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27 Cards in this Set

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three useful general questions referable to the nervous system:
Where is the lesion? What is the cause of the lesion? Why does this lesion cause this problem?
electrical membrane potentials range from
-70mV to -90mV
Three important aspects that give rise to membrane potential:
1) Concentration & distriburion of certain key ions. 2) membrane permeability. 3) Na/K pumps or ATPase
The ions primarily responsible for generation of membrane potentials:
Na+, K+, A- (Cl- to smaller extent), A- referes to large negetively charged intracellular proteins
In a neuron at rest, a membrane is about _________ times more permeable to ______ than to ________.
50 to 75 times, K+, Na+
About _______% of membrane potential is directly generated by Na+/K+ pump
20
Active transport mechanism of Na+/K+ pumps ___ ____ out and ____ _____ in.
Na/K pump 3 Na+ out for every 2 K+ it pumps in.
there is a greater concentration of _____ in the ECF and ________ has a higher concentration in the ICF
Na+ is higher in the ECF and K+ is higher in the ICF
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
potassium equilibrium potential (E sub K+) and is -90mV
the equilibrium potential for a given ion of differing concentration across membrane:
Nernst equation E= 61 log C sub O / C sub i
what is the sodium equilibrium potential (E sub Na+)
+60mV
what is the mV of the resting membrane potential (RMP)?
-70mV
what counterbalances the leakage of Na and K through their "leak" channels?
Na+ / K+ pump
What 3 channels in plasma membrane of dendrites and cell body allow a neuron to produce a graded potential?
chemical, mechanical, light-gated
a very small change in RMP as a result of a stimulus is called:
a graded potential
what are the two types of graded potentials?
post-synaptic potential and generator (receptor) potentials
graded potentials cause either _______ or ____________.
depolarization or hyperpolarization
Electrical phenomena that allow neurons to communicate with each other and with other tissues:
action potentials
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?
voltage-gated Na+ channels in the axon hillock
at a voltage of +30mV (depolarization), what 2 major events occur?
closing of voltage-gated Na+ channels and opening of voltage-gated K+ channels
in myelinated axons, mylelin sheath is wrapped around the axons except at:
nodes of Ranvier, there are only voltage-gated channels located here and not where myelin is present
when action potentials jump from node to node rather than move along the axon in series of tiny steps, this is called:
saltatory conduction
one of the most frequent types of demyelinating diseases
multiple sclerosis
the number and distribution of areas of demyelination are known as _________ and occur in this disease
plaques, multiple sclerosis
Common symptons of MS:
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
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
procaine, novacaine, lidocaine
agents that irreveribly block Na+ channels and cause death
the marine toxins tetrodotoxin and saxitoxin as well as some scorpion toxins