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CMB1004 Excitable Cells Exam with complete solutions 2024_2025
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CMB1004 Excitable Cells Exam with complete solutions 2024_2025
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CMB1004 Excitable Cells Exam withcomplete solutions 2024/2025
What are the four regions of a neuron? - ANSWER-Dendrites
Cell Body
Axon
Axon Terminal
Define an excitable cell - ANSWER-Any cell capable of generating an action
potential
Describe how the resting potential is maintained - ANSWER-Cell contains slight -
ve charge (70mv)
Maintained via high permeability of membrane to K+ and active transport of Na+
across membrane
Define an action potential - ANSWER-A rapid change in membrane potential
What is the equilibrium potential? - ANSWER-The point at which the electrical
gradient of the cell is equal and opposite to the concentration gradient
What is the Nernst equation? - ANSWER-
What occurs at each stage of an action potentials generation? - ANSWER-
Depolarisation: Membrane potential increases from RMP
, Repolarisation: Membrane potential decreases following depolarisation
Hyperpolarisation: Membrane potential falls below RMP
Describe the activity of voltage gated ion channels during action potential
generation - ANSWER-1) Resting state, no gates open
2) Slow rising phase, some Na+ gates open, small amounts of Na+ enters cell
3) Rapid rising phase, all Na+ gates open, some K+ gates open
4) Early repolarisation, all K+ channels open, some Na+ closed
5) Hyperpolarisation, all Na+ closed, some K+ open
Define absolute refractory period - ANSWER-The period immediately following an
action potential generation during which no action potential can be generated
regardless of stimulus size
Define relative refractory period - ANSWER-The period during hyperpolarisation
where an abnormally large stimulus can generate an action potential
How is the velocity of an action potential increased - ANSWER-Increase the
diameter of the axon
Increase the membrane resistance by insulating with myelin sheath
Define myelination - ANSWER-The process by which axons are insulated with
schwann cell membranes to prevent loss of charge down the axon body
What is saltatory conduction? - ANSWER-Action potentials "jump" between areas
of unmyelinated axons called nodes of Ranvier, increasing transmission of the
action potential
What is an endplate potential? - ANSWER-Depolarisation of the postsynaptic cell
to a level halfway between the equilibrium potential of the two ions (Na+ and K+
typically) involved
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