Muscle Memory Essay

LABORATORY REPORT Activity 2: Twitch Contractions and Summation PREDICTIONS Effect of Muscle Fiber Length on Contraction 1. As muscle fiber length increases: contraction force increases, becoming maximum at an optimal length, then decreasing at longer lengths. Effect of Stimulation Frequency on Contraction 2. As the frequency of stimulation increases, the force of contraction: increases. MATERIALS AND METHODS Measurement of Threshold Stimulus 1. Dependent Variable: contraction force. 2. Independent Variable: stimulation voltage 3. Controlled Variables: temperature, frequency of stimulation and muscle fiber length. Effect of Muscle Length on Contraction 1. Dependent Variable: contraction force. 2. Independent Variable: 60 Hz. 10. What was the maximum force generated in this experiment? 0.277 gf 11. How does increasing stimulation frequency affect force production? The tension produced during a sustained contraction is greater than that produced by a single twitch. The more stimuli per second, the greater the force generated by the muscle due to a

MATERIALS AND METHODS Experiment 1: Effect of Stimulus Strength on Action Potential Generation 1. Dependent Variable Membrane potential 2. Independent Variable Stimulus strength (voltage) 3. Controlled Variables Frequency of stimulation Type of neuron Experiment 2: Effect of Frequency of Stimulation on Action Potential Action potentials can occur more frequently as long there is a continued source of stimulation, as long as the relative refractory period has been reached, which in experiment 2 the refractory period was complete.

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.

References The Mechanism of Muscle Contraction. (n.a), (n.d) Retrieved on 26 June 2011 from http://meat.tamu.edu/muscontract.html 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

2. Depolarization in membrane potential triggers an action potential because nearby axonal membranes will be depolarized to values near or above threshold voltage.

11. Describe how the isolated muscle behaved as the stimulus interval was further decreased. As the intervals were reduced the twitches got closer together. Each curve, which represents a response to the stimuli, got closer until they finally became one. This represents summation which is when the muscle is unable to completely relax before

As the stimulus strengthens, action potentials are conducted at a greater speed, resulting in more tension and thus more force produced by the muscle. Wave summation occurs when a multitude of motor neuron signals are combined and increase to create greater muscle tension. As the stimulus strengthens the peak contractile force increases because the preceding twitch hasn't ended and is thus added to the new twitch - this building of tension increases the peak contractile force as stimulus

As result, the bonding causes the sodium and potassium gates to open. As result, end plate potential is formed and excites areas of muscle tissue. Action potential is created and the muscle moves or contracts.

Activity 7 1. Rank the conduction velocity in the axons A, B, C from fastest to slowest.

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

This is because once a contraction has started, the action potential has already fired, stimularing the muscle fibers. Once they

When a neuron depolarizes from its resting potential to its threshold potential, positively charged sodium ions rush down to the end of the neuron in the form of an action potential. Multiply the process by one-hundred billion, and you get the human brain. All these parts interact in a fast paced manner. Despite this, the

After the absolute refractory period, sodium channels begin to recover from inactivation and if strong enough stimuli are given to

As it is an extracellular recording, the sign of the voltage trace of the action potential is reversed. Besides, the amplitude is much smaller than for intracellular recordings. Then, we used Matlab to extract the waveforms from the first day and the waveforms from the second day from these extracellular data. The total number of observations for the first and second day’s data are 120407 and 80397, separately.

Elements 4 action causes the charge in the neuron to change from the negative passive to the positive firing state (Feldman, 2009, p.63). The velocity at which the neuron fires the message or impulse depends on the concentration level of the stimulus. As explained in the text, “when a nerve impulse comes to the end of the axon and reaches a terminal button, a chemical courier called a neurotransmitter is released (Feldman, 2009, p.65). For successful communication to happen between the neurotransmitter and the neuron, they must fit together perfectly. When a miscommunication happens, the chemical message is either excitatory or inhibitory.