2.2 The Nerve Impulse Flashcards Preview

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Flashcards in 2.2 The Nerve Impulse Deck (24):
1

Concentration gradient

The difference in distribution for various ions between the inside and outside of the membrane

2

Selective permeability

The ability of some molecules to pass much more freely through the membrane than others do

3

Sodium-potassium pump

A protein complex which transports three sodium ions out of the cell while simultaneous drawing two potassium ions into the cell

4

Electrical gradient

The difference in positive and negative charges across the membrane

5

Hyperpolarization

Increased polarization

6

Depolarization

Reduction of its polarization

7

Threshold of excitation

Any stimulation beyond a certain level; produces a sudden, massive depolarization of the membrane

8

Action potential

A rapid depolarization and slight reversal of the usual polarization

9

Voltage-activated channels

Membrane channels whose permeability to sodium or some other ion depends on the voltage difference across the membrane

10

Local anesthetic drugs

Attached to the sodium channels of the membrane, preventing sodium ions from entering; i.e. Novocain and Xylocaine

11

General anesthetics

Decrease brain activity by opening stern potassium channels wider than usual; i.e. ether and chloroform

12

All-or-none law

The size, amplitude, and velocity of an action potential are independent of the intensity of the stimulus that initiated it

13

Refractory period

During which the cell resist the production of further action potentials

14

Absolutely refractory period

The sodium gates are firmly closed and the membrane cannot produce an action potential, regardless of the stimulation; ~1 ms

15

Relative refractory period

The sodium gates are reverting to the usual state, but potassium gates remain open. Because of the free flow of potassium, a stronger than usual stimulus is necessary to initiate an action potential. ~2-4 ms

16

Where does an action potential begin?

On the axon hillock

17

Axon hillock

A swelling where the axon exits the soma

18

The propagation of the action potential

Describe does the transmission of an action potential down an axon

19

Myelinated axon

Found only in vertebrates; covered with myelin sheath, a coating composed mostly of facts

20

Nodes of Ranvier

Short unmyelinated sections of axon; each node is only about one micrometer wide

21

Saltatory conduction

The jumping of action potentials from node to node

22

Plural of soma

Somata

23

Graded potentials

Membrane potential is that vary in magnitude and do not follow the all-or-none law

24

Polarization

The neuron inside the membrane has a slightly negative electrical potential with respect to the outside