Muscle physiology Flashcards
Skeletal muscle structure + muscle fiber structure
How many muscles are there in the human body?
~ 650 muscles
What kinds of muscle cells are there in the muscular system?
+ skeletal muscle cells
+ smooth cell layered digestive system
+ cardiac muscle cells
What are the differences between types of muscle cells?
- smooth: spindle-shaped, walls of internal organs, blood vessels, etc., involuntary contraction, digestion, urination, blood flow
- cardiac: short, rectangular, walls of the heart, involuntary contraction, rhythmic, pumping blood
- skeletal: long, cylindrical, enable voluntary actions–> body movement
what are the common properties of all muscle cells?
+Excitable i.e. react to stimulus
+Contract i.e. cells shorten
+Extensibility i.e. cells stretch
+Elastic i.e. recoil/bounce back to original length
What are the different architectures of skeletal muscle?
muscle fascicle orientation (to the axis of pull)
1. fusiform: parallel to its tendon
+ parallel
+ unipennate
+ greater range of motion and shortening velocity
2. pennate: oblique to its tendon
+ bipennate
+ circular
+ more force per volume
what is the difference between an anatomical cross-sectional area (ACSA) and a physiological one (PCSA) in muscle?
(a) CSA perpendicular to the muscle longitudinal axis
(p) CSA perpendicular to the orientation of its muscle fibers–> related to the maximum force a muscle can generate
What is the structure of a skeletal muscle?
+ tendon connecting to bones
+ 3 connective tissue layers, wrapping
+ muscle fibers / cells –> bundled into fascicles
+ blood vessels
+ motor neuron innervate muscle fibers
What is the structure of a muscle fiber/cell?
+sarcolemma: membrane
+myofibril: basic functional unit of the muscle –> contract
+sarcoplasm: mitochondria, Golgi apparatus, reticulum (wrap around myofibrils)
+ T tubules: regulate Ca2+ concentration
What is the primary structural unit of a muscle fiber where the sliding filament theory occurs?
sarcomere
a contractile unit of a myofibril
smallest element that produces force
How is a sarcomere structured within a myofibril?
- 1 sarcomere = region between 2 Z lines
- Thin actin filaments anchor on Z lines
- Thick myosin filaments overlap the actin filaments, attach to action through cross bridges within 1 sarcomere
In the sliding filament theory, which part increases the length by a factor of 2 during contraction?
the zone of overlap in the sarcomere
i.e. thin and thick filaments occupy the same area
–> during contraction, shortening the sarcomere –> tension
In what form is the biochemical energy supplied to the muscle?
Adenosine triphosphate ATP
provide energy required for the sliding of actin and myosin filaments
What is the relationship between the force and number of fibers?
more fibers recruited –> higher force
fewer fibers –> lower force
What is the relationship between the force and the fiber length?
longer muscle fibers –> same maximum tension but longer force excursion
shorter muscle fibers –> same max. tension, shorter time
What is the relationship between the force and the sarcomere length?
length-tension curve:
increasing of active force, linear relation
optimal sarcomere length –> best overlap –> max force - plateau
decrease of overlap –> decrease active force, increase passive force due to stretching / elastic property
