Muscle Physiology 1 Flashcards
What are the 3 types of muscles in the body ?
Skeletal, cardiac and smooth muscles
Skeletal and cardiac muscle is striated and smooth muscle is unstriated - T/F?
True
What is the control over skeletal, cardiac and smooth muscles
- Skeletal muscle control is voluntary
- Cardiac and smooth muscles control is involuntary
What are the physiological functions of skeletal muscle ?
- Maintenance of posture
- Purposeful movement in relation to external environment
- Respiratory movements
- Heat production
- Contribution to whole body metabolism
What are skeletal muscles organised into and describe this
Oragnised into motor units -
The motor unit is a single alpha motor neuron and all the skeletal muscle fibres it innervates
What does the muscles per motor neurone depend on ?
Depends on the function served by that muscle - due to the fact that the fewer fibres supplied by a single motor neurone the more percise fine movements it can carry out
What are the different levels of organisation of muscles ?
What are some of the important differences between skeletal and cardiac muscles:
What intiated and propagates contraction
Excitation contraction coupling (whats the link between excitation and contraction)
Gradiation of contraction (what makes them stronger or weaker)
What does the pic show and what type of muscle are these present in ?
Neuromuscular junctions present in skeletal muscle
What does this pic show and what type of muscle are they present in ?
Gap junctions present in cardiac muscle
What is excitation contraction coupling ?
It is the process by which the surface AP results in activation of the contractile mechanism of the muscle fibre
Describe the steps of excitation contraction coupling in skeletal muscle
- Acetylcholine relased at neuromusclar junction
- AP generated in response which goes down T-tubules of muscle cells
- AP in T-tubules causes relase of Ca2+ from the sarcoplasmic recticulum
- Ca2+ binds to tropnin on actin filaments
- Tropomyosin is therefore physically moved aside to uncover cross-binding bridges on actin filament
- Myosin cross-bridges attach to actin and bend pulling actin filaments towards the centre of sarcomere (contraction)
- When no longer AP Ca2+ is taken back up in the sarcoplasmic recticulum
- Ca2+ no longer bound to troponin, tropomyosin slips back to original postition over binding sites on actin, contraction ends, actin slides back to original resting place
What is the neurotrasmitter at the neuromuscular junction in skeletal muscles ?
Acetylcholine
Appreciate this pic of T-tubules
What is ATP required for in terms of skeletal muscle contraction (excitiation-contraction coupling)
Required for pulling actin filaments towards the centre of the sarcomere
Describe the structure of muscles
- Muscles are comprised of parallel muscles fibres
- Each muscle fibre is made up of myofibrils
- Myofibrils have alternating segments of actin and myosin fibres
Match the appearance of myosin and actin:
- Thin and lighter in appearance
- Thick and darker in appearance
- Thin and lighter in appearance - actin
- Thick and darker in appearance - myosin
What structure is actin and myosin arranged into?
Arranged into sarcomeres
What is the functional unit of skeletal muscles and define what is meant by functional unit
- Functional unit is the smallest component capable of performing all the functions of that organ
- Sarcomere is the functional unit of skeletal muscles
What is the sarcomere found between ?
Two Z-lines
What are the 4 different zones of the sarcomere ?
Think HAMI
- H - lighter area within middle of A band, where thin filaments don’t reach
- A - Made up of thick filaments along with portions of thin filaments that overlap in both ends of thick filaments
- M - extends vertically down middle of A band within centre of H zone
- I - Consists of remaining portion of thin filaments that do not project in A-band
Learn the zones of the sarcomere under the microscope
What is ATP required for in terms of muscle movements ?
It is required for contraction and relaxation
What is Ca2+ required for in terms of muscle movements ?
Required for cross-bridge formation
Appreciate the relation of actin and mysoin filaments to each other
