vasodilation • sweating |
| What is vasodilation? | the blood vessels that supply blood to the skin capillaries dilate |
| What is the effect of vasodilation? |
• more blood flows close to the skin energy is transferred by radiation from the skin to the surroundings the body cools down |
| Where does sweat come from? | from the sweat glands in the skin |
| Why is the effect of sweating? | the water in the sweat evaporates, transferring energy to the environment, and cooling the body |
| When would sweating not work? | in humid weather, the water does not evaporate, making it harder to transfer energy from the body |
| What is sweat made of? | it is mainly water with small amounts of urea, sugar, and mineral ions |
| Why is it important to drink water in hot weather? | to replace the water lost through sweating |
| Why is it important to drink water when exercising? | to replace the water lost through sweating |
| Why is it not enough to only drink water when sweating? | because the body also loses important ions which need to be replaced |
| How can the mineral ions that are lost through sweating, be replaced? | by eating food or drinking juices that contain the ions |
| What is the effect on cells of the body getting very cold? |
• the rate of enzyme-controlled reactions in the cells falls • the cells do not do sufficient respiration to support their activities • the cells begin to die |
| What happens when the core body temperature starts to fall? |
• receptors in the core send impulses to the thermoregulatory centre • the thermoregulatory centre initiates action to reduce heat loss and/or generate body heat |
| What can the body do to raise the temperature of the body? |
• vasoconstriction • reduced sweating • shivering |
| Explain vasoconstriction. |
• the blood vessels that supply the capillaries in the skin contract • less blood reaches the surface of the skin • less heat is radiated to the environment |
| How does reduced sweating help combat a falling core temperature? | less sweating means less water evaporating and hence less energy transferred to the environment |
| What is shivering? | the skeletal muscles contract and relax repeatedly and very quickly |
| How does shivering help combat falling core body temperature? |
• muscle contractions increase respiration • respiration is an exothermic reaction • the energy released by the exothermic reaction increases body temperature |
| Question | Answer |
|---|---|
| How much urine does a person produce each year? | up to 900 litres |
| What is the main requirement of cells regards conditions? | conditions must be kept as constant as possible |
| List examples of things that change conditions in the body? |
• exercise increases respiration heating the body • respiration produces waste products contaminating the blood • distributing digested food to the cells increases concentrations of substances like amino acids and glucose |
| Name the process that keeps internal conditions constant in the body. | homeostasis |
| List activities included in homeostasis. |
• removing waste products • maintaining water balance • maintaining mineral levels • keeping levels of glucose constant |
| When are waste products produced by the body? | they are produced constantly, even during sleep |
| Where do these waste products come from? | they are produced by the chemical reactions in the cells of the body |
| Name the two main poisonous waste products produced by the body. |
• urea • carbon dioxide |
| What is the effect of waste products on the body? | they can cause major problems from damaging organs to death |
| What is the waste product from respiration? | carbon dioxide |
| Why must the waste product carbon dioxide be removed? | because the dissolved carbon dioxide makes the solution acidic which affects the working of the enzymes in the cell |
| Describe the journey of carbon dioxide in the body. |
• respiration produces carbon dioxide in the cell • carbon dioxide diffuses out the cell down a concentration gradient into the blood • carbon dioxide diffuses out the blood down a concentration gradient into the alveolus • carbon dioxide is expelled from the body by exhalation |
| What is the unwanted side effect of exhaling carbon dioxide? | the air in the lungs is moist so water is lost by the body |
| What is urea? | the nitrogenous bi-product when excess amino acids are converted to carbohydrates in the liver |
| Describe the journey of urea. |
• urea is a bi-product when excess amino acids are broken down in the liver • urea diffuses from the cells of the liver into the blood • urea is filtered out the blood by the kidney • urine (water, urea and slats) moves from the bladder • urine is expelled from the body by the bladder |
| What is the effect of urea in the body? | it will cause extensive damage to cells and ultimately death if the situation is not resolved |
| What is the unwanted side effect of urinating? | the body loses water and important minerals which can cause problems if not replaced |
| Where does excess protein come from in the body? |
• eating too much protein • breaking down worn out tissues |
| What does the body do with excess protein? | it converts the protein to carbohydrates that the body can use for fuel |
| Why does the body need to convert excess protein to carbohydrates |
