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B4: ORGANISING ANIMALS AND PLANTS (Helping the Heart (The resting heart…
B4: ORGANISING ANIMALS AND PLANTS
The Circulatory System
The Blood
Plasma has blood cells suspended in it and transports proteins and other chemicals (eg. urea) around the body
Your red blood cells contain haemoglobin that binds to oxygen to transport it from the lungs to the tissues. They have no nucleus, making more space for haemoglobin
White blood cells help to protect the body against infection
Platelets are cell fragments that start the clotting process at the wound sites
The blood, blood vessel and heart make up the human circulatory system which transports substances to and from the body cells
Blood Vessels
The valves in veins prevent backflow, ensuring that the blood flows in the right direction
Humans have a double circulatory system- this means one transport system carries blood from your heart to your lungs and back again (allowing gaseous exchange), and the other transport system carries blood from your heart to all other organs of the body and back again
Substances diffuse in and out of the blood in the capillaries
Blood flows around the body in the blood vessels. The main types of blood vessels are arteries, veins and capillaries
Arteries take blood away from the heart and veins take blood to the heart
The Heart
Stents can be used to keep narrowed or blocked arteries open
Statins reduce cholesterol levels in the blood, reducing the risk of coronary heart disease
Heart valves keep the blood flowing in the right direction
The heart is an organ that pumps blood around the body
The heart has 4 chambers
Ventricles pump blood out of the heart
Blood comes in from the veins into the atrium, through valves to the ventricles and then out via the arteries
Helping the Heart
The resting heart rate is controlled by a group of cells in the right atrium that form a natural pacemaker
Artificial pacemakers are electrical devices used to correct irregularities in the heart rhythm
Damaged heart valves can be replaced using biological or mechanical valves
Artificial 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
Breathing and Gas Exchange
The lungs are in your chest cavity, protected your ribcage and separated from your abdomen by the diaphragm
The alveoli provide a very large surface area and a rich supply of blood capilleries
This means gases can diffuse into out of the blood as efficiently as possible
Plant Tissues and Cells
The structure of the tissues in plant organs is related to their functions
The roots, stem and leaves form a plant organ system form a plant organ system for the transport of substances around the plant
Plant tissues are collections of cells specialised to carry out specific functions
Epidermal tissues cover the surface of the plant and protect them and also produce a waxy substance that waterproofs the leaf's surface
Palisade mesophyll tissue contains lots of chloroplasts, which carry out photosynthesis
Spongy mesophyll tissue contains some chloroplasts for photosynthesis but also have air spaces to make the diffusion of gas easier
Plants have two separate transport systems
Xylem tissue transport water and mineral ions from the roots to the stems and the leaves
Phloem tissue transports dissolved sugars from the leaves to the rest of the plant, including the growing regions and storage organs
Evaporation and Transpiration
Water is lost through the stomata, which open up to let in carbon dioxide for photosynthesis
The loss of water from the surface of the plant leaves is known as transpiration
The stomata and guard cells control gas exchange and water loss
Factors Affecting Transpiration
Transpiration is more rapid in hot, dry, windy or bright conditions
Factors which affect transpiration include temperature, humidity, airflow and light intensity