2.62 Understand that platelets are involved in blood clotting, which prevents blood loss and the entry of micro-organisms

BACKGROUND INFO
- when you cut yourself / are injured, you are at risk of losing blood
- platelets are fragments of cells
- platelets are produced in the bone marrow

EVERYTHING IS EXPLAINED :D
Platelets release chemicals when there is an open wound that turn fibrinogen into fibrin, which is a solid. This forms a mesh which traps red blood cells. It eventually dries over to form a scab, and underneath, the tissue begins to repair itself.

(life hack - if you want a wound to heal quickly, don't try to pull of the scab!!)

Figure 1: A lovely picture of trapped red blood cells under the mesh
of fibrin - view from a microscope :)

IN SUPER SIMPLE STEPS
P - Platelets release chemicals
FiFi - Fibrinogen turns to fibrin
M - Mesh is formed
T - Traps red blood cells
D - Dries over
S - Scab forms
R - Repair happens in tissue underneath scab

HOW TO REMEMBER THAT
Papa Fifi makes tiny dark snakes run

(whatever works for you, really)

OR 
Here's an embarrassing song which might actually help:
*to the tune of twinkle twinkle little star*

Platelets release chemicals
Fibrinogen turns to fibrin.
Mesh is formed,
Traps red blood cells
It dries over
Scabs are formed
Tissue begins to repair
*insert final line here*

Again, whatever works for you. I was just...having a musical moment. Great. Now I've put it out there for the internet to see. Oh well, if it works, it's worth it :)

2.61 Understand that vaccination results in the manufacture of memory cells, which enable future antibody production to the pathogen to occur sooner, faster and in greater quantity

Vaccination in 5 simple steps!

1. Person is injected with a weak or harmless sample of the pathogen / disease^
2. Body fights off the disease as usual**
3. Lymphocytes split, forming memory cells
4. Upon re-infection*, the body produces antibodies much quicker, sooner and in greater quantity^
5. Body develops 'immunity'^

(the ones that have a ^ beside it, see below for exam tips.)

Exam tips :) :)

 1. I reccommend using the word "pathogen" 

2. THESE ARE KEY WORDS - VERY VERY IMPORTANT TO MENTION! (the bold bit in step 4)

3. I'm not sure it's a great idea to say your body is immune because sometimes the disease does come back, or something very similar.

Extra words just for show ;)

** (step 2) this is the primary immune response.

* (step 4) this is the secondary immune response.

Figure 1 : Tee hee, hope you're okay with needles! :P

2.60 Describe how the immune system responds to disease using white blood cells, illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen

What are white blood cells?
They are specialized cells that protect your body from pathogens (which can be harmful and cause disease)

I accidentally explained this in a previous post but I'll do so again:

Phagocytes
These types of white blood cells detect pathogens through a chemical trail that they leave behind. Their cytoplasm forms feelers called pseudopodia  which engulf the pathogen and forms a vacuole. The phagocyte releases digestive enzymes into the vacuole which then kill / digest it (the pathogen)

This process is called phagocytosis.

Figure 1

Lymphocytes
These white blood cells stand back a bit compared to the phagocytes (don't say that in an exam, for the love of elves, don't!). They release antibodies which are specific / complimentary to the antigens on the surface of the pathogen (also how it recognizes it). There are various types of lymphocytes - some cause the pathogens to stick together so phagocytes can engulf them all (the string of pathogens, I mean) , others disable / neutralize the cell and others latch onto the pathogen to attract phagocytes. When a lymphocyte encounters a pathogen and produces an antibody specific to that pathogen, it splits - one of the cells becomes a memory cell (See how vaccination works) and the other releases antibodies.

Click here for image

(because for some reason when I tried to put an image in, it didn't work)

Basic points on memory cells

• Memory cells created when lymphocyte splits
• Allows immune system to "remember" the disease (do not say that in an exam!!)
• Upon re-infection, immune response is faster (secondary immune response is faster)
• When the organism is re-infected, antibodies are produced much much quicker

:)

Lymphocyte types summary

• Some cause pathogens to stick together (so phagocytes engulf them all)
• Some latch onto them to attract phagocytes
• Some neutralize the cell (or disable it, same thing)

Some also make pathogens explode but I'm not sure about that one so better not mention that in an assessment, be it an exam or just a test. Basically, do not mention that in an exam unless you have researched further and know how it works.

Little extra from Annabel: Just write all four things in an exam, even if it is a 3 mark question because you never know with the mark scheme... :)

2.66 Understand the general structure of the circulation system to include the blood vessels to and from the heart, the liver, the lungs and the kidneys

Quick overview of the meanings of some words:
Lung- pulmonary
Liver- hepatic
Kidney- renal
Stomach- gastric
Between the gut and liver is the hepatic portal vein.

