electrical properties (exam 1)
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52 Terms
What are neurons?
Specialized cells that use electrical + chemical signals
What are the two types of signaling in neurons?
Electrical (within) and chemical (between cells)
Why does electrical signaling matter?
Allows long-distance communication
What are the 5 key features of neuron electrical properties?
Resting membrane potential, graded potentials, action potentials propagate unchanged, AP → neurotransmitter release, neurotransmitters → postsynaptic change
What percentage of the body is water?
60-70%
What percentage of the brain is water?
~95%
What is an ion?
Charged atom
What is a negative ion?
More electrons
What is a positive ion?
Fewer electrons
What are the major ions?
Na⁺, K⁺, Cl⁻, Ca²⁺, Mg²⁺
Why can't ions cross the membrane freely?
Lipid bilayer is hydrophobic
What allows ion movement across the membrane?
Channels + transporters
What are the types of channels?
Passive (leak) and gated
What are the types of gated channels?
Voltage, ligand, mechanical
What is a concentration gradient?
Movement to equalize concentration
What is an electrochemical gradient?
Movement to equalize charge
What is the resting membrane potential value?
~ -70 mV
Why is the inside of the cell negative?
K⁺ leak, Na⁺ leak, pump, proteins
What is the ion distribution at rest?
High K⁺ inside, high Na⁺ outside
What is the charge of proteins inside the cell?
Negative
Which leak channels dominate?
K⁺
What is the Na⁺/K⁺ pump ratio?
3 Na⁺ out, 2 K⁺ in
What does the pump require?
ATP
What maintains resting potential?
Balance of leaks + pump + proteins
Where do graded potentials occur?
Dendrites + soma
What causes graded potentials?
Neurotransmitter receptors
What is the excitatory effect?
Depolarization
What is the inhibitory effect?
Hyperpolarization
Where are inputs summed?
Initial segment (axon hillock)
What triggers an action potential?
Threshold reached
What opens at threshold?
Voltage-gated Na⁺ channels
What causes depolarization?
Na⁺ influx
What causes repolarization?
K⁺ efflux
What happens to Na⁺ channels during repolarization?
Close/inactivate
What causes hyperpolarization?
K⁺ overshoot
What is the final step after an action potential?
Return to resting potential
What is the order of action potential phases?
Rest → Depolarization → Repolarization → Hyperpolarization → Rest
How does an action potential travel?
Depolarization triggers next segment
Does the action potential weaken over distance?
No (no decrement)
What is the all-or-none principle?
Full AP or none
What is the refractory period?
Time Na⁺ channels cannot reopen
Why is the refractory period important?
Prevents backward flow, limits frequency, ensures one direction
What is myelin?
Insulation around axon
What is the function of myelin?
Speeds conduction
What type of conduction does myelin facilitate?
Saltatory
What are myelin cells in the CNS?
Oligodendrocytes
What are myelin cells in the PNS?
Schwann cells
What is a demyelinating disease?
Loss of myelin
What is multiple sclerosis?
Autoimmune destruction of CNS myelin, common in women 20-40 y/o, symptoms include loss of touch sensitivity, poor motor coordination, vision problems
What is the effect of demyelination?
Slowed/failed action potentials
What does Lidocaine do?
blocks voltage gated Na channels and blocks action potentials, used a lot in dentistry
What does the babinksi reflex in kids represent? What does it represent in adults?
growth of pyramidal track myelination in babies, Upper motor neuron disease in adults