Smooth muscle cell

From The School of Biomedical Sciences Wiki
(Difference between revisions)
Jump to: navigation, search
(Added links and rearranged references,)
(Cleaned up the text. Moved image.)
 
(One intermediate revision by one user not shown)
Line 1: Line 1:
Smooth muscle has elongated spindle shaped cells with a single [[Nucleus|nucleus]]. Unlike [[Skeletal Muscle|skeletal muscle]], which appears [[Striated muscle|striated]] when stained and viewed under a light microscope, the contractile filaments in smooth muscle cells aren't arranged in such an ordered, linear way. The contractile proteins are [[Actin|actin]] and [[Myosin|myosin]], the same as in skeletal muscle cells.The amount of [[Myosin|myosin]] in smooth muscle cells is considerably less than in cells of skeletal muscle; the ratio of [[Actin|actin]] to [[Myosin|myosin]] is about 15:1 for smooth muscle, compared to only 2:1. Smooth muscle cells are located within the walls of tubular or hollow organs or vessels for structural support. These can be divided into subtypes of smooth muscle cells; those in the vascular system, [[Respiratory system|respiratory system]], intestines, the eye and reproductive organs.<ref>Alberts, B. (2002). Molecular biology of the cell (4th ed.). New York: Garland Science.</ref>  
+
[[Image:Smooth muscle.jpg|right|Smooth muscle.jpg]]Smooth muscle has elongated spindle-shaped cells with a single [[Nucleus|nucleus]]. Unlike [[Skeletal Muscle|skeletal muscle]], which appears [[Striated muscle|striated]] when stained and viewed under a light microscope, the contractile filaments in smooth muscle cells aren't arranged in such an ordered, linear way. The contractile proteins are [[Actin|actin]] and [[Myosin|myosin]], the same as in skeletal muscle cells.The amount of [[Myosin|myosin]] in smooth muscle cells is considerably less than in cells of skeletal muscle; the ratio of [[Actin|actin]] to [[Myosin|myosin]] is about 15:1 for smooth muscle, compared to only 2:1. Smooth muscle cells are located within the walls of tubular or hollow organs or vessels for structural support. These can be divided into subtypes of smooth muscle cells; those in the vascular system, [[Respiratory system|respiratory system]], intestines, the eye and reproductive organs<ref>Alberts, B. (2002). Molecular biology of the cell (4th ed.). New York: Garland Science.</ref>. [[Muscle contraction|Contraction]] of smooth muscle is controlled by the [[Autonomic Nervous System|autonomic nervous system]], meaning its movements are primarily involuntary. However, as opposed to skeletal muscle, it can also be controlled by chemical and physical signals. This means that either an action potential is required to cause a change in membrane potential, or the opening of stretch-mediated ion protein channels; they both bring about contraction<ref>American Physiology Society. Advances in Physiology Education: Smooth Muscle Contraction and Relaxation (2014) Available at: http://advan.physiology.org/content/27/4/201</ref>.
  
[[Muscle contraction|Contraction]] of smooth muscle is controlled by the [[Autonomic Nervous System|autonomic nervous system]], meaning its movements are primarily involuntary. However, as opposed to skeletal muscle, it can also be controlled by chemical and physical signals. This means that either an action potential is required to cause a change in membrane potential, or the opening of stretch-mediated ion protein channels; they both bring about contraction.<ref>American Physiology Society. Advances in Physiology Education: Smooth Muscle Contraction and Relaxation (2014) Available at: http://advan.physiology.org/content/27/4/201</ref>
+
Smooth muscle cell contraction is regulated by the calcium-binding protein [[Calmodulin|calmodulin]]. When there is an increase in calcium ion concentration, [[Calmodulin|calmodulin attaches]] to [[Caldesmon|caldesmon]], which is an [[Actin|actin]]-binding protein. [[Caldesmon|Caldesmon]] normally blocks the [[Myosin|myosin]]-binding sites on [[Actin filaments|actin filaments]]. As [[Calmodulin|calmodulin]] attaches to caldesmon it releases actin, causing the [[Myosin|myosin]] heads to bind to the [[Actin filaments|actin filaments]]. The globular heads that protrude from the [[Myosin|myosin molecule]] bind to the [[Actin|actin]] filament which forms cross-bridges. The [[Myosin|myosin moves]] along the actin and then releases from the actin (also requiring the use of ATP). [[Contraction|Contraction]] is initiated by calcium-regulated [[Phosphorylation|phosphorylation]] of myosin<ref>Walter F. Boron, E. L. (2009). Medical Physiology (2nd ed.). Philadelphia: Saunders Elsevier.</ref>. Apart from calcium ions, smooth muscle activity can also be regulated by external signalling molecules, for example, [[Adrenaline|adrenaline]]. When [[Adrenaline|adrenaline]] binds to the receptor and changes its shape, this in turns alters the structure of the [[G-protein|G- protein]] that binds to the receptor. This causes an increase of level of [[Cyclic AMP|cyclic AMP]] inside the cell, which activates [[Protein kinase|protein kinase]]. This then phosphorylates and inactivates [[Myosin light chain kinase|myosin light chain kinase]], eventually leading to relaxation of the smooth muscle. Smooth muscle contraction is significantly slower than skeletal muscle contraction. It usually takes nearly a second whereas skeletal muscle takes a few milliseconds<ref>Silverthorn D, Johnson B, Ober W and Silverthorn C. (2012) Human Physiology: An Integrated Approach. 6th Edition</ref>.  
 
