PGY 206 Exam 1 Study Guide
PGY 206 Exam 1 Study Guide PGY 206
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This 21 page Study Guide was uploaded by Sharon Liang on Tuesday February 9, 2016. The Study Guide belongs to PGY 206 at University of Kentucky taught by Dr. Dexter Speck in Spring 2016. Since its upload, it has received 263 views. For similar materials see Elementary Physiology in Physiology at University of Kentucky.
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Date Created: 02/09/16
PGY 206 Exam 1 Notes Course Intro While the scientific method is investigative science, physiology is a form of integrative science defined as the study of how living organisms work (function). Homeostasis Defined as the required stability of our internal environment A. Control Mechanisms 1. Variable: factor being regulated 2. Sensor (receptor): detects changes in environment from a specific set of point 3. Integrating center: receives information from the sensors and makes decisions on tasks 4. Effectors: makes changes based off information received from integrating center B. Negative Feedback - Change in variable leading to responses that move the variable in the opposite direction of the initial change - Variable sensor integrating center effector variable o Examples Thermostat: default at 70˚F increased temperature detected by sensor within thermostat integrating center activates effectors to kick on AC decrease temperature back to default C. Positive Feedback - Change in variable leading to responses that move the variable in the same direction of the initial change - Variable sensor integrating center effector variable - Weirdly, positive feedback can eventually lead to death - Examples include: blood clotting, contractions of the uterus during childbirth, opening of voltage-gated channels in the neurons D. Imbalance Most diseases result from occurrences of homeostasis imbalance Our ability to maintain homeostasis declines with aging Cell Structure Atoms: combine to form molecules Cell: basic unit of structure and function - About 200 cell types totaling trillions of cells in our bodies - All cells work together to function - Similar cell types group together to function as a tissue. Primary tissues are muscle, nervous, epithelial, and connective Tissues are organized to form organs Organs are part of an organ system I. Plasma Membrane (synonyms: cell membrane, plasmalemma) A. Structure 1. Lipid bilayer with embedded proteins Phospholipids: consists of a glycerol molecule with 2 fatty acids (tails/lipids) and a phosphate group (head) Lipophobic Phospholipid arrangements prevent hydrophilic substances from moving across the plasma membrane 2. Proteins Integral proteins: span entire width of plasma membrane (transporters, receptors, channels and carriers) Peripheral proteins: partially embedded on either side of the plasma membrane (enzymes, structural support, receptors) 3. Carbohydrates Glycoproteins Glycolipids 4. Fluid mosaic model There are no bonds between proteins and lipids that make up the membrane 5. Other associated structures Cilia: short cell surface projections with motile properties Flagella: longer than cilia; whip-like structures that propel sperm Microvilli: very small, finger-like extensions of the plasma membrane B. Functions 1. Separates intracellular fluid from extracellular material 2. Selectively permeable (size, charge, polarity) 3. Proteins in membrane Acts as receptors Provides structural support Help transport molecules across membranes Movement across plasma membrane: Diffusion through membrane (lipophilic) or pores (hydrophilic) Phagocytosis, endocytosis, exocytosis and pinocytosis II. Cytoplasm Cellular region between nucleus and plasma membrane Includes the cytosol and organelles A. Cytosol 1. Fluid in which the organelles are suspended 2. Composed of water and many dissolved substances 3. Contains protein fibers (microfilaments and microtubules), which function as a cytoskeleton B. Organelles 1. Ribosomes Small granules composed of protein and RNA Site for protein synthesis 2. Endoplasmic reticulum a. Rough Extensive, enclosed network of membranes with ribosomes on the surface Packs proteins and distributes them to other