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Neurophys 2 - pcc
Neruophys 2
| Question | Answer |
|---|---|
| How does a nerve impulse cause a muscle contraction? | 1. AP arrives at neuromuscular junction 2. Ca diffuse into synaptic knobs 3. Synaptic vesicles release Ach 4. Ach binds to nicotinic sites in sarcolemma 5. Ion channel opens in sarcolemma, Na moves in and cause dep. 6. AP spreads in all directions |
| AP arrives at the _________ | Neuromuscular junction |
| In a muscle contraction, what do the synaptic vesicles release? | Ach |
| In a muscle contraction, what does Ach bind to? Where? | Nictotinic receptor sites in sarcolemma |
| In a muscle contraction, what cause depolarization? | Ion channels open in sarcolemma and Na+ moves in |
| After depolarization, where does the AP go? | It spreads in all directions and reach the T-Tubules |
| AP reach t-tubles which does what? | Carries depolarization from outside of muscle to the inside |
| T tubules depolarization causes what? | Ca+ to be released in the sarcoplasm |
| Ca+ then binds to troponin-C which does what? | Causes conformational change in troponin complex |
| In the presence of Ca+, the conformational change in troponin causes what to get out of the way to expose myosin binding sites on actin? | Tropomyosin moves to expose binding sites |
| Cross bridges form by the binding of _____ and _____. ____ hydrolyses ATP inbto ADP and Pi. This releases energy to create the ___. Myosin then binds to another ATP which releases the actin and myosin head. What causes this? | 1. Actin 2. Myosin 3. Myosin ATPase 4. Power stroke 5. Recovery stroke |
| Durinf muscle contraction, what is actually moving to shorten the muscle? | The actin is sliding down the myosin heads via power and recovery strokes |
| Relaxation of a muscle occurs when Ach is inactivated by ____. This inhibits nerve impulse conduction. Then ___ is pumped from sarcoplasm to the ___ via the Ca+ ATPase pump | 1. AchEsterase 2. Ca+ 3. SR |
| In the SR, Ca+ binds to ___ and is stored until the fiber is stimulated again. Exiting Ca+ from sarcoplasm causes the troponin complex to do what? | 1. Calsequestrin 2. Revert to its original shape covering up the binding sites once again |
| In the resting state, Na+ volatage channels are closed because the ___ gate is closed | Activation gate |
| As soon as Na+ starts to rush in after its activation gates are opened, the ___ gate closes after 2msec. Simultaneously, ___ gates are opened | 1. Inactivation 2. K+ activation gate |
| Period in which Na+ inactivation gates are closed and cannot be reopened until repolaization has occured | Absolute refractory period |
| Begins when absolute refractory period end? Lasts about ___ to ___ as long as ARP and overlaps with period of ___ | 1. Relative refractory period 2. 1/4 to 1/2 3. Hyperpolarization |
| Depolarization cause ___ gates to close. Which gates remain open? At the same time ___ openes. ___ gates stay open longer than the ___ gates. | 1. Na inactivation gates to close and Na activation gate remain open 2. K+ gates 3. K+ gates stay open longer than Na+ gates |
| Whewn a neuron is in Reletive refractory period, a ____ can elicit a second AP. | Stronger than normal |
| Spider toxin blocks ___ channels | N-Calcium channels |
| Activation of voltage gated Na and K channels | 1. Both inactivation and activation gates open allowing Na+ in. 2. Inactivation gates start to close while K+ gates start to open 3. K+ gates open when there is an increases in memebrane potential via the Na comming in. 4. Depolarization has occured! |
| Ca/Na pumps in the heart : What enters the heart? How many of what enters and leaves? | Ca enters the heart and this cause contraction. As Ca+ increases in heart an antiport system of Na-Ca pumps it out. 3Na+ enter the cell and 1Ca+ leaves at the expense of 1 ATP |
| Cardiac glycolysis disrupts the phosphorylation-dephosphorilation...because of this, ___ cannot get out of the cell and ___ cannot get in | Na cannot get out and K cannot get in...pumps is non-functional |
