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Function of the endocrine system
- * Helps regulate metabolic process
- * Aids in transport of various molecules across cells
- * Maintains water balance
- * Important in reproduction
- * Promotes growth on many tissue
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Mechanism of hormone action
- * Hormone affects only certain tissues or organs (target cells)
- * Target cells must have specific protein receptor[matching protein to the TC]
- * Hormone building influence the working of the cells
- [hormones use blood to circulate]
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The endocrine system
- * includes many endocrine glands
- * Uses chemical messengers called hormones, released into the circulation
- * Differ in its mode of release compared to the nervous system
- * [glands and hormones make up endocrin system]
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Hydrophilic hormones (image)
- * Hydrophilic hormones bind to the receptor protein on the membrane
- * They start a second messenger system
- * First, the hormone activates another protein calles adenylate cyclase (AC)
- * AC activates cAMP
- * cAMP activates protein kinase A (PKA)
- * PKA stimulates changes in the cell
- [cannot access the cell but can affect the cell indirectly-cascading event ]
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Hydrophobic hormone (image)
- * Hydrophobic hormones can freely cross the membrane
- * They get to the nucleus and bind to the receptor
- * The receptor-protein complex bind to the DNA
- * RNA is made from the DNA
- * RNA binds to ribosomes and makes specific proteins
- * Proteins made cause changes in the cell
- [can acces the cell & directly affect the cell]
- Around about way in to the cell
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Differences between endocrine release and nervous release
- * Neurons release neurotransmitter into synaptic cleft to affect the postsynaptic cell
- * Glands release hormones into the circulation to affect target cells
- Physical can get in to the cell directly
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Major endocrine glands
- * Hypothalumus
- * Pituitary
- * Parathyroid
- * Kidney
- * Testes
- * Pineal
- * Thyroid
- * Thymus
- * Adrenal glands
- * Kidneys
- * Pancreas
- * Gonads
- [know what hormones are released & what it does for each gland]
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Hormonal control
- * Homonal release is activated by other hormones
- * For example, glucose levels are measured constantly in the blood. If the level is high, insulin is released
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Hormonal secretion
- * The level of hormones in the blood is always controlled by the brain
- * different glands are controled by different mechanism s
- * Humoral, neuronal, or hormonal
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Adrenal glands
- * Sit on top of the kidneys
- * Made of two glands:
- o The adrenal cortex
- o The adrenal medulla
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Humoral control
- * The level of certain chemical is always measured in the blood and based on this hormone may or may not be released
- * For example, glucose level are measured constantly in the blood. If the level is high, insulin is released
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Neuronal control
The glands are stimulated directly bty
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Adrenal cortex
- * Release two hormones:
- * Aldosterone
- * Acts on the kidneys to retain sodium and secrete potassium
- o Cortisol
- * Stress hormone that increases nutrients (glucose, fat, aand amino acids) in the blood
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Anterior pituitary gland (6)
- * Made of epithelial cell
- * Growth hormone
- * Prolactin: milk production
- * Thyroid stimulating hormone (TSH): stimulate the thyroid gland to release its hormone
- * Adrenalcorticotropic hormone (ACTH); causes the adrenal gland to relea
- * Follicle stimulating homone (FSH) act on the testes and ovaries
- * Luteinizing hormone: acts on the testes and ovaries
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Thyroid gland
- * Located below the larynx
- * Made of two lobes connected by isthmus
- * Produceed two hormones:
- o Thyroid hormone
- o Calcitonin:
- * Thyroid hormone
- o Increase cell metabolism
- * Calcitonin
- o Decrease calcium levels in in blood
- o Increase calcium levels in the bones
- * Parathyroid hormone increase
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Posterior pituitary gland (2)
- * Made of neurons
- * Antidiuretic hormone (ADH): prevents water loss
- * Oxytocin: smooth muscle contraction and milk ejection
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Adrenal medulla
- * Releases the hormones epinephrine and norepiphrine
- o Stress hormones that increase heart rate breathing rate and glucose level in the blood
- o Stimulate the sympathetic nervous system activates the flight or fights
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How can hormones stimulate changes in target cells?
- * Hormones have different chemical composition
- * Some are hydrophilic and some are hydrophobic
- * The hybrophobic ones can cross the cell membrane very easily
- * The hydrophilic ones can not cross the membrane and therefore bind to receptor proteins on the membrane
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Pancreatic hormone
- * Glucagon
- o Increase glucose level in the blood
- o Released furing fast
- * Insulin
- o Decreased glucos level in the blood
- o Released after a sugar meal
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What is the difference between the stress hormones released from the cortex and the medulla
- * Epinephrine and norepinephrine are released due to short-term stress such as a bio exam
- * Cortisol is released to chronic stress
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Other endocrine glands
- * Pineal gland
- o Releases melatonin that helps circadian rhythm
- * Thymus gland
- o Releases thymosins that is important in the immune system
- * Ovaries and testes
- o Secrete hormone important reproduction
- * Kidneys
- o Release erythropoitientin to stimulate bone to release red blood cells
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Pancreas
- * Located behind the stomach
- * Release two hormone that are antagonistic to each other
- * Disorder associated with pancreatic hormone cause diabetes
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What are the effects caused by hormones?
- * Change in plasma membrane, permeability, or electrical state
- * Synthesis of protiens and enzymes
- * Activation of inactive enzymes
- * Stimulation of cell division
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Parathyroid gland
- * Located posterior to thyroid gland
- * Releases parathyroid hormone (PTH)
- o Increase calcium level in the blood
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