Lecture Seven - Musculoskeletal system Flashcards
How does the reflex arc work when one’s hand is touched by fire?
What is the appearence difference between skeletal, smooth and cardiac muscle?
What is the structure of skeletal muscle?
Bundles of muscle fibre -> Single muscle fibre -> Within the cell/fibre = highly specialised series of miofibrals.
Made up of thick and thin filaments.
Thick filaments predominantly made of myosin.
Thin filaments predominantly made of actin (with smaller amounts of tripsmyosin and tropomin).
What is the sliding filament model?
Filaments of consistant length slide past each other as a result of forces deceloped between the actin and myosin filaments by the activity of the myosin cross-bridges - Eckert 1988.
How do myosin and actin interact (rachet mechanism)?
Myosin essentially rachets its self along the actin filament.
What is the role of Ca2+ in skeletal muscle?
Tropomyosin = Fibrous.
Tropomin = Changes configuration/conformation depending on Ca2+.
Inorder for a contraction to occur, the Ca2+ must bind to the tropomin complex, which changes the tropomin conformation to allow myosin binding sites on the actin to be avaliable for myosin to bind to.
Ca2+ is contained within the muscle in the T tubule sarcoplasmic reticulum (SR).
How is the message passed from the axon to the muscle?
T-tubule is depolarized, which opens the voltage gated Ca2+ channels.
Ca2+ can then activate the muscle fibres by exposing binding sites for myosin on the actin.
What is the different results of one fibre controlled by one neuron, vs many fibres controlled by one neuron?
Many fibres controlled by one neuron produces a strong contraction with less precision.
One fibre controlled by one neuron produces a less strong contraction with greater motor movement precision.
How is the strength of contraction controlled (action potentials)?
The more action potentials sent, the greater the strength of contraction.
They add on to one another when sent at the same time.
Describe the different kinds of muscle fibre types (fast and slow twitch).
Slow twitch fibres have only oxidative abilities (aerobic respiration only).
Have greater indurance, weaker contractions and greater blood supply.
Have many mitochondria and much myoglobin (rich blood supply).
Fast twitch have both oxidative and glycolitic abilities (anaerobic and aerobic respiration).
Have lesser endurace but faster, stronger contractions, less blood supply.
Speed of contraction is dictated by:
Myosin ATPase activity.
Rate of release and uptake of Ca2+.
Number of mitochondria.
Describe the basic characteristics of cardiac and smooth muscles.
Cardic muscles:
Heart.
Forms of striated muscle.
Intercalated disks.
IGenerate action potential without neural imput.
Do not have continuous cytoplasm (unlike skeletal muscle).
Network, rather than linear arrangement (unlike skeletal muscle).
Smooth muscle:
Walls of hollow organs and around blood vessels.
Not lined up - less regular pattern.
Lacks striations.
Slow contractions.
Initiated by muscle itsself or neurons of automatic nervous system.
Ca2+ regulates contractions but through different mechanisms.
What are the three kinds of skeleton?
Hydrostatic.
Endoskeleton.
Exoskeleton.
What is the structure of the human skeleton?
What are connective tissues and cartilage?
Connective tissue:
Fibrous connective tissue dense with collagenous fibres.
Tendons attach muscle to bones.
Ligaments attach bone to bone.
Cartilage:
Collagenous fibre with embedded condroitin sulphate.
Chondrocytes secrete these in extracellular matrix.
In which cases does connective tissue form elaborate extracellular matrices?
Loose connective tissues.
Adipose tissues (fat storage).
Blood.
Fibrous connective tissues (ligaments and tendons).
Cartilage.
Bone.
What is the structure of the bone?
Bone - mineralized connective tissue.
Osteoblast - Deposit collagen matrix. Ca, Mg, P ions harden into mineral.
How do opposing (antagonistic) muscles work?
Muscles can only contract (pull).
Levers provide a range of motions.
Work with endo or exoskeleton.
One muscle will contract, pulling the level one way, and another muscle will contract, pulling the lever in another way.
What are the three level conformations?
