Muscle Physiology Flashcards
What are the two major classes of muscle?
Striated and smooth.
What are the three major types of muscle?
Skeletal, cardiac and smooth.
What muscle types are voluntary?
Skeletal.
What muscle types are involuntary?
Cardiac & smooth.
What muscle types are straited?
Skeletal and cardiac.
What muscle typed are unstraited?
Smooth.
What is the role of skeletal muscle?
- Locomotion
- Heat production
- Energy store/management
- Sound production
- Electricity production
- Primary food for predators.
What is the role of cardiac muscle?
Regulates blood circulation.
What is the role of smooth muscle?
Movement of fluids, gases and solids through internal organs e.g. digestion.
Define myomere.
Separated sheets of connective tissue called myosepta.
What is the approximate diameter of a skeletal muscle fibre/ muscle cell?
5um - 10um.
Define sarcolemma.
Striated muscle cell membrane.
Define myofibrilis.
Main contracting unit of skeletal muscle fibre.
Define T tubule.
An infolding of the sarcolemma.
Define terminal cisternae.
Enlarged part of sarcoplasmic reticulum that sits either side of T tubule.
Apart from muscle cells, what other cells do you get in muscles?
- Endothelial cells
- Immune cells
- Fibroblasts
- Stem/progenitor cells.
What three stages does skeletal muscle contraction depend on?
- Events at the neuromuscular junction
- Excitation contraction (EC) - coupling
- The cross-bridge cycle.
Define triad.
One portion of a T tubule plus the two adjacent terminal cisternae.
Define tetanus contraction.
The maximal contraction a muscle fibre can achieve i.e. maximal number of actin binding sites available for myosin heads.
Define motor units.
A group of muscle fibres that all get their signals from the same, single motor neuron.
Define fatigue.
Inability to maintain muscle contraction at a given level of exertion.
Define asynchronous recruitment.
During sustained sub-maximal contraction - motor units take turns to be recruited. This optimises the overall time that an activity can occur.
What factors influence the level of muscle contraction?
- Size of muscle group
- Starting muscle length sets maximum tension possible
- Specialisation of muscle fibre characteristics.
What level of activity can type 1/slow oxidative fibres produce?
Endurance low-power activity.
What level of activity can type 2a/fast oxidative fibres produce?
Sustained power activity (sub-maximal).
What level of activity can type 2b/fast glycolytic fibres produce?
Short bursts of maximal or near maximal activity.
What do muscles use energy for?
ATP used in cross bridge cycle, to re-establish ion gradients across muscle membrane and transport Ca2+ back to sarcoplasmic reticulum.
How can ATP be generated for muscle contraction?
- Oxidative phosphorylation
- Glycolysis in muscle
- Glycogenolysis in muscle and liver.
What method of ATP generation do muscles use when resting or recovering?
Oxidative phosphorylation.
What method of ATP generation do muscles use when undergoing intense exercise?
Glycolysis.
Why is muscle recovery crucial?
- Replenish glycogen, ATP and creatine phosphate
- Re-establish normal ion gradients, Ca2+ stores and pH
- Deal with lactate accumulation
- Repair damaged muscle fibres and stimulate growth.
What is the Bohr effect?
Haemoglobin’s oxygen binding affinity inversely related both to acidity and to the concentration of carbon dioxide.
What structural and biochemical features of skeletal muscle make it efficient at oxygen delivery?
- Muscle capillaries are organised in a weaving pattern optimising transit time for blood
- Activity induces muscle blood vessel vasodilation increasing blood flow during exercise
- Muscle activity increases oxygen release by haemoglobin, mainly by reducing the partial pressure of oxygen and reducing pH (Bohr effect).
What is myoglobin?
- Its what makes muscles red
- found in striated muscle
- aids delivery and storage of oxygen.
What are thin filaments made of?
Actin.
What are thick filaments made of?
Myosin.
What do troponin and tropomyosin do?
Prevent myosin from binding to actin. When Ca2+ binds to troponin it stops tropomyosin from preventing myosin binding to actin.
What do skeletal and cardiac muscles have in common?
- Have same sarcomere organisation (overlapping thin/thick filaments)
- Have extensive SR & T tubules
- Identical contraction mechanism.
How do skeletal and cardiac muscles differ?
- Cardiac muscles contract regularly, slowly and involuntary
- Possess pacemaker cells
- Possess gap junctions
- Possess desmosomes.
What are the similarities between skeletal and smooth muscle?
Have thick and thin actin and mysoin filaments.
What are the similarities between smooth and cardiac muscles?
- Smooth and mononucleated
- May have gap junctions and desmosomes.
What are the differences between striated and smooth muscle?
- Spindle shaped cells in sheets
- Lack T tubules and SR
- Lack troponin.
Define neurogenic and myogenic.
Neurogenic - contraction originates from external innervation
Myogenic - Contraction originates from within muscle.
Define tonic and phasic.
Tonic - continuous state of partial contraction
Phasic - Pronounced rhythmic increase in contraction.
Define excitation contraction coupling.
The process linking an action potential to muscle contraction.
