6 Hormones - 1 Biology 5B Signaling: Hormones Two systems...

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Unformatted text preview: 1 Biology 5B Signaling: Hormones Two systems coordinate communication throughout the body: the endocrine system and the nervous system The endocrine system secretes hormones that coordinate slower but longer-acting responses including reproduction, development, energy metabolism, growth, and behavior The nervous system conveys high-speed electrical signals along specialized cells called neurons; these signals regulate other cells Overarching control in Organisms 2 Overview: The Bodys Long-Distance ( but slower ) Regulators Animal hormones are chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body Hormones reach all parts of the body, but only target cells are equipped to respond CONCEPT: Hormones and other signaling molecules bind to target receptors, triggering specific response pathways Secreted chemical signals include: Hormones Local regulators Neurotransmitters Neurohormones Pheromones 3 Hormones and Local Regulators Endocrine signals (hormones) are secreted into extracellular fluids and travel via the bloodstream Endocrine glands are ductless and secrete hormones directly into surrounding fluid Hormones mediate responses to environmental stimuli and regulate growth, development, and reproduction Local regulators are chemical signals that travel over short distances by diffusion (two types) Paracrine signals act on cells near the secreting cell Autocrine signals act on the secreting cell itself Blood vessel Response Response Response (a) Endocrine signaling (b) Paracrine signaling (c) Autocrine signaling 4 Neurotransmitters and Neurohormones Neurons (nerve cells) contact target cells at synapses At synapses, neurons often secrete chemical signals called neurotransmitters that diffuse a short distance to bind to receptors on the target cell Neurotransmitters play a role in sensation, memory, cognition, and movement Neurohormones are a class of hormones that originate from neurons in the brain and diffuse through the bloodstream Response (d) Synaptic signaling Neuron Neurosecretory cell (e) Neuroendocrine signaling Blood vessel Synapse Response 5 Pheromones Pheromones are chemical signals that are released from the body and used to communicate with other individuals in the species Pheromones mark trails to food sources, warn of predators, and attract potential mates Chemical Classes of Hormones Three major classes of molecules function as hormones in vertebrates: 1. Polypeptides (proteins and peptides) 2. Amines derived from amino acids 3. Steroid hormones Lipid-soluble hormones (steroid hormones) pass easily through cell membranes, while water-soluble hormones (polypeptides and amines) do not The solubility of a hormone correlates with the location of receptors inside or on the surface of target cells 6 Signaling by hormones involves three key events: 1. Reception 2. Signal transduction 2....
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6 Hormones - 1 Biology 5B Signaling: Hormones Two systems...

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