CMB1004 Excitable Cells Exam Questions With 100% Verified Answers
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Course
CMB1004
Institution
CMB1004
CMB1004 Excitable Cells Exam Questions
With 100% Verified Answers
What are the four regions of a neurone? - answerDendrites
Cell Body
Axon
Axon Terminal
Define an excitable cell - answerAny cell capable of generating an action potential
Describe how the resting potential is maintained - answ...
CMB1004 Excitable Cells Exam Questions
With 100% Verified Answers
What are the four regions of a neurone? - 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
Describe the process of signal transmission at the synaptic cleft - answer✔1) Presynaptic
membrane depolarised by action potential, causing Ca2+ gates to open
3) Ca2+ rushes into the axon terminal from outside of the cell
4) Increase in Ca2+ triggers vesicles containing Ach to release them into the synaptic cleft via
exocytosis
5) Ach diffuses across cleft and binds to receptors on the post synaptic membrane, opening
ligand-gated Na+ channels
6) Na+ rushes into the post synaptic cell, K+ rushes out
7) An EPP (Endplate potential) is generated, triggering an action potential
What happens to Ach after binding? - answer✔They are broken down by Acetylecholinesterase
What happens during muscle contraction? - answer✔H zone shortens, A band and I band remain
same size as thin filaments slide over thick filaments
Describe the structure of the thick muscle filament - answer✔Myosin molecules held together by
M line
Describe the structure of the thin muscle filament - answer✔Made of actin, tropomyosin, myosin
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