Problems of, and solutions to a changing environment

• A chemical substance that affects the central nervous system, causing changes in psychological behaviour, as well as addiction

Painkillers

• Block pain impulses and are largely available
• If nerve impulses are blocked => no sensation => morphine molecules are very good at this

Halluciogens

• Create hallicinations and distort sense of perception => normal nerve impulse is interfiered with

Depressants

• Slow down your responses and increase your reaction times to a physical/mental situation

• Nicotine is an addictive drug => smokers become dependant on it
• Tar as a carcinogen can cause mutations in the cells of the throat and lungs => could result in lung cancer/throat cancer
• Carbon monoxide reduces the oxygen in blood => gets converted to carboxyhaemoglobin

• Blurred vision => when highly intoxicated, balance is effected => blurry vision
• Slowing of reactions => Alcohol is a depressant and slows down brain activity 
• Brain damage => Is associated to significant brain lesions => causes permanent brain damage

• Water: when in contact with contaminated water, pathogens are spread => why pools are treated to kill bacteria with chlorine
• Food: eating food contaminated with pathogens => can cause food poisoning
• Airborne: sneezing => producing a fine mist of water droplets containing millions of bacteria
• Contact: touching a contaminated surface => e.g athlete's foot is spread widely by swimming baths

• Chemical defense: our eyes produce Iysozymes that kill bacterial microorganisms on surface of eye, stomach producing HCl to kill off bacteria
• Physical defense: mucous traps bacteria before it enters the the lungs, skin is quick in recovery (releases PAF hormone and plugs wounds)