| Cystic fibrosis is caused by genetic defects in ___? What is the result? | CFTR : Cl- flow is defective resulting in increaswe in salt through sweat, reccurent respiratory infections and increased absorption of electrolytes. Net result = dehydration of repiratory secretions |
| K+ ions leaving are greater than Na+ entering which may cause a ___. Gradually, diffusion and Na-K pump restores normal resting state. | Hyperpolarization (slightly more negative than normal) |
| Largest protein in the body, springy and acts as a framework that lines up actin and myosin to make the contractile mechanism work. | Titin |
| Titin is responsible for : | Acts as a framework that lines up the myosin and actin to make the contractile mechanism work |
| Toxin that blocks voltage gates Na+ channels and prevents action potentials | Lidocaine |
| Toxin that blocks Na+ channels on the ISF side | Tetradotoxin (TTX) |
| Toxin that blocks Na+ channels and causes lethal paralysis within half an hour (shellfish) | Saxitoxin |
| What is the importance of Ca+ channels? | Increase intracellular Ca+ which promotes neurotransmitter relase and activation of enzymes |
| Significance of voltage gated channels? | Producing eletrical impulases over long distances in a nerve fibers |
| Significance of ligang-gated channels? Why are they so fast? | Enables rapid communication between neurons and other organs : saltatory conduction |
| Describe the donnan effect? | 1. If there is a higher distribution of charges on one side of a memebrane they will flow down the gradient 2. This leads to higher concentration of solute on one side... Water will move towards the high solute via osmosis |
| Primary active transport? | ATP is the main source of energy. 1. Na-K pumps, Ca ATPase in SR, H-K pumps in stomach |
| Secondary ative transport | Electrochemical gradient is main source of energy: glucose-Na |
| Transport of molecules in diffrent directions? | Antiport = primary active transport |
| Transport in which 2 solutes move in the same direction (in secondary active transport) What is usually transported? | 1. Symport 2. Na + glucose, Na + amino acids |
| Describe the Na-K pumps? How many Na and K are pumped? Is it electrogenic? How mnay ATP used? | 1. 3 Na pumped out and 2 K pumped in 2. Yes 3. 1 ATP |
| The Na-K pump makes for a ___ environment in the cell | Negative |
| The Ca+ pump in skeletal muscles pumps __ Ca against their gradient at the expense of ___ ATP | 1. 2 2. 1 |
| The H-K pump is found in the ___ It pumps ___ into the stomach making it acid. | Stomach : H |
| 2 types of ion channel gates? | Voltage gates channels and Ligand gated channels |
| What controls the 2 ion channel gates? | VG channels = change in membrane potential LG channels = Hormones and neurotransmiters |
| What passes through the ion channel gates? | VG channels = Na+ and K+ LG channels = Na+, K+ and Ca+ |
| Two types of Ca+ channels? | L channels and N channels |
| L-type Ca channels are involved in? | Muscle excitation |
| To treat ___ disorders, the L-channels are blocked | Cardiovascular |
| How many mV needed for depolarization? Hyperpolarization? | 1. -90 to -60 2. -92 |
| What is the refractory period? | Period after an AP in which another AP connot occur |
| What is the effect of hypercalcemia on AP and muscle contraction? | Na channels open with very little stimulus therefor fibers start firing impulses rapidly with no stimulus creating tetany |
| True or false, Na+ channels open with very little stimulus? | True |
| In the resting state, 2 types of channels that are always opened? | Na+ and K+ leak channels |
| Electrical charge developed across a membrane when ions diffuse down their concentration gradient? | Diffusion potential |
| Diffusion potential that ballances or opposes the tendancy for diffision down the concentration gradiant | Equilibrium potential |
| Example of equilibrium potential | Na-K voltage gates 1. When Na moves in you have the diffusion potential but when the K+ moves out you acheive equilibrium potential |
| Purpose of the Nearnst equation? | To determine the voltage necessary to acheive equilibrium potential |
