Electrical Signals In Neurons

Front 1

Neurons are electrically excitable due to ____________________

Back 1

voltage differences across their membranes

Front 2

how do neurons communicate with each other and effector cells?

Back 2

electrochemically

Front 3

what is a nerve impulses?

Back 3

An electrical signal

Front 4

What types of electrical signals do neurons communicate with?

Back 4

• Actions potentials
  
• Graded potentials
  

Front 5

What are characteristics of action potentials?

Back 5

• Most famous are nerve impulses
  
• Can travel long distances
  
• Involves the movement of 2 specific ions
  

Front 6

What are characteristics of graded potentials

Back 6

• Local membrane charges only
  
• Occur between cell bodies and dendrites
  
• Involve the movement of more types of ions
  

Front 7

What are the types of ion channels?

Back 7

Leakage (non gated) channels

Gated Channels

Front 8

Describe leakage channels?

Back 8

Always open

Nerve cell membrane more permeable to K+

Front 9

What causes the resting membrane potential of the cell to be -70mV in nerve tissue?

Back 9

That the membrane is more permeable to K+

Front 10

Describe gated ion channels

Back 10

Open and close in response to stimuli, results in neuron excitability

Front 11

What are electrical signals generate by?

Back 11

Differences across the neurolemma

Front 12

Is the plasma membrane permeable to ions?

Back 12

No, they must move through ion channels that are specific to which ions they let across

Front 13

Why don't ion channels require energy?

Back 13

Because ions move with their concentration gradient

Front 14

Which ions have a higher concentration inside the cell?

Back 14

Potassium

Front 15

Which ions have higher concentration outside the cell?

Back 15

• Sodium
  
• Calcium
  
• Chloride
  

Front 16

What are the types of gates ion channels?

Back 16

• Voltage-gated channels
  
• Ligand gated channels
  
• Mechanically gated ion channels
  

Front 17

Which channels are mostly in action potential?

In graded potentials?

Back 17

Action potentials: voltage-gated

Graded potentials: Ligand and mechanically gated channels

Front 18

what causes voltage gated ion channels to open?

Back 18

Respond to direct change in the membrane potential due to changes brought on by flow through leakage channels

Front 19

What is membrane potential established by?

Back 19

The difference in distribution of charges in the inside and outside of the cell directly adjacent to the membrane

Front 20

What is the distribution of charges if the potential is negative?

Back 20

There are more cations on the inside of the membrane than the outside

Front 21

when is the cell polarized

Back 21

When the energy difference is -70mV (@rest)

Front 22

What are the 2 ways that the resting potential is established?

Back 22

• Action of the sodium potassium pump
  
• Membrane (neurolemma) permeability
  

Front 23

How does the sodium-potassium pump work?

Back 23

active pump that uses ATP to cycle sodium and potassium against their concentration gradient

Pumps 3 Na+ out and 2 K+ in for each cycle causing a positive charge outside the cell

Front 24

What are graded potentials?

Back 24

Small deviations from resting potential (-70mV)

Graded because their intensity is vary in size depending on strength of stimulus and whether it is localized

Front 25

Which type of potential can be hyperpolarizing or depolarizing

Back 25

graded potentials

therefore can be inhibitory or stimulatiory to the receiving cell

Front 26

What is depolarization?

Back 26

Bringing the potential difference of the membrane closer to zero

Stimulatory to neurons and may trigger an action potential

Occurs when Na or Ca flow into the cell via mechanically or ligand gated channels

Front 27

What is hyperpolarization?

Back 27

The difference brought further from zero and is inhibitive to neurons

Occurs when K ions move out of cell or Cl move in via mechanically or ligand gated channels

Front 28

Can action potentials very in intensity?

Back 28

No, they occur in the same way every time

(is neither inhibitory or excitatory)

Front 29

Which type of potential is a local electrical situation

Back 29

A graded potential

Flow of current/ions is local change only

Only for stimuli directly adjacent

Front 30

What are the events that occur in the generation of an action potential/impulse?

Back 30

Depolarization

Repolarization

After-hyperpolarization

Return to resting state

Front 31

Which gate is open in the resting membrane

Back 31

inactivation gate of Na+

Front 32

Describe Depolarization

Back 32

Chemical or mechanical stimulus causes graded potential to reach the threshold of -55mV

Voltage gated Na+ channels open and Na+ rushes into the cell

Na+ let in until membrane potential is +30mV

Front 33

Describe repolarization

Back 33

When the threshold potential of -55mV is reached voltage gated K+ channels open (much slower than Na+ channels therefore by the time K+ channels open Na+ channels have already closed)

Front 34

Describe after-hyperpolarization

Back 34

K+ outflow returns membrane potential to -70mV

If enough K+ leave the cell it will reach -90mV and enter the after-hyperpolarizing phase

(Na+ gate in resting state,K+ open)

Front 35

Describe return to resting state

Back 35

K+ chanel closes and the membrane returns to resting potential by action of the sodium potassium pump

Front 36

What is the period in which the neuron cannot generate another action potential?

Back 36

The refractory period

Front 37

Which steps are included in the absolute refractory period?

Back 37

Steps 1-3

Another action potential cannot be generated no longer how strong the stimuli is

Inactivate Na+ channels must return to resting state before they can be reopened

Front 38

What is the relative refractory period?

Back 38

After step 3

An action potential can be generated if significantly strong (suprathreshold) stimulatory signal is encountered

Graded potential must be strong enough to compete with the influx of K+ as channel is still open

Front 39

Which type of potential is generated at one segment of the axon?

Back 39

Action potential

Front 40

What is an impulse?

Back 40

A wave through the axon from axon hillock to synaptic end bulb

Front 41

How are action potentials propagated?

Back 41

self propagated

As Na+ flows into the cell during depolarization the voltage of adjacent areas are affected and their voltage gated Na+ channels open

Front 42

What is continuous conduction?

Back 42

step by step depolarization of each portion along the length of the axolemma

(unmyelinated fibers)

Front 43

What is saltatory conduction?

Back 43

Skips myelinated portions of axon=shorter distance to travel=faster

Depolarization only at nodes of ranvier where there is a high density of voltage gated channels

current carried by ions flow through extracellular fluid from node to node because the myelin insulated the axon membrane

Front 44

What is the speed of impulse propagation determined by?

Back 44

NOT related to stimulus strength

Larger, myelinated fibers conduct impulses faster due to size and saltatory conduction

Front 45

What are the types of nerve fibers in order from largest to smallest diameter?

Back 45

• A fibers
  
• B fibers
  
• C fibers
  

Front 46

Which types of fibers are myelinated?

Back 46

Type A and B fibers

Front 47

Where are Type A fibers mostly located?

Back 47

Primarily in the somatic nervous system (both sensory and motor neuron)

Front 48

Where are B fibers located?

Back 48

Visceral sensory and autonomic preganglionic (preganglionic autonomic fibers)

Front 49

Where are C type fibers used?

Back 49

as sensory as autonomic motorr post ganglionic autonomic fibers

Front 50

Which fibers play a part in your fight or flight response?

Back 50

B Type

Front 51

Which fibers play a part in feeling and reacting immediately?

Back 51

A fibers