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27 Cards in this Set
- Front
- Back
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three useful general questions referable to the nervous system:
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Where is the lesion? What is the cause of the lesion? Why does this lesion cause this problem?
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electrical membrane potentials range from
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-70mV to -90mV
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Three important aspects that give rise to membrane potential:
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1) Concentration & distriburion of certain key ions. 2) membrane permeability. 3) Na/K pumps or ATPase
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The ions primarily responsible for generation of membrane potentials:
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Na+, K+, A- (Cl- to smaller extent), A- referes to large negetively charged intracellular proteins
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In a neuron at rest, a membrane is about _________ times more permeable to ______ than to ________.
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50 to 75 times, K+, Na+
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About _______% of membrane potential is directly generated by Na+/K+ pump
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20
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Active transport mechanism of Na+/K+ pumps ___ ____ out and ____ _____ in.
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Na/K pump 3 Na+ out for every 2 K+ it pumps in.
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there is a greater concentration of _____ in the ECF and ________ has a higher concentration in the ICF
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Na+ is higher in the ECF and K+ is higher in the ICF
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If the only ion affecting membrane potential was K, On one hand, K+ tends to diffuse out along concentration gradient and on the other hand, the neg charge inside membrane tends to attract K+ into cell: this balance is called
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potassium equilibrium potential (E sub K+) and is -90mV
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the equilibrium potential for a given ion of differing concentration across membrane:
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Nernst equation E= 61 log C sub O / C sub i
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what is the sodium equilibrium potential (E sub Na+)
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+60mV
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what is the mV of the resting membrane potential (RMP)?
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-70mV
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what counterbalances the leakage of Na and K through their "leak" channels?
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Na+ / K+ pump
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What 3 channels in plasma membrane of dendrites and cell body allow a neuron to produce a graded potential?
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chemical, mechanical, light-gated
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a very small change in RMP as a result of a stimulus is called:
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a graded potential
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what are the two types of graded potentials?
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post-synaptic potential and generator (receptor) potentials
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graded potentials cause either _______ or ____________.
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depolarization or hyperpolarization
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Electrical phenomena that allow neurons to communicate with each other and with other tissues:
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action potentials
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As Na+ moves into area of axon hillock and changes RMP to less negative, if enough Na enters axon of post-synaptic neuron, what channels open?
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voltage-gated Na+ channels in the axon hillock
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at a voltage of +30mV (depolarization), what 2 major events occur?
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closing of voltage-gated Na+ channels and opening of voltage-gated K+ channels
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in myelinated axons, mylelin sheath is wrapped around the axons except at:
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nodes of Ranvier, there are only voltage-gated channels located here and not where myelin is present
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when action potentials jump from node to node rather than move along the axon in series of tiny steps, this is called:
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saltatory conduction
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one of the most frequent types of demyelinating diseases
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multiple sclerosis
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the number and distribution of areas of demyelination are known as _________ and occur in this disease
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plaques, multiple sclerosis
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Common symptons of MS:
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most common is weakness of limbs, sensory abnormalities my occur and take form of numbness or tingling, 30% suffer vision symptoms, vestibular symptoms, loss of sphincter control, some intellectual reduction, average life span is 25 years
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local anesthics that act directly on neural membranes to decrease permeability to Na+ by reversibly blocking voltage-gated Na+ channels to prevent action potential generation and propagation
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procaine, novacaine, lidocaine
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agents that irreveribly block Na+ channels and cause death
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the marine toxins tetrodotoxin and saxitoxin as well as some scorpion toxins
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