Immunesystem and neurons

Pathogens

a disease causing organism

Bacteria

• Prokaryotes (no real nucleus)

• Divide by binary fission

• Can cause: food poisoning, ear/eye infections, cholera, tetanus, syphilis

Virus

• Acellular (non-living)

• Need a host cell to carry out functions of life, including reproduction

• Can be DNA or RNA virus

• Mutate, evolve, and recombine quickly

• Can cause: flu, HIV/AIDS, smallpox, measles, common cold, ebola, COVID

Fungi

• Eukaryotes, reproduce with spores

• Can cause: athlete’s foot, mold, ringworm, allergic reactions, respiratory problems

Protozoa

• Eukaryotic organisms - simple parasite

• Can cause: malaria, leishmaniasis, toxoplasmosis

Methods of transmission of pathogens

• Inhaled droplets (influenza)

• Direct contact (herpes, varicella)

• Bodily fluids (strep throat, HIV)

• Animal Vectors (rabies, malaria)

• Blood contact (hepatitis B)

• Ingested/swallowed (salmonella)

1st Physical barrier against pathogens

Skin 

• Continuous/hard to find an opening

• Many layers/though

• Dry

• pH is not favorable to pathogens

• Lysozyme enzymes break down pathogens

• Natural organisms competitive exclusion by non harmful microbes

2nd Physical barrier against pathogens

Mucus Membranes (for when there are openings)

• Sticky mucus traps invaders

• pH is not favorable to pathogens

• Lysozyme enzymes break down pathogens

• Natural organisms competitive exclusion by non harmful microbes

How does blood clot?

Wounds (such as cuts) causes opening in which pathogens can potentially enter the body

• Platelets and damaged tissue release clotting factors

• Clotting factors cause a series of reactions to form mesh across wound site

Clotting factors turn into thrombin which mix with fibrinogen (soluble) that turns thrombin into fibrin (fibrous) which captures erythrocytes and clots

Phagocytes

WBC, first line of defense, “eating” cells, non specific immune response (they just recognize whats foreign)

Lymphocytes

B-cells, T-cells, Killer cells

Action of phagocytic Leukocytes

• Chemotaxis (movement in response to chemicals) attracts the phagocytes to the area of invasion as response to: proteins produced by pathogen, phospholipids released by damaged cells

• Ingested through endocytosis because the membrane is fluid it is easy for phagocyte to engulf pathogen

• A phagosome forms (vesicle that contains pathogen)

• Lysosomes (vesicles of digestive enzymes) deposit the enzymes into the phagosome

• The digestive enzymes break down pathogen and waste products are expelled from the cell

Antigen

a substance or molecule, found on a cell or virus surface that causes antibody formation

Antibody

a globular protein that recognises a specific antigen and binds to it as part of an immune response

Antibiotics

drugs used in the treatment and prevention of prokaryotic bacteria

Lymphocytes

different types of the cells recognize one specific antigen, responds when immune system is challenged by a pathogen, creates clones of itself (clonal selection) which produce antibodies to the pathogen, some cloned cells remain as memory cells (immunity)

Clonal selection

lymphocyte that creates clones of itself

Memory cells

cloned lymphocyte cells that remain to remember antibody to create future immunity

How antibiotics work

disrupt structures or metabolic pathways in bacteria and fungi:

• Cell walls and membranes

• Protein synthesis (translation)

• DNA/RNA synthesis

• Other metabolic processes (e.g. enzyme function)

drugs that inhibit prokaryotes often have little or no effect on eukaryotes

Viruses and antibiotics

Viruses lack a metabolism and cannot therefore be treated with antibiotics

• Some strains of bacteria have evolved with genes that confer resistance to antibiotics 

• Some strains of bacteria have multiple resistance

antibiotic resistance in bacteria

• An example of evolution by natural selection

• Bacteria mutate and resistance to an antibiotic naturally arises

• Bacteria divide rapidly therefore a resistant strain of bacteria can quickly proliferate

• Over time strains of bacteria can become resistant to multiple strains of antibiotics

Phage

a virus that attacks bacteria

Human Immunodeficiency Virus (HIV)

• Gradually attacks the immune system, RNA virus

• Transmitted by exchange of bodily fluids

• AIDS (acquired immunodeficiency syndrome) is a syndrome caused by HIV

• There is no cure, but there are certain medications to increase period of clinical latency

• Overtime the number of helper t cells drops, amount of RNA (carrying the virus) increases

• Clinical latency: there's a period of recovery (depends on genetics/health)

Central nervous system (the body’s master control unit)

• Spinal cord: column of nerves between brain and peripheral nerves

• Brain Stem: connects brain and spinal cord

• Brain: hindbrain, midbrain, forebrain

Peripheral nervous system (the body’s link to the outside world)

• The autonomic nervous system: regulates involuntary body functions

  • Sympathetic nervous system: prepares the body for fight or flight

  • Parasympathetic nervous system: calms the body down

• The somatic nervous system: carries sensory information to command movement

Neuron

cells that carry rapid electrical impulses

Synapse

the junction between two neurons