L10 Flashcards
(42 cards)
Provide a brief summary of skeletal muscle characteristics
- striated
- controls body movement
- attaches to bone
- voluntary control (responds to somatic motor neurons)
- multinucleated
Provide a brief summary of cardiac muscle characteristics
- main goal is to move blood
- cardiac muscles provide own contraction
- striated muscles
- non voluntary (responds to autonomic NS, contraction, modulated by endocrine system)
- uninucleated
Provide a brief summary of smooth muscle characteristics
- primary muscles of internal organs and tubes
- influences the movement in and out of the body
- involuntary control
- non striated
- uninucleated
Explain:
Origin
Insertion
Flexor
Extensor
Origin- closest to midline or stationary more
Insertion- more distal to midline, or mobile bone
Flexor- brings bones together
Extensor- moves bones away
What is another name for muscle cells— what’s are satellite cells?
Muscle cells are called muscle fibres, and satellite cells are stem cells which can specialize
What’s the purpose of T-Tubules in fibres?
To allow for AP to penetrate nearest internal structure of the fibre. These are extensions fo the sarcolemma thats associated with the end of the SR
Thin filaments—>_____
Thick filaments—> ____
Regulatory proteins—> ___, ____
Accessory proteins—> ____, _____
Thin filaments—> actin
Thick filaments—> myosin
Regulatory proteins—> troponin and tropomyosin
Accessory proteins—> titin and nebulin
What is the contractile unit of the myofibril?
The sarcomere is the contractile unit of the myofibril.
What components of the sarcomere causes contraction? Name and describe the components.
Z-disks= have actin filaments bonded together
I-Band= made of thin (actin) filaments only
A-Bands= darker regions where both thin and thick filaments overlap
H-Zone= within the middle of the A band, has thick filaments only
M-Line= only area where thick myosin filaments bind
What are the two types of accessory proteins that muscle fibres consist of? What are the functions?
Titin- this is an elastic protein which stabilizes position of contractile elements. Elasticity returns stretched muscles to their resting length
Nebulin- inelastic protein which aligns filaments, stabilizes position, lines with the thin filaments attached to Z disk
When muscles contract the sarcomere ______
When muscles lengthen the sarcomere ______
When muscles contract the sarcomere shrinks
When muscles lengthen the sarcomere lengthens
Instead of shrinking in size, during contraction myosin heads and actin do what?
Slide past each other
When the sarcomere is under contraction, what happens to the
Z-Disks I-Bands A-Bands H-Zone M-Line
Z-Disks= nothing changes, still has actin filaments I-Bands= smaller in size, but still contain actin A-Bands= nothing changes, actin just moves closer to the M line H-Zone= smaller in size, still contains myosin heads M-Line= nothing changes, still has myosin
Three basic steps for a skeletal muscle to contract
- Event at neuromuscular junction
- Excitation contraction (E-C coupling)
- contraction-relaxation cycle
What are the contraction steps involving calcium?
- calcium is released from terminal cisternae (within SR)
- calcium binds to troponin
- troponin pulls tropomyosin away from actin binding sites
- myosin binds to actin and pulls on its heads
- cycle repeated until lack of calcium and ATP is present
What are the contraction steps involving ATP?
- ATP binds to myosin and decreases affinity for actin
- ATP hydrolyses provides energy for myosin head to rotate and reattach to actin
- ATPase break ATP into ADP and Pi
- power stroke begins in response to Ca and Pi
- myosin releases ADP and makes room for ATP
- cycle continues
Contractile cycle summary in 4 steps, name them.
- ATP binds to myosin, relabeling actin from myosin
- Myosin hydrolyses ATP, energy from ATP puts myosin head into cocked position
- Power stroke begins when tropomyosin moves away from binding sites
- Myosin releases ATP at end of power stroke
Provide the ten steps for E-C coupling
- When neuron is activated, signal is relayed to muscle via Ach
- Ach is released in synaptic cleft and binds to Ach receptors in motor end plate
- Depolarization of Na+ channels which allow for change in membrane potential
- Change in membrane potential allows for AP to occur
- AP in muscle fibre transported via T-tubules in motor end plate to muscle fibre
- Ap travels to DHP (voltage gated) channels that change physical form
- DHP receptors are connected to RyR receptors that connect to SR
- DHP, RyR and SR allow for opening and release of Ca+ into cytoplasm from [high] to [low]
- Ca+ binds to troponin which moves tropomyosin out of binding sites
- myosin heads then attach to actin and begin powerstroke
What is a latent period and why is it caused?
A latent period is just before the contraction phase of a muscle where there is a delay in between AP and contraction.
- may be caused by time required for calcium release and binding of troponin
Name the type of energy systems for skeletal muscles and their descriptions.
Phosphocreatine= breakdown produces a short burst of energy
Carbohydrates= most rapid and efficient store of energy
Anaerobic glycolytic= produces lactic acid, quick system, no oxygen required, small amount of energy released
Aerobic respiration= slow, oxygen needed, large amount of energy released
Name the various types of fatigue in skeletal muscles and their causes
Central fatigue= due to CNS
Peripheral fatigue= if you utilize all glycogen you will get tired and there will be an Imbalance (K+ leaving cells) we alter likelihood of generating AP.
- with this, short duration and maximal exertion leads to increased level of Pi
- maximal exercise leads to ion imbalance—> K+ alters membrane potential
Explain the difference and characteristics of slow twitch and fast twitch fibres? Which ones are stronger? Which has more mitochondria?
Slow twitch fibres (type I)= not as powerful as other fibres, myosin are slow with hydrolization and rely on oxidative phosphorylation. Has more mitochondria and capillaries for rapid oxygen consumption.
Fast twitch fibres= these develop tension faster, split ATP rapidly and hydrolyze quicker. TYPE IIA (FOG)- oxygen is present, uses oxidative glycolic metabolism TYPEIIB (FG)- oxygen is not present, relys on anaerobic glycolysis
What does chronic stimulation allow for?
The transition between fibres to a certain extent (type IIB-type IIA)
Tension generated is directly proportional to _______
Tension generated is directly proportional to number of cross bridges
- sarcomere contracts with optimal force at optimal length
