Neurophysiology Flashcards
Diseases caused by defective Ion Channels
Channelopathy
When does Hyperkalemic Periodic Paralysis flare up?
Episodic~ weakness and decreased muscle tone after exercise of K+ rich food
Symptoms of Hyperkalemic Periodic Paralysis
weakness and decreased muscle tone
What’s going on with the muscles fibers in Hyperkalemic Periodic Paralysis
Involved msl fibers ≠fire Aps (cells are depolarized by 30-40 mV)
What Voltage Gated Ion in involved in Hyperkalemic Periodic Paralysis
d/t mutation of muscle Voltalge Gated Na+ channels
What is going on with K+ channels in Hyperkalemic Periodic Paralysis?
What does this result in?
some % of them can’t completely INACTIVE after depolarization
Results in SMALL but CONSTANT INWARD current: thus INACTIVATES normal Na channel—Muscle is UNEXCITABLE
Hard to Relax mscle once they’ve been Contracted: describes what disease?
Myotonia
What are the two forms of Myotonia?
Thomsens Disease + Beckers Disease
After a sudden contraction, muslces of patients with myotonia…..
muscles relax really slow after a sudden contraction
What channel is abnormal in fainting goats?
Cl- channel
Differnce between skeletal and neurons for Cl- permeability?
Normal Skeleteal muscles, UNLIKE neurons, have HIGH Cl- Permeability → gives resting membrane potential influenced by Cl conc gradient
Mutated Cl- channels in fainting goats have increased/decreased/same conductance?
have DECREASED conductance
What is the result of the decreased conductance of Cl- channels in fainting goats?
thus reducing amt of Depolarizing current needed to reach threshold, it’s EASIER to REACH threshold
What signal in fainting goat results in repeated AP?
in fainting goat a small signal of 48 na will get us REPEATED AP
Oligodentricytes located in?
CNS
Schwann cells located in:
PNS
Result of increasing RM (resistance of membrane)
Increases Length constant thus increases conduction velocity… more myelination
Increasing diameter will increase/decrease/no change to length constant?
Increase length constant = propagates faster
What is length constant
amount for potential to drop by 63%
Determined by RI and RM
What will decrease length constant
a LARGE RI (longitudinal resistance
Antidromic is towards?
Soma: unusual… seen in artificial AP
What ensures that AP is generated in one direction?
Absolute refractory
Dependence on Peak Voltage reached during AP is which ion?
Na+
What is responsible for RMP
K+
What states make up K+?
open and closed, thats it… prefers to be at -95mv so will never go beyond but is repsonible for hyperpolarization
How many states does Na+ have?
Resting→ Open (at depolarization)→ Inactivated (ion can’t get through…need to go back to resting before can open)→ back to Resting
What is the Absolute Upper Limit of the AP
1kHz
What is the time delay between cause and effect
Latency
What does the AP look like during Relative Refractory Period?
you CAN generate AP with higher then normal stimulus and results in lower then usual AP→ function is to limit rate of AP
Cable properties of Neurons: PASSIVE
Amplitude of Potential DECAYS EXPONENTIALLY as moves away from source
Change in Vm PASSIVEY spreads in BOTH directions along axon and dendrites
Order of size of ions
Na+ < K+ < Cl- < organic cations
Negative and positve charges would be identical to each side =
0 membrane potential
