3a Flashcards
What is osmosis?
The movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration
What is a partially permeable membrane?
Just one with very small holes in, only tiny molecules like water can pass through them
How does water move into and out of cells?
Osmosis
How are exchange surfaces adapted to maximise effectiveness?
Thin- short distance to diffuse, large surface area- lots of a substance can diffuse at once, lots of blood vessels- get stuff into and out of the blood quickly, ventilated
Why does the structure of a leave need to allow gases to diffuse easily in and out of cells?
Carbon dioxide diffuses into air spaces then into the cells where photosynthesis happens, oxygen and water vapour diffuse out through the stomata
How is a plants exchange surface adapted to maximise effectiveness?
Flattened shape of leaf increases surface area, air spaces inside leaf increase area of surface so theres more chance for carbon dioxide to get into the cells
In what conditions is evaporation quickest/
Hot, dry, windy conditions
Explain the process of air through the body
The air that you breathe goes in through the trachea. This splits into two tubes called ‘bronchi’, one going to each lung. Bronchi split into smaller tubes- bronchioles which end at small bags- alveoli where the gas exchange takes place
What is the definition of ventilation?
The movement into and out of the lungs
What happens when you breathe in?
Intercostal muscles and diaphragm contract, thorax volume increases, decreases the pressure drawing air in
What happens when you breathe out?
Intercostal muscles and diaphragm relax, thorax volume decreases, increases the pressure so air is forced out
What is a ventilator?
A machine that moves air into or out of the lungs
How did the iron lung use to work?
Air pumped out of the case, pressure dropped, lungs expanded, air drawn into lungs. Air pumped into case had opposite effect
Name two disadvantages of the iron lung
Had to be in the machine for the neck down for weeks and could interfere with the blood flow of the body
How do modern ventilators work?
Pumping air into the lungs, expands the ribcage, stops pumping, ribcage relaxes, pushes air back out of the lungs
Give a possible disadvantage of the modern ventilator
Can occasionally cause damage by bursting alveoli
What is the job of the lungs?
To transfer oxygen to the blood and to remove waste carbon dioxide from it
How do the lungs achieve their job of transferring oxygen to the blood and removing waste carbon dioxide from it?
They contain millions of alveoli where gas exchange takes place
How are alveoli specialised to maximise the diffusion of oxygen and carbon dioxide?
They have an enormous surface area, a moist lining for dissolving gases, very thin walls and a good blood supply
What do villi do?
Really big surface area so that digested food is absorbed much more quickly into the blood
Where are villi?
Inside the small intestine
What is active transport?
When substances are absorbed against a concentration gradient
How are root cells specialised for absorbing water and minerals?
They have root hair cells that stick out into the soil, this creates a very big surface area
How do root hairs take in minerals?
Active transport
How does active transport work in a root hair cell?
Allows the plant to absorb minerals from a very dilute solution, against a concentration gradient.
What does active transport need?
Energy from respiration
Give an example of where active transport happens in humans
Taking glucose from the gut and from the kidney tubules
Why is active transport needed in the gut?
There is low concentration of nutrients in the gut, but a high concentration in the blood
What do Phloem tubes do?
Transport food thats made in leaves to growing regions and storage organs- the transport goes in both directions
What do Xylem tubes do?
Take water and minerals from the roots to the stem and lives in the transpiration stream
What is transpiration?
Loss of water from the plant
What is transpiration caused by?
The evaporation and diffusion of water from inside the leaves, slight shortage in leaf, more water drawn up through xylem vessels to replace it, more water drawn up from roots, constant transpiration stream. More water inside the plant than in the air outside water escapes through stomata
What is the circulatory systems main function?
To get food and oxygen to every cell in the body
In the double circulatory system, what does the first one do?
Pumps deoxygenated blood to the lungs to take in oxygen. The blood then returns to the heart
In the double circulatory system, what does the second one do?
Pumps oxygenated blood around all the other organs of the body. The blood gives up its oxygen at the body cells and the deoxygenated blood returns to the heart ti be pumped out to the lungs again
Why does the heart contract?
To pump blood around the body
Why does the heart have valves?
To make sure that the blood goes in the right direction- prevents it flowing backwards
Explain how the heart uses its four chambers to pump blood around in five stages
Blood flows into the two atria from the vena cava and the pulmonary vein. The atria contract, pushing the blood into the ventricles. Ventricles contract forcing blood into pulmonary artery and aorta and out of the heart. Blood flows to the organs through arteries, and returns through veins. Atria fill and whole cycle starts over.
