What are the physical and chemical barriers against disease in our bodies?
eyes - enzymes in tears
nose - nosal hair, mucus, sneezing refles
mouth - enzymes in saliva, coughing reflex
stomach - stomach acid, pepsin
vagina - acidic secretions
skin - waterproof, impermeable
respiratory system - mucus, ciliated epithelial cells
How does our immune system defend against disease?
platelets - blood clotting
white blood cells:
phagocytes - phagocytosis
lymphocytes - antibodies
lympochytes - antitoxins
What are platelets?
platelets are small cells in the blood, the function of which is blod clotting
How do platelets and blood clotting defend against disease?
When the skin is injured (e.g. through a cut), the most important thing is to seal the wound quickly, so the microbes cannot enter and blood loss is limited
Platelets are tiny cells in the blood which help close a wound. When a blood vessel is cut or broken, platelets stick together and activate the formation of a mesh made of a protein called fibrin
More platelets and red blood cells are trapped in this mesh. This leads to the formation of a clot/scab which seals the cut
Label this diagram of a phagocyte
Why is a lobed nucleus necessary in a phagocyte?
the lobed nucleus is necessary because cells need to change shape to squeeze through, e.g. ciliaped epithelial cells
How does phagocytosis defend against disease?
phagocytes can easily pass through blood vessel walls into the surrounding tissue and move towards pathogens
they engulf the pathogen
once the pathogen is engulfed they release enzymes to digest and destroy the pathogen
Phagocytes are specific/non-specific
Phagocytes are non-specific - they attack anything that's not meant to be there
What are antibodies?
antibodies are proteins that recognise and bind to antigens
What are antigens?
antigens are substances on the surface of a pathogen that can be recognised by an antibody
Different pathogens carry the same/different antigens (the same/different shape)
Different pathogens carry different antigens (different shape)
Different lymphocytes produce the same/different type of antibody which is specific/non-specific for a particular antigen (i.e. can bind to one/multiple types of antigen)
Different lymphocytes produce a different type of antibody which is specific for a particular antigen (i.e. can bind to only one types of antigen)
Explain lymphocyte and antibody action
when a lymphocyte meets a pathogen with an antigen that is recognised by its antibodies, it reproduces quickly and releases man ycopies of the antibody which bind to the pathogen
binding of antibodies to the antigens on the pathogen can directly destroy the pathogen or help phagocytes to engulf and digest pathogens more easily
What can bacteria (and some viruses) release?
bacteria (and some viruses) can release toxins that make us ill
What are antitoxins?
a chemical produced by a lymphocyte that can neutralise toxins
What is blood clotting?
the formation of a scab to prevent infection and blood loss
What are phagocytes?
a white blood cell that can engluf and digest pathogens
What is phagocytosis?
the process of engulfing and digesting pathogens
What are lymphocyte?
a white blood cell that can produce antibodies or antitoxins
What is a toxin?
a chemical produced by a pathogen which can make you ill
What happens during your first infection with a virus?
The person feels unwell
Lymphocytes are stimulated by the antigens on the surface of the virus and release antibodies
They also make memory cells which stay in the blood
Antibodies attach to the antigens - agglutination (microbes stick together so they can't reproduce)
The person recovers
What is agglutination?
microbes stick together so they can't reproduce
What happens during your second infection?
Memory cells, made by the lymphocytes in the first infection, can repridcue very quickly if the same antigen enters the body a second time
the memory cells are stimulated by the same antigens on the surface of the virus
Antibodies are released and attach to the antigens - agglutination
The person recovers
What do vaccines contain?
antigens of the pathogen
What can vaccines be?
parts of the pathogen
similar but less infectious pathogen
What do vaccines trigger?
lymphocyte activation (antibody prdocution and memory cell formation)
How do vaccines work?
When you're infected with a new pathogen it can take your lymphocytes a while to produce the antibodies to deal with it. In that time you can get very ill, or maybe even die
To avoid this you can be vaccinated against some diseases, e.g. polio or measeles
Vaccination involved injecting dead or inactive pathogens into the body. These carry antigens, so even though they're harmless they still trigger an immune repsonse - your lymphocytes produce antibodies to attack them
Some of these lymphocytes will remain in the blood as memory cells so if live pathogens of the same type ever appear, the antibodies to kill them will be producd much faster and in greater numbers
What is the consequence of having too few platelets in the blood?
the blood would not clot; you would loose too much blood
Phagocytes ... antigens
Lymphocytes ... antibodies and antitoxins
Phagocytes engulf antigens
Lymphocytes produce antibodies and antitoxins
Describe the advantages to the human body by producing memory cells
antibodies produced faster
faster repsonse to the infection