| What muscle is used for the digestion process? | Smooth muscle |
| Where can smooth muscle tissue be found (in terms of the digestive system) | Smooth muscle is primarily found in the walls of Viscera |
| What are characteristics of smooth muscle tissue? | Fibers are elongated
One centrally located nucleus
Grouped into sheets
- creates a longitudinal and circular layer |
| Name structures (both blue and green region) | blue region: Longitudinal layer of smooth muscle
green region: Circular layer of smooth muscle |
| What is the function of the Longitudinal layer? | The longitudinal layer causes organ dilation and shortening |
| what is the function of the circular layer? | the circular layer causes organ constriction and elongation |
| What innervates the smooth muscle? | Autonomic nervous system fibers
- sympathetic motor fibers
-parasympathetic motor fibers
- Visceral sensory fibers |
| Name structure covered | Autonomic nerve fibers in smooth muscle |
| Name structure covered | Varicosities |
| Define Varicosities | release their neurotransmitters into a wide synaptic cleft. |
| What stimulates contraction? | Entry of Calcium into the Sarcoplasm stimulates contraction |
| What is the process of contraction? | 1. Calcium enters the sarcoplasm from the sarcoplasm reticulum or extracellular fluid and makes it way to the cytosol.
2. Calcium binds and activates calmodulin
3. The activated calmodulin activates the kinase enzymes
4. Kinase enzymes catalyze transfer of phosphate to myosin
5. Activated myosin forms cross bridges with actin of the thin filaments and shortening begin. |
| Is smooth muscle contraction fast or slow? | contraction is slow and sustained
- takes 30x longer to contract and relax
- resistant to fatigue
-energy requirements are low (so mitochondria is not abundant) |
| Where are contractions over long periods needed? | smooth muscle of arteries and visceral organs must sustain contraction over long periods. |
| Smooth muscle fibers contract or relax in response to.... | - action potentials from ANS
- stretching
-hormones
-changes in pH, oxygen/carbon dioxide levels, tempature |
| Name the structure covered | Intermediate filament bundles
- thick filaments (myosin)
- thin filaments (actin) |
| Name structure covered | Dense Bodies |
| Define Dense bodies | Dense bodies function the same way as Z discs.
During contraction, sliding myofilaments shorten the muscle cell by pulling on the dense bodies and overall the cytoskeleton.
Causes a squeezing movement |
| Name structure covered | Caveolae |
| Define Myenteric Nerve Plexus | a nerve plexus situated in the muscular layers of the intestines |
| Where is the myenteric nerve plexus? | Myenteric nerve plexus lies between the circular and longitudinal muscularis. |
| What is the function of the Myenteric Nerve Plexus | Controls peristalsis and segmentation
- mainly controls GI motility (increases number and speed of contractions) |
| Name the structure | Myenteric nerve plexus |
| Where is the Submucosal nerve plexus found? | lies in the submucosa of the intestinal wall and is derived from the myenteric plexus. |
| What is the function of the submucosal nerve plexus? | signals glands to secrete.
- helps control intestinal secretion, absorption, blood flow, and local contraction. |
| Name structure | submucosal nerve plexus |