| Define action potential | Property of electric excitibility that underlies basic nerve impulse |
| Rapid phase of AP where the inside of the membrane becomes positive. From ___ to ___ mV? | Depolarization : -90 to 35 mV |
| Returns the membrane to resting potential? From ___ to ___ mV? | Repolarization : -70 to -90 mV |
| Membrane potential becoming more negative than the normal resting state for a few milisecondes? | Hyperpolarization |
| Define threshold. What is the threshold for an AP? | The minimum amount of stimulus that can elicit and AP : -60mV |
| What is the resting membrane potential? What is reponsible for this? | -70 to -90 mV. K+ leak channels are opened, thus K+ conductance is high and Na+ conductance is low. K+ leaks out for a net charge of -90 inside the cell. |
| During depolarization the membrane becomes very permeable to ___. The membrane potential rises in the ____. | 1. Na 2. Positive |
| In what way is the Na-K pump electrogenetic? | More Ca (3) and leaving than K (2) comming in |
| ___ channels are slow channels and are prevalent in what type of muscles? | Voltage gates Ca-Na and are present in cardiac and smooth muscles |
| ___ channels are fast and are located in which type of muscle? | Na+ channels and are located in skeletal muscles. |
| 3 factors that account for plateaus | 1. Opening of fast Na+ channels cause a pike 2. Slow but prolonged opening of slow channels 3. Very slow opeing of K+ channels delays the return of RMP |
| Which channels oppen at the end of the plateau? | Very slow volatage gates K+ channels |
| Where do we have plateaus? | Cardia muscles |
| Rythmicity in some excitable cells are important for what? | 1. Heart beat 2. Peristalsis 3. Rythmic Breathing |
| AP that occurs in one spot on the axon excites nearby segments of the membrane top produce their own AP. This wave of movement is called what? | Propagation |
| Sequence of events in propagation? | 1. AP is triggered by axon hillock 2. Electrical signals encountered VG Na+ channels 3. Current is carried by inflow of Na+ ion that fidduse in both directions of axon 4. Local depol initiates a new AP at adjacent seg. 5. Self propagates |
| What part of the axon triggers the AP? | Hillock |
| In propagation, the current is carried by an inflow of what ion? | Na+ |
| Does initial AP travel all the way down to axon terminal or does it decay? | It decays but does propogate itself |
| Speed at which APs are conducted along a nerve or muscle fiber | Conduction velocity of nerve fiber |
| 2 factors that increase conduction velocity | 1. Increase in the diameter of nerve 2. Myelinating the nerve |
| Myelation allows nerve impulses to jump very rapidly between segments. What is this called? | Saltatory conduction |
| 2 disease of nerve impulse conduction | 1. MS (demyselination) 2. Tay-sachs (ganglisides, hexoseaminidase, demyelimation) |
| Which muscle have intercalated discs? What do they do? | Cardiac muscles. Enables electrical impulse to travel rapidly from one cell to another |
| Which muscles are not striated? | Smooth |
| Muscle cell that contains sarcolemma, sarcoplasm and all organelles. | Muscle Fiber |
| Contractile protein filament responsible for muscle contraction. | Myofilament |
| In the sarcoplams, 1 to 2 micrometers in diameter, thousands in muscle fiber | Myofibrils |
| Contractile unit of muscle | Sarcomere |
| Filament composed of myosin | Thick |
| Filament composed of actin | Thin |
| Actin is ___ in globular form and ___ in filament form. It is ___ in structure | 1. G-Actin 2. F-Actic 3. Double hellical |
| Blocks binding site on actin in resting state. It is a filamentous protein | Tropomyosin |
| 3 globular proteins located at regular intervals along the tropomyosin | Troponin (T, I, C) |
| Troponin T does what? | Attaches troponin to tropomyosin |
| Troponin I does what? | Inhibits actin and myosin interaction |
| Troponin C does what? | Binds calcium and plays crucial role in initiation of contraction |
| The 4 light chains of myosin for the myosin ___ | Tails |
