4th Exam: Diversity

cells specialized to control other cells

neurons, endocrine cells

nervous system

control fine, fast movements; can end abruptly

endocrine system

controls widespread, prolonged processes; slower to end once affecting cells; reaches many cells

nervous and endocrine systems working together

brain can signal release of hormones and hormones can control nervous system

spatial scales of signaling (short to long)

local diffusion, local diffusion following long-distance electrical signaling, transport in blood throughout body, transport in the outside environment

endocrine glands

no ducts; secrete into the bloodstream; has intracellular effects (ex. alter metabolism/ physiology)

endocrine gland structure

high density of capillaries; fenestrated; easy access for hormones to go straight into bloodstream

exocrine glands

secrete products through ducts onto epithelial surfaces; has extracellular effects (ex. digestion of food, poison, mucus/ slime coat)

hormones

chemical messengers traveling in blood; effective at low concentrations; presence of receptor on target cell determines interaction; properties of target cell determine action

types of endocrine cells

neurosecretory, non-neural endocrine cells

neurosecretory

endocrine cells behave and look like neurons, but release hormones instead of neurotransmitter

neurohemal organ

structures with neurosecretory cells; have neural tissue and needs circulatory blood tissue nearby

non-neural endocrine cells

epithelial endocrine cells; ordinary cells; no nervous tissue communicating with cell directly; has receptors to detect blood and trigger release of hormones

3 classes of hormones

steroids, monoamines, peptides

steroids

made from cholesterol; ex. progesterone, testosterone cortisol

monoamines

made from amino acids; ex. dopamine, epinephrine, melatonin, TH

peptides

3-200 amino acids (relatively large); ex. releasing and inhibiting hormones of hypothalamus, most pituitary hormones

transport of hormones

through blood; monoamines and peptides hydrophilic/ water-soluble so travel freely; steroids and TH hydrophobic/ fat-soluble so must travel with transport proteins for help (prolongs half-life)

receptors and action of steroids

can diffuse through membrane; pass straight into nucleus; gene activation; lag time due to transcription and translation

receptors and action of peptides

can’t pass through membrane; cell surface receptors activate second messenger systems/ signal cascades

hormone action dependencies

function can change over evolutionary time (ex. prolactin) and be different within an individual (ex. epinephrine in heart vs digestive tract)