A Message to Teachers Part I: Modeling the Resting Potential
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Glossary - Cellbiology
1 Glossary - Cellbiology Blotting: (Blot Analysis) Widely used biochemical technique for detecting the presence of specific macromolecules (proteins, mRNAs, or DNA sequences) in a mixture. A sample first is separated on an agarose or polyacrylamide gel usually under denaturing conditions; the separated components are transferred (blotting) to a nitrocellulose sheet, which is exposed to a radiolabeled molecule that specifically binds to the macromolecule of interest, and then subjected to autoradiography. Northern B.: mRNAs are detected with a complementary DNA; Southern B.: DNA restriction fragments are detected with complementary nucleotide sequences; Western B.: Proteins are detected by specific antibodies. Cell: The fundamental unit of living organisms. Cells are bounded by a lipid-containing plasma membrane, containing the central nucleus, and the cytoplasm. Cells are generally capable of independent reproduction. More complex cells like Eukaryotes have various compartments (organelles) where special tasks essential for the survival of the cell take place. Cytoplasm: Viscous contents of a cell that are contained within the plasma membrane but, in eukaryotic cells, outside the nucleus. The part of the cytoplasm not contained in any organelle is called the Cytosol. Cytoskeleton: (Gk. ) Three dimensional network of fibrous elements, allowing precisely regulated movements of cell parts, transport organelles, and help to maintain a cell’s shape. • Actin filament: (Microfilaments) Ubiquitous eukaryotic cytoskeletal proteins (one end is attached to the cell-cortex) of two “twisted“ actin monomers; are important in the structural support and movement of cells. Each actin filament (F-actin) consists of two strands of globular subunits (G-Actin) wrapped around each other to form a polarized unit (high ionic cytoplasm lead to the formation of AF, whereas low ion-concentration disassembles AF). -
Biopsychology 2012 – Sec 003 (Dr
Biopsychology 2012 – sec 003 (Dr. Campeau) Study Guide for First Midterm What are some fun facts about the human brain? - there are approximately 100 billion neurons in the brain; - each neuron makes between 1000 to 10000 connections with other neurons; - speed of action potentials varies from less than 1 mph and up to 100 mph. What is a neuron? A very specialized cell type whose function is to receive, process, and send information; these cells are found in the central nervous system (CNS – brain, spinal cord, retina) and the peripheral nervous system (PNS – the rest of the body). What is a nerve? They are axons of individual neurons in bundles or strands of many axons. What are the major parts of a neuron? - cell membrane: “skin” of the neuron; - cytoplasm: everything inside the skin; - nucleus: contains chromosomes (DNA); - ribosomes: generate proteins from mRNA; - mitochondria: energy “generator” of cells (produce ATP); - mitochondria: moves “stuff” inside the neuron (like a tow rope); - soma: cell body, excluding dendrites and axons; - dendrites and spines: part of the neuron usually receiving information from other neurons; - axons: part of the neuron that transmits information to other neurons; - myelin sheath: surrounds axons and provides electrical “insulation”; - nodes of Ranvier: small area on axons devoid of myelin sheath; - presynaptic terminal: area of neuron where neurotransmitter is stored and released by action potentials. What are the different neuron types according to function? 1. Sensory neurons: neurons specialized to “receive” information about the environment. 2. Motor neurons: neurons specialized to produce movement (contraction of muscles). 3. Interneurons or Intrinsic neurons: neurons, usually with short axons, that handle local information. -
Chapter 1 Zoom in On… Patch Configurations in the Jargon of Electrophysiologists, a Patch Is a Piece of Neuronal Membrane
