Neuronal Communication

Question 1

How does the pacinian corpuscle detect a stimulus and generate an action potential?

Answer 1

1. The lamellae deform, pressing on the sensory neurone ending
2. This stretches the neurone’s membrane, causing it to change shape
3. This opens stretch mediated Na+ channels in the membrane, increasing its permeability to Na+
4. Na+ diffuses into the neurone, depolarising it and resulting in a generator potential
5. If this signal reaches the threshold, an action potential is triggered

Question 2

Describe the differences in structure between the 3 types of neurones

Answer 2

• Sensory - one dendron that leads into many smaller dendrites, and one long axon. Cell body in middle of axon
• Relay - many short dendrites and axons
• Motor - many short dendrites and one long axon. Cell body at start of axon

Question 3

What is the importance of the refractory period?

Answer 3

• Ensuring action potentials don’t overlap
• Limits the frequency at which impulses are transmitted
• Guarantees impulses only travel in one direction
• Allows other stimuli to affect the synapse and prevents continuous stimulation

Question 4

What is summation and describe the two types?

Answer 4

• Where low frequency action potentials trigger a new action potential in the post synaptic neurone through the rapid build up of NT concentration
• Spatial - multiple presynaptic neurones release enough NT together
• Temporal - a single presynaptic neurone releases NT multiple times in a short period

Question 5

Describe inhibitory synapses

Answer 5

Release NT that hyperpolarise the postsynaptic membrane, preventing triggering of a new action potential in the postsynaptic neurone