Contraction in Smooth vs. Skeletal Muscle

Smooth muscle



Smooth muscle is a type of non-striated muscle, found within the tunica media layer of large and small arteries and veins, the bladder, uterus, male and female reproductive tracts, gastrointestinal tract, respiratory tract, the ciliary muscle, and iris of the eye. The glomeruli of the kidneys contain a smooth muscle-like cell called the mesangial cell. Smooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure, function, excitation-contraction coupling, and mechanism of contraction.

* Cystolic Ca2+ binds with calmodulin in cytosol
* Ca2+ calmodulin complex binds to myosin light chani kinase
* myosin light chain kinase used ATP to phosphorylate myosin cross bridges.
* Phosphorylated cross bridges bind to action filaments
* Cros-bridge cycle produces tension and shortening







Skeletal muscle



Skeletal muscle is a type of striated muscle, which usually attaches to tendons. Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction. They generally contract voluntarily (via somatic nerve stimulation), although they can contract involuntarily through reflexes. The whole muscle is wrapped in a special type of connective tissue, epimysium.

* Cytosolic ca3+
* ca 2+binds to troponin on the filaments
* Conformatioal change in troponinm moves tropomyosin out of blocking position
* Mysosin cross bridges bund to action
* Cross-bridge cycle produces tension and shortening

Synaptic Transmission

Synaptic transmission is the process whereby one neuron (nerve cell) communicates with other neurons or effectors, such as a muscle cell, at a synapse. A typical neuron has a cell body (soma), branching processes specialized to receive incoming signals (dendrites), and a single process (axon) that carries electrical signals away from the neuron toward other neurons or effectors. Electrical signals carried by axons are action potentials. Axons often have thousands of terminal branches, each ending as a bulbous enlargement, the synaptic knob or synaptic terminal. At the synaptic knob, the action potential is converted into a chemical message which, in turn, interacts with the recipient neuron or effector. This process is synaptic transmission.








Steps in Synaptic Transmission



Information has to travel from one neuron to next, it must be transferred across synaptic cleft, neuro transmitters are chemical messengers that bridge the gap formed by synapes, neurotransmitters are stored in synaptic vesicles at the end of axons. As the action potential reaches the terminal end of the axon, calcium influx through the calcium channels causes these vesicles to fuse with pre-synaptic membrane, the vesicles then dump their contents which are neuro transmitters into the synaptic cleft, the neuro transmitters then diffuse with the post synaptic membrane and bind to specific receptors, however neuro transmitters only act for the brief time, their action is terminated by reuptake pumps that force neurotransmitters back into axon terminal or sometimes by enzymatic degradation in the synaptic cleft ,this removes the neurotransmitters from the synaptic cleft and terminates its effect on post synaptic membrane. Animation showing neurotransmission across the synaptic cleft.