how do neurons communicate?
DESCRIPTION
How do neurons communicate?. 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 down neuron. How do neurons communicate. - PowerPoint PPT PresentationTRANSCRIPT
a
b
c
Need to think about this question 2 ways
1. within neurons –
2. between neurons-
Neuron receiving info
Information traveling down neuron
within neurons – electrically
between neurons – chemically◦ Synapse – space between neurons
developed Golgi Stain
first determined space between neurons
“synapse”
the “resting” state
the “active” state◦ neuron is firing◦ action potential
the “refractory” state
giant squid axon
inside of the axon has a slightly negative charge relative to outside the axon◦ called the membrane potential◦ usually around -70mV
inside of the axon has a slightly negative charge relative to outside the axon◦ called the membrane potential
why?
action potential or
spike
see depolarization (change from negative inside neuron to more positive)
action potential or
spike
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
action potential or
spike
Hyperpolarization return to negative this is the refractory or recovery period
action potential or
spike
All axons and cells have a membrane thin 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
Ions flowing across the membrane causes the changes in the potential
Ions are molecules that contain a positive or negative charge anion – negative charge cation – positive charge
Na+ sodium◦ HIGHER CONCENTRATION OUTSIDE THE AXON
Cl- chloride ◦ HIGHER CONCENTRATION OUTSIDE AXON
K+ potassium◦ higher concentration inside the axon
A- anions -large (-) molecules with a negative charge (stuck inside the axon)
INSIDE AXON(intracellular)
OUTSIDE AXON (EXTRACELLULAR FLUID)
Na+
Na+
Na+
Na+
Na+Na+
Na+
Na+ and Cl- are in higher concentrationin 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-
INSIDE AXON OUTSIDE AXON (EXTRACELLULAR FLUID)
Na+
Na+
Na+
Na+
Na+A-
A-
K+ and negative anions are in higher concentrationin the intracellular or inside the axon
Cl-
Cl-
Cl-
K+K+ Cl-
K+
Neuron at Rest
K+
K+
K+
A-
A-
Na+
Cl-
K+
concentration gradient –◦ ions diffuse from higher concentration to lower
concentration
example of concentration forces
Na+Na+
K+K+
Cl-Cl-
What would each ion do if the ion channel opened based on the concentration gradient?
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!
example of electrostatic forces
Na+Na+
K+K+
Cl-Cl-
What would each ion do if the ion channel opened based on electrostatic forces ?
INSIDE AXON(intracellular)
OUTSIDE AXON (EXTRACELLULAR FLUID)
Na+
Na+
Na+
Na+
Na+Na+
Na+
Na+ and Cl- are in higher concentrationin 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-
opening of Na+ channels and influx of Na+ ions
lidocaine, novocaine, cocaine
TTX – tetrototoxin
Sagitoxin-◦ red tides
Na+Na+
K+K+
Cl-Cl-
ConcentrationGradient
ElectricalGradient
after the AP (+ intracellular)
INSIDE AXON OUTSIDE AXON (EXTRACELLULAR FLUID)
Na+
Na+
Na+
Na+
Na+A-
A-
K+ and negative anions are in higher concentrationin the intracellular or inside the axon
Cl-
Cl-
Cl-
K+K+ Cl-
K+
Neuron at Rest
K+
K+
K+
A-
A-
Na+
Cl-
K+
Sodium-potassium pump – active force that exchanges 3 Na+ inside for 2 K+ outside
INSIDE AXON OUTSIDE AXON (EXTRACELLULAR FLUID)
Na+
Na+
Na+
Na+
Na+A-
A-
K+ and negative anions are in higher concentrationin 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+
myelin sheath (80% fat and 20% protein)◦ produced by glia
http://www.blackwellpublishing.com/matthews/channel.html
nodes of ranvier
myelin sheath (80% fat and 20% protein)◦ produced by glia
◦ nodes of ranvier
nodes of ranvier
myelin sheath (80% fat and 20% protein)◦ produced by glia
◦ nodes of ranvier
◦ saltatory conduction (200 ft/sec)
http://www.blackwellpublishing.com/matthews/actionp.html
speed, efficiency of neurotransmission
speed, efficiency of neurotransmission
disease: Multiple Sclerosis progressive, autoimmune disease onset ~ 20 years of age early symptoms: motor symptoms, such as
weakness, leg dragging, stiffness, a tendency to drop things, a feeling of heaviness, clumsiness,
What about communication between neurons?