Week 6 Muscle Physiology Flashcards
5 Functions of muscle tissue are
1.Producing body movements
2.Stabilizing body positions
3.Regulating organ volumes
bands of smooth muscle called sphincters
4.Movement of substances within the body blood, lymph, urine, air, food and fluids, sperm
5. Producing heat, involuntary contractions of skeletal muscle (shivering)
5 Properties of muscle tissue are
Excitability- respond to chemicals released from nerve cells
Conductivity- Ability to propagate electrical signals over membrane
Contractility- ability to shorten and generate force
Extensibility- ability to be stretched without damaging the tissue
Elasticity- ability to return to original shape after being stretched
3 Characteristics of Smooth muscle tissue
Attached to hair follicles in the skin
Not striated
Involuntary
4 Characteristics of Cardiac muscle tissue
Only in the walls of the heart
Striated
Involuntary
Auto-rhythmic because of built in pacemaker
3 Characteristics of Skeletal muscle tissue:
Attached to bones and skin
Striated
Voluntary an involuntary
3 Types of muscle tissue are
Smooth, Cardiac, Skeletal
Supaficial fascia is
loose connective tissue & fat underlying the skin
Deep fascia is
dense irregular connective tissue around muscle
Describe Epimysium
dense regular connective tissue surrounding entire muscle
Describe Perimysium
fibrous connective tissue surrounding fascicles (groups of muscle fibers)
Describe Endomysium
fine areolar connective tissue surrounding each muscle fiber
Characteristics of Red fibres (Slow)
Small; high oxidative capacity; ATP from β-oxidation of fatty acids
Describe the characteristics of White fibres “Fast-twitch”
Large; lower oxidative capacity; mostly anaerobic glycolysis;
Fatigue rapidly
Briefly describe a myofibril
Densely packed, rod-like elements
Exhibit striations: perfectly aligned repeating series of dark A bands and light I bands
3 characteristics of a sarcomere
Smallest contractile unit of muscle is the sarcomere
Sarcomere contains the protein filaments actin &
myosin. Each muscle cell contains many thousands of sarcomeres.
What are the two requirements for skeletal muscle contraction
Activation: neural stimulation at aneuromuscular junction
Excitation-contraction coupling:
Generation and propagation of an action potential along the sarcolemma
Final trigger: a brief rise in intracellular Ca2+ levels
3 characteristics of thick filament’ head and tail
Composed of protein myosin
Tail- Interwoven, polypide chains
Head- binding sites for actin of thin filaments
Binding site of atp
3 characteristics of thin filament (actin)
Twisted double strand of fibrosis protein of f actin
G actin bears active site for myosin head.
Tropomyosin and troponin- regulatory proteins bound to actin.
What is the sarcoplasmic reticulum ?
Network of smooth endoplasmic reticulum surrounding each myofibril
Regulates intercellular ca2+ levels
Briefly explain the innervation of a skeletal muscle
Stimulated by somatic motor neurons
Axons from motor neuron travel from the cns via nerves to skeletal muscles
Each axon forms server all branches as it enters a muscle.
Each axon ending forms a neuromuscular junction with each muscle fibre.
Explain the 4 events that occur in local depolarisation
–ACh binding opens chemically (ligand) gated ion channels
–Simultaneous diffusion of Na+ (inward) and K+ (outward)
–More Na+ diffuses, so the interior of the sarcolemma becomes less negative
–Local depolarization – end plate potential
Explain the 4 events of Generation and propagation of an action potential:
–End plate potential spreads to adjacent membrane areas
–Voltage-gated Na+ channels open
–Na+ influx decreases the membrane voltage toward a critical threshold
–If threshold is reached, an action potential is generated
Explain the 3 events of re polarisation
- Na+ channels close and voltage-gated K+ channels open
- K+ efflux rapidly restores the resting polarity
- Ionic conditions of the resting state are restored by the Na+-K+ pump
List the 2 requirements for skeletal muscle contraction.
1.Activation: neural stimulation at a
neuromuscular junction
2.Excitation-contraction coupling:
–Generation and propagation of an action potential along the sarcolemma
–Final trigger: a brief rise in intracellular Ca2+ levels
Briefly describe Excitation-Contraction (E-C) Coupling
- Sequence of events by which transmission of an AP along the sarcolemma leads to sliding of the myofilaments
- AP is propagated along sarcomere to T tubules
- Voltage-sensitive proteins stimulate Ca2+ release from SR
Explain the role of calcium in muscle contraction
•At low intracellular Ca2+ concentration:
–Tropomyosin blocks the active sites on actin
–Myosin heads cannot attach to actin
–Muscle fiber relaxes
•At higher intracellular Ca2+ concentrations:
–Ca2+ binds to troponin
–Troponin changes shape and moves tropomyosin away from active sites
–Events of the cross bridge cycle occur
Describe the 3 stages to sliding filament model
- In the relaxed state, thin and thick filaments overlap only slightly
- During contraction, myosin heads bind to actin, detaches, and binds again, to propel the thin filaments toward the M line
- As the H zones shortens and disappears, sarcomeres shorten, muscle cells shorten, and the whole muscle shortens
What is the difference between small motor units and large motor units
- Small motor units in muscles that control fine movements
* Large motor units in large weight-bearing muscles
