Nervous System

Front 1

Resting Membrane Potential

Back 1

A difference in electrical charge from the inside of the cell to the outside

-70mv

Maintained by different concentration in ions:
More K+ inside cell than outside
More Na+ outside cell than inside
Inside cell membrane is negative; outside of cell membrane is positive

Cell uses energy to maintain the gradient

Front 2

Ion channels

Back 2

-Leakage channels
-Voltage-gated channels
-Chemically (ligand) gated channels
-Mechanically gated channels
Are Integral or transmembrane

Channels are specific

Sodium Ion channels only allow sodium through

Front 3

Leakage channels

Back 3

Randomly alternate between open and closed positions. Typically more K+ leakage channels

Found in nearly all cells, including the dendrites, cell bodies and axons of all types of neurons

Front 4

Voltage-gated channels

Back 4

Opens in response to a change in membrane potential (voltage)

Voltage-Gated channels participate in the generation and conduction of action potentials found in axons of all types of neurons

Front 5

Chemically (ligand) - gated channels

Back 5

Opens or closes in response to a specific chemical stimulus like neurotransmitters

Dendrites of some sensory neurons such as pain receptors and dendrites and cell bodies of interneurons and motor neurons

Front 6

Mechanically gated channels

Back 6

Opens or closes in response to mechanical stimulation in the form of vibration such as sound waves, touch, pressure, or tissue stretching.

Dendrites of some sensory neurons such as touch receptors, pressure receptors and some pain receptors

Front 7

Graded (local) Potential

Back 7

Short distance transmission

Occurs in dendrites and cell body

May be depolarizing or hyperpolarizing

Signals decrease in strength with distance

No Refractory period

Involves summation fo impulses at axon hilock

Involves voltage-gated Na+ channels

Front 8

Action Potential

Back 8

Transfers impulses over longer distances

Occurs along axons

Always depolarizes then Repolarizes

All or Nothing Principle

Signal does not lose strength over distance

Involves voltage-gated Na+ channels and voltage-gated K+ channels

Front 9

Dendrites

Back 9

Gather input and relay signals through cell body to axon hillock in graded potentials

Front 10

Cell body

Back 10

Summates input (adds up) input signals converge at axon hillock

Front 11

Axon hillock

Back 11

Trigger zone where cell reaches
-55mv in order to reach threshold to send action potential

Front 12

Graded potential

Back 12

a small deviation from the membrane potential that makes the membrane either more or less polarized

Front 13

Depolarizing

Back 13

Making inside of cell more positive

Front 14

Hyperpolarizing

Back 14

making inside of cell more negative

Front 15

In action potentials

Back 15

When stimulated to threshold, the axon depolarizes, beginning the action potential

The action potential (nerve impulse) propagates along the axon

The action potential is generated; it is ALWAYS exactly the same strength and duration

Involves voltage-gated Na+ and K+ channels

Front 16

Impulse conduction Process

Back 16

Begins with stimuli coming through dendrites
Types of ion channels involved are Mechanical-gated channels or chemical (ligand)-gated channels

Summation occurs:
-Depolarizing stimuli make inside of cell more positive
-Hyperpolarizing stimuli make inside of cell more negative

Front 17

Summation

Back 17

Adding up the exitatory and inhibitory impulses at the trigger zone (axon hillock) determines if an action potential is generated

Front 18

Spatial summation

Back 18

Impulses come from many synaptic end bulbs

Front 19

Temporal summation

Back 19

Impulses come repeatedly from the same synaptic end bulb

Front 20

Results of summation

Back 20

Action potential is generated- there are enough exitatory impulses to reach threshold -55mv

Front 21

Depolarization

Back 21

-55 to +30 is depalarization

All or nothing principle

Requires stimulus strong enough to reach threshold of -55mv

Action potential is always the same strength

Voltage-gated Na+ channels upen

Membrane potential becomes 30mv

Inactivation gates close - no more Na+ enter

Front 22

Repolarization

Back 22

Cell returns to -70mv

Voltage gated K+ channels open and K+ flows OUT of cell

Na+ is being pumped out via pumps

Anions remain in cell

Membrane potential of -70mv is established once again

May hyperpolarize to -90mv

Front 23

Refractory Period

Back 23

Absolute- Cell CANNOT generate another action potential no matter how strong the stimulus is

