resting neuron

Question 1

Who is Luigi Galvani?

Answer 1

• frog experiment
• Living tissues contained inherent electrical charge
• believed electricity was produced in the brain as stored in the nerves and muscles.

Question 2

Who is Alessandro Volta?

Answer 2

• Believe nerve and muscle and cells don’t have charge but are simple electrically stimulated
• built a battery-

Question 3

What are nerve and muscle tissues ?

Answer 3

are both electrically charged and electrically stimulated.

Question 4

What are the 2 fundamental discoveries that allowed the elucidation of basic neural function?

Answer 4

1. Micro-electrode- a very thin hollow tube with glass, which you can penetrate individual neruon
2. Squid giant axon

Question 5

What is the basic set up for recording from a neuron?

Answer 5

• Take your Squid giant axon and one microelectronics and place inside axon
• Take second electrode and place it outside the axon
• Then see the difference in electrical charge inside and outside the axon- Potential difference

Question 6

What is the potential difference of 2 electrodes resting on the surface of a cell?

Answer 6

-record no potential difference = 0

Question 7

What happens when you put one electrode inside the cell?

Answer 7

• Record the inside the cell is negatively charge in respect to outside

Question 8

What is the Resting potential ?

Answer 8

When the inside of the cell is negatively charged- negative resting potential

Question 9

What is the resting potential of a neuron?

Answer 9

-60mV

Question 10

What is an electrical signal?

Answer 10

change in resting potential

Question 11

What are the 2 ways a resting membrane potential can change ?

Answer 11

• Hyperpolarisation- -60mV- -80mV (neutrons become more negative)
• Depolarisation- -60mV to -40mV (neutrons become less negative)

Question 12

What is the ionic composition of a resting neuron?

Answer 12

• The outside of axon- positive in charge - has lots of Na+ and Cl-
• Inside of axon has lots of K+ ions and A- (which are big negatively charged molecules)

Question 13

What are the 2 types of force can act on an ion- to make an ion move?

Answer 13

1- Chemical force: ion will move from an area of high conc to an area of low conc- move down conc gradient.
2- Electrostatic force- an ion will be attracted to the opposite polarity- Na+ attracted to negative charged area

Question 14

What is the experiment to see the 2 forces in action?

Answer 14

• Movement of sodium ions through a semi permeable membrane to establish an equilibrium
• down the middle of beaker is membrane that only lets in NA+
• Left side -strong solution of NaCl. and right side- weaker solution of NaCl
• The way the sodium moves is down its conc gradient.
• Wont let through Cl- ions.
• As its lost from left side and gained. by right hand side- as sodium is positive right side become spositive and left side becomes negative
• The negative charge b building on the left will hold the Na+
• Equilbirum is then established- when the chemical force pushing sodium to the right is equal tot electrostatic force which is holding sodium in the left hand side- establishment off equilibrium potential.

Question 15

What does this mean for sodium in a neuron?

Answer 15

• Outside of neuron has lots of positively charged na+ ions
• chemical force pushes sodium in neuron
• force shoving sodium in neuron is 50mV
• Since sodium is positive and inside is negative there is an electrostatic force pulling sodium into the cell at around 60mv.
• total

Question 16

What is the total driving force in a resting neuron?

Answer 16

110mV- pushing sodium into a resting neuron

Question 17

What forces act on potassium in a resting neuron?

Answer 17

• 75mV chemical force pushing potassium out of the neuron- leaves the cell down its conc gradient
• K is positive and inside of neuron is negative- be a electrostatic force which is opposing and hold the k+ in the neuron
• There is a weak resultant force pushing K+ out of the cell.
• Weak tendency for potassium to leave

Question 18

What are the 2 factors that will determine the movement of an ion across a membrane?

Answer 18

1. Size of electrochemical gradient

2. Permeability of the membrane

Question 19

Why do these movements not happen in the resting neurone?

Answer 19

• as the membrane is not very permeable to these ions.

- Although there is a strong driving fore for sodium into a cell and a weak tendency for potassium to leave it

Question 20

What leakage occurs in the resting neurone?

Answer 20

3 Na+ leak in 2K+ leave the cell/

Question 21

What is the sodiumpotassoium pump?

Answer 21

Enzyme that is a protein in. the plasma membrane of the axon

• When. it binds 3 Na+ ions from inside neuron which have leaked in neurone it changes the shape and pushes these sodium ions out of the neuron and 2K+ back in as they bind to the same pump.
• Resting distribution of the ions in an neruron are maintained
• Nobel prize-1997

Question 22

What are nervous signals?

Answer 22

changes in this resting potential