Properties of the Isolated Mammalian
( G. I. Motility Lab )
By : K Boparai
Instructor : S Sundaram
December 09, 2002
If we were to compare smooth muscle with skeletal muscle we notice that they are very different from one another. Firstly, smooth muscles have a slow cycling of myosin cross bridges as compared to skeletal muscle. However, the fraction of time that the cross bridges remain attached to the actin filaments is believed to be greatly increased in smooth muscle. Secondly, Less energy is required to sustain the same tension of contraction in smooth muscle as in skeletal muscle. Thirdly, The maximum force of contraction of smooth muscle is often even greater than that of skeletal muscle. This great force of smooth muscle contraction results from the prolonged period of attachment of the myosin cross-bridges to the actin filaments.
The Gastrointestinal tract has 2 major networks of nerve fibers - Myenteric plexus and the Submucous plexus. The plexuses are interconnected, and they contain motor neurons that innervate the smooth muscle. This is the enteric nervous system. The intestine also receives a dual extrinsic innervation from the autonomic nervous system, with p
This causes an increase in the acetylcholine levels everywhere Acetylcholinesterase is found. Cold Water - From all the chemistry classes that we"tmve taken over our course of classes, we know that decreasing temperature results in decrease of rate of reaction. arasympathetic cholinergic activity generally increasing the activity of intestinal smooth muscle and the sympathetic noradrenergic activity generally decreasing it while causing the sphincters to contract. Vasopressin (ADH) - It is a polypeptide hormone secreted by the posterior pituitary gland. Therefore, the force of contraction of smooth muscle is highly dependent on the extra cellular fluid calcium ions concentration. Multi-unit smooth muscle is made up of individual units without interconnecting bridges. Its because the sarcoplasmic reticulum loses its supply of calcium ions and hence no calmodulin can bind to the calcium. Hall Textbook of Medical Physiology (10th edition). ADH secretion by the pituitary is regulated by neural connections from the hypothalamus, which is believed to monitor either the volume of blood passing through it or the concentration of water in the blood. Stretch is followed by a decline in membrane potential, an increase in the frequency of spikes and a general increase in tone. This can be explained by the following mechanism : In the smooth muscle, we find a large amount of calmodulin which is similar to troponin C in skeletal muscles. Its effects are mediated by V1 receptor found in vascular smooth muscle.