What are the three types of blood vessel?
Arteries, capillaries and veins
What is the function of arteries?
These carry the blood away from the heart
What is the function of capillaries?
These are involved in the exchange of materials at the tissues
What is the function of veins?
These carry the blood to the heart
Describe an artery
The walls are strong and elastic, thick walls compared to size of the lumen, thick layers of muscle w/ elastic fibres
What do arteries branch into?
Capillaries
Why do capillaries have permeable walls?
So that substances can diffuse in and out
What do capillaries supply and what do they take away?
Supply food and oxygen, take away waste like CO2
How thick are the walls of capillaries?
One cell thick
Why do capillaries have walls that are only one cell thick?
It increases the rate of diffusion by decreasing the distance over which it occurs
What do capillaries eventually join up to form?
Veins
Where is the blood at a higher pressure, the veins or the arteries?
The arteries
How do Veins keep the blood flowing even with a lower pressure?
Bigger lumen, valves to keep it in the right direction
What are the four main things in blood?
Red blood cells, white blood cells, platelets and plasma
What is the job of red blood cells?
To carry oxygen from the lungs to all the cells in the body
How are red blood cells adapted to carry oxygen?
Doughnut shape to give a large surface area for absorbing oxygen, no nucleus allows more room to carry oxygen
What red pigment do red blood cells contain?
Haemoglobin
In the lungs, haemoglobin combines with oxygen to become what?
Oxyhaemoglobin
In body tissues, what happens to oxyhaemoglobin?
It splits up into haemoglobin and oxygen, to release oxygen to the cells
What is the job of white blood cells?
To defend against disease
How do white blood cells defend against disease?
Change shape to gobble unwelcome microorganisms, produce antibodies to fight microorganisms, produce antitoxins to neutralise any toxins produced by the microorganisms
Do white blood cells have a nucleus?
Yes
What is the job of platelets?
To help blood to clot at a wound
Why is it important that platelets help blood clot?
To stop all your blood pouring out and to stop microorganisms getting in
What can lack of platelets lead to?
Excessive bleeding and bruising
What is plasma?
The liquid that carries everything in the blood
Give as many examples as you can of things that the plasma carries
Red and white blood cells, platelets, nutrients like glucose and amino acids, carbon dioxide from the organs to the lungs, urea from liver to kidneys, hormones, antibodies and antitoxins produced by the white blood cells
What is artificial blood?
A blood substitute used to replace the lost volume of blood, gives patient time to produce new blood cells.
Can an artificial blood product replace the function of the red blood cells so that there is no need for a blood transfusion?
No, they are currently being developed but are having issues with side-effects
What are artificial hearts?
Mechanical devices that are put into a person to pump blood if their own heart fails.
What is the main advantage of artificial hearts?
They are not rejected by the body’s immune system, made from metals or plastics so not seen as foreign
Give three main disadvantages of artificial hearts
The surgery to fit an artificial heart can lead to bleeding and infection, don’t work as well as healthy natural hearts- parts of the heart could wear out, blood doesn’t through through artificial hearts as smoothly so can cause blood clots- has to take drugs to thin their blood
What is coronary heart disease?
When the arteries that supply he blood to the muscle of the heart get blocked by fatty deposits, causes arteries to become narrow and the blood flow is restricted- can result in a heart attack
What are stents?
Tubes that are inserted inside arteries, they keep them open, making sure blood can pass through to the heart muscles- keeps heart beating.
What do stents lower the risk of?
Heart attacks in people with coronary heart disease
Name a disadvantage of stents
Patient has to take drugs to stop blood clotting on stent
Define homeostasis
Homeostasis is the maintenance of a constant internal environment
What are the main six things that need to be controlled in your body (homeostasis)?
Body temperature, water content, ion content, blood sugar level, carbon dioxide levels, urea
Why must body temperature be carefully controlled?
All enzymes work best at a certain temperature, In human body- 37ºc
Why must water content be carefully controlled?
Too much water moves in or out of cells -damage them
Why must the amount of carbon dioxide in the body be carefully controlled?
Toxic in high quantities
How does your body know to respond to temperature?
There is a thermoregulatory centre in the brain, it contains receptors that are sensitive to the temperature of the blood flowing through the brain and receives impulses from the skin about skin temperature.
What happens when you are too hot?
Hairs lie flat, sweat is produced by sweat glands and evaporates from the skin, blood vessels supplying skin dilate so blood flows close to the surface of the skin, easier form heat to be transferred from the blood to the environment
What happens when you are too cold?
