Endocrine II - Endocrine System II First, Lets Compare Some...

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Endocrine System II
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First, Let’s Compare Some General Aspects of the Nervous and Endocrine Systems
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Nervous vs. Endocrine Systems Communication nervous - both electrical and chemical endocrine - only chemical Speed and persistence of response nervous - reacts quickly (1 - 10 msec), stops quickly endocrine - reacts slowly (hormone release in seconds or days), effect may continue for weeks Adaptation to long-term stimuli nervous - response declines (adapts quickly) endocrine - response persists Area of effect nervous - targeted and specific (one organ) endocrine - general, widespread effects (many organs)
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What is an Endocrine Axis? This is a Relationship between the hypothalamus, pituitary and a more remote gland…………. There are Three: 1. Hypothalamic-Pituitary-Gonadal Axis 2. Hypothalamic-Pituitary-Thyroid Axis 3. Hypothalamic-Pituitary-Adrenal Axis
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The HPA Axis REMEMBER the Dry Lab data analysis using stressed mice. There was a control group of mice with a complete HPA. Subsequent groups had variations with missing pieces of this axis. The HPG and HPT axis each work in a similar manner
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General Properties Of Hormones
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You Only Need A Small Amount A Small Amount of Hormone Goes A long Way: ---One molecule activates thousands of enzymes molecules through a process called enzyme amplification
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Enzyme Amplification
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Hormones are Cleared By The Liver AND…. Different hormones vary in their rates of clearance. The rate of hormone removal is called the metabolic removal clearance rate ( MCR). The length of time required to clear 50% of the hormone is from the blood is the half-life . Each hormone have a specific Half-life which differs due to different molecule structure, weight , whether it is bound or unbound to a transport protein.
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Target Cells Modulation of Sensitivity Target cells can modulate (adjust) their sensitivity to a hormone. Upregulation - A Cell increases the number of hormone receptors and becomes MORE SENSITIVE to a hormone. Downregulation - A cell reduces its receptor number and become less receptive to hormone.
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Modulation of Target Cell Sensitivity Long-term use of high pharmacological doses bind to receptor sites of related hormones target cell may convert to different hormone
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Hormones So Similar In Structure…. .
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Paradoxical Effects A target cell can convert one hormone such as testosterone to estrogen, during its pharmacological use. This may have paradoxically, feminization effects!
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Hormone Transport Monoamines and peptides are hydrophilic mix easily with blood plasma Steroids and thyroid hormone are hydrophobic must bind to transport proteins for transport bound hormone - attached to transport protein, prolongs half-life to weeks protects from enzymes and kidney filtration unbound hormone leaves capillary to reach target cell (half-life a few minutes) Transport proteins in blood plasma
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Endocrine II - Endocrine System II First, Lets Compare Some...

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