Cells Membranes and Cell Excitation

Question 1

Two types of excitable cells

Answer 1

Muscle - CONTRACT
Nerve - CONDUCT

Question 2

Excitable cells

Answer 2

Transmit electrochemical signals along their membranes by moving charged ions across the cell membrane = action potentials

Question 3

Transmembrane resting potential

Answer 3

Electrical gradient between extracellular and intracellular fluid; inside cell slightly negative

A form of stored or “potential” energy which can be used to open voltage gated membrane channels and send electrical signals

Question 4

What creates the transmembrane resting potential

Answer 4

Diffusion of potassium channels
Sodium pump
Negatively charged proteins inside cell

Question 5

Electrogenic pump within Sodium pump

Answer 5

Net loss of one positive charge from cytoplasm helps maintain electrical gradient

Question 6

Distribution of ions across cell membranes at rest

Answer 6

Sodium ions pumped out by potassium/sodium/ATPase
Voltage gated sodium channel closed (sodium cannot enter cell)

Potassium ions pumped in by sodium/potassium/ATPase
Potassium leaks out through potassium ion channel as the membrane is permeable
Voltage gated potassium ion channel closed

Ion imbalance created -70mV internal TRP as potassium moves out but anions cannot follow

Excitable cells use electrochemical disequilibrium to generate action potentials

Question 7

Two types of response

Answer 7

Local - Non propagated (usually at dendrites and cell body)
Propagated disturbance = action potential

Question 8

Absolute refractory period

Answer 8

cell cannot fire = no more AP = ensures one way travel of AP

Question 9

Relative refractory period

Answer 9

Only larger than normal stimulus can initiate new AP

Question 10

Action potentials travel faster in which axon

Answer 10

Myelinated axons