- Created by: maddieecarr
- Created on: 26-11-19 15:35
B4.1: The Blood
- the blood, blood vessels and heart make up the circulatory system which transports substances to and from body cells.
- plasma has blood cells suspended in it and transports proteins and other chemicals around the body.
- red blood cells contain haemoglobin that binds to oxygen to transport it from the lungs to tissues.
- white blood cells help protect the body from infection.
- platelets are cell fragments that start the clotting process at wound sites.
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B4.2: The Blood Vessels
- blood flows around the body in the blood vessels.
- the main types of blood vessel are arteries, veins and capillaries.
- substances diffuse in and out of the blood in the capillaries.
- the valves prevent backflow, ensuring that blood flows in the right direction.
- humans have a double circulatory system.
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B4.3: The Heart
- the heart is an organ that pumps blood around the body.
- heart valves keep the blood flowing in the right direction.
- stents can be used to keep narrowed or blocked arteries open.
- statins reduce cholestorol levels in the blood, reducing the risk of coronary heart disease.
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B4.4: Helping the Heart
- damaged heart valves can be replaced using biological or mechanical valves.
- the resting heart rate is controlled by a group of cells in the right atrium that form a natural pacemaker.
- artifical pacemakers are electrical devices used to correct irregularities in the heart rhythm.
- artifical hearts are occasionally used to keep patients alive while they wait for a transplant or for their heart to rest as an aid to recovery.
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B4.5: Breathing and Gas Exchange
- the lungs are in your chest cavity, protected by your ribcageand separated from your abdomen by the diaphragm.
- the alveoli provide a very large surface area and a rich supply of blood capillaries. this means gases diffuse in and out of blood as efficiently as possible.
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B4.6: Tissues and Organs in Plants
- plant tissues are collections of cells specialised to carry out specific functions.
- the structure of the tissues in plant organs is related to their functions.
- the roots, stem and leaves frm a plant organ system for the transport of substances around the plant.
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B4.7: Transport Systems in Plants
- plants have separate transport systems.
- xylem tissue transports water and mineral ions from the roots to the stems and leaves.
- phloem tissue transports dissolves sugars from the leavesto the rest of the plant, including the growing regions and storage organs.
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B4.8: Evaporation and Transpiration
- the loss of water vapour from the surface of leaves is known as transpiration.
- water is lost through the stomata which open to let in carbon dioxide for photosynthesis.
- the stomata and guard cells control gas exchange and water loss.
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B4.9: Factors Affecting Transpiration
- factors that increase the rate of photosynthesis or increase stomatal opening will increase the rate of transpiration.
- these factors include: temperature, humidity, air flow, and light intensity.
- transpiration is more rapid in hot, dry, windy, or bright conditions.
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