Summary
Summary of IB Biology Topic 6 (Human Physiology)
- Course
- Institution
- Book
Summary of IB Biology Topic 6 (Human Physiology)
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
More summaries for
-
All the information for topic 5 IB Biology SL
-
All the information for topic 4 IB Biology SL
-
Information for topic 3 IB Biology SL
Seller
Follow
bellakim
Content preview
Unit 6 - Human Physiology6.3 - Defence Against Infectious Disease
6.3.1 - Surface Barriers
The rst line of defence are the surface barriers:
• Skin: protects external structures
• Consists of dead surface cells
• Contains glands that secrete enzymes and chemicals which inhibit microbial growth on skin
• Secretes lactic acid and fatty acids to lower pH
• Mucous membranes: protects internal structures
• Consists of living surface cells that release uids to wash away pathogens (e.g mucuous,
saliva, tears)
• Secrete lysozymes which destroy cell walls
• May possess cilia to help remove pathogens
6.3.2 - Clotting
Clotting: repairs damaged blood vessels to prevent blood loss and block pathogens from
entering blood stream
Key components of blood clots:
• Platelets: become sticky to plug damage
• Fibrin strands: form mesh to trap blood cells
Coagulation cascade: set of reactions involved in blood clotting
1. Clotting factors cause platelets to become sticky and plug damaged area
2. Factors cause vessel to constrict, reducing blood ow
3. Factors activate thrombin, which causes brinogen to transform into brin (insoluble)
4. Fibrin strands form mesh to trap blood cells
5. After reparation, an enzyme dissolves the clot
Coronary thrombosis: formation of blood clot in coronary arteries
If blood clot blocks artery (occlusion), a heart attack may occur.
Caused by atherosclerosis:
• Atheromas (fatty deposits) reduce diameter of lumen
• Increased blood pressure damages arterial wall
• After reparation, elasticity decreases
• Over time, lesions/plaque forms
• If plaque ruptures, blood clotting occurs, creating a thrombus that restricts blood ow
6.3.3 - Phagocytes
The second line of defence is the innate immune system.
• Phagocytes (white blood cells): engulf /digest foreign bodies
• In ammation
• Fever
• Antimicrobial chemicals
Main properties:
fl fi fifl fl fi fl
, • Non-speci c: doesn’t di erentiate between di erent types of pathogens
• Non-adaptive: responds to infection same same way every time
Phagocytosis: process where phagocyte ingests pathogens (via endocytosis)
Di erent types of phagocytes include macrophages and dendritic cells.
• Phagocytes circulate through blood stream
• Damaged body tissue releases chemicals that attract white blood cells
• Phagocyte engulf pathogen, trapping it in an internal vesicle
• Lysosome (organelle) fuses with vesicle and digests pathogen
• Fragments of pathogen may be presented as antigens (stimulating third line of defence)
6.3.4 - Lymphocytes
The third line of defence is the adaptive immune system.
Main properties:
• Speci c: can di erentiate between and target speci c pathogens
• Adaptive: responds faster when re-exposed to a pathogen (building immunity)
Lymphocytes: cells that aid in the production of antibodies
• B cells: recognise and target speci c antigens to produce antibodies
• T cells: regulatory, release cytokines to activate B cells
Process:
• Some phagocytes (dendritic cells) present antigens on surface
• Dendritic cells migrate to lymph nodes and activate T cells
• T cells release cytokines that activate B cells
• B cells di erentiate into plasma cells that produce speci c antibodies
• Antibodies bind to speci c antigens and cause them to agglutinate (stick together), making
them easier to recognise and be destroyed
• Small portion of lymphocytes develop into memory cells to provide long-lasting immunity
Antigen: pathogen fragments that elicit an immune response
Antibody: protein speci c to an antigen
Antigens form Y-shaped molecules with unique antigen-binding sites at the ends.
ff
fi ff fi ff fififf fi ff fi fi
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller bellakim. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.70. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
51292 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 15 years now