Transmission of Nervous impulses

Question 1

describe how a nervous impulse is carried in unmyelinated fibres

Answer 1

the nerve impulse is carried continuously through the length of the nerve

Question 2

describe how a nervous impulse is carried in myelinated fibres

Answer 2

The nerve impulse is able to move down the myelinated axon by jumping from one node of Ranvier to the next.

Question 3

what is the process of nerve impulses jumping

Answer 3

Salatory Conduction

Question 4

what does the myelin sheath surrounding the axon do

Answer 4

It will insulate the axon and therefore sodium and potassium cannot flow and repolarisation and depolarisation cannot occur.

Question 5

how fast can nerve impulses travel in unmyelinated fibres

Answer 5

2 milliseconds per second (max)

Question 6

how fast can nerve impulses travel in myelinated fibres

Answer 6

140 milliseconds per second (max)

Question 7

describe the transmission of nerve impulses across a synapse

Answer 7

• When a nerve impulse reaches the pre-synaptic terminal, this opens calcium channels to allow calcium to enter the synapse.
• This activates a calcium voltage-gated channel to release a neurotransmitter via exocytosis.
• The neurotransmitter diffuses across the synapse and binds to its receptors on the post-synaptic terminal (dendrite of the next neuron)
• This acts as a stimulus causing the ligand-gated protein channels to open, continuing the original impulse through to the next neuron.

Question 8

what occurs after when neurotransmitters attach to the receptors on the post-synaptic terminal

Answer 8

• The ligand-gated protein channels open allowing some sodium to enter the cells
• This is enough for the threshold to be reaches (-55mV0 causing the voltage gates to open allowing the rapid influx of sodium into the cells causing the depolarisation of the membrane.