9.2 1 Nervous Systems And Neurones

Question 1

what is the basis of a nerve impulse

Answer 1

the concentration of sodium ions, potassium ions and other charged particles outside the axon is different from that of the inside of the axon

Question 2

what is special about the membrane of an axon

Answer 2

it is partially permeable - difference in permeability to sodium and potassium ions
relatively impermeable to sodium ions but quite freely permeable to potassium ions

Question 3

when is an axon said to be at rest

Answer 3

when it is not conducting a nerve impulse

the extracellular concentration of ions is greater than the concentration in the axon cytoplasm

Question 4

sodium/potassium pump

Answer 4

has an enzyme called Na+/K+ ATPase that uses ATP to move sodium ions out of the axon and potassium ions into the axon

Question 5

first stage in resting potential

Answer 5

sodium ions are pumped out of the axon lowering concentration of sodium ions inside the axon and due to impermeability cannot diffuse back in