Human Biology Unit One 25/5/10

gravitywontgetyouhigh

Discuss

no one does it..

I do!
I've got geography on the same day too > <
I've only gone over immunology, biochemistry and lung structure and disease so far, so major cramming needed tomorrow after my C1 exam!

Reply 3

Rashdah77

what exam board is it?

Reply 4

gravitywontgetyouhigh

chipsnfish

no one does it..

Big assumption there :rolleyes:

Reply 5

gravitywontgetyouhigh

Rashdah77

what exam board is it?

AQA

Reply 6

gravitywontgetyouhigh

Jing_jing

I do!
I've got geography on the same day too > <
I've only gone over immunology, biochemistry and lung structure and disease so far, so major cramming needed tomorrow after my C1 exam!

Similar to me, though I still can't get my head round immunology :mad:

What do you think will come up?

Reply 7

Jing_jing

gravitywontgetyouhigh

Similar to me, though I still can't get my head round immunology :mad:

What do you think will come up?

Well, possibly the role of T cells and what happens once they're activated? Because there's quite a lot to write for it. Other than that, I've absolutely no idea XD

Okay, quick run down of immunology:

The body has specfic and non specific defense mechanisms.

The body's first barrier against disease is preventing pathogens from entering the body through barries e.g. Skin. The oil in skin, tears and ear wax all have antiseptic properties. The digestive system is protected by a very acidic pH in the stomach as hydrochloric acid is in the stomach which kills pathogets, and friendly bacteria in the gut outcompete pathogenic bacteria. Urine also has antiseptic properties and flushes out pathogens from the uretha. Epithelial cells in the respiratory system (bronchi) have goblet cells which secret mucus and trap pathogens, and cilia hairs beat in a uniform manner to move the mucus up the throat where it is swallowed into the stomach.

NON-SPECIFIC DEFENSE MECHANISMS: This is the same for all pathogens and does not provide immunity.
- When cells are damaged, mast cells release a chemical called histamine which produces an immflamtory response. Histamine causes the capillaries to become 'leaky' which allows phagocytes (macrophages and neutrophils) to pass from the bloody into the tissues through chemotaxis.

- When the phagocytes arrive, they kill pathogens through phagocytosis. First the pathogens are engulfed by the macrophage/neutrophil (or you could just use the word phagocyte to cover them both) and the pathogen is held in a phagocytic vaculole. Phagocytes contain lysosomes which contain lysozyme (digestive enzymes) and the lysomes fuse with the phagocytic vacuole and secrete these enzymes, which digest the pathogen. The useful produces of digestion are then absorbed into the cytoplasm of the phagocyte.

SPECIFIC DEFENSE MECHANISMS: These involve lymphocytes (B and T cells) and give long lasting immunity.

Heh, I looked back over the post and saw it was ridiculously long, so I've stopped, I can go on and write about specific defense too if you like? I wouldn't learn from what I've typed though, this is just off the top of my head and not from a textbook so I'm not sure which bits are right and which aren't, I think it's mostly right, or I hope so else I'm screwed XDD

I love biochem, but the bit I hate is learning about the different diseases, I always get confused between the different lung diseases!

Reply 8

gravitywontgetyouhigh

Jing_jing

Heh, I looked back over the post and saw it was ridiculously long, so I've stopped, I can go on and write about specific defense too if you like? I wouldn't learn from what I've typed though, this is just off the top of my head and not from a textbook so I'm not sure which bits are right and which aren't, I think it's mostly right, or I hope so else I'm screwed XDD!

YES PLEASE!! so helpful :biggrin:

thank you

Reply 9

Jing_jing

gravitywontgetyouhigh

YES PLEASE!! so helpful :biggrin:

thank you

Alrighty

SPECIFIC DEFENSE MECHANISMS: Specific defense mechanisms involve B and T Lymphocytes.

B Lymphocytes: Originate in the bone marrow and mature in the bone marrow, before migrating to organs.

T lymphocytes: Originate in the bone marrow and travel as monocytes to the Thymus Gland (they are not mature yet). They mature in the thymus gland. All T cells are exposed to self antigens in the thymus gland and any which have receptors that are complementary to self antigens are destroyed. (If this fails it results in auto-immune disease)

B LYMPHOCYTES:

B lympoctyes are are responsible for the humoral response (in the blood) and produce antibodies.
Each B lymphocyte produces a slightly different antibody and have diferent shaped receptors on their surface that are complementary to different antigens. Each type of B cell then undergoes mitosis to form a small number of B cells with each shaped receptors. (There are many antibodies as they are proteins, and then just talk about the primary, secondary and tertiary structure, and the large number of permutations of animo acids)

The Primary Response
This is the first time a pathogen invades. Any B cells which encounter the pathogen, and have a receptor complementary to the antigen will be selected to become active in clonal selection. The selected cells then divide rapidly by mitosis in clonal proliferation. This specific B cell is now activated.

Differention then occurrs, when some activated B cells become slightly larger plasma cells. These cells secrete antibodies. Other B cells become memory cells and circulate in the body for years. B memory cells are essential for the secondary response. They formour immunological memory.

The plasma cells secrete antibodies. However, as it relies on the division of relatively few B cells it takes a few days before there are enough plasma cells to release detectable amounts of antibody into the blood. During this time, the pathogen will have reproduced and you will feel ill. Eventually there are enough antibodies to overcome the pathogens.

Secondary response

The secondary response occurs when a pathogen previously overcome invades again. It is very rapid as there are memory cells, which when encountering the pathogen for the second time, divid rapidly by mitosis to form plasma cells. They secondary response is more rapid and releases increased concentration of antibodies. The pathogen is destroyed and removed before the symptoms of disease develop - so you don't feel ill!

T LYMPHOCYTES

T lymphocytes form the cell mediated response. T lymphocytes also have a receptor on their surface which is specific to one type of antigen. However, unlike B lymphocytes, they do not recognise free antigens. They only recognise antigens which are attatched to an MHC on the surface of the cell. MHC is attatched to an antigen when an antigen presenting cell e.g. a pathogen, sticks the antigen of the pathogen on its own surface!

A T helper cell with the approriate surface receptor interacts with the antigen presenting cell and it is activated, and it divides rapidly by mitosis. It then helps overcome the pathogen in a number of ways:

1) Some cloned T cells develop into memory cells that enable a rapid secondary response.

2) Some stimulate phagocytes to engulf pathogens by phagocytosis.

3) It stimulates B cells to divide forming B plasma cells, therefore antibodies etc. through the release of cytokines.

4) T killer cells are formed. These do not kill pathogens by phagocytosis, nor do they secrete antibodies. They produce a protein that makes holes in the cell surface membrane of the infected cell, making the cell freely permeable to all substances, and the cell, and therefore pathogen dies as a result. They also release chemicals e.g. hydrogen peroxide, that perforate the surface.