Exam 2: Cardiac Muscle and Smooth muscle Flashcards
Contraction Types
Contraction Types
Skeletal - attached to bone
* Striated Voluntary muscle
Caridac - form the walls of the heart
* Striated involuntary muscle
Smooth - forms the wallks of most hollow internal organs
* Non-striated involuntary muscles
Smooth Muscle
Smooth Muscle
Present in almost all organ systems
1. Integument - blood vessels, arrector pili muscles
2. Cardiovascualr - encircle blood vessels, control distribution of blood, help regulate blood pressure
3. Respiratory - contraction or relaxation alters diamaters of respiratory passageways
4. Digestive System - Control Movement of materials through digestive system
5. Urinary System - Urinary bladder, ureters, kidney blood vessels
6. Reproductive Tract - uterus
Multiunit Syncytium
Multiunit Syncytium
Syncytium = fused mass of cells
Skeletal muscles = not a syncytium
* multinucleate cells formed by fucsion of many myoblasts during embryogenesis
* cells linked by connective tissue layer that fuse to form tendons
Cardiac Muscle = Syncytium
* Cells linked by gap junctions and desmosomes into function syncytium
Smooth muscle = syncytium
* Cells linked by gap junctions and dense bodies into function syncytium
Cardiac Muscle Intercalated Disks
Cardiac Muscle Intercalated Disks
Desmosomes provide structural atachment
* Intergral membrane proteins and proteoglycans link opposing cell membranes
* myofibrils are anchored to desmosomes
Gap junctions hold cells together with membrane chanel proteins
* Form narrow passageways between cytoplasms of both cells
* Create eletrical connections
Comparison - Filament Originization
Comparison - Filament Originization
- Skeletal Muscle - Striated - actin and myosin fibers arranged in sarcomeres
- Cardiac Muscle - Striated - actin and myosin fibers arranged in sarcomeres
- Smooth Muscles - Non-striated - actin and myosin fibers not orginized sarcomeres
Smooth Muscle Myofilament Orginization
Smooth Muscle Myofilament Orginization
- Thick filaments scatterd through out sarcoplasm
- Thin filaments attached to dense bodies
- Some dense bodies at intersections of cytoskeletal frameworl
- Some dense bodies firmly attached to plasma membrane
- Dense Bodies can link adjacent muscles
- Sliding of thcik and thin filaments cause cell to shortern and twist
Smooth Muscle Contraction
Smooth Muscle Contraction
Length-Tension Relationship
* Tension development and resting length not directly related
* Plasticity - stretched muscle adapts to new length and retains ability to contract and produce tension
* Contractions can be just as powerful as those of skeletal muscles
* Can undergo sustained Tetanic contractions
Comparison Contraction Type
Comparison Contraction Type
Skeletal
* Tetanic contractions produce greatest tension
* Summation of tension as stimulus frequency increases
Cardiac
* Twitch contractions only
Smooth
* Tetanic contractions produce greatest tension
* Summation of tesnion as action potential frequency increases
Comparison - control mechanisms
Comparison - control mechanisms
Skeletal: Voluntary Muscle
* Controled by Motor Neuron of voulntary nervous system
* Motor Unit - motor neuron branches to synapse on several muscle cells
Cardiac: Involuntary muscle
* Controlled by pacemaker cells, autonomic nervous system
Smooth: involuntary muscle
* Controlled by pacesetter cells, hormones, autonomic nervous system
Cardiac Muscle - Control of Contraction
Cardiac Muscle - Control of Contraction
- Automaticity - can contract without neural stimulation
- Timing of contractions determined by specialized Pacemaker cells
- Rate of pacemaker cells and amount of tension can be modified
- Innervated by motor neurons of autonomic nervous system (Sympathetic - speeds up heart rate, Parasympathetic - slows down heart rate)
Smooth Muscle - Control of Contraction
Smooth Muscle - Control of Contraction
Visceral Smooth Muscle Cells
* Connected by gap junctions into large syncytia arranged in sheets or layers
* Automaticity - pacesetter cells can trigger rythmic contractions
* Stimuli from autonomic nervous system can control contraction frequency
Multi-unit smooth muscle cells
* Not connected by gap junctions
* Each cell innervated by oner or more motor neurons of the autonomic nervous system
Comparison - Energy Source
Comparison - Energy Source
Skeletal
* Aerobic metabolism at moderate activity, anaerobic metabolism during peak activity
Cardiac
* Aerobic metabolism
* Myoglobin and mitochondria content is high
Smooth
* Aerobic metabolism at moderate activity (typical), anaerobic metabolism during peal activity (rare)
