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Ch 5 Membrane Potentials & Action Potentials 1. Membrane Potentials membranes a. All cells have electrical potentials across their ____________ Nerve b. ____________...

Ch 5 Membrane Potentials & Action Potentials 1. Membrane Potentials membranes a. All cells have electrical potentials across their ____________ Nerve b. ____________ and muscle ____________ cells generate Action potentials- rapidly changing electrochemical impulses in their membranes to transmit signals c. Membrane potentials are caused by ionconcentration ____________and ____________ charge Nernst d. ____________ potential- the calculation for the equilibrium potential of an ion- the electrical diffusion potential across a membrane that exactly opposes the net diffusion of a particular ion through the membrane. enter i. Sodium wants to ____________the cell and will balance out positive at +61mV leave ii. Potassium wants to ___________the cell and will balance out negative at ~- 90mV e. Goldman Equation- When the membrane is permeable to several different ions three factors play a role in determining the membrane potential polarity the electrical charge of each ion i. The ____________of ii. The permeability ____________of the membrane to each ion iii. The concentration ____________ of each ion inside and outside the cell 2. Resting membrane potential a. Negative ____________ potential i. -90mV in nerve fibers ii. -70mV inADEPT muscle fibers b. Natkt ____________-establishes pump the concentration gradient for the resting membrane potential i. Primary Active Transport ii. Electrogenic (about –4 millivolts) both iii. Builds the concentration gradient. Pumps _________ions against their diffusion preference. iv. 3 Na+ OUT with 2 K+ IN c. Potassium ____________ ATP v. CAN be run in reverse to create____________ C hannel establish the majority of the electrical charge for the resting Leak membrane potential i. At rest the membrane is 100x more permeable to K+ than it is to Na+. ii. Contributes about –86 mV 3. Action potentials a. Terminology for changes in membrane potential i. Polarized ____________- at resting membrane potential ii. Depolarization ____________- making membrane potential less negative than resting iii. overshoot ____________- reversal in polarity, inside of the cell is more positive peak iv. ____________- The most positive point of the Action potential v. repolarization ____________- becoming more negative but still above the resting membrane potential vi. hyperpolarization ____________- AKA undershoot- more negative than the resting membrane potential b. Initiation of an Action Potential Nat i. Any factor that causes ____________ to diffuse into a cell can set off an AP 1. Mechanical If ated 2. Chemical 3. Electrical ii. Membrane potential must reach action potential threshold RMP -70mVooooh 1. ____________- muscle, -90mVmuscale nerve 2. Threshold ____________ is about 15mV more positive than RMP iii. ____________- summation adding multiple subthreshold potentials to reach threshold and generate an action potential 1. Temporal Summation- 2 or more presynaptic inputs arrive at a postsynaptic cell in rapid succession singlesource spatial 2. ____________ Summation- 2 or more presynaptic inputs arrive at a post synaptic cell simultaneously multiplesources iv. Action potential sequence 1. Polarized state- resting membrane potential, cell is -70 to -90mV closed a. Na+ activation gate____________ b. Na+ inactivation gate ____________ open closed c. K+ activation gate ____________ 2. Depolarization stage- upstroke of the action potential, threshold reached and initiates the following: a. Quick opening ofNat ____________gates activation Natinactivationgates fullyclosed at peak b. slow closing of ____________ K activation gates c. slow opening of ____________ d. Na+ rushes in, membrane potential becomes more _______ positive 3. Repolarization phase- at the __________of the AP the sodium isked channel inactivation gates are __________ and potassium activation gates are ____________. napen a. ____________stops moving in b. K+ rushes out, membrane potential becomes more_______negative 4. Hyperpolarization ____________ a. K+ activation gates are slow to close i. Pushes membrane more ___________than resting negative membrane potential ii. Once closed will return membrane to resting potential c. Refractory periods i. Absolute Natinactivation 1. No AP can be generated because the ____________gates are closed ii. ____________ Relative R Period efractory 1. AP can be elicited if a greater than usual stimulus is applied, corresponds with Hyperpolarization _______________ phase of the AP  d. Accommodation ____________ i. Membrane is held in a hypo-polarized state and not permitted to return to the resting membrane potential ii. Na+ inactivation gates cannot ____________ open iii. A means