organelles b. Smooth Membrane system composed of tubules without attached ribosomes Site of lipid and steroid synthesis; also stores calcium in some cell types 3. Golgi apparatus Stack of smooth membrane sacks with associated vesicles Modifies proteins received from the rough ER and packs them into vesicles 4. Mitochondria Double membrane structure Power house of cell 5. Lysosomes Membrane bound sacs containing digestive enzymes 6. Peroxisomes Membrane bound sacs containing enzymes which break down toxic substances Cell membrane separates extracellular fluid from cytoplasm---lipophilic (hydrophobic) is directed toward the anterior of the membrane. Membranes of lysosomes, peroxisomes, and vesicles are recycled. III. Nucleus A. Structure 1. Surrounded by nuclear envelope 2. Nuclear pores join the 2 membranes of the nuclear envelope together 3. Nucleoli: dense structures which contain genes for forming the RNA associated with ribosomes 4. Chromatin: threadlike material composed of DNA and histone proteins B. Function Control center of cell Responsible for transmitting genetic information and providing instructions for protein synthesis C. Genetic material humans have 46 chromosomes Each chromosome has thousands of genes made from DNA - In nucleus i. DNA DNA replication ii. DNA mRNA transcription - In cytoplasm i. mRNA protein translation (mRNA serves as a template; tRNA helps bring amino acids to the ribosomes) D. Stem cells Specialized cells that haven’t been differentiated They’re “undeclared” cells meaning that they can change into multiple kinds of tissue Can be collected from different sources - Embryonic stem cells - Adult stem cells (especially from blood) Membrane Transport 20-40-60 rule About 60% (it may range from ~55-70% depending on body structure) of mass is water 1/3 of water (~20% of body mass) is extracellular 2/3 of water (~40% of body mass) is inside cells I. Membrane Transport Intracellular fluid (ICF) Extracellular fluid (ECF) - Interstitial fluid (tissue fluid): fluid “between cells” making up 80% of ECF volume - Plasma: noncellular portion of blood making up 20% of ECF volume A. Plasma is selectively permeable Size of molecule, charge, polarity, and solubility (lipophilic vs hydrophilic) Allows nutrients enter cells and harmful substances exit cells Keeps proteins and other substances needed for cell function in the cell and allows wastes products to move out B. Membrane Transport Processes 1. Passive transport Doesn’t require energy in form of ATP though it requires some form of energy for movement; gradient (concentration, electrical) Movement of a substance across a membrane from higher to lower concentration (substance is moving down its concentration gradient) 2. Active Transport Requires energy in the form of ATP Movement of a substance across a membrane from lower to higher concentration (substance is moving against its concentration gradient) II. Passive Transport Processes A. Simple Diffusion: occurs when there’s a concentration difference between 2 regions Molecules in a solution or gas are in constant state of random movement (Brownian movement) A solution consists of a solvent (water) and a solute (molecules dissolved in water) Membrane must be permeable to molecules When concentration of molecules become equal on both sides, net diffusion is zero 1. Substances that diffuse across the plasma membrane Lipid soluble substances (phospholipid bilayer, lipophilic vs hydrophobic) Very small polar molecules; typically require a channel or pore 2. Rate of diffusion Concentration difference across membrane Temperature of solution Permeability of membrane Surface area of membrane B. Facilitated Diffusion: movement of large polar substances across the plasma membrane by carrier proteins (integral proteins that span the plasma membrane) 1. Characteristics of carrier-mediated transport Specificity: carrier proteins only interact w/specific molecules Competition: 2 different molecules can be transported by the same carrier, but compete for the carrier protein Saturation: when all carrier proteins in a cell are being utilized to move molecules, they’re saturated Glucose transport across the cell membrane C. Osmosis: diffusion of water across a