| The 2 heavy chains of myosin for the ___ | Heads |
| Do light or heavy chains of myosin interact with the actin filaments? | Heavy |
| Fillamentous molecule of protein that allows side by side relationship of actin and myosin filament | Titin |
| Links thick filaments to Z-Lines | Titin |
| Links thin filament to Z-Lines | Nebulin |
| Myosin binding protein present on the M-Line | Myomesin |
| Bundles of actin filaments attached to the Z-Lines | Alpha actin |
| What cause rigor mortis and why do muscles relax after a day or two? | 1. Body runs out of ATP 2. Deterorating SR releases Ca+ into sarcoplasm 3. Ca+ cannot be removed because of lack of ATP therefor the muscle stays contracted. 4. Muscles relax after a few days because the proteins are gradually borken down |
| Continuous contraction of muscle is called ___. Caused by what? | Spastic paralysis : ACHesterase inhibitor don<t allow ACH to be broken down |
| Phenomena in which there is no contraction. What can cause this? | Flaccid paralysis : Poison such as curare competes with ACH and dosen't allow it in the nicotonic receptors to allow contraction |
| The sum of active tension developed by contractile elements of the sarcomere + passive tension = ? | Total tension |
| Total tension - passive tension = ? | Active tension |
| Tension developed when a muscle is stimulated to contract at diffrent preloads? | Total tension |
| Define rest lenght | The lenght at which a muscle develops maximum tension in response to a stimulus |
| When is Vmax of muscle contraction? | When afterload is zero |
| When will a muscle have a zero velocity contraction? | When the afterload increases to higher levels |
| Rapid force response to a single stimulus. A quick cycle of stimulus and relaxation. Lasts 7-100 msecs | Muscle twitch |
| Weakest stimulus from a neuron that can initiate a contraction? | Threshold stimulus |
| A delay of about 2 miliseconds between the stimulus and the onset of a twitch. | Latent period |
| Staircase phenomena of successive contraction increasing in force from repeated force at regular time intervals? | Treppe |
| Two stimuli ariving close together. Second arrives after refractory period but before it relaxes. | Temporal summation |
| In treppe contraction, does the muscle have ample time to recover between stimuli? | yes |
| Muscle is able to relax only partially between contractions. Occurs when stimuli are so frequent . Muscle cannot completely relax. | Incomplete tetany |
| Muscle does not relax between contraction. Twitches fuse to form a smooth, prolonges contraction | Complete tetany |
| What is ATP required for in the muscle? | 1. Provides energy for Na-K pumps 2. Cross bridge cycle 3. Ca+ pump in SR 4. Detaching cross bridge |
| Source of ATP: Anerobic respiration. What does this produce? | Glucose and FA catabolize in mitochondria (anerobic glycolisis). This produces lactic acid |
| How is ATP made in aerobic respiration | Surplus ATP is used to build energy reserves of ATP, PCr and glycogen |
| Resting muscle stores ATP as what? | PCr = phosphocreatine |
| Muscle cramps are a result of what? Because of this what may occur? | Low O2 levels. ATP synthesis will be reduces due to slow anerobic respiration (glycolysis) This slows 1. Na-K pump 2. Increases lactic acid production 3. Increases pH |
| How do pro athletes develop endurance a few days before a game? | Carb-loading. 4-5 grams of glycogen in 100 grams of muscle |
| What is malignant hyperthermia? | Sensitivity to anethetics |
| What causes hyperthermia? | Anethetic agents fully activates skeletal muscles - enormus amount of heat generated - positive feedback loop - death |
| Fast twitch (type 2) | low mitochondria, low oxidative enzymes, high glycolitic function, low myoglobin, high SR, low capillary bed density |
| Slow twitch (type 1) | Small diameter, high mitochondria, high oxidative enzymes, low glycolytic function, high myoglobin, low SR, High capillary bed density |
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LrB
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