Daily dangers threaten human survival. The body’s defenses fight damage, control fears, and regulate functions; see laboratory conception. All life stages require precise conditions.
Heat and Cold (10:40)
Maintaining 98.6 degree Fahrenheit temperature is the body's top priority; see Norwegian children plunging in a freezing lake. Professor Mike Tipton studies survival in extreme environments. Skin receptors alert the brain to severe cold, triggering mechanisms such as shivering; increased carbon dioxide levels threaten chemical balance.
Humans are exposed to 60,000 virus and bacteria types daily. Diana Northup and Debbie Buecher study bacteria and investigate caves covered in bat guano; billions of potentially lethal pathogens are present in the excrement. Vulnerable areas in the body are protected by the immune system; antimicrobial agents in tears and mucus in nasal passages help build defenses.
Killing Invaders (03:56)
Lungs and lymphatic system are the main defenses against infection. Pathogens that land on lung lining attract dendrocytes, delivering samples to lymph nodes, which triggers specified antibody production. Professor Daniel Davis studies Natural Killer Cells; see the white blood cells destroying viruses.
Disgust Instinct (04:50)
Disgust is a primitive response that helps prevent infection. Professor Valerie Curtis tests reactions to bizarre foods. See the defense processes and expressions of dinner guests presented with repulsive courses.
Damage and Reaction (04:08)
Injury is unavoidable; wounds become bacterial entry points and blood loss causes oxygen deprivation. Ballerina Kate Byrne discusses various foot trauma and resulting discomfort. Mast cells detect damage and release histamine, allowing plasma flow to harmed areas; the repair process triggers nerves and pain.
Professor Steve McMahon conducts pain tests; volunteers undergo heat probe and cold immersion. Research reveals thresholds are not fixed. Byrne discusses the ability to perform with injuries. Signals traveling up the spinal cord are blocked by those from the brain, effectively suppressing pain.
Fear Response (04:40)
Fear is a survival tool and a learned reaction not present in infants. Rattlesnake catchers discuss their profession. When threats are perceived, the amygdala generates physical reactions aiding in fight or flight defense.
Managing Terror (08:07)
Professor Fredrik Ahs studies the brain's control of fear; see MRI scans of patients shown threatening images. Prefrontal cortex reactions, gained through logic and experience, suppress panic. Snake catchers capture and remove rattlers from homes and yards.
Summary and Credits: Survive (01:13)
Summary and Credits: Survive
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