lec 15, 16 anth 105

Epidemiological transition

Shift from infectious diseases to chronic diseases as main causes of death

Homeostasis

Maintaining stable internal conditions in the body

Allostasis

Achieving stability through change; set-points adjust based on context and stress

Stressor

Any environmental factor that triggers a stress (allostatic) response

Human stress uniqueness

Humans experience chronic stress, which is more damaging over time than short-term stress seen in most animals

Autonomic nervous system (ANS) components

Sympathetic = fight or flight; parasympathetic = rest and digest

Neurotransmitter vs hormone

Neurotransmitter = local signaling between neurons; hormone = travels through bloodstream to affect entire body

Epinephrine vs norepinephrine

Epinephrine increases heart rate and blood flow; norepinephrine regulates blood vessel constriction and flow

HPA axis

Hypothalamus-Pituitary-Adrenal system controlling stress hormone response

HPA axis hormone sequence

Hypothalamus releases CRH → pituitary releases ACTH → adrenal glands release cortisol

Cortisol functions

Increases blood glucose, supports metabolism, suppresses immune system, reduces bone formation

Shortest timescale adaptation

Allostasis (rapid physiological response)

Effects of chronic stress

Causes hypertension, memory issues, digestive problems, immune dysfunction, and metabolic disease

Reducing stress effects

Exercise, meditation, and therapy help lower or reverse stress-related damage

Allostatic load

The cumulative wear and tear on the body caused by chronic stress and repeated activation of the stress response

Acute vs chronic stress

Acute = short-term immediate response; chronic = long-term ongoing stress that damages health

Sympathetic nervous system

Activates fight-or-flight response, increasing heart rate and energy use

Parasympathetic nervous system

Promotes rest-and-digest, conserving energy and slowing heart rate

Acute stress response

Causes increased blood pressure and rapid physiological activation

UV radiation risks

Leads to premature aging, skin cancer, eye damage, and folate degradation

Folate function

Essential for red blood cell formation and cell growth, especially in embryonic development

Melanin types and roles

Eumelanin = dark pigment + UV protection; pheomelanin = red pigment, no UV protection; neuromelanin = found in neurons

Melanocyte

Skin cell that produces melanin

Melanin function

Absorbs UV radiation to protect deeper skin cells from damage

UV radiation (UVR)

High-energy radiation from the sun that can damage DNA but also enables vitamin D production

Vitamin D role

Helps absorb calcium and phosphorus for bone growth and maintenance

Vitamin D dietary sources

Oily fish, egg yolks, liver, butter, and mushrooms

Evolution of light skin

Skin lightened in low-UV regions to allow sufficient vitamin D production

MC1R gene

Regulates melanin production; activation increases eumelanin (protective pigment)

Melanocortins

Hormones that enhance DNA repair and reduce UV-induced damage during tanning

Tanning response

Increased melanin production after UV exposure to protect skin from further damage

Tanning beds vs sunlight

Can emit up to 4x more UVA than sun and provide no protective benefit

Animal UV adaptations

Includes pigmentation (giraffe tongues), chemical protection (hippos), and behaviors like burrowing

Eumelanin

Dark pigment that provides strong protection against UV radiation

Pheomelanin

Red/yellow pigment that provides little to no UV protection