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Clinical Neuroscience weeks 1-3 > Neural Signaling > Flashcards

Flashcards in Neural Signaling Deck (33):
1

Charge in biological systems is carried by what?.

Ion movement

2

What are ions

Ions are charged particles which are charged due to an excess or deficit of electrons in their outer shell.

3

Ion channels are the equivalent of ----- in an electrical system?

Resistors (or conductors depending on whether ion flow is being sped up or slowed down.

4

Lipid bilayers have properties of a capacitor (two plates which conduct electricity very well with a thin insulation strip between the plates).

ok

5

Membranes are said to be semi-permeable which means what

They are permeable to some ions and impermeable to others.

6

At rest, neuronal cell membranes are primarily permable to what?

Potassium

7

High K concentration inside the cell and high Na outside the cell primarily maintained by>

Na/K pump

8

What makes the Na/K pump electrogenic?

Pumps 3 Na out for every 2 potassium moved in. Electrogenic means it contributes to the membrane potential of the cell

9

Cell membrane potential at rest

-70mv

10

Events which enhance membrane potential (make the membrane more negative) are referred to as

hyperpolarizing

11

Larger depolarizing stimuli that result in rapid and sizeable depolarization followed by repolarization and undershoot is called?

Action potential

12

What is the "threshold" of an action potential?

Threshold is the point at which depolarization (inward) current is just balanced out by repolarization (outward current). ANy further depolarization leads to AP.

13

During an action potential is ion selectivity maintained?

Yes, but it changes. The fact that membrane potential doesnt stop at 0 means that the membrane is still selective for a certain ion...Na in this case vs K at rest.

14

Upon repolarization, membrane potential undershoots original resing potential. what is this called

Afterhyperpolarization

15

Action potential upstroke due to

Increase in membrane permeability to Na

16

Action potential downstroke is due to

Inactivation of Na channels as well as activation of voltage gated ion channels

17

Afterhyperpolarization due to

increased potassium conductance relative to original resting potential

18

Relative refractory period of an AP

Due to increased K permeability during repolarization, a larger action potential is required to elicit another AP

19

Absolute refractory period

No stimulus, no matter how large, will wlicit an AP

20

A larger electical stimulus = larger AP?

NO....potentially more APs but not larger

21

KNOW Signaling via Action Potentials is advantageous because it allows rapid signaling with no decrease in signal over distance. How?

Because it is regenerated at each node of ranvier. This is all in contrast to a graded potential where the signla loses amplitude as it travels away from its point of origin. This makes action potentials better at carrying signals over long distances.

22

Conduction velocity for an axon (the rate of advance for an AP) can be increased how?

By increasing the diameter of the axon

23

Conduction velocity also increased by myelination

Decreases the ability of the membrane to act as a capacitor (store charge) so that more more charge passes to the next node of ranvier

24

The conduction velocity of an unmyelinated axon is proportional to what

Axon diameter

25

In myelinated axons, conduction velocity is increased by restricting the APs to the nodes of Ranvier and by facilitating electronic movement of cahrge between nodes.

The latter is done by increasing the resistance of the membrane to leakage of ions (myelination) and decreasing the ability of the membrane to act as a capacitor.

26

What is saltatory conduction

Describes the conductance of myelinated axons...saltatory means "leap". APs jump between nodes

27

Multiple Sclerosis

loss of myelin

28

Point mutations ot the alpha subunit of the sodium channel can lead to what disease

GEFS....Generalized Epilepsy with Febrile Seizures...cause slowed inactivation of Na channels

29

Myotonia and Periodic Paralysis are caused by

Na channel mutations in skeletal muscle

30

Familial hemiplegic migraine associated with what?

P/Q type Ca channels mutations

31

Episodic ataxia type 2

calcium channel mutation

32

Congenital Stationary Night Blindness

truncated L-type calcium channels in the retina

33

Eaton-Lambert Syndrome

small cell carcinomas produce antibodies to voltage gated calcium channels leading to dysfunction of the NMJ