Neural Signaling

Question 1

Charge in biological systems is carried by what?.

Answer 1

Ion movement

Question 2

What are ions

Answer 2

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

Question 3

Ion channels are the equivalent of —– in an electrical system?

Answer 3

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

Question 4

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

Answer 4

ok

Question 5

Membranes are said to be semi-permeable which means what

Answer 5

They are permeable to some ions and impermeable to others.

Question 6

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

Answer 6

Potassium

Question 7

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

Answer 7

Na/K pump

Question 8

What makes the Na/K pump electrogenic?

Answer 8

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

Question 9

Cell membrane potential at rest

Answer 9

-70mv

Question 10

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

Answer 10

hyperpolarizing

Question 11

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

Answer 11

Action potential

Question 12

What is the “threshold” of an action potential?

Answer 12

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

Question 13

During an action potential is ion selectivity maintained?

Answer 13

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.

Question 14

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

Answer 14

Afterhyperpolarization

Question 15

Action potential upstroke due to

Answer 15

Increase in membrane permeability to Na

Question 16

Action potential downstroke is due to

Answer 16

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

Question 17

Afterhyperpolarization due to

Answer 17

increased potassium conductance relative to original resting potential

Question 18

Relative refractory period of an AP

Answer 18

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

Question 19

Absolute refractory period

Answer 19

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

Question 20

A larger electical stimulus = larger AP?

Answer 20

NO….potentially more APs but not larger

Question 21

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

Answer 21

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.

Question 22

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

Answer 22

By increasing the diameter of the axon

Question 23

Conduction velocity also increased by myelination

Answer 23

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

Question 24

The conduction velocity of an unmyelinated axon is proportional to what

Answer 24

Axon diameter

Question 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.

Answer 25

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.

Question 26

What is saltatory conduction

Answer 26

Describes the conductance of myelinated axons…saltatory means “leap”. APs jump between nodes

Question 27

Multiple Sclerosis

Answer 27

loss of myelin

Question 28

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

Answer 28

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

Question 29

Myotonia and Periodic Paralysis are caused by

Answer 29

Na channel mutations in skeletal muscle

Question 30

Familial hemiplegic migraine associated with what?

Answer 30

P/Q type Ca channels mutations

Question 31

Episodic ataxia type 2

Answer 31

calcium channel mutation

Question 32

Congenital Stationary Night Blindness

Answer 32

truncated L-type calcium channels in the retina

Question 33

Eaton-Lambert Syndrome

Answer 33

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