Unit 3 Physiology

What neurons carry a signal from a sensor to the integrating center?

Afferent neurons

What neurons carry a signal from the integrating center to the effectors?

Efferent neurons

What are the four types of ion channels?

What is the resting membrane potential of neurons?

-70 mV (due to negatively charged proteins)

Depolarization

The inside of the cell becomes more positive due to influx of Na+

What is the equilibrium potential of Na+?

+60 mV

Repolarization

The inside of the cell becomes more negative due to efflux of K+

Hyperpolarization

The inside of the cell becomes highly negative (-90 mV) due to efflux of K+

What is the equilibrium potential of K+?

-90 mV

What is the equilibrium potential of Ca2+?

+122 mV

What is the relationship between membrane permeability and membrane potential?

• Increase permeability = membrane potential goes towards ion’s equilibrium potential

• Decrease permeability = membrane potential goes away from ion’s equilibrium potential

Na+/K+ ATPase

• Returns neurons to resting membrane potential

• Primary active transport

Action potential

• Occurs in the axon

• A potential that transmits a signal (neurotransmitter)

Graded potential

• Occurs in dendrites

• A potential that may or may not result in an action potential

Threshold potential

• -55 mV

• Minimum depolarization required for an action potential

• Occurs at axon hillock (trigger zone)

Describe a graph of membrane potential throughout an action potential

• Voltage gated Na+ channels open first and fast

• Voltage gated K+ channels open second and slow

• Voltage gated Ca2+ channel at the axon terminal triggers exocytosis of NT