membrane In order for osmosis to occur: There must be a difference in solute concentration across the membrane Membrane must be selectively permeable to water but not solute 1. osmotic pressure Pressure required to prevent osmosis An indirect measure of the solute concentration of a solution 2. Osmolality Total solute concentration of a solution 1 molar solution = 1 mole of solute in enough water to make 1 liter of solution (# moles/liter of solution) 1 molar solution = 1 mole of solute dissolved in 1 kg of water (# moles/kg Water) A kg of water with 1 mole of glucose and 1 mole of fructose has a total osmolality of 2 osmoles/L (2 Osm) 3. Tonicity Describes effects of solution on the volume of the cell Isotonic: solution with the same osmolality as the inside of the cell Hypotonic: solution with lower osmolality than inside of the cell Hypertonic: solution with higher osmolality than inside of cell III. Active Transport Processes Requires ATP Requires carrier molecule Moving substances against concentration gradient A. Primary Active Transport 1. Movement of calcium across membrane 2. Sodium-potassium pump The carrier protein is an enzyme that hydrolyzes ATP Pumps sodium and potassium in opposite directions “Electrogenic”: pumps 3 sodium for every 2 potassium in 200 red blood cells B. Secondary Active Transport Indirectly utilizes the energy released by hydrolysis of ATP The sodium-potassium pump maintains the sodium concentration gradient across the smile As sodium moves back into the cell, other substances are transported by the same carrier proteins C. Bulk Transport Movement of large molecules across plasma membrane Requires energy 1. Exocytosis: movement of substances within a vesicle from the cell interior to the extracellular space 2. Endocytosis: movement of substances from the extracellular fluid into the cell Neurons and Excitable Cells I. Organization of the Nervous System A. Central Nervous System (CNS): brain and spinal cord Brain - Cerebellum - Cerebrum - Brain stem B. Peripheral Nervous System (PNS): primarily nerves that project to and from the CNS, which are spinal and cranial nerves 1. Afferent division (sensory): transmits impulses from sensory receptors to CNS receptors including photoreceptors, chemical receptors, pressure/touch, etc. 2. Efferent division (motor): transmits impulses from CNS to effector organs a. Somatic nervous system (SNS): motor neurons that stimulate contraction of skeletal muscles b. Autonomic nervous system (ANS): motor neurons that stimulation contraction of smooth and cardiac muscles as well as glandular tissues C. Cells 1. Neurons 2. Glia II. Cells of the Nervous System A. Neurons: basic structural and functional unit 1. Structure a. Cell body: enlarged portion containing the nucleus and other organelles Nuclei: group of cell bodies within CNS Ganglia: group of cell bodies within PNS b. Dendrites: branched processes that extend from the cell body c. Axon: single process that extend from the cell body Axon hillocks Axon terminals Synapses Tract: group of axons in CNS Nerve: group of axons in PNS 2. Neuron classification by structure 3. Neuron classification by function a. Sensory or afferent neurons: carry information from sensory receptors to CNS b. Motor or efferent neurons: carry information from CNS to effector organs c. Interneurons or association neurons: found in CNS to connect efferent and afferent neurons together B. Supporting Cells 1. Found in PNS a. Schwann cells: wrap around the axons forming myelin sheath Nodes of Ranvier: spaces between adjacent Schwann cells; where action potentials are conducted b. Satellite cells: surround neuron cell bodies within ganglia in PNS 2. Found in CNS Supporting cells of the CNS are glia a. Oligodendrocytes: functionally similar to Schwann cells; form myelin sheath around axons of CNS b. Microglia: phagocytes that get rid of foreign substances in CNS c. Astrocytes: maintains normal external environment around neurons; help maintain blood brain barrier d. Ependymal cells: lines cavities of brain and spinal cord; make CSF (cerebrospinal fluid) III. Resting Membrane Potential A. Electrical Potentials 1. At rest, a neuron has excess of positive charges on the outside of the