CELLULAR NEUROPHYSIOLOGY CONSTANCE HAMMOND Chapter 1 Zoom in on… Patch configurations In the jargon of electrophysiologists, a patch is a piece of neuronal membrane. Researchers invented a technique known as a patch-clamp, which records the current through a single ion channel, some ion channels or through all open ion channels in the neuron membrane. To obtain these recordings, researchers use different patch configurations. We'll explain here only the three configurations used in the course: the cell-attached configuration, the whole-cell configuration, and the "outside-out" excised patch configuration. According to the type of recording to perform, a particular type of configuration will be chosen: 1. to record a unitary current: cell-attached or outside-out configuration; 2. to record a total current: whole-cell configuration; 3. to record changes in membrane potential (action potentials or postsynaptic potentials): whole-cell configuration. The cell-attached configuration (attached to the pipette - Figure a) First, the pipette is filled with an extracellular fluid. Positive pressure is applied in the electrode by means of a syringe connected to the electrode, so that the intrapipette fluid tends to leave the pipette. The electrode is then brought near to the soma of a neuron. When the electrode touches the membrane, the positive pressure is withdrawn to draw the membrane toward the mouth of the pipette. We wait without moving the pipette; a seal is made between the walls of the pipette and the soma membrane. This seal strength can be measured by applying a low level of amplitude current in the pipette. Since V = RI, one can measure the resistance of the seal. -
7.016 Introductory Biology Fall 2018
7.016: Fall 2018: MIT 7.016 Recitation 15 – Fall 2018 (Note: The recitation summary should NOT be regarded as the substitute for lectures) (This material is COPYRIGHT protected.) Summary of Lecture 22 (11/2): Neurons and action potentials: Ions can move across membranes through pumps and channels. Integral membrane proteins like these cross the membrane via transmembrane domains. Pumps are ATPases that set up the concentration gradients of ions across cell membranes, such that K+ is high inside cells and other ions (such as Cl–, Na+, and Ca2+) are high outside cells. A membrane potential is only set up by ions that move freely across the membrane through open channels, creating one side of the membrane that is more positive relative to the other side. This movement of ions does not dissipate the concentration gradient because the number of ions that move to generate a membrane potential is very small compared to the number of ions that need to be pumped to create a concentration gradient. Most cell membranes only contain open K+ channels and thus only K+ flows freely across membranes through channels; K+ is high inside, causing it to flow outside, giving the inside of cells a negative membrane potential. Ions can move across the membrane through open ion channels. Two forces act to dictate this movement – the concentration gradient and the electrical gradient. Ions move down their concentration gradient through channels, and ions move towards the side of the membrane that harbors the opposite charge. Neurons are the cells of your nervous system that make connections with each other to transmit impulse/ signals. -
Nernst Potentials and Membrane Potential Changes
UNDERSTANDING MEMBRANE POTENTIAL CHANGES IN TERMS OF NERNST POTENTIALS: For seeing how a change in conductance to ions affects the membrane potential, follow these steps: 1. Make a graph with membrane potential on the vertical axis (-100 to +55) and time on the horizontal axis. 2. Draw dashed lines indicating the standard Nernst potential (equilibrium potential) for each ion: Na+ = +55 mV, K+ = -90mV, Cl- = -65 mV. 3. Draw lines below the horizontal axis showing the increased conductance to individual ions. 4. Start plotting the membrane potential on the left. Most graphs will start at resting potential (-70 mV) 5. When current injection (Stim) is present, move the membrane potential upward to Firing threshold. 6. For the time during which membrane conductance to a particular ion increases, move the membrane potential toward the Nernst potential for that ion. 7. During the time when conductance to a particular ion decreases, move the membrane potential away from the Nernst potential of that ion, toward a position which averages the conductances of the other ions. 8. When conductances return to their original value, membrane potential will go to its starting value. +55mV ACTION POTENTIAL SYNAPTIC POTENTIALS 0mV Membrane potential Firing threshold Firing threshold -65mV -90mV Time Time Na+ K+ Conductances Stim CHANGES IN MEMBRANE POTENTIAL ALLOW NEURONS TO COMMUNICATE The membrane potential of a neuron can be measured with an intracellular electrode. This 1 provides a measurement of the voltage difference between the inside of the cell and the outside. When there is no external input, the membrane potential will usually remain at a value called the resting potential. -