Front 24

Relative Period

Back 24

While the K+ ions are moving back into cell; requires a larger than normal stimulus to generate an action potential

Front 25

Moving along Axon

Back 25

Propagation or Conduction

One way impulse transmittion
-refractory period prevents impulse from moving backwards

Front 26

Continuous conduction

Back 26

Slower, in unmyelinated axons

Front 27

Saltatory

Back 27

Faster, in myelinated axons, requires less energy: ion moves through extracellular fluid

Front 28

Factors affecting speed of impulse

Back 28

Myelination
Axon Diameter: Larger diameter has bigger surface area and impulse moves faster

Temp affects speed: Warmer is faster

Front 29

Intensity of Stimulus

Back 29

Action potential is All-or-Nothing

Difference in intensity of stimulus are determined by
-Frequency of impulse
-Number of sensory neurons stimulated

Front 30

Electrical Synapses

Back 30

Electrical transfer of impulse occurs at gap junctions

Found in visceral smooth muscle, cardiac muscle, CNS, and embryo

Advantages:
Faster
Synchronization of cell responses

Front 31

Chemical Synapses

Back 31

Neurons and effector do not touch

Requires carrier molecules to cross the space, called a neurotrasmitter

Chemical exchanges delays impulse by about 0.5 msec

Front 32

Excitatory postsynaptic Potential

Back 32

Bring neuron closer to threshold; cell becomes more positive inside

Front 33

Inhibitory Postsynaptic Potential

Back 33

Takes cell farther away from threshold, same as hyperpolarizing cell becomes more negative inside

Front 34

Signal Transmission at Chemical Synapse

Back 34

More than 50 substances act as neurotransmitters

Cells usually can release more than one type

Transmitters may be exitatory or inhibitory

Classified by chemical structure

Front 35

Small Molecule Neurotransmitters

Acetylcholine

Back 35

1st one identified
Activates all Motor neurons

Deactivated by enzyme Acetylcholinesterase

Front 36

Small Molecule Neurotransmitters

Glutamate and Aspartate

Back 36

Acive in CNS

Amino Acids

Glutamate main Excitatory

Glutamate is responsible for Ischemic Strokes

Inactivated by reuptake

Front 37

Small Molecule Neurotransmitters

GABA and Glycine

Back 37

Amino acids

GABA is only in CNS

INHIBITORY

Valium enhances GABA

GABA-main inhibitory

Front 38

Biogenic Amines Neurotransmitters

Catecholamines

Back 38

Hormones responsible for Fight or Flight:
Epinephrine, Norepinephrine and Dopamine
Serotonin
Can either be Excitatory or Inhibitory Depending on the receptors

Front 39

Dopamine

Back 39

Emotional Response, Addictive behavior, Pleasure pathway,

Inactivated by reuptake and enzymatic action (MAO-MonAmine Oxidase)

Front 40

Seratonin

Back 40

Sensory perception, mood, appetite, sleep induction

Inactivated by reuptake

Prozac blocks reuptake

Blocked by LSD
Enhanced by Ecstasy

Front 41

Neuropeptides

Back 41

Consists of 3-40 amino acids

Found in both CNS and PNS

Excitatory and Inhibitory

Front 42

Opiod Peptides

Back 42

BLOCK SUBSTANCE P

Enkephalins
Endorphins
Dynorphins

Front 43

Substance P

Back 43

Enhances pain signal transmission

Front 44

Influencing Neurotransmitters

Back 44

Synthesis may be stimulated or Inhibited

Released is enhanced or blocked

Receptors are activated or blocked

Removal can be stimulated or Inhibited

Front 45

Removal or Neurotransmitter

Back 45

Neurotransmitter MUST be removed after transmission to allow for cell recovery

Diffusion
Enzyme degradation
Reuptake by cells or uptake by neuroglia