A Biphasic Compound Action Potential

Next, the axon hillock, which is located at the end of the soma; controls the firing of the neurons. If the total strength of the signal exceeds the threshold limit of the axon hillock, the structure will fire a signal down the axon. The axon is the elongated fiber that extends from the cell body to the terminal endings and passes on the neural signal. The faster the information moves, the larger the axon is. Lastly, the terminal buttons, which are located at the end of the neuron are responsible for delivering the signal on to other neurons. At the end of the terminal button is a gap known as a synapse. The All-Or-None Law means that a neuron either fires or it doesn't, depending upon the number of excitatory and inhibitory inputs it gets. Each time it fires it does so with the same level of intensity; it has the possibility to fire more often, such as in signaling a tight squeeze from your head basketball coach, or less often, such as in signaling a gentle touch from a significant figure in you life. No matter the neuron, each time the action potential will be

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

Lightly myelinated Aδ fibers and unmyelinated C fibers have thinner axons and a higher threshold of activation. Nociceptors of Aδ fibers can be either mechanosensitive or thermosensitive. Polymodal nociceptors (of C fibers), may respond to both mechanical and thermal stimuli, as well as chemicals [261-263]. When nociceptors are activated, the fibers transmit action potentials along the axon to the spinal cord [264, 265]. The spinal cord mediates sensory and motor communication between the periphery and the brain, and is organized into four regions; cervical, thoracic, lumbar, and sacral. The gray matter contains cell bodies of neurons and glia and is divided into the dorsal horn, intermediate column, lateral horn, and ventral horn. The dorsal horn is comprised of sensory nuclei that receive and process incoming sensory information [266], and like the rest of the spinal gray matter, is organized histologically into parallel laminae based on the size and density of neurons [267]. In general, laminae I to IV are involved in exteroceptive sensation whereas laminae V and VI are involved in proprioceptive sensations [263]. Nociceptors terminate in the dorsal horn laminae in a

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.

The sciatic nerve is the one of the largest nerves in the human body. It is the major nerve of the lower limb and its approximately 2 cm wide (Savastrano). The sciatic nerve originates in the nerve roots of L4-S3, which begins in the lower back. The nerve then branches off down to the gluteal region and then down to the lower limb. One of its main functions is supply a pathway that provides a connection to the nervous system for all the sensory input that comes from the skin and muscles of the leg. The sciatic nerve comes from a formation of nerves called the lumbosacral plexus. This formation of nerves is made of anterior divisions of the lumbar, sacral and coccygeal nerves. As the nerve travels down to the pelvic area it divides into two nerve branches the tibial nerve and the common peroneal nerve. When patients under going a hip

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

The resting membrane potential is the difference between the outside and the inside cell membrane polarity. It is called a resting potential because it occurs when a membrane is not being stimulated or conducting impulses (Ritchison n.d.). This polarity can be measured and it is about -70mv. In the resting membrane potential, outside the cell has a more positive polarity and inside the cell has more negative polarity. There are more Na+ and Cl- on the outside and larger negative proteins (because they cannot go through the tiny pores to outside) and more K+ inside the cell (Ceballos, 2016).

The all-or-none principle states that the strength at which a muscle fiber or nerve may respond to a stimulus is independent of the strength of the stimulus. The axon hillock, or trigger zone, is the first place we see voltage gated ion channels. The action potentials from the trigger zone then go down the axon to the axon terminal. The action potential then communicates with it’s target.The nerve or muscle fiber will give a complete response if the stimulus exceeds the threshold potential, otherwise it will give no response at all. The “all” part of the all-or-none principle happens when the stimulus produces a depolarizing graded potential that is able to reach threshold and are constant in magnitude.If it does not reach threshold its returns

For this experiment, different aspects of the nervous system and skeletal neuromuscular system were analyzed. The nervous system is important when it comes to senses and this connects to the afferent and efferent systems and integrating centers (Sherwood, 2010). Afferent systems are responsible for collecting sensory information and relaying it to the integrating center where the efferent neurons then send a response back to the muscles (Sherwood, 2010). This is important and was focused on in many of these labs. Another important aspect of this lab was the spinal cord reflex arcs. The main function of this mechanism is again related to the body sensing a sensation and the spinal cord receiving the information and sending out a response. (Stevens, 1960) The spinal cord is in charge of responding to the different information that the body senses. If this was not such, the body would not be able to feel sensations. This can be seen when there is damage to the spinal cord. If there is any damage then the information “felt” below the damage would not be sensed (Sherwood, 2010). These experiments were done in order to connect the functions of the nervous system to their effect on the muscles coordinating movements and actions. There were four separate hypotheses that needed to be tested for this lab report. First, body parts that are primarily used for touch will have a lower two-point threshold than parts that are not primarily used for touch. Second, stimulation will cause a

Chapter two of our textbook explains the cells of the nervous system and nerve impulses. The nervous system consists on two types of cells: neurons and glia. “Neurons receive information and transmit it to other cells” (Kalat 28) . Glia do not transmit information, but they have many different types with many different functions (Kalat 33) . Dendrites and axons both branch off from the neuron. Dendrites receive information from other neurons and axons send the information to other neurons (Kalat 30) . Dendrites and axons “can change their branching patterns as a function of experience, age, and chemical influences” (Kalat 27). Each adult has an estimate of 100 billion neurons in their brain alone (Kalat 28).

The early evidences of presynaptic modulation of sensory afferents were important for the development of a model to explain how nociception processing happens, the Gate Theory of Pain. In this model, the balance between nociceptive input from large and small sensory fibers determines whether or not T-cells (pain afferent cells that projected to the forebrain) will fire and trigger the Action System, which will promote responses to the painful stimuli. Increase in T-cells excitability can be produced by small fibers (Aδ and C fibers) activation, thus unbalancing the net nociceptive input towards the activation of pain pathways. On the other hand, selective activation of large fibers (Aα and Aβ fibers) reduces excitability of T-cells by reducing

There are five steps in a reflex arc, which allows for impulse actions to occur called reflexes. The first step is when the receptor senses a stimulant. The next step occurs when the sensory neuron transmits nerves impulses to the spinal cord from the nerve and root. The third phase is when the sensory neuron goes through a neuronal junction with an interneuron; this occurs in the spinal cord. The fourth step is when the interneuron goes through neuronal junction with a motor neuron. Then the last step is when the motor neuron impulses through the spinal nerve and root to an effector structure. In summary, the receptor senses the action, then the sensory neuron transports the stimulus near the spinal cord, then the interneuron spreads the urge

Action potential is an all-or-none response like firing a gun. It begins with a membrane that is outwardly positive and inwardly negative in terms of charge. Sodium is on the outside, and potassium is on the inside. When a stimulus occurs, depolarization takes effect and sodium diffuses into the cell. The reversed polarity initiates an action potential.

For all aspects of this lab to be properly understood, the following principles and associated information of the following must be known: the relationship between nerves and their associated muscle(s), how electrical activity is

A standard nerve chamber called BIPOAC was used in this experiment; the nerve along with the muscle was placed on the electrodes of this chamber. An amplifier with a 100 AC gain and filter band pass of 0.1-Hz to 10Hz sampled by IGOR software was used to amplify the response of the nerve when stimulus is applied. IGOR is an integrated program for visualizing, analyzing, transforming and presenting data. Using this program the thresholds of the compound action potential, end plate potential, the conduction velocity and the paired pulse facilitation in the sciatic nerve of the frog was found. IGOR traces obtained using various stimuli are important in understanding nerve stimulation and