Week 3 Notes
Week 3 Notes HSC 308
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This 6 page Class Notes was uploaded by Ana Lossing on Friday September 18, 2015. The Class Notes belongs to HSC 308 at Central Michigan University taught by Micah Zuhl in Fall 2015. Since its upload, it has received 21 views. For similar materials see Physiology of Sport and Exercise in Nursing and Health Sciences at Central Michigan University.
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Date Created: 09/18/15
Skeletal Muscle Cont Fiber Types Fibers per Motor Neuron Common in of all Motor Unit Neuron Firing Training fibers Size Speed Type Distributio ns Typel lt300 Small Slow endurance 50 low force high endurance Type Ila gt300 Larger Fast strength 25 high force low endurance Type llx gt300 Larger Fast untrained 25 Because Type motor units contain fewer fibers they can control finer movements Fewer fibers contract at once allowing for greater control gt smaller and more refined movements Typical Fiber Type Preference high amounts of fiber type in specific types of athletes Type I Endurance eg marathon runners Type Ila Strength eg weightlifters Type llx Untrained eg couch potatoes 1 Factors that determine fiber type A Genetic Determine which alpha motor neurons innervate undifferentiated fibers during development of new fibers Fibers then differentiate become a specific type based on what type of neuron innervated them Training Can cause small changes in fiber type up to 10 Aerobic exercise Type I 4 Type a Type llx Resistance Training Type Type Ila 4 Type llx Sedentary No Training Type gtType Ila Type llx C Aging Type II motor units are lost Generation of Additional Force At a neuronal level 1 Recruitment of Fibers A Fibers are recruited in order of their fiber type Type First Type Ila Type llx Last This order corresponds to motor neuron size smallest gt largest B For low force production less or smaller motor units are recruited C For high force production more or larger motor units are recruited 2 Frequency of Stimulation Rate Coding A Twitch a single electrical stimulus B Summation Greater force production caused by a series of stimuli C Tetanus Peak force production caused by continuous stimulation Generate greater force by 1 Recruiting more motor units 2 Firing motor units more frequently 3 These methods are used preferentially depending on force production A At low force production more units are recruited to increase force B At high force production motor units are fired more frequently Types of Muscle Contractions 1 Static isometric muscle generates force but does not move change length A Myosin crossbridges form release and reform but mechanism does not slide 2 Dynamic muscle generates force AND changes length A Concentric Contraction Muscle shortens while producing force Sarcomere shortens Most familiar type of contraction B Eccentric Contraction Muscle lengthens while producing force CrossBridge forms but sarcomere lengthens eg lowering a heavy weight n isolated skeletal muscles eccentric contractions produce greater force Muscle Contraction Types 1 Static 2 Dynamic a Concentric b Eccentric Contraction and Generation of Force 1 LengthTension Relationship B 2 Sp A Optimal force generation occurs at optimal sarcomere length when the actin and myosin overlap enough to grip each other efficiently and not too much that they can not shorten any farther If the muscle is too short or too stretched little or no force will be produced eedForce Relationship At higher speeds maximal force for concentric contraction decreases maximal force for eccentric contraction increases Factors Affecting Muscle Force Production 1 Increase in Muscle Temp A 2 A Leadsto increase in max isometric tension increased speed of conduction along axons increased enzyme activity Increase in Core Temp Decreased force during prolonged exercise The Endocrine System 1 Homeostasis the ability to maintain a stable internal environment A Requires coordinated input of many systems primarily the Nervous and the Endocrine Systems 2 Function uses chemical messengers to regulate and integrate organ function A B Hormone a regulatory chemical that acts on specific cells or organs A chemical communication system that regulates cellorgan activity by secreting hormones into the bloodstream that act on target cells Communication via hormones is slower and effects are longer lasting than neurotransmission During exercise Controls substrate metabolism Regulates fluid and electrolyte balance affects blood pressure Endocrine System A regulatory system that secretes hormones into the blood stream to act on target cells and maintain homeostasis binds to target cells can only affect cells that have the corresponding receptor Circulation of hormones 2 ways Free unbound Fastacting acute metabolic responses Bound to Proteins Binding proteins provide reservoir of hormonecontrol levels extend hormone halflife Secretion Pulsatile in bursts plasma concentrations change over time Regulated by negative feedback High levels of hormone decrease secretion low levels increase secretion High plasma concentration does not necessarily mean hormone activity is high Activity can depend on number of receptors or sensitivity of the target cells Downregulation Decreasing number of receptors when plasma concentration of hormones is high desensitization Upregulation Increasing number of receptors when plasma concentration of hormones is high sensitization 4 Receptors A B C Typical cell has 200010000 receptors Receptors are hormonespecific which helps limit their effects When a hormone binds to a receptor it s called a hormonereceptor complex Hormone Classifications 1 Steroid made from cholesterol Lipid soluble diffuse through membranes which are made of lipids likedissolveslike receptors located in the cell bind to DNA for direct gene activation regulate mRNA and protein synthesis Secreted by 1 Adrenal Cortex cortisol aldosterone 2 Ovaries progesterone estrogen 3 Testes testosterone 4 Placenta estrogen progesterone 2 Nonsteroid A Not lipid soluble receptors on cell membrane activate second messenger systems 1 2nd Messenger Systems can increase the effects of the signal common 2nd messengers cAMP cGMP lP3 DAG Func on Activate cellular enzymes Change cellular metabolism rate Change membrane permeability Promote protein synthesis Stimulate cell secretions ProteinPeptide Secreted by 1 Pancreas 2 Hypothalamus 3 Pituitary Gland Amino Acidderived Thyroid hormones Thyroxine and Triiodothryonine Adrenal Medulla Hormones epinephrine norepinephrine Types of Hormones Steroid Non Steroid ProteinPeptide Amino Acid Derived Important the focal point of hormonal control of metabolism is blood glucose regulation Glucose homeostasis 90100 mgdL 1 Blood Glucose Increases Levels brought down by insulin 2 Blood Glucose Decreases A increase liver glucose production B increase fatty acid release C block entry of glucose into tissue glucose remains in plasma D gluconeogenesis synthesis of new glucose from amino acids lactate and glycerol Metabolism Hormones A summary Released From In Response To Main Action Acts on Insulin Beta cells of hyperglycemia Glucose uptake Most tissues Pancreas parasympathetic Glucagon Pancreas Hypoglycemia release of glucose liver and skeletal into bloodstream muscle Catecholamines Adrenal Medulla Symp Activation Iipolysis Most tissues exercise glycogenolysis hypoglycemia increase in blood glucose Growth Hormone Anterior Pituitary Hypoglycemia tissue growth All cells stress exercise increase in blood glucose Cortisol Adrenal Cortex falling blood maintains blood Most cells glucose exercise glucose levels stress Thyroid Hormone Thyroid Gland cold stress increase oxygen All cells increased energy consumption requirements increase in blood glucose Hormonal control of metabolism know the role each hormone plays in regulating blood glucose 1 Resting Metabolism A Major Hormones Insulin and Glucagon After eating insulin levels increase to promote glucose uptake After fasting or amino acid ingestion glucagon levels increase to inhibit glucose uptake and increase plasma glucose levels Catecholamines Norepinephrine and Epinephrine Growth Hormone Cortisol Thyroid Hormone At Resting Metabolism After Moderate Intensity Exercise High Intensity Exercise Prolonged Exercise reduced levels due to greater PNS control Increase Large Increase Large Increase follows circadian rhythms per normal Increase Large Increase Large Increase based on stress levels Decrease Increase Increase based on energy needs and feeding Increase Increase Increase
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