membrane and an excess of negative charges on the inside ECF (outside neuron) 0 mV + + + + + lipid membrane - 70 mV - - - - - - - ICF (inside neuron) This separation of charge across the membrane creates an electrical potential or a membrane potential (measured in millivolts) 2. Resting membrane potential: potential across a membrane in a resting neuron Negative sign indicates inside of cell is more negative than outside B. Generation of the Resting Membrane Potential (RMP or just MP) 1. Ion distribution between ICF and ECF ICF ECF [K ] 150 mM 5 mM [Na ] 12 mM 145 mM - These charges are balanced by the Cl in the ECF and large, negatively charged proteins in the ICF 2. Permeability of the cell membrane At RMP, potassium is 75 times more permeable than sodium 3. Sodium/potassium pump (Na /K ATPase) Pumps 3 sodium ions for every 2 potassium ions Maintains concentration gradients for these ions Contributes to the generation of a more negative intracellular environment --- “electrogenic“ about 6 mV C. Changes in RMP 1. Depolarization Membrane potential becomes less negative Inside of cell becomes more positive with respect to RMP 2. Hyperpolarization Membrane potential becomes more negative Inside of cell becomes more negative with respect to RMP 3. Repolarization Return to RMP 4. Changes in RMP are produced by Change in membrane permeability to any of the ions Change in ion concentrations on both sides of the membrane D. Ion Channels 1. Passive: ion channels that are always open and allow ions to move down their concentration gradients 2. Chemically gated channels (aka ligand gated channels): open when a substance binds to a receptor on the channel to allow ions to move down their concentration gradients 3. Voltage-gated channels: open or close when detected a change in membrane potential Autonomic Nervous System I. Terminology Review Axon or nerve fiber: long extension from a single neuron Nerve: group of axons in PNS Ganglia (singular ganglion): groups of neuron cell bodies in PNS II. Review of Nervous System A. ANS: classically defined as efferent systems, but afferents do exist in nerves of ANS Sympathetic: “flight or fight” Parasympathetic: “rest or digest” - Usually though not always thought of as antagonists Motor neurons from both divisions innervate smooth muscle, cardiac muscle, and glands resulting in an appropriate response Controls involuntary activity Enteric nervous system III. General Arrangement of ANS A. Consists of 2 neurons that connect the CNS to effector cells Preganglionic fiber: this neurons has its cell body in the CNS and synapses in the second neuron at an autonomic ganglion outside the CNS Postganglionic fiber: this second neuron extends from the autonomic ganglion to the effector cells Muscle cells glands ganglion blood vessels CNS effector cells preganglionic fiber postganglionic fiber IV. Anatomy of the Sympathetic Nervous System (“fight or flight”) A. Preganglionic sympathetic nerve fibers leave the spinal cord between T1 and L2 (thoracolumbar division) B. Preganglionic sympathetic nerve fibers synapse with postganglionic fibers in sympathetic ganglia 1. Paravertebral ganglia: 2 chains of sympathetic ganglia that lie outside spinal cord 2. Prevertebral (collateral) ganglia: 3 sympathetic ganglia that lie in the abdominal cavity Celiac ganglia Superior mesenteric ganglia Inferior mesenteric ganglia C. Preganglionic sympathetic nerve fibers 1. Synapse with the postganglionic sympathetic nerve fibers at a paravertebral ganglion at a spinal level where they enter 2. Branch once they reach the paravertebral ganglion and synapse with the postganglionic sympathetic nerve fibers located at different levels in the chain 3. Pass without interruption through the paravertebral sympathetic ganglia and synapse with a postganglionic sympathetic nerve fiber at a prevertebral ganglion D. Most preganglionic sympathetic nerve fibers are short in comparison to postganglionic sympathetic nerve fibers (except those that synapse in the prevertebral ganglia) E. Postganglionic sympathetic nerve fibers 1. Originate in paravertebral or prevertebral ganglia 2. Are relatively long fibers compared to preganglionic fibers 3. Innervate effector cells F. SNS exhibits