Vertebrates 14 - Phys. of Nervous system Flashcards Preview

Vertebrates 305 > Vertebrates 14 - Phys. of Nervous system > Flashcards

Flashcards in Vertebrates 14 - Phys. of Nervous system Deck (35)
Loading flashcards...
1

Galvani

Discovered electrical signals needed to contract frog legs. Also created battery (Zn/Cu)

2

Early 1900’s nerve studies

use oscilloscopes, amplifiers, probes. Discovered membrane potential. Negative in (proteins), positive out (Na+ pumped out): -70mV)

3

Resting membrane potential factors

Depends on permeability of membrane to ions. Leak channels (G L) always open. RMP closest to E ion that is most permeable. Na/K pump maintains gradient.

4

Passive Electrical properties of membranes

Steady state of ion movement through channels. Nernst equation and Ohm’s law.

5

Ohm’s law

V=IR. Channels like resistors (or rather conductor**), membrane like capacitor. Conductance G = 1/R. Rearrange = I (Amps) = G (Siemens) x V

6

How does V affect ion movement?

Positive charge won’t flow out as much if other positive charge there. Only affects ion movements when it is NOT at equilibrium potential

7

Nernst equation

Eion = (58mv/Z) log([ion]out/[ion]in). Calculate equilibrium potential when ion won’t flow.

8

Electromotive force

Driving force, electrical gradient, difference b/w voltage of membrane and equilibrium potential (Em - Eion). I = G x emf (volts)

9

What does conductance (G) tell you?

Can tell you the number of channels available to move the ion in question

10

Research on action potentials

Cole and Curtis (USA) and Hodgkin and Huxley (UK). Studied the giant axons of squid about 50 years ago.

11

Giant axons in squid

Line the mantel, cause the mantel to contract rapidly and move via jet propulsion

12

Study of current in action potentials

Used voltage clamp and amplifier to affect potential, then changed variables to see what was causing the current flow (eliminate K, see difference in current)

13

Steps in action potential

Threshold, Na channels open and Na goes in. K channels open and flow out. Na/K pump not involved in the depolarization but is important to reestablish gradient.

14

Patch clamp

Measure voltage across one channel. Help to study

15

Molecular biology and action potentials

Many genes isolated, can close and study them. Also, there are many different types for each kind (ie many Na channels).

16

Toxins and ion channels

Many toxins affect ion channels. Used to study ion channels and in drug design to help pain.

17

Tetrodotoxin

From bacteria in pufferfish. Blocks Na channels, so many action potentials are blocked.

18

Saxitoxin

From shellfish. Causes paralyzation. Blocks Na channels

19

Conotoxin

From exotic snail which eats fish. Toxin paralyzes fish. Different types block Na channels, Ca channels, K channels, Ach receptors, or block inactivation of Na channels

20

Charybdotoxin

In scorpions. Block K channels.

21

Agatoxins

From the funnel-web spider. Also paralyzes. Block Na channels, voltage dependent Ca channels

22

Apamin

In bee stings. Not paralyzing, but affects ion channels. Block calcium gated K channels

23

Dendrotoxins

From black mamba snake. Paralysis. Block K channels

24

Voltage gated sodium channel. States.

Close, open, inactivated. Opens when membrane is depolarized. Then shifts to inactivated, happens automatically. Goes back to close when membrane repolarizes.

25

Voltage gated sodium channel details.

Some sensitive to tetrodotoxin and saxitoxin. Isolated from electroplaques of electric eel. Multisubunit. Many genes cloned.

26

Voltage gated potassium channel

Open or close. Opens because of depolarization. Some sensitive to apamin, charybdotoxin, dendrotoxin. Multisubunit, many genes.

27

Voltage gated calcium channel.

Roles: electrical excitability, Ca entry, NT release, excitation/Contraction couple (DHPR). Some sensitive to conotoxins, agatoxins, drugs (ie for blood pressure). Many genes cloned.

28

Reading: Why do vertebrates need ability to sense heat?

So they don’t die!

29

Reading: How do vertebrates sense heat?

Specialized nerve ending in skin. Two types: cold or warm. Usually only really activate at noxious temp. Also neurons in hypothalamus to measure core temp

30

Reading: Pit vipers

Pits on snout have infrared receptors. innervated by trigeminal nerve. They have overlapping fields which helps them focus. Very senesitive, even .02˚C.