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Lecture 34

BIOLOGY 172 Lecture 34: Neuronal Signaling

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Stephen Clark

Biology 172 Dr. Clark- Winter 2017 Lecture 24: Endocrine Signaling Neuronal signaling are transient, rapid responses; signal travels along neuron Endocrine signaling are slow and sustained o Growth o Homeostasis o Sexual development o Signals travel via hormones in blood and have extensive feedback control Usually tightly linked with neuronal system  function together, called the neuroendocrine system Long distance signaling o Pituitary gland releases hormones into body that affect distal tissues o Blood stream acts as highway o Issue of DILUTION o When cell releases hormones, it is diluted into 15L of blood and is diluted more as it gets into the tissues o Endocrine glands are tightly interwoven with blood vessels so that there is a rapid secretion of signals Types of Endocrine Hormones 1) Peptide hormones (ADH, oxytocin) a. Small proteins 2) Amine Hormones (dopamine and epinephrine) a. Derived from tyrosine or tryptophan; modified amino acids 3) Steroid hormones (testosterone) a. Look like cholesterol; made from cholesterol Peptide signals encoded for by genes, typically released from larger precursor proteins (short) and are stored in secretory vesicles (pre-made); let out in an immediate burst Amines are modified from amino acids by enzymes; stored in secretory vesicles; released in immediate bursts Steroids are modified from cholesterol. Hydrophobic; synthesized on demand and released in a slow ramp up of signals Hormone Receptors 1) Steroid hormones have intracellular receptors in cytoplasm  it moves into nucleus and changes gene expression; slow responses because it requires transcription and translation 2) Peptides and amines have cell surface receptors; fast responses from help by signal amplification and post transcriptional regulation; most do not require a change in gene expression Most endocrine signals act through G-protein coupled receptors  PKA pathway! Many endocrine glands  hypothalamus and pituitary glands act as master regulators Feedback Positive feedback reinforces a signal or process Negative feedback moderates a signal or process Organization of neuroendocrine system Hypothalamus is how brain communicates with pituitary gland  se
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