Compound Effects Of Stimulus Intensity

If the frequency of action potentials in the excitatory presynaptic cell increases than the number of action potentials in the postsynaptic cell will increase as well. This is due to temporal summation of EPSP at very frequent times. This causes the postsynaptic cell to produce many action potential in succession.

The peak of the CAP changes with different strength stimulus because the sizes and thresholds of the nerve fibres within the nerve is different. Larger nerve fibres have lower threshold stimuli than smaller ones, hence larger fibres were activated first, followed by smaller ones. As stimulus strength increased, the larger nerve fibres began firing followed by the activation of the smaller ones (refer to Figure 2). At the maximal stimulus a constant pattern was formed. This was because all the nerve fibres were now firing and there were no further fibres to be activated.

Every minute of the day, there are billions of sensory information that neurons collect and translate into action potentials and neurotransmitters. Depending on the stimulus, the action potential could change in amplitude, frequency, and velocity. This phenomenon is an allusion to what I have done in lab. Increasing the stimulus would increase amplitude, frequency, and decrease the time duration. A classic example that is related to the experiment I have performed is pinching the skin. When we were all little kids, pinching was a generic behavior done when someone made us angry. However, pinching is pertinent to the electric stimulus that was used on the earthworm's nerve cord. When someone gets pinched, stretch receptors detect this information

Caliandro et al. have reported that in normal subjects FDI-CV is faster than ADM-CV. Considering that the conduction velocity of each axons is associated with the external nerve fibre diameter ,they suggested that , higher diameter of fastest fibers to FDI than ADM could explain the findings. Moreover, susceptibility to damage is higher in fibres to FDI than ADM(19).

To test the possibility that inhibition effect was generated from the use of only two alternative peripheral stimuli, following experiment was carried out. A central box and four peripheral boxes were used in the experiment and the positive IOR result ruled out the possible explanation that inhibition limited to the two alternative boxes.

Large, fast-conducting fibres (α and β fibres) inhibit small, multi-synaptic, slow-conducting fibres (C-fibre) at the dorsal horn.13 Gaps were missing within this research due to available research resources; Noordenbos13 was unable to investigate past the spinal cord. This statement was unexplained yet it was a development in pain research. Melzack and Wall2 developed the pain-gate theory based from the research by Noordenbos13. The theory explained what Noordenbos13 was unable to prove; impulses are projected to the brain via the dorsal column, where central processes influence the activity of the gate-control system.2

Briefly, CVs were estimated for epochs of 30 consecutive trials. Sample variances (SVs) were calculated for EPSC amplitudes and for noise sweeps. The CV was calculated as the square root of the difference for the sample variances [SV(EPSC) - SV(Noise)], divided by the mean. For minimal stimulation experiments, the frequency of presynaptic stimulation was set at 0.33 Hz. After obtaining small (>40 pA) EPSCs at -80 mV, stimulation intensity was reduced in small increments to the point that failures versus successes could be clearly distinguished visually. Stimulation intensity and frequency were then kept constant for the rest of the experiment. Failures versus successes were defined visually. Percent silent synapses were calculated using the following equation: 1 - Ln(F -80 )/Ln(F +40 ), in which F -80 was the failure rate at -80 mV and F +40 was the failure rate +40mV.In the CV and minimal stimulation assays, the types of cells were blinded for the experimenters. The phenotypes of the cells were decoded only after all data analysis was completed.

Voluntary and involuntary reactions to intense sensory stimulation provide a gateway to investigate underlying psychophysiological processes in the brain such as attention, motor planning, and fear conditioning. Yet, little attention has been paid to how time varying fluctuations in brain excitability affect these reactions. Using a combination of classic psychophysiological techniques and novel neuromodulatory techniques, this project seeks to provide greater understanding of how the dynamic changes occurring in the brain shape the manifestation of voluntary and involuntary responses. This fundamental knowledge will have important implications across many fields, including cognitive neuroscience, sports science, and applied

Many factors, including receptor function, neuron stimulation, length/complexity of neuronal pathway, difference between sensory/motor neuron conduction velocities and synaptic transmission, influence the reaction time. Of utmost importance is the synaptic transmission, which refers to how presynaptic cells communicate with postsynaptic cells by releasing neurotransmitters which, when collected at the postsynaptic cells receptors, work to engage a response. This process has the potential to be altered for any duration of time by either improving or impairing its potential. Postsynaptic neurons receive both excitatory and inhibitory inputs, which have the capability to increase or decrease the likelihood of the nerve firing an action potential. Both types of input are being applied to the receptor at all times while

The time needed to perceive a sensory input and then formulate a response is influenced by several factors. The multifaceted nature of transforming the detected stimulus into an electrical signal that can be communicated by the means of action potentials, the quantity of neural synapses before the impulse is derived to the cortex, and the length the signal must travel before arriving at the cortex are all factors that influence this process. We can observe these effects by using two push buttons, a reflex hammer, a goniometer with straps, and the Jendrassik maneuver. In addition, we can gain insight into how a motor response can be generated without first being communicated to the cortex by pairing the patella tendon stretch

Learning is described as reasonably lasting change in behavior through a variety of experiences (Terry, 2009). Typically, learning evolves sensory learning such as habituation, perceptual learning, experiencing different stimulus influences, or simple stimulus learning (Terry, 2009). Normally stimulus in an individual’s environment will evoke a response. When a person is exposed to the same stimulus continually it causes a decrease in the response, this is called habituation. For instance, the sound of a bell might at first capture your attention. However, after hearing the sound of the bell over and over again, you might become less distracted as the response to the stimulus decreases. The decreased response

Neurophysiology provides a range of important clinical investigations to that aid in the diagnosis and management of patients suffering from neurological disease. This experiment investigates the mechanisms behind two pathologies pertaining to channelopathies and demyelination: epilepsy and multiple sclerosis. This is done using a patch clamp technique, a laboratory technique in electrophysiology that allows the study of single or multiple ion channels in cells. Conditions were simulated using computer software to test the hypothesized mechanism behind epilepsy with understanding that it was due to an increase in the time constant, which would enable frequent neuron activations to occur simultaneously. Manipulations of stimulus impulse in refractory periods had proven this mechanism to be correct. Investigating the basis for multiple sclerosis, it was hypothesized that the cooling of impulse invasions would improve the demyelinated region of an axon by decreasing voltage, which was found to be an accurate phenomenon.

The series of EPSPs added together is the process of summation. If the threshold is reached, then an action potential is generated. There is a synaptic delay within the arrival of stimuli at the presynaptic knob and the result of the stimuli on the postsynaptic membrane. This delay is about 0.2 to 0.5 milliseconds long. The synaptic delay is a result of the increased concentration of calcium ions and the release of the ACh.

The purpose of this lab is to examine the waveform characteristics of action potentials using standard intracellular recording techniques. In the first set of experiments, students will use a glass microelectrode to record from a giant algal cell. Then, students will generate an action potential in a giant algal cell. If ion concentrations remain constant inside the cell, then the

 Attach a copy of your experimental recordings showing a period of spontaneous contractions and the response to stimulating the nerves at 20 Hz with both a voltage that produced only a modest response and the voltage that produced the maximal response.