Unit 4 - Response to infection Flashcards
(56 cards)
Communicable disease
when a disease is passed from one infected person to another
contagious
passed from human to human
vectors
passed to humans via animals such as mosquitoes
Bacteria Characteristics
- No nucleus. DNA floats freely
- slime layer around the outside
- cell membrane
- cell wall provides structural support & protection
- flagella for movement in some bacterias
· Unicellular and microscopic
· Shape determines their classification
Have plasma membrane, ribosomes, single circular strand of DNA (chromosome), and plasmids (small circular pieces of DNA)
Pathogen
disease causing organisms
transmission of pathogens through contact
- Physical contact
- Direct touching the infected person
- Indirect touch an object that an infected person has touched
Eg. Skin infections + STI’s
transmission of pathogens through bodily fluids
- Blood or other bodily fluids (infected person) transported to mucous membrane or bloodstream (uninfected person)
- Mucous membranes: nose, mouth, throat, genitals
- Enter through a needle or broken skin (pathogens enter)
Eg. HIV, Hepatitis B
transmission of pathogens through droplets
- Drops are emitted containing pathogens
- Breaking, talking, sneezing
Eg. Measles, mumps, cold, flu
transmission of pathogens through vectors
- Transfer of pathogens by other animals (mites, ticks, insects)
- Can be indirect àhouse flies contaminating food
Spread by a specific vector/vector born disease àmalaria & dengue by mosquitoes
non-specific defences
works on all pathogens
specific defences
directed at a particular pathogen
External Defence Mechanisms Against Pathogens
· Digestive tract: contains acids + enzymes that can destroy pathogens before they cause infection
· Urogenital tract: contains mucous membranes and other defence mechanisms that prevent pathogens from entering the body
· Respiratory system: includes nose, throat and lungs, lined with mucous membranes and cilia that trap and remove pathogens
· Ear: ear canal contains wax and other substances that prevent pathogens from entering body
Eye: eye is protected by tears, contain enzymes that can destroy pathogens
Non-Specific Defences Against Disease - skin, mucus, hairs, cilia
· Skin:
o acts as physical barrier
o prevents pathogens from entering body
o Bacteria occupies area and pathogens find it difficult to enter
o Sebum: oily secretion by oil glands in skin that contain substances that kill some pathogens
o Sweat: secreted onto skin and contains salts and fatty acids that prevent the growth of many micro-organisms
· Mucus:
o Mucous membranes line body cavities to open to the exterior
o Secrete mucus which traps particles and stops entry of micro-organisms
o Digestive, urinary and reproductive are all protected this way
· Hairs:
o Found in nasal cavity, ears and nose
o Hairs + layer of mucus trap 90% of particles when inhaled
· Cilia:
o Tiny-hair like projections from cells
o Are on the mucous membranes lining the nasal cavity, trachea and other air passages
Cilia moves mucus (containing particles) to throat where it is coughed up or swallowed
non-specific defences against disease - acids, lysozyme, cerumen, movement of fluid
· Acids:
o Kills many of the bacteria taken in with food or in mucus swallowed.
o Stomach juices
o Vaginas have acid secretion
o Urine
o Sweat
· Lysozyme:
o Enzyme that kills bacteria
o Found in saliva, sweat, secretions of nose, tissue fluid, and tears
· Cerumen:
o Called ear wax
o Protects outer ear against infection
o Acidic and contains lysozymes
· Movement of fluid
o Flushing action of body fluids helps keeps some area free of pathogens
o Urine - flowing through urethra, prevents bacterial growth, helps to stop bacteria reaching bladder and kidneys
o Also includes tears, sweat and saliva
Protective Defences/Reflexes
Automatic involuntary response to a stimulus
· Sneezing:
o Stimulus = irritation of walls of nasal cavity
· Coughing:
o Stimulus = irritation in the lower respiratory tract (bronchi + bronchioles)
· Vomiting:
o Stimuli = psychological
o Excessive stretching of stomach and bacterial toxins can all induce vomiting
· Diarrhoea:
Stimuli = irritation of the small and large intestines by bacteria, viruses or protozoans
Internal Non-Specific Defences: Phagocytosis
· This process by which certain immune cells engulf and destroy pathogens or other foreign substances in the body
· This process can be broken down into 6 stages
1. Phagocyte moves to the bacterium
2. Phagocyte changes shape to completely enclose bacterium
3. Lysosomes in phagocyte contains destructive enzymes
4. enzymes are released and destroy bacterium
Harmless particles are released from phagocyte
Neutrophils
first cells to arrive at the site of infection and are the most abundant immune cells involved with phagocytosis. Short-lived cells that can engulf and destroy bacteria, but are not as effective against larger pathogens
Macrophages
long-lived cells that can engulf and destroy a variety of pathogens, as well as dead cells and debris. They are also involved in presenting pieces of the pathogens to other immune cells, which helps to activate the adaptive immune response
Dendritic cells
specialised cells that can engulf and present pieces of the pathogens to other immune cells, which helps to activate the adaptive immune response
Natural killer cells
cells that can recognise and destroy infected cells or cells that are displaying abnormal behaviour
Purpose of Inflammatory Response
o Reduce the spread of any pathogens, to destroy them and to prevent the entry of additional pathogens
o Remove damaged tissue and cell debris
o Begin repair of the damaged tissue
Four signs: redness, swelling, heat, and pain
Inflammatory Response 7-steps:
- Mechanical damage / local chemical change activate mast cells which release histamine, heparin and other chemicals to the tissue fluid
- Histamine increase blood flow via vasodilation making capillary walls more permeable causing heat, redness & swelling
- Heparin prevents clotting and slow down spread of pathogen
- Complement proteins released by the mast cells attract phagocytes, like neutrophils which actively consume microorganisms
- Inflammation in the tissue stimulates the pain receptors.
- Phagocytes eventually die, forming pus
- New cells are produces by miosis for tissue repair
Fever
- Elevation in blood temperature
- Caused by the hypo, resetting to a higher level than usual in response to pyrogens (interleukin-1, released by WBC during inflammatory response)
Increase heat production = vasoconstriction & sweating occurs
Lymphatic System
Network of lymph capillaries joined by a larger lymph vessel