Neurotransmitter Actions
Central University of South Bihar Panchanpur, Gaya, India E-Learning Resources Department of Biotechnology NB: These materials are taken/borrowed/modified/compiled from various resources like research articles and freely available internet websites, and are meant to be used solely for the teaching purpose in a public university, and for serving the needs of specified educational programmes. Dr. Jawaid Ahsan Assistant Professor Department of Biotechnology Central University of South Bihar (CUSB) Course Code: MSBTN2003E04 Course Name: Neuroscience Neurotransmitter Actions • Excitatory Action: – A neurotransmitter that puts a neuron closer to an action potential (facilitation) or causes an action potential • Inhibitory Action: – A neurotransmitter that moves a neuron further away from an action potential • Response of neuron: – Responds according to the sum of all the neurotransmitters received at one time Neurotransmitters • Acetylcholine • Monoamines – modified amino acids • Amino acids • Neuropeptides- short chains of amino acids • Depression: – Caused by the imbalances of neurotransmitters • Many drugs imitate neurotransmitters – Ex: Prozac, zoloft, alcohol, drugs, tobacco Release of Neurotransmitters • When an action potential reaches the end of an axon, Ca+ channels in the neuron open • Causes Ca+ to rush in – Cause the synaptic vesicles to fuse with the cell membrane – Release the neurotransmitters into the synaptic cleft • After binding, neurotransmitters will either: – Be destroyed in the synaptic cleft OR – Taken back in to surrounding neurons (reuptake) Excitable cells: Definition: Refers to the ability of some cells to be electrically excited resulting in the generation of action potentials. Neurons, muscle cells (skeletal, cardiac, and smooth), and some endocrine cells (e.g., insulin- releasing pancreatic β cells) are excitable cells. -
Genetic Alteration of the Metal/Redox Modulation of Cav3.2 T-Type
Genetic alteration of the metal/redox modulation of Cav3.2 T-type calcium channel reveals its role in neuronal excitability Tiphaine Voisin, Emmanuel Bourinet, Philippe Lory To cite this version: Tiphaine Voisin, Emmanuel Bourinet, Philippe Lory. Genetic alteration of the metal/redox mod- ulation of Cav3.2 T-type calcium channel reveals its role in neuronal excitability. The Journal of Physiology, Wiley, 2016, 594 (13), pp.3561–74. 10.1113/JP271925. hal-01940961 HAL Id: hal-01940961 https://hal.archives-ouvertes.fr/hal-01940961 Submitted on 30 Nov 2018 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. J Physiol 594.13 (2016) pp 3561–3574 3561 Genetic alteration of the metal/redox modulation of Cav3.2 T-type calcium channel reveals its role in neuronal excitability Tiphaine Voisin1,2,3, Emmanuel Bourinet1,2,3 and Philippe Lory1,2,3 1Centre National pour la Recherche Scientifique UMR 5203, D´epartement de Physiologie, Institut de G´enomique Fonctionnelle, Universit´edeMontpellier, Montpellier, F-34094 France 2Institut National de la Sant´eetdelaRechercheM´edicale, U 1191, Montpellier, F-34094 France Neuroscience 3LabEx ‘Ion Channel Science and Therapeutics’, Montpellier, F-34094 France Key points r In this study, we describe a new knock-in (KI) mouse model that allows the study of the H191-dependent regulation of T-type Cav3.2 channels. -
Effect of Hyperkalemia on Membrane Potential: Depolarization
