Neurotransmission 1

Question 1

Structure of a Neuron

Answer 1

Dendrites: Receives information from other neurones
Soma: controls processing in the cell and integrates the information.
Axon: carries information from the soma to the other cells.
Terminal Boutons: found at the end of the axon, location of the synapse and communication point with other neurones.

Question 2

What is the neuronal membrane?

Answer 2

Separates the extracellular environment from the intracellular environment. Protein structure: allows access of certain substances into the cell.

Question 3

Resting Potential

Answer 3

Membrane Potential at rest: difference between inside and outside is approx 65 - 70 mV.

Question 4

What causes there to be a membrane potential?

Answer 4

Force of Diffusion: Molecules move from an area of high concentration to low concentration.
Force of electrostatic pressure: molecules with the same charge repel and opposite attract.

Question 5

Equilibrium Potential

Answer 5

1) P+ ions move from a high to a low concentration.
2) As they move there is an increase in electrical potential (more +’s on one side than the other).
3) Eventually a point of equilibrium potential is reached where force of diffusion and electrostatic force are equal. High concentration = large eq. potential and vice versa.

Question 6

The Resting Membrane Potential with NA+ and K+

Answer 6

1) High concentration of Na+ outside neuron, high concentration of K+ inside neuron
2) At rest: more K+ channels open than Na+ channels (resting or leak channels
3) Na+ move into neuron and K+ out of neurone due to diffusion
4) As more K+ than Na+ can diffuse, (40x) the membrane comes to rest near the K+ equilibrium potential (-85mV)

Question 7

Sodium Potassium Pump

Answer 7

Sodium-Potassium pump maintains the ionic concentration gradients (Na+ and K+) across the membrane and therefore resting membrane potential. ATP is broken down to release energy which forces the ions to move against their concentration gradient.

Question 8

Hyperpolarisation and Depolarisation

Answer 8

Hyperpolarisation
Membrane potential more –ve than RMP
A)  Injection of small –ve current
B)  +ve ions move out (e.g. K+)
C)  –ve ions move in (e.g. Cl-)

Depolarisation
Membrane potential more +ve than RMP
A) Injection of small +ve current
B) +ve ions move in (e.g. Na+)

Question 9

Stages of the Action Potential

Answer 9

1) Some K+ channels open: K+ begins to leave neuron
2) Na+ channels open: Na+ begins to enter neuron
3) Na+ channels become refractory, no more Na+ enters neuron. Remaining K+ channels open.
4) K+ continues to leave the neuron causing the membrane to return to the resting membrane potential
5) K+ channels begin to close, Na+ channels reset
6) Remaining K+ channels close.