(sorry if the diagram is a bit messy, it's hand made but hopefully accurate)

2.65 Describe the structure of arteries, veins and capillaries and understand their roles

ARTERIES
Arteries take the blood Away form the heart and to an organ (e.g.: lungs)
They have thick muscular walls and a small lumen, therefore, blood is under the highest pressure in them

VEINS
Take blood to the heart and away from an organ
They have a relatively thin wall and a large lumen, therefore blood is under the lowest pressure in them
They have watch pocket valves to prevent the blood from flowing backwards/in the wrong direction

CAPILLARIES
Where exchange is taken place
They have very thin walls (one cell thick) so that gas exchange can occur easily

2.59 Explain how adaptations of red blood cells, including shape, structure and the presence of haemoglobin, make them suitable for the transport of oxygen

ADAPTATIONS TO SHAPE
Have a biconcave shape (flat disk with a dip in the middle) which increases the surface area (this allows more oxygen to be absorbed more efficiently). Also, the fact that they are a flat disk allows them to pass through capillaries easily :)

NO NUCLEUS
This means the whole cell is full of haemoglobin

THIN OUTER MEMBRANE
Which lets oxygen diffuse through easily

HAEMOGLOBIN
(It's made from iron), and can bond with oxygen (very important for cell whose job is to carry around oxygen)

NO MITOCHONDRIA
Because the cells respire anaerobically so the cells don't use any oxygen.

2.64 Explain how the heart rate changes during excercise, and under the influence of adrenalin

EXERCISE

Basically, when we exercise our muscles need more energy to work. Energy is created during respiration, and we need oxygen for respiration. Carbon dioxide is produced during respiration, so if there is more respiration occurring, there will be more carbon dioxide produced, so the heart needs to increase its speed so that more blood, which is carrying oxygen which will be sent to the muscles (it will also carry away the deoxygenated blood). Carbon dioxide is no good for respiration!

WHAT IS ADRENALIN?
According to Hannah*, it is...
produced in the adrenal glands in top of the kidneys- stimulates adrenegic receptors in the heart which increase the rate that your heart cells work at.

MORE ABOUT ADRENALIN 
(this part is written by me)
Adrenaline is a hormone, so it is carried around in the plasma part of your blood (see post on plasma) which is yellow. As mentioned above, it is produced in the adrenal gland.

Figure 1 - Just because I wanted a picture

*There's a hyperlink on the word "hannah" to her blog, because it was written by her - full credit to her, no plagiarism intended :)

2.63 Structure of the heart and how it works

Structure of the heart:

HOW IT WORKS:

Blood enters the right atrium (from the vena cava) and the tricuspid valve is closed. 
The walls of the atrium squeeze, raising the blood pressure and forcing open the tricuspid valve, allowing the blood to flow into the right ventricle. 
The ventricle contracts, raising blood pressure which closes the tricuspid valve and forces open the semilunar valve, forcing the blood through the pulmonary artery where it is oxygenated at the lungs 
The pulmonary vein fills the left atrium with blood. 
A similar process forces the blood into the left ventricle (the valve is the bicuspid)
When the left ventricle contracts the blood is forced out through the aorta, which is then pumped around the body.

Things to remember:
Veins lead to the heart; arteries lead away.
Atrium means entrance hall in Latin; hence the atrium is where blood enters the heart.
The left side is bigger than the right as it has to pump blood through the whole body (therefor the aorta is found on the left side and the vena cava enters on the right).
You talk about the heart from right to left, as if you were examining someone's heart and using their own left and right.

2.58 Understand the role of plasma in the transport of carbon dioxide, digested food, urea, hormones and heat energy

Plasma is made up of mostly water and is pale yellow in color (though I'm pretty sure you don't need to know that). This is a solvent, so things dissolve into the plasma, which is how they are carried around This transports carbon dioxide,  digested food, urea (basically urine...lovely), hormones and heat. 

Digested foods = soluble sugars and amino acids :)

Heat is important to regulate body temperature.

Figure 1 (below) shows a sample of plasma and blood - the plasma is the (rather gross-looking) yellow stuff above the red.

Figure 1

2.57 Describe the composition of the blood: red blood cells, white blood cells, platelets and plasma

• 55% of the blood is plasma
• More red blood cells than white blood cells
• Platelets

Platelets are fragments of dead cells.

White blood cells can be lymphocytes or phagocytes.

I don't know if this is technically needed in this specification point, but I'll include it anyway because...well...it's good to know. :)

\/

Phagocytes are the white blood cells that swallow up the pathogen (which can be a bacterium, virus or protoctist). As can be seen below in figure 1, the cytoplasm forms little 'feelers' called pseudopodia. These surround the pathogen and form a vacuole. Then, digestive enzymes are released into the vacuole which digest and kill the pathogen.

Lymphocytes release antibodies which are complimentary to the antigens on the surface of a pathogen - that is how they (pathogens) are identified. Lymphocytes can cause the pathogens to stick together, leave a clearer chemical trail (so the phagocytes can follow them more easily) or explode.

Erythrocytes, aka red blood cells, have a bioconcave shape, no nucleus and have lots of haemoglobin. This allows them to carry oxygen around the body.

Plasma is used to transport stuff (see next posts(s))

Figure 1