❖ CASE 3 A 6-year-old boy is brought to the family physician after his parents noticed that he had difficulty moving his arms and legs after a soccer game. About 10 minutes after leaving the field, the boy became so weak that he could not stand for about 30 minutes. Questioning revealed that he had complained of weakness after eating bananas, had frequent muscle spasms, and occasionally had myotonia, which was expressed as difficulty in releasing his grip or diffi- culty opening his eyes after squinting into the sun. After a thorough physical examination, the boy was diagnosed with hyperkalemic periodic paralysis. The family was advised to feed the boy carbohydrate-rich, low-potassium foods, give him glucose-containing drinks during attacks, and have him avoid strenuous exercise and fasting. ◆ What is the effect of hyperkalemia on cell membrane potential? ◆ What is responsible for the repolarizing phase of an action potential? ◆ What is the effect of prolonged depolarization on the skeletal muscle Na+ channel? 32 CASE FILES: PHYSIOLOGY ANSWERS TO CASE 3: ACTION POTENTIAL Summary: A 6-year-old boy who experiences profound weakness after exer- cise is diagnosed with hyperkalemic periodic paralysis. ◆ Effect of hyperkalemia on membrane potential: Depolarization. ◆ Repolarization mechanisms: Activation of voltage-gated K+ conductance and inactivation of Na+ conductance. ◆ Effect of prolonged depolarization: Inactivation of Na+ channels. CLINICAL CORRELATION Hyperkalemic periodic paralysis (HyperPP) is a dominant inherited trait caused by a mutation in the α subunit of the skeletal muscle Na+ channel. It occurs in approximately 1 in 100,000 people and is more common and more severe in males. -
Electrical Activity of the Heart: Action Potential, Automaticity, and Conduction 1 & 2 Clive M
Electrical Activity of the Heart: Action Potential, Automaticity, and Conduction 1 & 2 Clive M. Baumgarten, Ph.D. OBJECTIVES: 1. Describe the basic characteristics of cardiac electrical activity and the spread of the action potential through the heart 2. Compare the characteristics of action potentials in different parts of the heart 3. Describe how serum K modulates resting potential 4. Describe the ionic basis for the cardiac action potential and changes in ion currents during each phase of the action potential 5. Identify differences in electrical activity across the tissues of the heart 6. Describe the basis for normal automaticity 7. Describe the basis for excitability 8. Describe the basis for conduction of the cardiac action potential 9. Describe how the responsiveness relationship and the Na+ channel cycle modulate cardiac electrical activity I. BASIC ELECTROPHYSIOLOGIC CHARACTERISTICS OF CARDIAC MUSCLE A. Electrical activity is myogenic, i.e., it originates in the heart. The heart is an electrical syncitium (i.e., behaves as if one cell). The action potential spreads from cell-to-cell initiating contraction. Cardiac electrical activity is modulated by the autonomic nervous system. B. Cardiac cells are electrically coupled by low resistance conducting pathways gap junctions located at the intercalated disc, at the ends of cells, and at nexus, points of side-to-side contact. The low resistance pathways (wide channels) are formed by connexins. Connexins permit the flow of current and the spread of the action potential from cell-to-cell. C. Action potentials are much longer in duration in cardiac muscle (up to 400 msec) than in nerve or skeletal muscle (~5 msec). -
The Excitable Cell. Resting Membrane Potential and Action Potential (1&2)
The excitable cell. Resting Membrane Potential and Action Potential (1&2) Dr Sergey Kasparov School of Medical Sciences, Room E9 THIS TOPIC IS ALSO COVERED IN TUTORIALS! Teaching home page: http://www.bristol.ac.uk/phys-pharm/media/teaching/ Why do we call these cells “excitable”? Real action potentials.avi The key point: Bioelectricity is generated by the ions moving across cellular membranes Concentration of selected solutes in intracellular fluid and extracellular fluid in millimols mM 160 140 120 100 Insi de the cell 80 60 In extracellular fluid 40 20 0 1 The Na+/K+ pump outside inside [[mMmM]] + + [[mMmM]] + + + + + + + Na 145 + + 15 + K 4 + + 140 ATPATP ••isis an active ion transporter (ATP‐dependent) ••isis responsible for creating and upholding Na+ and K+ concentration gradients ••isis electrogenic – pumps 3 Na+ versus 2 K+ ions Reminder: Movement of ions is affected by concentration gradient and the electrical field Chemical driving force _ _ + + _ + + Electrical driving force _ + + _ + + + _+ _ + _ + + + + _ + _ + _ + + _ Net flux + + + + _ + _ + + V REMINDER: Diffusion through Ion Channels A leak channel A gated channel Both leak and gated channels allow movement of molecules (mainly inorganic ions) down the electrochemical gradient. So, if the gradient reverses, the ions will flow in the opposite direction. 