ELECTROPHYSIOLOGY

Question 1

What was the idea of Rene Descartes regarding the control of movement in animals

Answer 1

Proposed the idea animal spirits responsible for movement of the body (muscles) These spirits being produced in the Pineal Gland- the seat of the soul

Question 2

Define the theory of Vitalism

Answer 2

The belief that organisms and particularly Man work by different principles from those governing the physical world

Question 3

Outline the 1st key Experiment of Galvani

Answer 3

1) SPARK EXPTS: friction machine generated sparks causing the frog legs to twitch

Question 4

Outline the 2nd key Experiment of Galvani

Answer 4

2) ATMOSPHERIC ELECTRICITY: placing short aerials that carried charge from lightning strikes caused the legs to twitch

Question 5

Outline the 3rd key Experiment of Galvani

Answer 5

3) BRIDGES: he constructed conducting bridges between nerve and muscle- legs twitch without external stimulation

Question 6

What was the principle behind Volta’s technical objection to Galvani’s idea of intrinsic electricity?

Answer 6

Galvani’s observations were artefacts triggered externally by the electrogenic properties of the metal /electrolyte interface.

Question 7

Name one finding that proved Galvani’s theory to be correct

Answer 7

Galvani + Aldini (nephew) showed that contraction occurred in a muscle in contact with a cut nerve of another muscle.

Question 8

Name a second finding that proved Galvan’s theory to be correct

Answer 8

Preparation of sectioned frog thighs in series by Matteucci - a biological pile- excluded idea that current is from metal electrodes

Question 9

Outline the findings and theories put forward by Du Bois Reymond regarding Intrinsic electricity.

Answer 9

• discovered that the interior of muscles were electrically negative with respect to the outside
• deduced that the muscle fibre membranes are electrogenic
• said they contain embedded dipoles that drive current flow in normal and injured nerves
• proposed that the dipoles change polarity during activity

Question 10

What is a Galvanometer and what significance did it have on electrophysiology?

Answer 10

It’s a type of sensitive ammeter. Was the first instrument to detect and measure current fluctuations in living tissue

Question 11

What is the Multiplikator and how was it devised?

Answer 11

An extra sensitive galvanometer, devised by Du Bois Reymond by winding the coil with 5km of fine wire.

Question 12

What is the Rheotome and how was it used by Bernstein?

Answer 12

Rheotome = current slicer. Bernstein used it to measure the time course of the nerve impulse in 1868

Question 13

Bernstein Membrane Theory

Answer 13

• The membrane separates conc. KCl inside the cell from dilute KCl outside the cell
• During activity the membrane becomes permeable to all ions (Cl- and K+) causing current flow

Question 14

What was the major flaw in Bernstein’s membrane theory?

Answer 14

Overton in 1902 showed that a high conc. of external Na+ is needed for muscle activity- Na+ not stated as important in the theory.

Question 15

Outline the experimental techniques of Hodgkin and Huxley

Answer 15

• They used the preparation of the giant squid axon outlined by JZ Young
• Used glass micropipettes as electrodes to measure intracellular and extracellular potential at rest and action

Question 16

What is the Refractory Period?

Answer 16

A transient period following the Depolarisation where the membrane cannot transmit another depolarisation- transient insensitivity

Question 17

What is the purpose of the Refractory period?

Answer 17

• sets an upper limit to the impulse frequency

- ensures that the AP only propagates forwards.

Question 18

What were the experiments of Cole and Curtis?

Answer 18

Used the same Squid preparations but measured membrane resistance. They found it dropped slightly below resting value and recovered slower than the AP in line with undershoot refractory period.