Biology 200B 1st Edition Lecture 18Chemical Signals in AnimalsI. Hormones II. Endocrine systemIII. Hydrophilic vs. LipophilicIV. Hypothalamus-Pituitary ComplexV. Hormones and behaviorHormones – carried by blood; secreted by glandsNeurotransmitters – secreted by neurons; act as hormonesParacrine – regulators do not travel in bloodPheromone – released into environment to signal othersKey points:- Hormones produce responses only in target cells with appropriate receptor- Occur in very low concentrations but have enormous affect on target cells- Have long lasting effects on distant target cells- Regulate cell processes across short and long time scalesEndocrine system: organs that secrete hormones into the bloodstream - Hypothalamus - Anterior pituitary gland- Thyroid gland- Adrenal gland- PancreasThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.2 Types of HormonesHydrophilic – can be dissolved in water; cell surface receptorLipophilic – fat loving; receptor inside cellTarget cell response: Hydrophilic peptidesEx: Epinephrine released by adrenal gland - fight or flight- target is glycogen – storing cells in liver - hydrophilic hormone – cell surface receptor- second messenger (cAMP) causes a signal transduction cascade- single molecule binding is amplified by second messenger process- immediate short term effects support fight or flight responseEx: Estrogen released by ovaries stimulate second sex characteristics at puberty in human females- same hormone can trigger different responses in differing cells because of different receptors, secondary messengers, amplification steps, or active genesHypothalamus-Pituitary Complex- Pituitary connected to and regulated by hypothalamus- Releasing factors from hypothalamus stimulate pituitary to secrete tropic hormones – target glands- Target glands release regulatory hormones - These hormones have negative feedback on complexIn action: Stress and Cortisol- Lipophilic glucocorticoid - Ensures availability of glucose for brain; during stress- Regulates short (hours) and long term (days/weeks/months); responses to stress- Consequences of long term stress are badThyroid hormones regulate amphibian metamorphosis- Bind to nuclear receptors - Regulate enzymes controlling carbohydrate and lipid metabolism - Often function synergistically with other hormones- Trigger metamorphosis in tadpolesLeptin and Obesity - A satiation (“stop eating”) hormone - Obese mouse has two defective genes for leptin- Secreted by adipocytes (fat cells) when total adipose mass is high - Its target cells are in the brainHormones and behavior – consistent “personalities” associated with glucocorticoidTestosterone and aggression - males more aggressive, castration reduces aggressive behavior - inter-male and territorial aggression increases after pubertyEndocrine disruption occurs when chemicals imitate natural
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