Nerve Communication Flashcards by Lauren Bell

How do nerves communicate?

Communicate w/ one another by electrical signals

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What are the different types of communication?

Graded potential
-short distance communication 
Action potential
-long distance communication 
     -nerve action potential (impulse)

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What do the production of graded & action potentials depend on?

Resting membrane potential

Presence of specific ion channels

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Why does resting membrane potential exist?

Consists of 5 facts

more negative ions inside cell membrane
more positive ions out cell membrane
- difference in charge causes electrical potential
  - measured in millivolts(mV)
  - normal resting potential is -70mV
  - membrane said to be “polarized”
  - NA-K pump stabilizes resting membrane potential
  - 3 NA ions out, 2 K into cell

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Role of ion channels?

What is this called? Definition?

Main path for current to flow across membrane
Called electrochemical gradient
-ion movement from high to low concentration

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Changes in membrane potential produce how many types of signals? What are they? What do they consist of?

2 types 
Graded potentials
-incoming signals -occur over short distances 
Action potentials 
-long distance signals of axon

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What does nerve communication involve? (3 things)

Graded potentials
Action potentials
Synapse

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Graded potentials

What is it? Location? What does it do? Description of distance?

Small changes in membrane potential
-either more polarized- inside more negative OR less polarized- inside less negative
Most occur in dendrites & cell bodies
Short distances- few millimeters
Initiates action potentials in axon

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Graded potentials
What does graded mean?
Depends on?

“Graded” means amplitude of electrical signal varies

depends on strength of stimulus
# of ligand-gated or mechanical gated channels open

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How do ions move?

Ions move using ‘gates’ (proteins) in cell membrane

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Leak channel

Channel

-randomly open & close

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Ligand-gated channel

Chemical stimulus opens the channel
Opens w/ neurotransmitters
(Muscle contraction)

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Mechanically gated channel

Mechanical stimulus opens the channel
-open w/ response to deformation of receptor (touch, pressure, sound)
(This is involving graded potentials)

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Voltage-gated channel

Change in membrane potential opens the channel

-opens w/ change in membrane potential

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Action potential

Where propagated?

Propagated along axon
Only in excitable membranes- neurons & muscle cells
Brief reversal of membrane potential & return to resting state
Long distance neuron communication
Do not decrease w/ distance
Use voltage gated ion channels (NA/K pump)

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What is a comparison for an action potential propagated along the axon?

The domino effect - not all at once, 1 part at a time

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Generation of action potential. 4 states

Resting state
Depolarization
Repolarization
Hyperpolarization

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Resting state

Type of channels? What do they do? Mv at this stage?

Voltage gated channels open (NA & K)

-70 mV membrane potential

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Depolarization
What is it?
What must happen for this to occur?
Channels?

Membrane potential becomes less negative reaching zero
-must reach threshold (-55mV)
- “all or none” principle (like muscle contraction)
NA channels open

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Repolarization
Channels?
What happens?

Na channels close, k channels open

Membrane potential restored to resting state (-70 mV)

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Hyperpolarization

Channels?

Some k channels open, Na channels reset.

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Factors affecting speed of axon potential what are they? (3)

Amount of myelination
Axon diameter
Temperature

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Amount of myelination

More rapid when myelinated

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Axon diameter

Larger diameter -> faster propagation

Less resistance to flow

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Temperature

Cooler temp -> lower speeds

Synaptic transmission is where? Definition?

Synapse - junction btwn neurons that action potential travels through (Btwn 2 neurons bulb to dendrites)

what are the two neurons in the synapse? function?

presynaptic neuron- sends signals (bulb) | postsynaptic neuron- receives signal (dendrites)

