Week4BMSnotes.pdf BMS 260
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Popular in Biomedical Sciences
This 6 page Class Notes was uploaded by Mikaela Maldonado on Saturday February 13, 2016. The Class Notes belongs to BMS 260 at Colorado State University taught by Dr. Russell Anthony in Spring 2016. Since its upload, it has received 36 views. For similar materials see Biomedical Sciences in Biomedical Sciences at Colorado State University.
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Date Created: 02/13/16
Refractory Period Depolarization is much quicker than repolarization Action potential moves in one direction but at a site on an axon fiber cannot be restimulated right away Absolute refractory period During depolarization and repolarization another action potential cannot be created o Forces action potential to move in one direction, speed will be the same from one end to the other o After refractory period action potentials can be regenerated Relative Refractory Period nd Start 2 action potential but the stimulus threshold has to be greater than the first Towards the end of repolarization or after hyperpolarization Slow conduction nerve will have a longer refractory period Cardiac nerves o Long refractory period to allow for relaxation Skeletal muscle nerves o Short refractory period allows to be held Conduction Velocities Constant for a give nerve fiber Types (myelination/not) of fiber Diameter – impacted by myelination Salutatory Conduction Action potentials jump from one node to the next as they propagate along a myelinated axon Nodes of Ranvier o Gap in myelin o Each of these are essentially cells with cell membrane that cover the “wires” (axon) in the nervous system o Action potentials jump from one node to the next Ex: Somatic nerve o Myelinated and spinal o Diameter 20 micrometers o 130 m/s or 250 mph o alpha fiber postganglionic fiber o parasympathetic o not myelinated o 0.5 microns in diameter o 0.5 m/s ~ 20 inches per second Synapses axons have a synaptic knob between 2 nerve cells, nerve/gland, nerve/tissue electrical energy transformed into chemical energy can be like telephone poles and attach to any pars of another nerve cell dendodendrites (named for what attaches where) are super rare and typically occur in the cerebellum Type I o Excitatory post synaptic potential (EPSP) o Acetyl choline, epinephrine, norepinephrine o Depolarize membrane o Increase Na influx Type II o Inhibitory post synaptic potential (IPSP) o Glycine, gamma amino butyric acid (GABA) o Hyperpolarize the membrane o Increase K influx and Cl influx Synaptic integration o You will have both Type I and II o Skeletal and somatic cells are the only ones with 1:1 action potentials Conduction neurotransmitter molecules are synthesized and packaged in vesicles an action potential arrives at the pre synaptic terminal voltage gated Ca channels open and Ca ions enter o smooth ER stores Ca o the influx of Na switches to Ca at the synaptic knob o increase in Ca concentration, increases migration in exocytosis or secretion of neurotransmitter vesicles rise in Ca triggers fusion of synaptic vesicles with the presynaptic membrane transmitter molecules diffuse across the synaptic cleft and bind to specific receptors on the post synaptic cell bound receptors activate post synaptic cell neurotransmitter breaks down is take up by presynaptic terminal or other cells or diffuses away from the synapse Transmission one direction synapse provides for modification of transmission speed not at 1:1 ration between pre and post synaptic action potentials neurotransmitters o excite or inhibit action of the postsynaptic cell Peripheral nervous System Synapses acetylcholine o abundant o nicotinic receptors – Ionotropic o muscarinic receptors – metabotropic norepinephrine and epinephrine o action through adrenergic receptor o metabotropic in nature Ionotropic Receptor acetylcholine is released into the synapse Na+ and acetylcholine driven co transport through ion channels into both the pre and post synaptic knobs Nicotinic Ach receptor channel is activated Membrane is depolarized Action potential is excited Muscle contraction results Results in a fast, rapid response Pores allow the ion through Metabotropic Receptor nd 2 messenger system is what opens the ion channel acetylcholine is released into the synapse Na+ and acetylcholine driven co transport through ion channels into the pre synaptic knob Acetylcholine binds to G protein couple receptor