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The Endocrine System. Chapter 10; p307-308. Video Link. http://www.youtube.com/watch?v=iDy_p9912ao&feature=channel. Hormonal pathways. Hormones – chemical compounds which act as intercellular messengers and regulate cell function.
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The Endocrine System Chapter 10; p307-308
Video Link • http://www.youtube.com/watch?v=iDy_p9912ao&feature=channel
Hormonal pathways • Hormones – chemical compounds which act as intercellular messengers and regulate cell function. • In cells, the hormonal system affects various metabolic functions: • rates of chemical reactions • transport of substances across the plasma membrane • secretion • growth
How hormones work • Target cells – possess a specific receptor for a particular hormone. • A hormone transmits its signal to a target cell by changing the biochemical reactions within it. • Hormones have effect in low concentrations at receptors outside the cell, or directly by passing through the cell membrane.
1. Specificity • Hormones are specific in two ways: • Only a particular stimulus will trigger a particular set of hormones. • Only those cells with particular receptors will be triggered by a particular hormone. • E.g. The hormone adrenaline only effects cells with adrenaline receptors such as muscle cells of the heart and blood vessels.
Hormones bind with target cells with specific receptors. A hormone transmits its signal to a target cell by changing the biochemical reactions within it.
A hormone is secreted (released) from a hormone secreting cell into the blood system.
2. Speed • Hormones, compared with nervous responses are quite slow. • However, some hormones are carried by certain blood vessels straight to their target cells.
Hormones • Two main types: • Synthesised from fatty acids • Synthesised from amino acids • Hormones derived from fatty acids: • Fat soluble • Easily pass through cell membranes • E.g. Steroid hormones (testosterone and oestrogen) - Enter the cell, continue through the nucleus and then act on a particular gene.
Hormones • Hormones derived from amino acids: • Protein based • Water soluble cannot pass through cell membrane. • Bind to receptors in the plasma membrane
Endocrine glands • Endocrine glands: organs with tissue containing cells which excrete (release) hormones. • E.g. Saliva, digestive and sweat glands.
Location of mainendocrine glands Hormones are produced in and secreted from various glands around the body.
Location of Hypothalamus and Pituitary glands The pituitary and pineal glands, the thalamus and hypothalamus are all closely connected.
Hypothalamus • Connected to the pituitary gland - it produces hormones which control the release of some hormones from the pituitary gland. • Receives information from rest of the body about the state of physical well-being such as: • Need for food and water. • Smell • Pain and other emotions
The pituitary gland • Central in endocrine regulation. • The pituitary gland is responsible for: • Regulation of growth • Lactation • Reproductive state • Skin pigmentation • Fat tissue • Kidney function • Activity of thyroid and adrenal glands.
Blurring of the boundary between endocrine and nervous systems • There is not always a clear distinction between the endocrine and nervous system. • Some hormones are produced in nerve cells.
