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Week 5 (characterstics pt 2. (t-tubules
-conduct electrical signal to…
Week 5
characterstics pt 2.
t-tubules
-conduct electrical signal to contract (action potential) from sarcolemma into muscle fibre
-enables all regions of muscle fibre to contract simultaneously
myofibrils
-cylindrical structures (length of muscle fibre))
-each muscle fibre contains thousands of myofibrils
-surrounded by T tubules and sarcoplasmic reticulum
-consists of bundles of proteins called myofilaments
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sarcoplasmic reticulum:
-tubular network around myofibril
terminal cisterna: enlarged region of sarcoplasmic reticulum near T tubules
-stores calcium ions (Ca2+)
-muscle contraction begins when Ca2+ are released from terminal cisterna into the cytosol
sarcomere
-smallest functional units of the muscle fibre
-thin and thick myofilaments arranged in repeating functional units
-produce striated (banded) appearance
-interactions between thick and thin filaments within sarcomeres are responsible for muscle contraction
skeletal muscle fibre
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characteristics
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resting membrane potential
-when positive/negative charges are held apart, a potential difference exists
-potential difference across a plasma membrane
-resting membrane potential (-85 mV)
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excitable
large temporary changes in membrane potential occur
(i.e. action potentials)
first step that leads to a muscle contraction
3 types
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smooth muscle
contraction pushes fluids and/or solids through internal organs and regulates diameter of small arteries
organisation
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endomysium: surrounds muscle fibre
perimysium: surrounds muscle fascicle
epimysium: surrounds entire muscle
:check: merge to form tendon/aponeurosis: attach to bone
skeletal muscle
Function
- produce movement by pulling on bones/tendons
- maintain posture and body position
- support soft tissues
i.e. abdominal wall supports and shields visceral organs
- guard body entrances and exits
i.e. enables voluntary control over swallowing, defecating, and urinating
- maintain body temperature
i.e. working muscles produce heat
- store nutrients
i.e. proteins are broken down and used by the body when diet contains inadequate proteins or calories
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Thin filaments
-strands of the proteins
actin, troponin, tropomyosin
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