The Ionic mechanism and propagation of action potentials. The action potential is the result of a large‚ sudden increase in sodium permeability of the membrane. The resulting rush of sodium ions into the membrane and accumulation of positive charge on its inner surface drives the potential towards Ena. This is followed by repolarisation‚ whereby there is a large increase in the membranes permeability to potassium ions‚ hence the membrane returns to Ek. Explanation of the (ionic) mechanisms underlying
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The formation of an action potential can be divided into five steps. (1) A stimulus from a sensory cell or another neuron causes the target cell to depolarize toward the threshold potential. (2) If the threshold of excitation is reached‚ all Na+ channels open and the membrane depolarizes. (3) At the peak action potential‚ K+ channels open and K+ begins to leave the cell. At the same time‚ Na+ channels close. (4) The membrane becomes hyperpolarized as K+ ions continue to leave the cell. The
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Action Potentials An action potential is the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell. An action potential occurs when a neuron sends information down an axon‚ away from the cell body. A threshold is the minimum amount of stimulation needed to start a neural impulse (you know‚ the electrical impulses that travel throughout your body carrying important information). Action potentials generated by neural impulses are
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RESTING POTENTIAL Resting potential is the membrane potential when a neuron is not conducting any electrical impulse or signal. The resting potential is around -75 mV. During resting potential‚ the inside of the axon is negative GRADED POTENTIAL ACTION POTENTIAL Action potential is a fleeting reversal of the membrane potential‚ caused by changes in permeability of the plasma membrane of neuron to potassium and sodium ions causing an electrical impulse to be transmitted along the axon.
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membrane Na cl ‚K and Ca ions and they just flow back and fourth without any gate keeper or obstruction‚ When the neuron is at rest its cytoplasm is Negatively charged. That means that it is not going under depolarization‚ we use the term resting potential. Modality gated channels- specific to sensory neurons‚ open in response to mechanical forces (i.e. stretch‚ touch‚ pressure‚ temperature changes or chemicals) Ligand- is a particular molecule that causes a receptor to open. The ligand gated
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A graded potential in physiology‚ is described as local changes in membrane potential that occur in varying grades or degrees of magnitude or strength. When compared to graded potential‚ an action potential is described as brief‚ rapid‚ large (100mV) changes in membrane potential during which the potential actually reverses so that the inside of the excitable cell transiently becomes more positive than the outside. As with a graded potential‚ an action potential involves only a small portion of
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The Action Potential An action potential‚ also called a spike‚ nerve impulse‚ and discharge‚ is the rapid reversal of charge of the cell membrane. These changes in charge occur within milliseconds‚ meaning the action potential travels very quickly down the axon in order to convey information over long distances. This transfer of information occurs within six phases and requires the presence of multiple pumps and channels embedded in the membrane to control ion concentration. Phase 1: The Resting
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allow an Action potential to occur in a neuron. This will be achieved by firstly‚ defining the purpose of neurons in the body along with a description of the components within a neuron and how they enable information to be passed through the cell membrane and on to other neurons. Secondly‚ the resting potential of a neuron will be explored with relation to the concept of selective permeability and the purpose of the Sodium - Potassium pump. Thirdly‚ the molecular basis of the Action Potential will
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and convert them to nerve impulses • Alternating graded and all-or-none signals on the membrane of a single neuron • Graded potentials decay with distance (electrotonic conduction); longdistance transmission depend on transforming signals to APs • Typically‚ alternating electric (within neuron) and chemical signals (between neurons) • Postsynaptic potential affected by number and frequency of APs Passive spread of electric signal Sub-threshold current flowing along the membrane decays
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which of the following? You correctly answered: c. autorhythmicity 2. Phase 2 of the cardiac action potential‚ when the calcium channels remain open and potassium channels are closed‚ is called the You correctly answered: a. plateau phase. 3. Which of the following is true of the cardiac action potential? You correctly answered: b. The cardiac action potential is longer than the skeletal muscle action potential. 4. The main anatomical difference between the frog heart and the human heart is that the
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