Chapter 12 Neurons

Question 1

Two major cell types in the nervous system

Answer 1

• Neurons
• Gilia

Question 2

Answer 2

Cell body (soma) – basic maintenance of the cell.

Dendrites – extend from the soma and receive info from other neurons and direct that info to the cell body.

Axons – conduct signals away from the cell body

Axon Terminals – signals from this area can be sent to other neurons, glands or muscle fibers.

Question 3

Neuron Function

Answer 3

• Transmit electrical signals
• Release neurotransmitters
• Integrate information

Question 4

Resting Membrane Potential

Answer 4

Two major factors determine:

• Selective ion channels
• Unequal distribution of ions by the cell membrane

range: –20mV to -100mV depending on the cell and ionic environment.

The resting membrane potential is largely determined by the potassium ion concentration gradient across the cell membrane because of the K+ selective leak channels are usually open.

Question 5

Na+/K+ ATPase pump and “RMP”

Answer 5

The Na+/K+ pump has an indirect effect on maintaining the resting membrane potential by maintaining the concentration gradient of K+ higher intracellularly.

Question 6

Resistance

Answer 6

(R, ohms, Ω): a measure of membrane impermeability.

Question 7

Conductance

Answer 7

(g, siemens,S) : a measure of membrane permeability

formula: g=1/R

Question 8

The lower the resistance of a membrane (the greater its conductance), the more ionic charges will cross the membrane via ion channels per unit time

Question 9

The Nernst Equation

Answer 9

Question 10

The Goldman-Hodgkin-Katz Equation

Answer 10

Used for calculating the equilibrium potential for a single ion.

Question 11

Describing Changes in Electrical Potential

Answer 11

Question 12

Electrical Signals

Answer 12

Graded Potentials

• Short distance
• Postsynaptic potentials
• Receptor potentials
• End-plate potentials
• Pacemaker potentials
• Slow-wave potentials

Action Potentials

• Long distance

Question 13

Graded Potentials

Answer 13

• The size of graded potentials depends on stimulus strength
• Loses strength the more spread out they are
• The size of graded potentials decreases with distance
• causes action potential to get to its threshold

Question 14

Action Potentials

Answer 14

• Stimulus must reach threshold
• All or nothing event
• Propagated without decrement

Question 15

Action Potentials: Voltage-gated Na+ Channels

Answer 15

• Opened by depolarization
• Dual gates

Question 16

Action Potentials: Voltage-gated K+ Channels

Answer 16

Voltage-gated (delayed)

Question 17

Refractory Period

Answer 17

• absolute refractory period- canNOT generate an action potential no matter what. Inactivation gate is blocking it. (voltage-gated Na+ channels)
• relative refractory period- you can have an action potential. You’ll need a bigger stimuli to get to threshold

Question 18

Types of Action Potential Propagation

Answer 18

• Contiguous
• Saltatory

propagation- down the axon

Question 19

Contiguous Propagation of Action Potentials

Answer 19

• Contiguous- right next to one another
• absolute refreactory period makes sure the action potenial only goes in one direction

Question 20

Myelinated Axons: Schwann Cells

Answer 20

• provides insulation
• in the peripheral nervous system
• The myelin sheath is composed of fatty layers that greatly increase the resistance across the plasma membrane while reducing the capacitance.These factors greatly increase the length constant.

Question 21

Myelinated Axons: Oligodendrocytes

Answer 21

• in the CNS (brain and spine)
• functions are to provide support and insulation

Question 22

Saltatory Conduction

Answer 22

Question 23

Summary of potentials

Answer 23