Nervous System - Action Potentials

Question 1

What types of substances move through ion channels in neurons? (4)

Answer 1

Potassium, sodium, calcium, chloride

Question 2

Types of channels (2)

Answer 2

Leakage (always open or alternate between open and closed)

Gated

Question 3

Types of gated ion channels (3)

Answer 3

Voltage gated (respond in changes to charge)
Chemically/ligand gated (change in chemical concentration)
mechanically gated (respond to mechanical stimuli)

Question 4

How many of each ion is pumped in and out of a Na+/K+ pump? Does it require energy?

Answer 4

pumps 3 Na+ ions out and 2 K+ ions into cell against concentration gradient
requires ATP

Question 5

Is the outside of the cell more positive or negative? And why?

Answer 5

more positive as it contains a higher number of positively charged ions

Question 6

Is the inside of the cell more positive or negative? And why?

Answer 6

more negative as it contains less positively charged ions and more negatively charged proteins

Question 7

What is the voltage of the resting membrane potential?

Answer 7

-70 mV

Question 8

What is the action potential threshold/initiation value?

Answer 8

-55 mV

Question 9

What happens after the action potential is initiated? What happens and what voltage does it reach?

Answer 9

depolarization
influx of positive ions into cell 
voltage gated Na+ ion channels open
increase to +40 mV
explosive and fast

Question 10

What happens after depolarization? What voltage does it reach?

Answer 10

repolarisation
exit of positive ions out of cell
voltage gated Na+ ion channels close
voltage gated K+ ion channels open
restoration of resting membrane potential

Question 11

When does hyperpolarization occur and what happens?

Answer 11

sometimes happens after repolarization

too many positive ions leave the cell

Question 12

What is happening to a neuron cell when it is at rest? What ions are at the highest concentrations where?

Answer 12

Na+ and K+ voltage gated channels closed
Na+/K+ pump maintaining potential at -70 mV
high concentration of Na+ on outside
high concentration of K+ on inside

Question 13

What are the two types of conduction?

Answer 13

saltatory and continuous

Question 14

What is saltatory conduction?

Answer 14

myelinated axons
fast
long axons
signal jumps between Nodes of Ranvier

Question 15

What is continuous conduction?

Answer 15

unmyelinated axons
slow
short axons