of the nervous system to down regulate neurological pathways. e. Action Potential Propagation- the spread of local currents to adjacent inactive regions i. Initiated in the axon hillock when it depolarizes to an action potential 1. Electrical charge moves to neighboring area to depolarize which opens voltage gated Na+ channels, depolarizes and passes the current down the axon ii. Conduction ____________- Velocitythe speed at which AP are conducted along a nerve or muscle fiber 1. Saltatory ____________-Myelination Conduction increases conduction velocity by providing a lipid insulator in between the nodes of Ranvier allowing the AP to jump from node to node 2. Diameter- the larger the diameter of themater never cell that _________ increases the speed of the AP Ch 6 Skeletal Muscle 1. Skeletal muscle a. Voluntary, Striated, Long, Cylindrical, multinucleated cells b. ___________ – made up of myofilaments (actin and myosin) arranged into sarcomeres Myofibril actin i. Thin (aka ____________) filaments 1. Also contain the regulatory proteins, troponin and____________ tropomyosin 2. Held in place by the structural protein nebulin _________, which attached the thin/actin filament to the Z disc myosin ii. Thick (aka ____________) filaments 1. Two heads- contain an ATPase enzyme 2. Tail- double stranded, contains hinge area for the head 3. Held in place by the structural protein titin ______, which attaches the thick/myosin filament to the Z disc and to the M line c. Sarcomere ____________– the functional unit of muscle contraction, bounded by two adjacent Z discs/lines Aband i. ____________dark band, made up of thick/myosin filaments (plus thin/actin filaments in the zone of overlap) stays thesame lengthofmyosinfilament M line 1. ____________- center of the A band, made up of the structural protein myomesin, holding the thick/myosin filaments in place 2. H zone (aka bare zone) – lighter zone of either side of the M line, contains only thick/myosin filaments ii. ____________– light band, contains thin/actin filaments If line boundary between two sarcomeres, made up of the structural iii. ____________- protein α-actinin  1. Hold the thick/myosin and thin/actin filaments in place. 2. The ends of the sarcomere that will be pulled together. d. Skeletal muscle contraction i. Sarcolemma is stimulated by the nervous system an action potential which travels down the sarcolemma Ttubules ii. AP travels through the ____________to the myofibrils sarcoplasmicreticulum iii. Action potential triggers release of calcium ions from the ____________ iv. calcium ____________ions cause exposure of binding sites on the actin molecules. 1. Calcium ions bind to ____________, causing tropomyosin to move away troponin and uncover the binding sites of the actin molecules a. Troponin - a complex of 3 globular proteins, binds to Ca++ to regulate cross bridge formation i. Troponin has 3 binding sites: 1. Troponin T- attaches the troponin complex to tropomyosin 2. Troponin I- inhibits the interaction of actin and myosin 3. Troponin C ____________-binds Ca++ to permit the interaction of actin and myosin v. Cross bridge cycle- Myosin binds to actin and causes the actin filaments to slide past the myosin filaments, toward the M line, resulting in shortening of the ____________of sarcomere the myofibril 1. ATP binds to the myosin head and immediately hydrolyzes into 2. theAffosin infinite ____________, a ____________and stored energy ____________ head binds to an actin molecule on the actin filament; this causes the release of the Pi inorganic 3. Release of the Pi from the myosin head initiates thePhosphate stroke ‘____________, which pulls the thin/actin filament toward the center of the sarcomere; ADP 4. At the end of the power stroke, the ____________molecule is released from the myosin head returning to the rigor state ATP molecule binds to the myosin head, which causes the 5. Another ________ myosin head to detach from the actin molecule, cross bridge detachment calcium ATP are depleted, or the sarcomere is 6. Repeat steps until __________or maximally shortened e. Energy sources for Skeletal muscle contraction anaerobic i. Breakdown of creatinine phosphate, stored within the muscle (____________) ii. Glycogenolysis of glycogen, stored within the muscle and in the liver (________) anaerobic iii. Oxidative metabolism of lipids, carbohydrates and proteins (___________) aerobic f. Muscle fibers TYPE 1 Red Muscle) i. Slow Fibers (____________, 1. smaller than fast fibers. 2. innervated by smaller nerve fibers. slow twitch fibers  3. more extensive blood vessel system and more capillaries to supply extra amounts of oxygen compared with fast fibers, 4. High numbers of____________to mitochondria support high levels of oxidative metabolism. Oxidative phosphorylation 5. contain large amounts of myoglobin ____________, an iron-containing protein similar to hemoglobin in red blood cells and it gives the slow muscle a reddish appearance. 