o Beta and gamma subunits release to activate the movement of K+ back outside of the cell Alpha subunit releases and activates muscarinic Ach receptor Membrane is hyperpolarized through release of K+ ions out of the cell that causes a decrease in heart rate Slow and sustained response Voluntary control CNS -> nicotinic receptor that responds to acetyl choline -> skeletal muscle activation Involves one neuron Involuntary Control Involves 2 neurons Rest and Digest o Parasympathetic o Long preganglionic neuron o Acetyl choline and muscarinic receptor Fight or Flight o Sympathetic o Short preganglionic neuron o Adrenergic receptors Endocrine System Hormone o Excite or inhibit something o Travels in blood o Chemical compounds o Adapt responses from neurons o Neurohormones Regulatory Secreted by neuroendocrine transducers Electrical energy Hormonal response conversion Ex: Pituitary Posterior – nervous tissue Anterior – secretes hormones Endocrine o Regulate rather than initiate o Stores hormones o Not the same rate of secretion o Secretion into the blood is ductless o Hormones secreted into the blood do 4 things Excretion in urine or feces Inactivated through metabolism Activated through metabolism Bind to a receptor on target cells and produce a cellular response o Signaling Endocrine – through the blood over large distances Paracrine – neighboring cells Autocrine – cells that activate themselves Exocrine o Secretion onto a surface from the blood o Involves ducts o Outward bound 4 Types of Endocrine Hormones o steroids derived from cholesterol intracellular receptors complex acts as transcription factor and increase mRNA expression and transcription testosterone, cortisol o biogenic amines – more soluble when it is not nonpolar uses surface receptors thyroid hormone, catecholamines o prostenoids – fatty acid derivatives pathway for creation through CDX1 and 2 and fatty acids o protein hormones peptide (oxytocin, ADH) <polypeptide (relaxin, insulin) <protein (prolactin, GH)<glycoprotein (LH and FSH) Membrane-Bound Receptors o Ion channels, G protein couple receptors, kinase pathway receptors, 7 pass alpha helix structure, intrinsic enzymatic activity, enzyme associated receptor o Activate intracellular signaling cascades that affect cell function o Activate downstream mediators that activate DNA transcription and also effect other parts in the cell o Faster than a lipid, steroid receptor, but is less sustained nd o Polar, hydrophilic, rapid, 2 messengers, temporary o NE, E, Oxytocin, ADH Lipid Soluble Messengers o Diffuse through the plasma membrane o Intracellular receptors o Bind directly to recognized sequences in DNA and alter transcription o Slow but sustained o Non polar, intracellular, hydrophobic, slower, more permanent o Steroids and thyroid hormone Water Soluble Messengers nd o Kinase, receptor tyrosine, cascades, G proteins, 2 messenger ion channels, amplification Pituitary Posterior o Hormones Oxytocin -> uterine muscles, mammary glands Contraction of myoepithelial cells in mammary ADH -> kidney tubules Vasopressin Increase blood pressure Stimulate glycogenosis Reabsorption of water o Neurohypophysis Neural tissue o Hypothalamus Generates hormones Travel through nerve cells (axoplasmic transport) directly to posterior Stored until released to the blood Anterior o Gland tissue o Hypothalamus Releasing hormones Travel to anterior pituitary through portal vessels Stimulate release/inhibition of endocrine hormones o Hormones FSH -> testes or ovaries LH -> testes or ovaries TSH -> thyroid ACTH -> Adrenal cortex, secretes cortisol Prolactin -> mammary glands GH -> entire body Stimulates protein synthesis Anti insulin effects Increase fat and CHO metabolism and mobilization Mediated by IGFs in the liver Problems o Gigantism – too much GH prior to epiphyseal plate closure o Acromegaly – excess GH after epiphyseal plates close o Dwarfism – insensitivity to or a mutant GH receptor Hypothalamus o Hormones for regulation GnRH +FSH and LH GHRH + GH SS – GH TRH +TSH Dopamine – prolactin CRH + ACTH Thyroid o T4 and T3 follicular cells Increase O2 consumption and metabolism Normal growth and tissue differentiation Increase protein synthesis Increase glucose absorption Increase CHO absorption (intestine) Regulate lipid metabolism o Calcitonin – parafollicular cells (C cells) o Hypothyroidism Lack of T3/T4 production Sluggish, obese, hypertrophy, goiter, lack of iodine
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