4.2 Stimulus Strength, Firing Frequency & Conduction + End of Action Potentials

Question 1

What is the definition of the Firing Rate?

Answer 1

Firing Rate (Frequency) = Action Potentials per Second = Spikes (above threshold) / Second = [Hz]

Question 2

Does longer refractory period = slower maximum firing rate?

Answer 2

O, Maximum firing rate depends on the duration of the refractory period, as the refractory period is a function of the inactivation length.

Question 3

Does Higher Firing Rate = Weak Stimulus?

Answer 3

X, Stimulus Strength can be represented in Firing Rate, whereas as the Firing Rate increases it represents a strong stimulus that overcomes the relative refractory period

Question 4

Different types of neurons still have the same firing patterns

Answer 4

X, Different types of neurons have different firing patterns

Question 5

Action Potential Conduction in Motor Neurons
1. Do they travel in both directions or only one direction?
2. What is the difference between Non-myelinated Axons & Myelinated Axons’s conduction?
How do each of them travel (name of conduction method if existing) + which is faster and why?

Answer 5

1. Only in one direction due to refractory period & undershoot
2. Non-myelinated Axons : Actional Potential propagates continuously (by current) + depolarization (followed by repolarization) spreads through the axon. => Slower conduction that Non-myelinated Axons
   Myelinated Axons : Saltatory Conduction by using Nodes of Ranvier (as the Voltage-gated channels are clustered there) as the Myelination blocks current leak => Faster than Non-myelinated

Question 6

Action Potential Conduction in Sensory Neurons
1. How are they different from Motor Neurons?

Answer 6

No axon hillock for stimulus collection = NO SUM! + unlike EPSPs, stimulus activates a receptor / ion channels (such as mechanically-sensitive ion channels) causing depolarization phase => If the respective stimulus is strong enough (enough depolarization) then Rising Phase (voltage-gated channels open) ~ Propagation

Question 7

What is the named of the channel used in Touch Neurons?

Answer 7

Question 8

Answer 8

Since Sensory has to be Presynaptic (Sensory => Brain => Motor) => The PIEZO channel basically causes a “presynaptic” graded potential

Touch => opens the mechanically-sensitive PIEZO channel => causes a graded potential where no synaptic integration is needed => Depolarization (Na+ comes in), Repolarization (K+ goes out), Hyperpolarization (K+ goes more out) + Absolute Refractory (Na+ Inactive) + Relative Refractory (Na+ Active) => Resting Membrane Potential

Very slow

Question 9

A sensory neuron is what type of neuron (depending on the number of Neurites)

Answer 9

Psuedo-unipolar

Question 10

Sensory neurons…
1. Have integration at the Axon Hillock?
2. Are initiated at where?

Answer 10

1. X
2. Sensory Nerve Ending

Question 11

1. Graded Potentials go through Synaptic Integration, where the sum has to be above the Threshold to activate an AP?
2. For Sensory Neurons, they don’t have an axon hillock to sum them up! So their single Graded Potentials have to be strong enough to fire an AP?

Answer 11

O, O