Nerve Cells and Impulses

Question 1

Nerve Impulse

Answer 1

electrical message that is transmitted down axon of neuron

Question 2

Nerve impulse travel

Answer 2

not directly down axon, regenerated at points along axon so not weakened

Question 3

Speed of nerve impulse

Answer 3

1m/s to 100m/s (shoulder distance faster than foot distance)

Question 4

Resting Potential of Neuron

Answer 4

Messages in a neuron develop from distrubances of resting potential

Question 5

Polarization

Answer 5

difference in the electrical charge inside and outside of cell

Question 6

charge of inside of membrane

Answer 6

slightly negative, -70 millivolts

Question 7

resting potential of neuron

Answer 7

state of neuron BEFORE sending nerve impulse

Question 8

Protein Channels

Answer 8

structures embedded in membranes that permit certain ions to cross at certain rate

Question 9

Membrane Permeability

Answer 9

selective, allowing only some chemicals to pass through

Question 10

Ions that can cross

Answer 10

Na, K, Ca, Cl

Question 11

State of Membrane at Rest

Answer 11

Na channels closed, K channels partially closed

Question 12

Na/K pump

Answer 12

protein complex that continuously pumps 3 NA ions out while drawing 2 K ions in

Question 13

Na/K pump #2

Answer 13

helps maintain electrical gradient

Question 14

Na/K pump #3

Answer 14

uses active transport (requires ATP)

Question 15

Electrical gradient + concentration gradient

Answer 15

difference in distribution of ions

Question 16

Function of electrical/concentration gradietn

Answer 16

work to pull sodium ions into cell

Question 17

Mechanism of electrical/conc gradient

Answer 17

pulls K+ into cell, but slowly leaks out carrying + charge w/

Question 18

Hyperpolarization

Answer 18

Increasing the polarization or the difference between electrical charge of two places

Question 19

Depolarization

Answer 19

decreasing the polarization to zero

Question 20

Excitation Threshold

Answer 20

level above which any stimulation produces massive Depolarization

Question 21

Action Potential

Answer 21

rapid sequence of changes in the voltage across a membrane.

Question 22

Action potential

Answer 22

rapid depolarization of neuron

Question 23

Action potential Threshold

Answer 23

varies from one neuron to next but consistent for each neuron

Question 24

Stimulation of neuron past excitation Threshold

Answer 24

triggers nerve impulse or action potential

Question 25

Voltage Activated Channels

Answer 25

Membrane channels whose permeability depends on voltage diff across membrane (eg Na K)

Question 26

What happens after Na channels are opened

Answer 26

positively charged Na rush in and nerve impulse happens

Question 27

Return Neuron to resting state

Answer 27

open K channels

Question 28

What happens after action potential happens

Answer 28

Na channels closed quick

Question 29

Why do K ions flow out

Answer 29

due to conc gradient and take + charge w/ them

Question 30

Na/K pump after action potential happens

Answer 30

Na channels are closed

Question 31

Restoration of Na K pump

Answer 31

takes long time to get to original distribution

Question 32

Rapid series of action potentials can lead lead to buildup of Na within axon

Answer 32

this is toxic, but rare, usually after stroke or drug use

Question 33

Where do action potentials back propagate

Answer 33

into cell body and dendrites

Question 34

Dendrites and learning

Answer 34

Dendrites become more susceptible to structural changes responsible for learning

Question 35

All or None Law

Answer 35

States that amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it: Action potentials are equal in intensity and speed within a given neuron

Question 36

Action potential variance

Answer 36

Vary from one neuron to another in terms of amplitude, velocity, shape

Question 37

Mammalian axons

Answer 37

There are variations in types of protein channels and therefore in the characteristics of the action potentials

Question 38

Refractory Period

Answer 38

The period after an action potential during which the neuron resists production of ANOTHER action potential

Question 39

Absolute refactory period

Answer 39

The first part of the period in which the membrane cannot produce an action potential

Question 40

Relative Refractory Period

Answer 40

Second part of refractory period in which it takes a stronger than usual stimulus to trigger an action potential

Question 41

Myelin Sheath

Answer 41

this is interrupted by short unmyelinated sections called nodes of Ranvier

Question 42

Myelin

Answer 42

An insulating material composed of fats and proteins

Question 43

Nodes of ranvier

Answer 43

At each node the action potential is regenerated by a chain of positively charged ions pushed along by the previous segment

Question 44

Saltatory Conduction

Answer 44

The jumping of the action potential from node to node

Question 45

What does Saltatory Conduction do

Answer 45

Provides rapid conduction of impulses, conserves energy for cell

Question 46

Multiple Sclerosis

Answer 46

Disease in which the myelin sheath is destroyed: causes poor muscle coordination and visual impairments

Question 47

Local Neurons

Answer 47

Have short axons, exchange info w/ only close neighbors. Do not produce action potentials

Question 48

Local Neurons 2

Answer 48

when stimulated, produce graded potentials, membrane potentials that vary in magnitude and do not follow all or none law`

Question 49

Local neurons 3

Answer 49

Depolarize or hyperpolarize in proportion to the stimulation

Question 50

Local neurons 4

Answer 50

Difficult to study due to small size. Most of our knowledge comes from study of large Neurons