1. The channels are aqueous pores through the membrane. 2. The channels are usually quite selective, for example some only pass Na+, others K+, still others – Cl- 3. Gated channels may be opened or closed by various factors -
4-Nervous-System-Structure-PPT.Pdf
Nervous Systems: Neuron Structure and Function Integration An animal needs to function like a coherent organism, not like a loose collection of cells. Integration = refers to processes such as summation and coordination that produce coherency and result in harmonious function. Integration Cellular integration = processes within cells Whole-animal integration = selective combination and processing of sensory, endocrine, and central nervous system (CNS) information in ways that promote harmonious functioning of the whole organism within its environment. ◦ This includes its all its cells, tissues, and organs Integration Nerve cells are specialized for control and coordination. Integration ensures that an animal’s responses are smooth and coordinated rather than clashing or disjointed. Excitable Cells Neurons are a type of excitable cell ◦ Specially adapted to generate an electrical signal Can rapidly alter their membrane potential in response to an incoming signal. Vary in structure and function but use the same basic mechanism to send signals. Neuron Function – Main Points Specialized for processing and conveying information. Information is coded into changes in electrical potential across cell membranes. Neurons use action potentials to transmit these signals across long distances. Neurons allow animals to sense and respond to their environment. Benefits of Neurons Plants (no neurons): Action potentials travel @ 1-3 cm/sec Animals (neurons): Action potentials travel @ 100m/sec or 10,000cm/sec CNS to Muscles Signal Reception Dendrites & Cell Body Signal Integration Axon Hillock Signal Conduction Axon Signal Transmission Axon Terminals Signal Reception Dendrites sense and convert incoming signals into electrical signals by changing membrane potential. Cell Body = routine metabolic functions Signal Integration Incoming signals are conducted to the axon hillock If signal is sufficiently large an electrical signal, or action potential, is initiated. -
The Action Potential
See discussions, stats, and author profiles for this publication at: http://www.researchgate.net/publication/6316219 The action potential ARTICLE in PRACTICAL NEUROLOGY · JULY 2007 Source: PubMed CITATIONS READS 16 64 2 AUTHORS, INCLUDING: Mark W Barnett The University of Edinburgh 21 PUBLICATIONS 661 CITATIONS SEE PROFILE Available from: Mark W Barnett Retrieved on: 24 October 2015 192 Practical Neurology HOW TO UNDERSTAND IT Pract Neurol 2007; 7: 192–197 The action potential Mark W Barnett, Philip M Larkman t is over 60 years since Hodgkin and called ion channels that form the permeation Huxley1 made the first direct recording of pathways across the neuronal membrane. the electrical changes across the neuro- Although the first electrophysiological nal membrane that mediate the action recordings from individual ion channels were I 2 potential. Using an electrode placed inside a not made until the mid 1970s, Hodgkin and squid giant axon they were able to measure a Huxley predicted many of the properties now transmembrane potential of around 260 mV known to be key components of their inside relative to outside, under resting function: ion selectivity, the electrical basis conditions (this is called the resting mem- of voltage-sensitivity and, importantly, a brane potential). The action potential is a mechanism for quickly closing down the transient (,1 millisecond) reversal in the permeability pathways to ensure that the polarity of this transmembrane potential action potential only moves along the axon in which then moves from its point