Essay Activity of Gastrointestinal Smooth Muscle Worksheet

Contractility of ASM requires an increased levels of intracellular Ca2+. When surface receptors are not activated, Ca2+ levels are low. Upon activation of these cell surface receptors by contractile agonists e.g. acetylcholine, serotonin and histamine, intracellular Ca2+ increases causing a contraction (9). Smooth muscle cell contraction is controlled by both receptor and mechanical activation of proteins actin and myosin and also changes to membrane potential.

The more stimuli per second, the greater the force generated by the muscle due to a

If acetylcholine is not liberated than it would also not cause an action potential which would not cause a muscle contraction.

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When the tissue was immersed in calcium free solution and stimulated with Ach via the PMC pathway, a small contraction (1.15g) was observed compared to the baseline contraction trace (6.37g). Contraction recovered when the bathing solution was changed back to normal Krebs (5.63g). For the next stimulus, K+-depolarising solution, the baseline control produced a force of 6.17g in normal Krebs solution. When calcium free K+-depolarising solution was used to stimulate the tissue in calcium free solution, via the EMC pathway, the tissue barely contracted at 0.09g. In the second experiment, verapamil was added to the bathing solution. When the tissue was stimulated by Ach in the presence of verapamil, it

As a result of the contractions in the Muscle- Skeletal Longitudinal Section cells and the Muscle- Skeletal Cross Section cells, it allows your muscle to be able to contract in response to nerve stimuli. This means that the movements of most of these muscles are not involuntary, you can control them. Therefore, once the stimulation stops, the muscles relax.

Next with a stimulation duration of 50us, the stimulus amplitude should be set to the maximal tolerable stimulus intensity. With stimulus frequency of 2Hz, observe and record the leg movement, increase it by 5Hz but should not exceed 50Hz. With the electrodes connected to the analogy output channel and ground of the DAQ board. With the corresponding LabVIEW program, the frequency and amplitude (voltage) of the stimulation supplied to the leg can be controlled. With this the “sweet spot” of the lowest amplitude and best frequency to cause evoked movement can be found and recorded. Now the stimulation frequency should be set to 10Hz and the duration of stimulation pulse to 5ms or less. The range if leg movement changes can be observed as amplitude changes. Electrical stimulation in increments of 0.01V should be delivered and the minimal voltage required to generate muscle twitch should be recorded. The pulse duration should then be increased by durations of 10ms and the minimum voltage should be recorded this should be repeated for a variety of pulse

Provide detailed descriptions and show all calculations used to arrive at solutions for the following questions:

In this exercise, you examined the effect of increasing stimulus intensity on the nerve. What other stimulus parameter

There are two neurons that link the CNS to the effector organ namely the pre-ganglionic neuron with a cell body in the CNS and a post-ganglionic neuron with a cell body located in an autonomic ganglion. The adrenal medulla is an exception, with it being connected directly to the preganglionic neuron. The main neurotransmitters are acetylcholine (ACh) and adrenaline. Preganglionic neurons for both sympathetic and parasympathetic are cholinergic, Releasing ACh. The ACh released binds to nicotinic receptors on the post-ganglionic neuron. Post-ganglionic neurons are also cholinergic in the parasympathetic, releasing ACh. This ACh bind to muscarinic receptors in target organs. However, the sympathetic post-ganglionic neurons are noradrenergic, releasing

f) Account for the response to acetylcholine in the two preparations. Which receptor(s) mediates the effects of acetylcholine in the rings with and without endothelium?

7. What effect does stretching the muscle have on contraction strength? Is this effect linear?

Exercise 2: Skeletal Muscle Physiology: Activity 3: The Effect of Stimulus Frequency on Skeletal Muscle Contraction Lab Report Pre-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1. During a single twitch of a skeletal muscle You correctly answered: b. maximal force is never achieved. 2. When a skeletal muscle is repetitively stimulated, twitches can overlap each other and result in a stronger muscle contraction than a stand-alone twitch. This phenomenon is known as You correctly answered: c. wave summation. 3. Wave summation is achieved by You correctly answered: a. increasing the stimulus frequency (the rate of stimulus delivery to the muscle). 4. Wave summation increases the force produced in the muscle.

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