• excess protein and amino acids cannot be stored in the body • excess protein cannot be used directly as fuel |
| Where are proteins and amino acids converted to carbohydrates? | in the liver |
| What is the process of converting proteins and amino acids to carbohydrates called? | deamination |
| What is actually done to convert amino acids to protein? | the amino group is removed from the amino acid |
| What is the byproduct of removing an amino group from amino acids? | ammonia NH3 |
| What happens to the ammonia produced by deamination? | it is immediately converted to urea |
| Why is the ammonia of deamination immediately converted to urea? | ammonia is highly toxic, and while urea is toxic, it can be removed by the body safely |
| Why must water levels be kept constant in the body? | if the cells of the body lose or gain too much water by osmosis, they cannot function effectively and efficiently |
| In what ways does the body lose water where it has no control? |
• water is lost every time a person exhales • water, mineral ions, and urea are lost through the skin when sweating |
| How does the body control the levels of water and mineral ions in the body? | the kidneys remove urea, excess water, and excess mineral ions which are then excreted in the urine, |
| What are the main tasks of the kidneys? |
• to remove urea from the blood • to maintain water and mineral ion content of the blood within narrow limits |
| Question | Answer |
|---|---|
| How many kidneys does a person have? | 2 |
| What do the kidneys do? | the kidneys remove • urea • excess water • excess mineral ions |
| Where is urine produced? | in the kidneys |
| How often is urine produced? | it is produced constantly |
| What happens to urine once it has been produced? | it is stored in the bladder before being expelled |
| When does a person gain water? |
• from drinking • from eating |
| When does a person lose water? |
• sweating • breathing • urinating |
| What is the role of the kidneys in the homeostasis of water? |
• if short of water, kidneys conserve it and urine is very concentrated • if there is too much water, kidneys expel it and urine is very dilute |
| How does the body lose mineral ions? |
• sweating • urinating |
| How does the body get rid of excess mineral ions? | the kidneys remove excess mineral attempts and excrete them in the urine |
| Where are the kidneys? | below the liver and the diaphragm and above the bladder |
| What are the renal arteries? | the blood vessels that bring blood to the kidneys |
| What are the renal veins? | the blood vessels that carry blood away from the kidneys |
| What happens to the blood first when it enters the kidneys? | glucose, mineral ions, urea, and water all move out of the blood into the kidney |
| What part of the blood does not enter the kidneys and why? |
• the blood cells and proteins do not leave the blood • because they are too large |
| How long does it take all the blood in your body to pass through the kidneys? | once every 5 minutes |
| How much water do the kidneys filter out the blood every day on average? | 180 litres |
| On average, how much of the water filtered out the blood is returned to the body? | around 99% of it |
| How much urine is produced each day on average? | 1800 cm3 |
| What happens to the urine removed by the kidneys? |
• it trickles into the bladder where it is stored • when the bladder is full, it is emptied |
| What is reabsorped back into the blood? |
• all the glucose • all or some of the mineral ions depending on what is needed • all or some of the water depending on what is needed |
| What is selective reabsorption? | the amount of water and mineral ions reabsorped into the blood varies according to what the body needs |
| Where does selective reabsorption take place? | along the millions of tiny tubules that make up the kidney |
| How is the water level in blood maintained at a constant level? | by a negative feedback loop the uses the hormone ADH |
| Where does ADH come from? | it is secreted by the pituitary gland in the brain |
| How are changes in concentration levels of solutes in the blood monitored? | detectors in the brain monitor the concentration of solutes in the blood plasma |
| What happens when the blood becomes too concentrated? |
• detectors in the brain detect an increased concentration of solutes in the blood plasma • the pituitary gland increases the amount of ADH it releases into the blood • the increased ADH makes the kidney tubules reabsorp more water • this reduces the amount of water in the urine • less urine is produced • the urine is more concentrated |
| What happens when the blood becomes too dilute? |
• detectors in the brain detect a decreased concentration of solutes in the blood plasma • the pituitary gland reduces the amount of ADH it releases into the blood • the reduced ADH makes the kidney tubules reabsorp less water • this increases the amount of water in the urine • more urine is produced • the urine is very dilute |
| Give an example of when urine will be concentrated and relatively dark yellow. | a hot day, exercising a lot and drinking very litte |
| Give an example of when urine will be dilute and almost colourless. | a cool day, doing very little and drinking lots of liquids |
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