Electric eels are capable of generating powerful shocks that can immobilize prey. Discharges emitted from volleys into the environment can cause prey in hiding to experience involuntary muscle twitching causing it to be revealed to the eel. The revelation of hidden prey allows the eel to continue its attack and go into predatory strike mode. This study (Catania, 2014) sets out to show that the powerful shocks produced by eels activate motor neurons in their prey causing muscle contractions in the prey to be temporarily halted and the eel to be able to control their target through high-frequency volleys.
An eel was placed in a naturalistic experimental environment with other fish and the fishes’ response to high-voltage pulses was observed. If there was a strong enough discharge, the fish was unable to move on its on accord and was captured by the eel. A pitched fish was placed behind an agar barrier, which received the same discharge as the eel directed toward earthworms placed in the same environment. In order to determine if the discharges induced the muscle movement by initiating action potentials or by activating the motor neurons in the fish, two fishes were pitched; one of the fish was injected with an AcH antagonist and the other was injected with a placebo. To test doublet and triplet discharges
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A sharp rise in fish tension occurred after the pitched fish received a strong pulse. When the eel was separated from the fish by an agar barrier, the eel was still able to detect the fish movements and attack accordingly. When the two pitched fishes were compared, the results suggested that the motor neurons were activated to cause muscle movement. In response to the artificial movements of the fish in the plastic bags, the eels only followed a doublet if there was confirmation that there was actual movement from the fish, so it could release the full strength
Remove the cockroach from it habitat and submerge it in ice water for a few seconds to paralyze it. After the cockroach is paralyzed, using the surgical tools cut a leg (at the hip). The leg should be placed on the cork of the spike box, allowing a bit of the leg to overhang. The stimulation electrode should be placed on the femur and COXA then the electrodes should be connected to the output of the TENS electrical stimulator. Using the provided LabVIEW program, the onset stimulation delivered to the leg as well as its duration can be controlled. The stimulator should be turned on with the correct corresponding channels by turning the knob clockwise, the current intensity of the impulse increase further when the knob is turned clockwise. A
To send a message, a neuron will send a ripple of electrical energy down its axon. This ripple is called "action potential." The way it works is by changing the chemical makeup of the axon's negatively charged interior. Positively charged sodium ions move into the cell and negatively charged potassium ions move out, then the ions move to their original positions. This produces a wave of positively charged
Part 1: Recording the responses to sub-threshold, threshold, sub-maximal, maximal, and supra-maximal stimulation. The electrophysiological experiment of compound action potentials on bullfrog sciatic nerve trunk is a classic experiment in neuroscience. It is used to measure the conduction velocity of the nerve fibers in the
This creature emits a current of electricity when it feels threatened: Jelly Fish/ Electric Eel
Both electrical and chemical forces combine to determine the resting membrane potential of the cell. Although the resting membrane potential of most cells is normally negative, the selective permeability of the membrane allows certain ions in and out, causing the neuronal membrane voltage to become depolarized (more positive), or hyperpolarized (more negative). Key ions involved in muscle membrane potential are sodium, potassium, and chloride, which move via passive or active diffusion through ion channels and transporter pumps (Baierlein et al. 2011). The Nernst equation predicts the membrane voltage based on the assumption that the membrane is only permeable to one type of ion. In this investigation, we are seeking to understand the basis for how different ions interact to produce the membrane potential of DEM, DEL1, and DEL2 crayfish muscle
The results in Figure 2. show that increasing the stimulus strength (V) from 0 to o.40V will result in an increase of Active Muscle force generated by the gastrocnemius muscle in the Buffo Marinus, confirming the hypothesis. The force generated plateaus when the stimulus is beyond o.40V.