6. Not easily fatigued 7. Example: one slowsmallredox _____________ ii. Fast Twitch ____________Fibers (Type II, White Muscle) 1. large for great strength of contraction. calcium 2. extensive sarcoplasmic reticulum for rapid release of ____________ions to initiate contraction. 3. Glycolysis ____________- Large amounts of glycolytic enzymes are present in fast fibers for rapid release of energy by the glycolytic process. 4. less extensive blood supply than slow fibers. 5. fewer mitochondria than slow fibers. 6. A deficit of red myoglobin in fast muscle gives it the name white muscle. 7. Easily fatigued sprinter Large fast white chickens 8. Example: ____________ 2 g. Types of muscle contraction i. Isometric ____________- Muscle length does not change, and tension will change doesnotchange ii. Isotonic- Muscle length changes, and tension ____________ 1. Concentric- muscle shortens ____________ 2. Eccentric- muscle____________ lengthens Ch 7 Neuromuscular Transmission & Excitation Coupling of Skeletal Muscle 2. Synapse- area of communication in between cells a. Electrical ____________Gap Junction i. Bidirectional, simultaneous contraction fast candirectlytransfer ii. cardiac ____________and muscles some smooth muscle b. Chemical- Synaptic cleft i. Cleft- space between the cells ii. Regulated by neurotransmitter ____________ iii. Unidirectional ____________: Pre to Post synaptic iv. Synaptic delay- transmission takes longer than electrical 3. Motor Unit a single motor neuron and the muscle fibers it innervates ____________- a. Small motor unit forfine motor control ____________ b. Large motor unit for gross muscle activity neuromuscular 4. ____________- Junction the Chemical synapse between motor neurons and skeletal muscle a. Presynaptic nerve cell axon i. Bouton- bulb like portion of the terminal end of the____________ calcium ii. Contains voltage gated ____________channels triggered by action potential from nervous system  iii. Acetylcholine vesicles leave the membrane via exocytosis iv. Acetylcholine ____________ is released into the synaptic cleft ECF b. Postsynaptic muscle fiber i. Motorendplate ____________- the portion of the muscle fiber that interacts with the cleft ii. ____________ Nicotinic acetylcholine receptors on motor endplate attach the released acetylcholine ligand iii. Nicotinic receptors act as____________gated Na+ and K+ channels iv. Multiple end plate potentials summate to open enough Na+ channels to depolarize the muscle cell membrane to ____________ threshold and create an AP v. Currents cause depolarization and action potentials in the surrounding muscle tissue and initiate contraction of the muscle c. Acetylcholine formation and release i. Vesicles are formed by the ____________of the motoneuron and transported to Ap tus the neuromuscular junction ii. Acetylcholine is synthesized in the ____________ cytosol and immediately transported and stored into vesicles calcium iii. ____________channels open causing the exocytosis of the acetylcholine into the synaptic cleft. iv. After a few milliseconds the acetylcholine is split by ____________ acetylcholinesterase into acetate ion and choline v. The choline is reabsorbed into the neural terminal to combined with Acetyl COA ____________and form new acetylcholine. vi. New vesicles are reformed rapidly by a process of the invagination of the nerve Clathrin cell membrane caused by the contractile protein____________and new acetylcholine is transported into these vesicles. d. Mechanism of skeletal muscle contraction i. Sarcolemma stimulates by AP from the nervous system fibrils transverse tubules ii. AP travels to the ____________via myo iii. AP triggers the release of calcium ions from the ____________ e m iv. Calcium ions bind to troponin changing the configuration of___________ tropomyosin_ and uncovers the myosin binding sites on actin ____________, molecules initiating the cross bridge cycle v. calcium ____________- pump pumps calcium back into the sarcoplasmic reticulum away from atpase the myofibrils so muscle relaxation can occur 1. Primary active transport  Ch 5 13 14 questions 50 questions 50 points 1h6 24 ish questions 1h7 13 ish questions Di erences in what is going on in action potential What does threshold mean What polarized means Goldman vs nernst Refractory periods Summations Accommodation Di erent lines/bands Di erences between type 1 and 2 What power stroke means, di erent steps of cross bridge cross bridge detachment What does rigor mortis demonstrate Skeletal muscle Electrical vs chemical synapses Di erent gates: what is open and closed at di erent points of action potential What needs to be added to myosin so it can bind to actin to initiate cross bridge cycle Di erence between sodium potassium pump and potassium leak channels