divergence and convergence Divergence: a single preganglionic fiber branches to synapse with many postganglionic fibers located at different levels in the sympathetic chain; acts to “amplify” the signal Convergence: postganglionic neurons can receive input from many preganglionic fibers Mass activation: when entire SNS activates V. Anatomy of the Parasympathetic Nervous System (“rest and digest”) A. Preganglionic parasympathetic nerve fibers exit from the brain stem and leave the spinal cord at the level of the sacrum (craniosacral division) B. Preganglionic parasympathetic nerve fibers synapse with postganglionic fibers in terminal ganglia that are close to or within effector organ 1. Cranial nerves a. Cranial nerve III b. Cranial nerve VII c. Cranial nerve IX d. Cranial nerve X (vagus nerve): provides the majority of parasympathetic innervation to the body 2. Sacral spinal nerves (pelvic nerves) Innervates lower half of large intestines, bladder, and reproductive organs C. Preganglionic parasympathetic nerve fibers are longer than postganglionic parasympathetic nerve fibers D. Postganglionic parasympathetic nerve fibers: 1. Originate in the terminal ganglia near or within effector organ 2. Are relatively short compared to preganglionic parasympathetic nerve fibers 3. Innervates effector cells E. PNS exhibits little divergence so that results in very specific responses of individual organs VI. Neurotransmitters and Receptors Associated with the PNS and SNS A. Neurotransmitters 1. All preganglionic neurons release acetylcholine (ACh) Nerve fibers that release ACh are cholinergic fibers 2. Postganglionic neurons a. PNS – release ACh b. SNS – primarily release norepinephrine (NE, aka noradrenaline) Nerve fibers release NE are called adrenergic fibers or catecholaminergic fibers B. Receptors 1. Cholinergic fibers (released by ACh) a. Nicotinic receptors (also at neuromuscular junction) Located on sympathetic and parasympathetic postganglionic neurons b. Muscarinic receptors Found on effector cells stimulated by parasympathetic postganglionic neurons PNS: ganglion CNS Effector cells Ach N Ach M 2. Adrenergic Fibers (activated by norepinephrine and epinephrine) a. Found on effector cells stimulated by the sympathetic postganglionic neurons b. 2 types (α/β ½) SNS: CNS effector cells Ach NE N and/or VII. Autonomic Regulation of Specific Organs A. In general, actions of the sympathetic and parasympathetic inputs to an organ have opposite effects Mimetic effects – mimic the action Parasympathomimetic and sympathomimetic a. PNS – “rest and digest” Associated with conservation of energy and maintenance of organ function during times of minimal activity b. SNS – “fight and flight” Prepares body for responding to fear, stress, etc 1. Heart a. PNS Decreases heart rate Decreases force of contraction b. SNS Increases heart rate Increases force of contraction 2. Lungs a. PNS Contacts bronchial muscle b. SNS Relaxes bronchial muscle 3. GI Tract a. PNS Increases motility Increases secretions b. SNS Decreases motility Decreases secretions though may increase mucus 4. Blood vessels a. PNS No direct innervation of vascular smooth muscle b. SNS Constriction of most blood vessels Dilation of blood vessels that may supply the skeletal muscles 5. Eye a. PNS: dilate pupil b. SNS: constrict pupil Normal control is mostly PNS VIII. Adrenal Gland adrenal medulla CNS effector cells release EPI and NE into bloodstream ACh , N A. Anatomy 1. Small pair of glands sitting above the kidney 2. Adrenal cortex: outer portion; secretes glucocorticoids, mineralocorticoids, and sex steroids 3. Adrenal medulla: inner portion; secretes catecholomines - epinephrine (EPI 85%) and norepinephrine (NE 15%) B. Adrenal Medulla is part of the SNS 1. Preganglionic sympathetic nerves pass uninterrupted from the spinal cord through the sympathetic chain and synapse on chromaffin cells of the adrenal medulla 2. The adrenal medulla is analogous to the ganglion; the chromaffin cells are analogous to the postganglionic nerve fibers 3. Chromaffin cells release EPI and NE into the circulation where they’ll eventually bind to adrenergic receptors at their effector organ
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