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Glands

Glands. Exocrine Gland : secretory gland that secretes externally through a duct. Eg . Salivary glands Endocrine Gland : ductless gland that secretes hormones into the bloodstream. Hormones.

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Glands

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  1. Glands • Exocrine Gland: secretory gland that secretes externally through a duct. • Eg. Salivary glands • Endocrine Gland: ductlessgland that secretes hormones into the bloodstream.

  2. Hormones • Hormones are chemical substances such as proteins, steroids or fatty acids secreted by endocrine glands in vertebrates and secreted directly into blood stream.

  3. Target cell • Most hormones circulate in blood, coming into contact with essentially all cells. However, a given hormone usually affects only a limited number of cells, which are calledtarget cells. A target cell responds to a hormone because it bears receptors for the hormone. • The effector is usually an organ. • Only a small amount of hormone is required to alter cell metabolism.

  4. Hypothalamus Parathyroid

  5. The Pituitary Gland • Central role in overall endocrine regulation • More than half of the hormones in mammals are released from the Pituitary Gland

  6. The Hypothalamus • Collection centre for information regarding the body’s state of well-being • This information is used in regulating secretion from the pituitary gland by producing releasing hormones that control secretion of some hormones from the pituitary glands

  7. The Hypothalamus • The hypothalamus, a collection of specialized cells that is located in the lower central part of the brain, is the primary link between the endocrine and nervous systems. Nerve cells in the hypothalamus control the pituitary gland by producing chemicals that either stimulate or suppress hormone secretions from the pituitary

  8. Animal hormones • One way to group hormones is in terms of the distance they travel to exert their effect on a target cell. • Endocrine signals: usually secreted into circulating blood and travels long distances • Paracrine signals:act on cells in the local neighbourhood: travel to site of action by diffusion through extracellular fluid • Autocrine signals: chemical signals that act on the receptors of the secreting cell.

  9. Endocrine signalling Target cell with specific receptor Hormone secreting cells that make up endrocrine tissue in ductless glands (endocrine organ) Target cell with out specific receptor Secreted directly into circulating blood and distributed widely throughout the body

  10. Paracrine signals Communication between cells in the local neighbourhood Secreting cell Paracrine signals are released into the extracellular fluid and act on cells in the local neighbourhood. Neurotransmitters and cytokines are paracrine signals Target cells

  11. Autocrine signals Cell Responds Receptor Stimulus

  12. What are cytokines • Cytokine is the general name for a large group of signalling molecules that communicate between different cells of your immune system • They act in a paracrine or autocrine manner and are extremely potent signals.

  13. Hormonal Pathways answer these questions: 1. What is the name given to cells that respond to hormones? 2. Why is this communication specific? Explain. 3. Why are hormonal effects generally slower than nervous responses? Explain.

  14. ~END~

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