Skeletal Muscle Physiology 1 Flashcards
What are muscles capable of?
of developing tension and producing movement through contraction
Are smooth muscles striated?
No
What kind of muscle are skeletal and cardiac?
striated muscle
What causes the light and dark bands in striate muscles?
light - actin thin filaments
dark - myocin thick filaments
What innervates skeletal muscles?
Somatic nervous system and are therefore subject to voluntary control
What kind of nerve innervates cardiac and smooth muscle?
autonomic nervous system - involuntary
List the functions of skeletal muscle
- Maintenance of posture
- Purposeful movement in relation to external environment
- Respiratory movements
- Heat production - shivering
- Contribution to whole body metabolism
What is a motor unit?
The motor unit is a single alpha motor neuron and all the skeletal muscle fibres it innervates
Why do muscles which serve fine movements have fewer fibres per motor unit? Give examples of these muscles
because precision is more important than strength
intrinsic hand muscles and extra-occular muscles
What is a sarcomere?
Functional unit made up of actin and myocin filaments
What do actin and myocin form?
cytoskeletal elements of skeletal muscle
Why are there no gap junctions in skeletal muscle?
to allow rapid propagation of AP through muscle cells
Does Ca induced Ca release occur in cardiac or skeletal muscles or both?
cardiac muscles only
In skeletal muscle, where does the Ca required for excitation contraction coupling come from?
Entirely from the lateral sacs of the sarcoplasmic reticulum
What is excitation contraction coupling?
process whereby the surface action potential results in activation of the contractile mechanism of the muscle fibre
After the AP is initiated, where does it spread down in skeletal muscle?
the tranverse (T)-tubules - this traiggers the release of Ca from the lateral sacs of SR
Which molecule acts as the neurotransmitter at the neuromuscular junction?
Acetylcholine
What is the function of myofibrils?
contractile structures made up of actin and myocin filaments arranged into sarcomeres
How long are skeletal muscles?
Usually extend the entire length of muscle
What are skeletal muscles usually attached to?
attached to bone by means of a tendon
What actually is a functional unit of an organ?
The smallest component capable of performing all the functions of that organ
What separates sarcomeres?
Z line
What are the 4 zones of sarcomeres?
A-band
H-zone
M-line
I-band
How is muscle tension produced?
Sliding filaments theory - sliding of actin filaments on myocin filaments
What does force generation within muscles depend on?
ATP-dependent interaction between thick (myosin) and thin (actin) filaments
When is Ca2+ needed?
- switch on cross bridge formation
- Ca2+ is the link between excitation and contraction
- Ca2+ is entirely derived from sarcoplasmic reticulum in skeletal muscle
When is ATP required?
during muscle contraction to power cross bridges
during relaxation to release cross bridges and to pump Ca2+ back into the sarcoplasmic reticulum
