Neurophysiology

Question 1

Diseases caused by defective Ion Channels

Answer 1

Channelopathy

Question 2

When does Hyperkalemic Periodic Paralysis flare up?

Answer 2

Episodic~ weakness and decreased muscle tone after exercise of K+ rich food

Question 3

Symptoms of Hyperkalemic Periodic Paralysis

Answer 3

weakness and decreased muscle tone

Question 4

What’s going on with the muscles fibers in Hyperkalemic Periodic Paralysis

Answer 4

Involved msl fibers ≠fire Aps (cells are depolarized by 30-40 mV)

Question 5

What Voltage Gated Ion in involved in Hyperkalemic Periodic Paralysis

Answer 5

d/t mutation of muscle Voltalge Gated Na+ channels

Question 6

What is going on with K+ channels in Hyperkalemic Periodic Paralysis?
What does this result in?

Answer 6

some % of them can’t completely INACTIVE after depolarization
Results in SMALL but CONSTANT INWARD current: thus INACTIVATES normal Na channel—Muscle is UNEXCITABLE

Question 7

Hard to Relax mscle once they’ve been Contracted: describes what disease?

Answer 7

Myotonia

Question 8

What are the two forms of Myotonia?

Answer 8

Thomsens Disease + Beckers Disease

Question 9

After a sudden contraction, muslces of patients with myotonia…..

Answer 9

muscles relax really slow after a sudden contraction

Question 10

What channel is abnormal in fainting goats?

Answer 10

Cl- channel

Question 11

Differnce between skeletal and neurons for Cl- permeability?

Answer 11

Normal Skeleteal muscles, UNLIKE neurons, have HIGH Cl- Permeability → gives resting membrane potential influenced by Cl conc gradient

Question 12

Mutated Cl- channels in fainting goats have increased/decreased/same conductance?

Answer 12

have DECREASED conductance

Question 13

What is the result of the decreased conductance of Cl- channels in fainting goats?

Answer 13

thus reducing amt of Depolarizing current needed to reach threshold, it’s EASIER to REACH threshold

Question 14

What signal in fainting goat results in repeated AP?

Answer 14

in fainting goat a small signal of 48 na will get us REPEATED AP

Question 15

Oligodentricytes located in?

Answer 15

CNS

Question 16

Schwann cells located in:

Answer 16

PNS

Question 17

Result of increasing RM (resistance of membrane)

Answer 17

Increases Length constant thus increases conduction velocity… more myelination

Question 18

Increasing diameter will increase/decrease/no change to length constant?

Answer 18

Increase length constant = propagates faster

Question 19

What is length constant

Answer 19

amount for potential to drop by 63%

Determined by RI and RM

Question 20

What will decrease length constant

Answer 20

a LARGE RI (longitudinal resistance

Question 21

Antidromic is towards?

Answer 21

Soma: unusual… seen in artificial AP

Question 22

What ensures that AP is generated in one direction?

Answer 22

Absolute refractory

Question 23

Dependence on Peak Voltage reached during AP is which ion?

Answer 23

Na+

Question 24

What is responsible for RMP

Answer 24

K+

Question 25

What states make up K+?

Answer 25

open and closed, thats it… prefers to be at -95mv so will never go beyond but is repsonible for hyperpolarization

Question 26

How many states does Na+ have?

Answer 26

Resting→ Open (at depolarization)→ Inactivated (ion can’t get through…need to go back to resting before can open)→ back to Resting

Question 27

What is the Absolute Upper Limit of the AP

Answer 27

1kHz

Question 28

What is the time delay between cause and effect

Answer 28

Latency

Question 29

What does the AP look like during Relative Refractory Period?

Answer 29

you CAN generate AP with higher then normal stimulus and results in lower then usual AP→ function is to limit rate of AP

Question 30

Cable properties of Neurons: PASSIVE

Answer 30

Amplitude of Potential DECAYS EXPONENTIALLY as moves away from source
Change in Vm PASSIVEY spreads in BOTH directions along axon and dendrites

Question 31

Order of size of ions

Answer 31

Na+ < K+ < Cl- < organic cations

Question 32

Negative and positve charges would be identical to each side =

Answer 32

0 membrane potential