Hairs stand up to trap an insulating layer of air, no sweat is produced blood vessels supplying skin capillaries constrict to close off the skins blood supply, shiver which needs respiration which releases some energy to warm the body
What main three roles does the kidney perform?
Removal of urea from the blood, adjustment of ions in the blood, adjustment of water content in the blood
How is urea produced?
Excess amino acids are converted into fats and carbohydrates, which can be stored urea is the waste product of this reaction
Why does the amount of urea in the body need to be carefully controlled?
It is poisonous
Why does the ion content of the body need to be carefully controlled?
Could upset the balance between ions and water, meaning too much or too little water is drawn into the cells by osmosis, could damage cells
How are excess ions removed?
By the kidneys, also lost in sweat
What is the balance of ions in the body maintained by?
The kidneys
What are the 3 main ways that water is lost from the body?
In urine, sweat, air that we breathe out
Describe what will happen on a cold day if you don’t sweat
You’ll produce more urine which will be pale and dilute
Describe what will happen on a cold day if you don’t sweat
You’ll produce less urine which will be dark-coloured and concentrated
What do sports drinks replace?
Lost water, sugar and ions
What is the job of the kidneys?
Get rid of toxic waste like urea as well as adjusting the amount of dissolved ions and water in the blood
What are the filtration units in the kidneys?
Nephrons
What are the 3 stages of the process through the kidneys?
Ultrafiltration, reabsorption, release of wastes
Describe what happens during the first stage, ultrafiltration, in the kidneys?
A high pressure is built up which squeezes water, urea, ions and sugar out of the blood and into the bowman capsule. The membranes between the blood vessels and the bowman capsule act like filters, so big molecules like proteins and blood cells are not squeezed out. They stay in the blood.
Describe what happens during the second stage, reabsorption, in the kidneys?
As the liquid flows along the nephron, useful substances are reabsorbed back into the blood, all sugar is reabsorbed (active transport), sufficient ions are reabsorbed (active transport), sufficient water is reabsorbed.
Describe what happens during the last stage, release of wastes, in the kidneys?
The remaining substances (including urea) continue out of the nephron, into the ureter and down to the bladder as urine
What happens if the kidneys don’t work properly?
Waste substances build up in the blood and you lose your ability to control the levels of ions and water in your body
If kidneys stop working what treatments can be done?
Regular dialysis or a transplant
What do dialysis machines effectively do?
Filter the blood
Why does dialysis have to be done regularly?
To keep the concentration of dissolved substances in the blood at normal levels, and to remove waste substances
Describe the process of a dialysis machine
The persons blood flows alongside a selectively permeable barrier, surrounded by dialysis fluid. Only waste substances such as urea and excess ions and water diffuse across the barrier
Why are useful dissolved ions and glucose not lost from the blood during dialysis?
The dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood
In dialysis what is the selectively permeable barrier permeable to?
Its permeable to things like ions and waste substances, but not big molecules like proteins
Name two disadvantages of kidney dialysis
Many patients with kidney failure have to have a dialysis session three times a week, 3-4 hours each time, plus dialysis may cause blood clots or infections
What is the only cure for kidney disease?
To have a kidney transplant
What can happen to donor kidneys in the body?
They can be rejected
Why and how can donor kidneys be rejected by the patients immune system?
The foreign antigens on the donor kidney are attacked by the patients antibodies
What precaution are taken to prevent donor kidneys being rejected by the body?
Donor chosen with a tissue type that closely matches the patient, the patient is treated with drugs that suppress the immune system
What two hormones control blood glucose level?
Insulin and glucagon
Name two ways that the body removes glucose from the blood without hormones
Normal metabolism of cells, vigorous exercise
Where are changes in blood glucose monitored and controlled?
The pancreas
What happens if blood glucose level is too high?
Insulin is secreted by the pancreas, removed by liver, makes liver turn glucose into glycogen
What happens if blood glucose level is too low?
Glucagon is secreted by the pancreas, makes liver turn glycogen into glucose, glucose added to blood by liver
What is type one diabetes caused by?
A lack of insulin
How is type one diabetes controlled?
Limited intake of foods rich in simple carbohydrates, regular exercise, insulin therapy
What is insulin therapy?
Involves injecting insulin into the blood
What does the amount of insulin that needs to be injected in type one diabetes depend on?
The persons diet and how active they are
How is human insulin made?
Genetic engineering
Why don’t more diabetics have a pancreas transplant?
Body might reject tissue- take costly immunosuppressive drugs, which often have serious side-effects
