Graded & Action Potentials Exercise- The material of Chapter 8 can be overwhelmi
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Question
Graded & Action Potentials Exercise- The material of Chapter 8 can be overwhelming if you do not make necessary connections between key concepts. Concept mapping, as described in the Silverthorn text (pgs 6-7) is an active strategy that can help students meaningfully engage material and see relationships between critical concepts. However, some of the concept maps provided in the Silverthorn text could be expanded. Get together in your group and develop a concept map concerning graded and action potentials that is directly related to your answers to the instructor-designed questions 9 10 & 12 16 for Chapter 8 on a sheet of paper. Specifically, your concept map should address and show connections for all of the following topics/terms: Depolarizing & hyperpolarizing graded potential Strength vs distance for graded potentials Integration center Triggers & characteristics of action potentials Mechanism & phases of the action potential Types of refractory periods Functions of refractory periods Frequency of action potentials Conduction of action potentials Axon parameters that affect action potentials One you are satisfied with your group effort in creating your concept map on paper, recreate the concept mapExplanation / Answer
Action potential – when a nerve fibre receives a stimulus, the polarity of the membrane changes i.e., negative outside and positive inside the membrane (+30 inside and -60 outside). This change in membrane potential is referred as action potential. Voltage-gated channels are responsible for the generation of action potential. Two kinds of voltage-gated channels are present on the membrane – one selectively permeable to Na+ ions and other to K+.
Mechanism and phases of action potentials/ conduction of action potential -
1.Depolarization – When a nerve fibre receives a stimulus it result in the change of permeability in the membrane. Opening of voltage-gated Na+ channels increases the permeability of membrane to Na+ ions and voltage gated K+ ion channel increases movement of K+ ion outside the membrane. It results in the depolarization or the change in membrane potential from -60mv to +30mv. An action potential is generated when the membrane is depolarized.
2.Repolarization – The change in membrane potential flows passively along the axon resulting in the depolarization of the adjacent region of the axon. With increase in positive charge inside the membrane, Na+ ions channels get closed leading to the repolarization of the membrane. It is achieved by the increased permeability of K+ ions due to K+ ion channel opening, causing the K+ ion flow outward so the membrane potential returns to negative value i.e., the resting potential of -60mv is restored.
3.Hyperpolarization – Before K+ ion channel closes, excess K+ ions have moved out of the cell generating the polarized potential (-80mv). Thus the membrane becomes hyperpolarized.
Refractory period – During repolarization the nerve fibre cannot be stimulated. During this interval, nerve fibre recovers from the first stimulus and becomes ready for another stimulus. This interval is termed as refractory period. When K+ ion channel closes and the hyperpolarized membrane recovers its resting potential, it is when a second impulse can follow.
Types of Refractory period -
Its because of the Refractory period that
Axon parameters -
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