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Unformatted text preview: 1. I ntroducing the Vertebrate Endocrine System Signaling molecules help integrate cell activities in ways that keep the body working smoothly- Hormones, neurotransmitters, local signaling molecules and pheromones are signaling molecules in animals- Works on target cells; the target is a cell that bears receptors for it; receptors are located in the PR, cytoplasm or nucleus Hormones secretory products of endocrine glands, endocrine cells in tissues, and few neurons- i.e. insulin secreted by pancreatic cells into interstitial fluid, diffuses into blood capillaries then bloodstream and transported throughout body; diffuses out of blood into all tissues but only acts on cells that have functioning receptors for it neurotransmitters signaling molecules released from axon endings of neurons which then swiftly activate/inhibit target cells after diffusing across tiny synaptic cleft between them local signaling molecules change chemical conditions in local tissues, as when action of some prostaglandins restricts/enhances blood flow to a tissue pheromones diffuse through water/air to target cells in other individuals of the same species; help integrate social behavior- i.e. soldier termites secrete one pheromone that acts as an alarm signal when ants attack their colony first hormones discovered by W. Bayliss and E. Starling in early 1900s gene duplications and modifications may account for diversity in signaling molecules and the receptors for them endocrine system all sources of hormones inside the vertebrate body most endocrine sources and nervous system interact in intricate ways 2. The Nature of Hormone Action Hormone response requires 1. Activation of a receptor for that hormone 2. Transduction of receptors signal into a molecular form that can exert effects inside the cell 3. Functional response Responses to hormones vary- Different hormones act on different mechanisms- Not all types of cells are able to respond to a particular hormone...
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- Spring '08