+
Smooth muscle cell contraction is regulated by the calcium binding protein&nbsp;[[Calmodulin|calmodulin]]. When there is an increase in calcium ion concentration, [[Calmodulin|calmodulin attaches]] to [[Caldesmon|caldesmon]], which is an [[Actin|actin]]-binding protein. [[Caldesmon|Caldesmon]] normally blocks the [[Myosin|myosin]]-binding sites on [[Actin filaments|actin filaments]]. As [[Calmodulin|calmodulin]] attaches to caldesmon it releases actin, causing the [[Myosin|myosin]] heads to bind to the [[Actin filaments|actin filaments]]. The globular heads that protrude from the [[Myosin|myosin molecule]] bind to the [[Actin|actin]] filament which forms crossbridges. The [[Myosin|myosin moves]] along the actin and then releases from the actin (also requiring the use of ATP). [[Contraction|Contraction]] is initiated by calcium-regulated [[Phosphorylation|phosphorylation]] of myosin<ref>Walter F. Boron, E. L. (2009). Medical Physiology (2nd ed.). Philadelphia: Saunders Elsevier.</ref>. Apart from calcium ions, smooth muscle activity can also be regulated by external signalling molecules, for example, [[Adrenaline|adrenaline]]. When [[Adrenaline|adrenaline]] binds to the receptor and changes its shape, this in turns alters the structure of the [[G-protein|G- protein]] that binds to the receptor. This causes an increase of level of [[Cyclic AMP|cyclic AMP]] inside the cell, which activates [[Protein kinase|protein kinase]]. This then phosphorylates and inactivates [[Myosin light chain kinase|myosin light chain kinase]], eventually leading to relaxation of the smooth muscle. Smooth muscle contraction is significantly slower than skeletal muscle contraction. It usually takes nearly a second whereas skeletal muscle takes a few milliseconds<ref>Silverthorn D, Johnson B, Ober W and Silverthorn C. (2012) Human Physiology: An Integrated Approach. 6th Edition</ref>.&nbsp;
+
  
 
=== References  ===
 
=== References  ===
  
<references />&nbsp;
+
<references />  
  
 
<br>
 
<br>

Latest revision as of 19:45, 4 December 2017

Smooth muscle.jpg
Smooth muscle has elongated spindle-shaped cells with a single nucleus. Unlike skeletal muscle, which appears striated when stained and viewed under a light microscope, the contractile filaments in smooth muscle cells aren't arranged in such an ordered, linear way. The contractile proteins are actin and myosin, the same as in skeletal muscle cells.The amount of myosin in smooth muscle cells is considerably less than in cells of skeletal muscle; the ratio of actin to myosin is about 15:1 for smooth muscle, compared to only 2:1. Smooth muscle cells are located within the walls of tubular or hollow organs or vessels for structural support. These can be divided into subtypes of smooth muscle cells; those in the vascular system, respiratory system, intestines, the eye and reproductive organs[1]. Contraction of smooth muscle is controlled by the autonomic nervous system, meaning its movements are primarily involuntary. However, as opposed to skeletal muscle, it can also be controlled by chemical and physical signals. This means that either an action potential is required to cause a change in membrane potential, or the opening of stretch-mediated ion protein channels; they both bring about contraction[2].

Smooth muscle cell contraction is regulated by the calcium-binding protein calmodulin. When there is an increase in calcium ion concentration, calmodulin attaches to caldesmon, which is an actin-binding protein. Caldesmon normally blocks the myosin-binding sites on actin filaments. As calmodulin attaches to caldesmon it releases actin, causing the myosin heads to bind to the actin filaments. The globular heads that protrude from the myosin molecule bind to the actin filament which forms cross-bridges. The myosin moves along the actin and then releases from the actin (also requiring the use of ATP). Contraction is initiated by calcium-regulated phosphorylation of myosin[3]. Apart from calcium ions, smooth muscle activity can also be regulated by external signalling molecules, for example, adrenaline. When adrenaline binds to the receptor and changes its shape, this in turns alters the structure of the G- protein that binds to the receptor. This causes an increase of level of cyclic AMP inside the cell, which activates protein kinase. This then phosphorylates and inactivates myosin light chain kinase, eventually leading to relaxation of the smooth muscle. Smooth muscle contraction is significantly slower than skeletal muscle contraction. It usually takes nearly a second whereas skeletal muscle takes a few milliseconds[4].

References

  1. Alberts, B. (2002). Molecular biology of the cell (4th ed.). New York: Garland Science.
  2. American Physiology Society. Advances in Physiology Education: Smooth Muscle Contraction and Relaxation (2014) Available at: http://advan.physiology.org/content/27/4/201
  3. Walter F. Boron, E. L. (2009). Medical Physiology (2nd ed.). Philadelphia: Saunders Elsevier.
  4. Silverthorn D, Johnson B, Ober W and Silverthorn C. (2012) Human Physiology: An Integrated Approach. 6th Edition


Personal tools
Namespaces
Variants
Actions
Navigation
Toolbox