a b c How do neurons communicate Need to think about this question 2 ways How do neurons communicate 1 within neurons 2 between neurons Neuron receiving info Information traveling ID: 189560
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Slide1
How do neurons communicate?Slide2
a
b
cSlide3
How do neurons communicate?
Need to think about this question 2 waysSlide4
How do neurons communicate?
1. within neurons –
2. between neurons-Slide5
Neuron receiving info
Information traveling
down neuronSlide6
within neurons – electricallybetween neurons – chemically
Synapse – space between neurons
How do neurons communicate Slide7
Ramon Y Cajal
developed Golgi Stain
first determined space between neurons
“synapse”Slide8
the “resting” statethe “active” state
neuron is firing
action potential
the “refractory” state
Neurons can exist in one of 3 statesSlide9
giant squid axon
How do we know about what is happening in the neuron?Slide10Slide11Slide12
inside of the axon has a slightly negative charge relative to outside the axoncalled the membrane potential
usually around -70mV
At rest: Slide13
inside of the axon has a slightly negative charge relative to outside the axoncalled the membrane potential
why?
At rest: Slide14
action potential or
spikeSlide15Slide16
see depolarization (change from negative inside neuron to more positive)
Neuron stimulated (either electrically or by receiving a “message”Slide17
action potential or
spikeSlide18
see depolarization (change from negative inside neuron to more positive)
“threshold” – if a great enough depolarization occurs, an action potential will occur
action potential – very quick – milliseconds
Other terms – spike, firing, generating an AP
Neuron stimulated (either electrically or by receiving a “message”Slide19
action potential or
spikeSlide20
Hyperpolarizationreturn to negativethis is the refractory or recovery periodSlide21
action potential or
spikeSlide22
All axons and cells have a membranethin lipid (fat) bilayer
The membranes have channels (to allow ions in or out)
Ions – molecules with a charge
These channels can be open or shut
What causes these changes in electrical potential and the action potential?Slide23Slide24
Ions flowing across the membrane causes the changes in the potentialIons are molecules that contain a positive or negative charge
anion – negative charge
cation – positive charge
What causes these changes in electrical potential?Slide25
Na+ sodiumHIGHER CONCENTRATION OUTSIDE THE AXON
Cl- chloride
HIGHER CONCENTRATION OUTSIDE AXON
K+ potassium
higher concentration inside the axonA- anions -large (-) molecules with a negative charge (stuck inside the axon)
Some important ions for
neuronal communicationSlide26
INSIDE AXON
(intracellular)
OUTSIDE AXON (EXTRACELLULAR
FLUID)
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+ and Cl- are in higher concentration
in the extracellular fluid
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Neuron at Rest
Na+
Na+
Na+
Na+
Na+
Na+
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
A-
A-
A-
A-
A-
A-Slide27
INSIDE AXON
OUTSIDE AXON (EXTRACELLULAR FLUID)
Na+
Na+
Na+
Na+
Na+
A-
A-
K+ and negative anions are in higher concentration
in the intracellular or inside the axon
Cl-
Cl-
Cl-
K+
K+
Cl-
K+
Neuron at Rest
K+
K+
K+
A-
A-
Na+
Cl-
K+Slide28
concentration gradient –ions diffuse from higher concentration to lower concentration
Some forces that play a role in maintaining membrane potentialSlide29
example of concentration forcesSlide30
Na+
K+
Cl-
What would each ion do if the ion channel opened based on the concentration gradient? Slide31
concentration gradient –ions diffuse from higher concentration to lower concentration
electrical gradient -
opposite charges attract so ions are attracted to an environment that has a charge that is opposite of the charge they carry!
Some forces that play a role in maintaining membrane potentialSlide32
example of electrostatic forcesSlide33
Na+
K+
Cl-
What would each ion do if the ion channel opened based on electrostatic forces ? Slide34
INSIDE AXON
(intracellular)
OUTSIDE AXON (EXTRACELLULAR
FLUID)
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+ and Cl- are in higher concentration
in the extracellular fluid
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Axon depolarizing
Na+
Na+
Na+
Na+
Na+
Na+
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
A-
A-
A-
A-
A-
A-Slide35
opening of Na+ channels and influx of Na+ ions
What drives the action potential? Slide36
What happens if sodium channels
are blocked?
lidocaine
,
novocaine, cocaine
TTX –
tetrototoxin
Sagitoxin
-
red tidesSlide37Slide38
Na+
K+
Cl-
Concentration
Gradient
Electrical
Gradient
after the AP (+ intracellular)Slide39
INSIDE AXON
OUTSIDE AXON (EXTRACELLULAR FLUID)
Na+
Na+
Na+
Na+
Na+
A-
A-
K+ and negative anions are in higher concentration
in the intracellular or inside the axon
Cl-
Cl-
Cl-
K+
K+
Cl-
K+
Neuron at Rest
K+
K+
K+
A-
A-
Na+
Cl-
K+Slide40
Sodium-potassium pump – active force that exchanges 3 Na+ inside for 2 K+ outsideSlide41
INSIDE AXON
OUTSIDE AXON (EXTRACELLULAR FLUID)
Na+
Na+
Na+
Na+
Na+
A-
A-
K+ and negative anions are in higher concentration
in the intracellular or inside the axon
Cl-
Cl-
Cl-
K+
K+
Cl-
K+
After the action potential
K+
K+
K+
A-
A-
Na+
Cl
-
K+
Na+
Na+
Na+
Na+
Na+Slide42Slide43
myelin sheath (80% fat and 20% protein)produced by glia
conduction or propogation of the action potentialSlide44
http://www.blackwellpublishing.com/matthews/channel.htmlSlide45
nodes of ranvierSlide46
myelin sheath (80% fat and 20% protein)produced by glia
nodes of ranvier
conduction or propogation of the action potentialSlide47
nodes of ranvierSlide48
myelin sheath (80% fat and 20% protein)produced by glia
nodes of ranvier
saltatory conduction (200 ft/sec)
conduction or propogation of the action potentialSlide49Slide50Slide51
http://www.blackwellpublishing.com/matthews/actionp.htmlSlide52
speed, efficiency of neurotransmission
Advantages of Saltatory ConductionSlide53
speed, efficiency of neurotransmission
disease: Multiple Sclerosis
progressive, autoimmune disease
onset ~ 20 years of ageearly symptoms: motor symptoms, such as weakness, leg dragging, stiffness, a tendency to drop things, a feeling of heaviness, clumsiness,
Advantages of Saltatory ConductionSlide54Slide55
What about communication between neurons?