muscles 5 Flashcards
skeletal muscle
attached to bone
-striated voluntary msucle
cardiac muscle
form the walls of the heart
-striated involuntary muscle
smooth muscle
forms the walls of most hollow internal organs
-non-striated involuntary muscle
Where is smooth muscle present?
-integument
blood vessels, arrestor pili muscles
-cardiovascular
encircle blood vessels, control distribution of blood, help regulate bp
-respiratory
contraction or relaxation alters diameters of respiratory passageways
-digestive system
control movement of materials through digestive
-urinary system
urinary bladder, ureters, kidney blood vessels
-reproductive tract
uterus
skeletal muscle size
diameter
-100um
Length
-up to 30 cm
cardiac muscle size
diameter
10-20um
length
-50-100um
smooth muscle size
diameter
5-10 um
length
30-200 um
syncytium
fused mass of cells
How are multinucleate skeletal muscle formed?
- formed by fusion of many myoblasts during embryogenesis
- cells linked by connective tissue layers tat fuse to form tendons
cardiac muscle syncytium
Cells linked by gap junctions and desmosomes into functional syncytium
Smooth muscle syncytium
Cells linked by gap junctions and dense bodies into functional syncytium
desmosomes
provide structural attachment
- integral membrane proteins and proteoglycans link opposing cell membranes
- myofibrils are anchored to desmosomes
gap junctions
hold cells together with membrane channel proteins
- form narrow passageways between cytoplasms of both cells
- create electrical connections
skeletal filament organization
Striated – actin & myosin fibers arranged in sarcomeres
Cardiac filament organization
Striated – actin & myosin fibers arranged in sarcomeres
Smooth filament organization
Non-striated – actin & myosin fibers not organized in sarcomeres
smooth muscle myofilament organization
Thick filaments scattered through out sarcoplasm
Thin filaments attached to dense bodies
how are thin filaments in smooth muscle arranged
attached to dense bodies
- Some dense bodies at intersections of cytoskeletal framework
- Some dense bodies firmly attached to plasma membrane
- Dense bodies can link adjacent muscle cells
How do the filaments move in smooth muscle?
sliding of thick and thin filaments causes cell to shorten and twist
length- tension relationship of smooth muscle
Tension development and resting length not directly related
plasticity of smooth muscle
stretched muscle adapts to new lengths and retains ability to contract and produce tension
Type of contractions of smooth muscle
can undergo titanic contractions and anaerobic metabolism
- Tetanic contractions produce greatest tension
- summation of tension as action potential frequency increases
Type of contractions of skeletal muscle
- Tetanic contractions produce greatest tension
- summation of tension as stimulus frequency increases
type of cardiac contractions
Twitch contractions only
Skeletal control mechanism with nerves
- controlled by motor neurons of voluntary nervous system
- Motor unit - motor neuron branches to synapse on several muscle cells
Cardiac control mechanism with nerves
controlled by pacemaker cells, autonomic nervous system
Smooth control mechanism with nerves
controlled by pacesetter cells, hormones, autonomic nervous system
Cardiac muscle control of contraction
- Automaticity – can contract without neural stimulation
- Timing of contractions determined by specialized pacemaker muscle cells
- Rate of pacemaker cells and amount of tension can be modified
how can the rate of pacemaker cells be modified?
Innervated by motor neurons of autonomic nervous system (sympathetic, parasympathetic)
-speed up or slow down depolarization
Smooth muscle control of contraction
- visceral smooth muscle cells
- multi-unit smooth muscle cells
visceral smooth muscle cells
- Connected by gap junctions into large syncytia arranged in sheets or layers
- Automaticity – Pacesetter cells can trigger rhythmic contractions
- Stimuli from autonomic nervous system can control contraction frequency
multi-unit smooth muscle cells
- Not connected by gap junctions
- Each cell innervated by one or more motor neurons of the autonomic nervous system
skeletal energy source
Aerobic metabolism at moderate activity, anaerobic metabolism during peak activity
cardiac energy source
Aerobic metabolism
-Myoglobin & mitochondria content is high
smooth muscle energy source
-Aerobic metabolism at moderate activity (typical), anaerobic metabolism during peak activity (rare)
