BIOL 122 Chapter 17: The Endocrine System Part 2
BIOL 122 Chapter 17: The Endocrine System Part 2 BIOL 122
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This 3 page Class Notes was uploaded by Bridget Notetaker on Thursday February 4, 2016. The Class Notes belongs to BIOL 122 at University of Southern Indiana taught by Dr. Pilcher in Spring 2016. Since its upload, it has received 15 views. For similar materials see Human Anatomy & Physiology II in Biology at University of Southern Indiana.
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Date Created: 02/04/16
Chapter 17: The Endocrine System (Part Two) Wednesday, January 27, 2016 10:34 AM Control by humoral stimuli In response to changing blood level of certain compounds (ions and nutrients) Examples: PTH: response to altered blood calcium Insulin: in response to altered blood glucose Neural stimuli In response to signals from nervous system Can be stimulatory or inhibitory -‐An action potential (AP) in a neuron innervating an endocrine cell stimulates secretion of a stimulatory neurotransmitter -‐The endocrine cell secretes its hormone into the blood where it will travel to its target -‐The AP in the neuron stimulates secretion of an inhibitory neurotransmitter -‐The endocrine cell is inhibited and does not secrete its hormone SNS to adrenal medulla -‐-‐> release of catecholamines Epinephrine Norepinephrine Neuropeptides Peptide molecules released from nerve cells Acts as neurotransmitters From pituitary: oxytocin and ADH released Hormonal stimuli One hormone regulates the secretion of another Tropic hormones Example: hypothalamic hormones regulate release of anterior pituitary hormones -‐Neurons in the hypothalamus release stimulatory hormones called releasing hormones. Releasing hormones travel in the blood to the anterior pituitary gland -‐releasing hormones stimulate the release of tropic hormones from the anterior pituitary, which travel in the blood to their target endocrine cell -‐The target endocrine cell secretes its hormone into the blood, where it travels to its target and produces a response gland -‐releasing hormones stimulate the release of tropic hormones from the anterior pituitary, which travel in the blood to their target endocrine cell -‐The target endocrine cell secretes its hormone into the blood, where it travels to its target and produces a response RH TSH Thyroid hormone Hypothalamus - -‐> Anteri -‐ > --‐ > Target cells Negative feedback When the end product of a pathway has a negative impact on the functioning of earlier parts of the pathway As thyroid levels increase in the blood, they work to inhibit the hypothalamus and anterior pituitary Slows down the releasing of thyrotropin releasing hormone and release of thyroid stimulating hormone Positive feedback -‐The anterior pituitary secretes a tropic hormone, which travels in the blood to the target endocrine cell -‐The hormone from the target endocrine cell travels to its target -‐The hormone from the target endocrine cell also has -feedback effect on the anterior pituitary and increases secretion of the tropic hormone Effect of hormone binding Altered cell activity -‐Alteration of membrane permeability or membrane potential (via opening/closing channels) -‐Synthesis of proteins or enzymes -‐Activation/deactivation of enzymes -‐Induction of secretion -‐Stimulation of mitosis Hormone receptors Proteins with receptor site (active site) Affinity How tightly the hormone binds to the receptor High affinity=larger effect/longer lasting in target cell Low affinity=won't attach well or long Specificity Each hormone receptor will only bind to a specific hormone Location of receptors High affinity=larger effect/longer lasting in target cell Low affinity=won't attach well or long Specificity Each hormone receptor will only bind to a specific hormone Location of receptors Lipid-‐soluble hormones Can cross membrane Receptors within nucleus Water-‐soluble hormones Cannot cross membrane Receptors on cell surface Mechanism of action for lisidluble hormones Lipid-‐soluble hormones diffuse through the plasma membrane They bind to cytoplasmic receptors and travel to the nucleus or bind to nuclear receptors The hormone -‐receptor complex binds to a hormone response element on the DNA, acting as a transcription factor The binding of the hormo-‐receptor complex to DNA stimulates the synthesis of the messenger RNA (mRNA) The mRNA leaves the nucleus, passes into the cytoplasm of the cell, and binds to ribosomes The newly synthesized proteins produce the cells response to tpsidluble hormones… for example, the secretion of a new protein
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