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ways for cells to communicate
- 1. Direct: very fast, but also has a very short range. Ex gap junctions in heart cells)
- 2. Synaptic
: nerves (unit 3) - 3) Paracrine: extracellular fluid. Ex histamine
- 4) Endocrine: bloodstream, trigger responses that may last from a few seconds to a lifetime. Ex oxytocin, testosterone
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How Do Animal Hormones Work?
- Hormones act by binding to receptors on or in target cells
- Receptors for hormones are found in two general locations on target cells:
- On the plasma membrane
- Inside the cell, within the cytoplasm or the nucleus
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The major endocrine glands and organs are:
- The hypothalamus–pituitary complex
- The thyroid gland
- The pancreas
- The sex organs
- The adrenal glands
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The pituitary gland
is pea-sized gland connected to the hypothalamus by a stalk
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The pituitary consists of two distinct parts:
- The anterior pituitary: a true endocrine gland
- The posterior pituitary: capillary bed and the endings of neurosecretory cells
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Anterior pituitary
- Growth hormone acts on nearly all the body’s cells by increasing protein synthesis, promoting the use of fats for energy, and regulating carbohydrate metabolism
- During childhood, growth hormone stimulates bone growth, which influences human height
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Posterior pituitary
- synthesize and release either antidiuretic hormone (ADH) or oxytocin
- Alcohol inhibits the release of ADH and increases urination, resulting in dehydration
- Oxytocin may play a role in emotions, including trust and both romantic and maternal love
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Thyroxine
- iodine-containing amino acid derivative
- Stimulates glucose breakdown and elevates the metabolic rate of many body cells
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The thyroid and parathyroid glands influence
- metabolism and calcium levels
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Pancreas: islet cells
- produce one of two peptide hormones: insulin and glucagon
- Insulin and glucagon work in opposition to regulate carbohydrate and fat metabolism
- Insulin reduces the blood glucose level
- Glucagon increases it
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sex hirnibes
- The testes: androgens (testosterone )
- The ovaries: estrogen and progesterone
- Puberty: hypothalamus stimulate the anterior pituitary to secrete more luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
- LH and FSH stimulate target cells in the testes and ovaries to produce higher levels of sex hormones
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pineal gland
- melatoninsecreted in a daily rhythm, regulated by light entering the eyes
- regulate the seasonal reproductive cycles of many animals
- function in humans is still not known
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kidneys
- erythropoietin (low oxygen levels); renin (low blood pressure); angiotensin (low blood pressure )
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erythropoietin
kidneys (low oxygen levels)
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renin
- (low blood pressure
- secreted by kidneys
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angiotensin
- low blood pressure
- secreted by kidneys
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Fat cells
- leptin“tells” the body how much fat it has stored and therefore how much to eat
- stimulating the growth of capillaries and speeding wound healing
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