spread of nerve impulse

Question 1

describe there nerve impulse pathway through a neutron

Answer 1

• information arrives at the cell body via dendrites where it is assimilated and processed
• processed information is the digitised and transmitted along the axon
• at the end of the axon the information is passed to the target (muscle or neurone) via boutons

Question 2

What are the three different variations in the neuronal phenotype and where are they commonly found

Answer 2

multipolar neuron - most abundant in the CNS
bipolar neuron - cell body is located in the middle of the axon and found in retina
pseudo unipolar - cell body in the centre of the axon but out to the side and found in spinal ganglion

Question 3

Passive conduction

Answer 3

passive conduction will decay as distance increases, and can only transmit charge a short distance

Question 4

Absolute refectory period

Answer 4

the cell cannot be stimulated to its threshold potenical as all Na+ channels are closed

Question 5

relative refractory period

Answer 5

a stronger stimulus than normal could induce an action potential

• some Na+ are ready but more K channels are open than usual
• cell still hyper polarised

Question 6

Describe the effect of the refractory period pm the direction of the action potential

Answer 6

• voltage gated Na channels open and allow positive Na ions into the axoplasm
• these ions set up a more positive poetical which when great enough causes the next Na+ channel to open
• Refractory nature of Na+ channels keeps impulse moving in one direction

Question 7

What code is used in the CNS

Answer 7

action potencial frquency

Question 8

Factors effecting the speed of neurons

Answer 8

Resistance

Capacitance - surface area so more capacity to store charge across the membrane