what are the 2 types of synapse?

``` electrical synapses chemical synapses (muscle contraction, neurotransmitters) ```

describe electrical synapses | location? what happens? how? examples?

btwn 2 close neurons held together by GAP JUNCTIONS ionic current flows by passive transport through gap junctions current flows in both directions fast transmission (instantaneous) EX) areas of brain for eye movements, emotions, & memory

description of chemical synapse | job? location?

convert electrical signals (action potential) to chemical signals (neurotransmitter) uses neurotransmitters across a synapse

neurotransmitters (4)

acetylcholine norepinephrine & dopamine serotonin histamine

acetylcholine

muscles

norepinephrine & dopamine

"fell good" | fits depression, anxiety, make happy!

serotonin

sleep, regulating mood

histamine

wakefulness, appetite control | mediates inflammation, vasodilation (asthema, dialate bronchial tubes)

what part of the neuron when excited causes a generation of an action potential?

axon

where are electrical synapses made?

GAP JUNCTIONS

are electrical synapses excitatory or inhibitory?

excitatory

what is an advantage of electrical synapses over chemical synapses?

electrical synapses is FAST transmission (instantaneous). it also goes to a group instead of only 1

where are chemical synapses made?

synaptic cleft

what type of molecule is used to carry the chemical signal?

neurotransmitter

at a chemical synapse, neuronal membranes are separated by a gap called the ______

synaptic cleft

the calcium inside the synaptic knob initiates ______

release of neurotransmitter (or initiates the synapse)

what type of behavior are electrical synapses associated with?

areas of brain for eye movements, emotions, and memory

what are the steps in the process of a chemical synapse btwn neurons?

1) axon potential arrives at axon terminal 2) Na+ channels open & depolarization causes Ca2+ channels to open 3) Calcium causes synaptic vesicles to fuse w/ neuron membrane, dumping neurotransmitter into synapse 4) Neurotransmitter binds receptor, receptor opens 5) Na+ enters postsynaptic neuron & depolarizes cell, causing action potential (once ACh is released in there) (SAME AS NMJ)

the neuron conducting an action potential toward the synapses is called the __________ neuron

presynaptic

the axon terminal of the presynaptic neuron contains membrane sacs called _________ which are filled with _______

synaptic VESICLES | neurotransmitters

polarized means

unequal charge across the membrane

when a cell membrane is polarized, the inside is ______ charged with respect to the outside

negative

the polarization of a cell membrane is due to _______

the sodium/potassium pump

_____ is the major intracellular positive ion and ________ are the major extracellular cation

potassium (K+) | Sodium (Na+)

the measured value of resting potential is

-70 mV

at resting membrane potential, sodium channels are _____ but when threshold is reached, sodium channels _____

open | open

the measured value of threshold is

-55 mV

What happens during the absolute refractory period?

voltage gated Na channel activation gates are open then voltage gated K channels are open & Na channels are inactivating (hill of depolarization & repolarization)

Whats happens during the relative refractory period?

voltage gated K channels are still open; Na channels are in resting state (hyperpolarization to the start of resting)

explain the graph dealing with sodium (Na) & potassium (k)

resting- pump maintains Na Sodium outside and K Potassium inside Depolarization- Na (Sodium) in! Repolarization- K (Potassium) out! 1st part of hyperpolarization still going down- K (Potassium) out overshoot 2nd part going up- pump resting- pump maintains Na (Sodium) outside & K (Potassium) inside

what happens to the channels when the different ions move? give all situations on graph Na? K? Pump?

Na (sodium) in = Na channels open, K channels close K (potassium) out = K channels open, Na close Pump= 3 Na (sodium) pumped out, 2 K pumped in

what would happen is we didn't have Na or K?

No nerve conduction!

what channels are involved in resting membrane potential? What happens to them?

voltage gated Na channels and voltage gated K channels are closed!

what causes depolarization to threshold?

STIMULUS

electrical signals cannot do what? what do we use?

cannot jump across gap, so we use chemical signals!

whats a neuron?

basic unit of information processing & building block of the brain it's an excitable cell the receives a stimuli & either sends the signal on, or not

what ion is the high concentration outside the neuron?

sodium Na ions

what ion is in high concentration inside the neuron?

K potassium ions

what specialized protein exists in the neural cell membrane?

channels

what is the function of channels?

form pores in the membrane that are selectively permeable to particular ions

under resting conditions which ion leaks more, sodium leaking inward or potassium leaking outward?

potassium leaking outward

result of the leaks makes the outside of the cells charged ___ and the inside of the cell charged __. the cell is said to be what?

positive, negative | polarized

since sodium is in high concentration outside the cell, what happens if the sodium channel opens in the membrane? which way does the sodium move?

into the neuron

when the sodium moves in, the neuron is momentarily what? this is called?

positive | depolarized

the switch in membrane potential (when the inside is postive from sodium entering) is the what?

action potential

speed of an action potential is relate to?

size of the axon

what type of axon results in fast transmission rates?

big axons

what substance allows for rapid action potential?

myelin

where does the action potential take place on a myelinated neuron?

nodes of ranvier

what does the myelin sheath allow action potentials to do?

allows action potential to jump from 1 node to another, greatly increasing the rate of transmission

multiple sclerosis

demyelinating disease that affects bundles of axons in the brain, spinal cord, and optic nerve, leading to lack of co-ordination muscle control (and difficulties with speech and vision). this proves that w/o myelin sheath, we cannot function.

Nerve Communication Flashcards

(78 cards)