A simple spinal reflex is a reflex—involuntary, graded, patterned response to a stimulus—that is produced via a single synapse between sensory axons and motor neurons and confined to the spinal cord. In this experiment, two simple spinal reflexes—the myotactic reflex and the H-reflex—were stimulated. We compared a) the latency period—the amount of time between a stimulus and the effector response— and the amplitude—magnitude of an electrical signal—of each reflex; then, b) the effect of the Jendrassik Maneuver (JM) upon the latency period and amplitude of each respective reflex. For the myotactic response, a mechanical stimulus, a sharp strike of the patellar tendon, was utilized to elicit a signal in stretch receptors; however, to trigger the H-reflex, an electrical impulse was applied. These reflexes originate from an action potential produced by a sensory neuron when a stimulus is applied. Sensory neurons transmit the action potentials to an integrating center—the spinal cord—where a response is determined. Then, this response is taken back to the effector organ via motor neurons. The reflex occurs while the brain is becoming aware of the stimulus. Furthermore, the myotactic reflex is
Encyclopedia of Nursing & Allied Health. Bioelectricity: Transmission of nerve impulses to muscle. Retrieved on 26 June 2011 from http://www.enotes.com/nursing-encyclopedia/bioelectricity
Extracellular recording electrodes were used to measure the compound action potentials (CAPs) in a cockroach leg nerve. CAPs are the summations of all present action potentials (APs) in the individual axons of the nerve. When an AP is conducted along an axon, sodium channels open and positively charged sodium ions enter the axon. Therefore the inside and the outside voltage changes. The voltage changes in the extracellular fluid were measured. A depolarisation of the axonal membrane causes a local negative charge in the extracellular fluid. The summation of all the voltage changes in the extracellular fluid at a specific position is measured by the recording electrodes.
1. Number the events in the action potential in the order in which they occur.
Post-lab Quiz Results You scored 50% by answering 2 out of 4 questions correctly. 1. Which of the following is not one of the ways that the body can increase the force produced by a skeletal muscle? Your answer: b. application of high-frequency stimulation by a motor neuron Correct answer: d. application of higher voltages to the whole muscle 2. When a muscle receives a stimulus frequency that causes non-overlapping twitches to follow each other closely in time such that the peak tension of each twitch rises in a stepwise fashion up to a plateau value, the result is known as You correctly answered: c. treppe. 3. In this experiment the isolated skeletal muscle was repetitively stimulated such that individual twitches overlapped with each other and resulted in a stronger muscle contraction than a standalone twitch. This phenomenon is known as You correctly answered: c. wave summation. 4. Wave summation is achieved by Your answer: c. summating action potentials so that their depolarizing magnitude is greater. Correct answer: a. increasing the rate of stimulus delivery (frequency)
Homarus americanus has long served as an essential animal model for physiological and behavioral studies. Despite living in the water, the lobster is considered to have a sophisticated nervous system, where the heart is controlled by a central power generator (nine neurons form the cardiac ganglion). Its simple yet well-developed nervous system consequently establishes the lobster as an ideal model for understanding the effect of neuropeptides on the modulation and control of rhythmic movements in animals. The lobster’s growth and reproduction also operates under neuropeptidergic control, making neuropeptides a significant part of H. americanus’ physiology.
The compound action potential adds up all the action potentials that each individual neuron experiences in the sciatic nerve. Different stimulus amplitudes cause different neurons to fire an action potential; this is due to the fact that each neuron has a different threshold potential, or the minimum voltage the neuron needs to fire an action potential. The individual neuron action potential is an ‘all-or-nothing’ event, but the CAP, as a summation of different individual neurons, is not. The CAP amplitude will increase with larger stimulus potentials because more neurons with higher individual thresholds will be recruited. For this frog sciatic nerve, there are three fiber types, A, B, and C. A fibers are further divided, in the order of decreasing diameter, into α, β, γ, and δ fibers. There is an inverse relationship between the diameter of the nerve fiber and the threshold potential: the larger the diameter, the lower the threshold. Thus, as the largest fibers, the Aα neurons will be the first to be stimulated at a low stimulus potential, and the Aδ neuron fibers will be the last to be recruited. Because the sciatic nerve is mostly composed of A fibers, the recruitment of A-subtype nerve fibers are more readily distinguishable from the data. The minimum potential required to stimulate the Aα fibers was between 75 mV and 80 mV. Once the stimulus potential reached 90 mV, Aβ neurons were recruited and contributed to the increase in amplitude of the CAP. At a stimulus
Pinnington, N., Elliott, A., Sciences, F. of L., Manchester and Kingdom, U. (2007) Proceedings of the physiological society. Available at: http://www.physoc.org/proceedings/abstract/Proc%20Physiol%20Soc%208PC39 (Accessed: 3 March 2016).
The modalities could be utilised for multiple therapeutic purposes, as demonstrated, such as electric stimulation, neural recording and directed drug delivery. The combined use of the different modalities was shown to restore locomotion in paralyzed animals.