What factors influence conduction velocity?
Conduction velocity is influenced by myelin sheath thickness and internode distance (i.e. the distance along the axon between the nodes of Ranvier) (Hursh, 1939), and both parameters are linearly related to axon diameter.
Why are we using two pairs of recording electrodes?
Biphasic recording In this lab you will study the response of the sciatic nerve of the frog to electrical stimulation using two pairs of stainless steel wire electrodes that are both in contact with the nerve, therefore recording the potential difference between two points on the nerve.
When a maximal response of the nerve is reached What does this mean?
The stimulus strength that just gives a response is termed a threshold stimulus; any stimulus of greater strength is suprathreshold. The strength that just gives the maximal response is a maximal stimulus; any strength greater is supramaximal. The response of the nerve is called the compound action potential.
What is the difference between intra and extracellular recording?
Intracellular recordings can provide information on ionic reversal potentials, resting membrane potentials, single-channel conductance, second messenger roles in receptor function, and synaptic plasticity in neurons. However, unlike extracellular recordings, intracellular recordings are invasive to the neuron.
Why do larger axons have lower thresholds?
In general, axons with the largest diameter have the lowest threshold for extracellular current. The larger the diameter of the axon, the lower the axial resistance to the flow of longitudinal current because of the greater number of intracellular charge carriers (ions) per unit length of the axon.
Why do compound action potentials vary in amplitude?
A compound action potential (CAP) is a signal recorded from a nerve trunk made up of numerous axons. The different conduction velocities of the axon population results in a shift in time of the amplitude peaks as the recording site moves further from the stimulation site.
How does axon diameter affect threshold?
For example, a neuron with a large diameter has more ionic channels in its membrane than a smaller cell, resulting in a lower resistance to the flow of ionic current. The current spreads quicker in a cell with less resistance, and is more likely to reach the threshold at other portions of the neuron.
Why the peak of the compound action potential changes with different stimulus strength?
Q: Why does the CAP increase in size and duration with increasing stimulus strength? A: The CAP is the algebraic sum of all individual fibre action potentials of the nerve. As stimulus strength increases, we recruit more fibres, therefore more APs add up to produce a larger bell-shaped curve.
Why does the frog sciatic nerve give a graded response?
The frog sciatic nerve gives a graded response because the nerve is a bundle of axons (CAP) and not a single axon (thus it does not show the all or none response of an axon-either generating an action potential or not). Thus the nerve impulse is graded (it can be none, small, medium, large, larger, maximal).
What does each distinct cluster of CAP amplitudes represent?
As mentioned earlier, the main hypothesis for sorting CAP waveforms into different groups (clusters) is that different CAP waveform shapes and amplitudes represent the activity of different groups of nerve fibers.
Why does the amplitude increase with increasing stimulus?
As noted in Figure 1 and Table 1 the amplitude of the muscle response increases with increasing stimulus voltages. This is so because more and more of the muscle mass is stimulated as the voltages increase. At high stimulus voltages, the muscle response reaches maximum amplitude.
What happens when maximal stimulus is achieved?
What has happened in the muscle when the maximal stimulus is achieved? Cross bridge cycle and when the muscle tension exceeds the load, muscle shortening happens. The latent period increases as the weight of the load gets heavier, this is for the necessary force to be generated by the muscle.
Does the amplitude of the action potential increase as you increase the stimulus intensity?
As stimulus intensity is increased, the action potential amplitude remains the same (all-or-none events) , but frequency at which the neuron responds to the stimulus increases.
What happens to the finger twitch amplitude as the stimulus current is increased?
4. Above a certain stimulus current, the amplitude of the finger twitch no longer increases.
Why didn’t a finger twitch occur at a lower stimulus current?
Why didn’t a finger twitch occur at a lower stimulus current? 15g. There was no graded potential. Above a certain stimulus current, the amplitude of the finger twitch no longer increases.
Why does the muscle force increase as voltage stimulus is increased?
Increasing the stimulus voltage on isolated skeletal muscle increases the amount of active force produced by the muscle. This happens because more fibers and motorneurons are activated and leads to an increase in muscle force.
Does the latent period change with different stimulus?
The latent period did not change with changes in stimulus voltage.
Does the duration of the latent period change with different stimulus voltages How well did the results compare with your?
No, the duration of the latent period does not vary with variations in the stimulus voltage. The results matched with the prediction and the latent period remained constant.
What is the difference between stimulus frequency and stimulus intensity?
What is the difference b/w stimulus intensity & stimulus frequency? Stimulus intensity describes the amount of force generated to administer the stimulus. The more force that is used will increase the stimulus intensity. Stimulus frequency refers to the rate of delivered stimulus to the muscle.
Which of the following describes the relationship between stimulus frequency and muscle tension?
Which of the following describes the relationship between stimulus frequency and muscle tension? When stimulus frequency increases, muscle tension increases to a maximum value. No greater muscle force can be generated and the muscle has reached maximal tetanic tension.