Muscles Flashcards
2 functions of muscles?
- produce tensile forces “pulling”
2. produce heat
How do muscles produce tensile forces “pulling”?
- body movement (moving arm) and locomotion (walking)
- joint stabilization
- pumping fluid and air
- control flow of fluid and air
- transporting and digesting food
Events that occur at neuromuscular junction?
- Action Potential reaches terminal
- Ca2+ channels open/release Ca2+
- Vesicles fuse to postsynaptic cell membrane and release N.T ACh
- ACh binds to Na+ ligand gated channels at motor end plate of muscle cell
- Influx of Na+ at motor end plate causes EPSP
- Voltage gated Na+ channels allow Na+ to flow in
- If motor end plate potential reaches threshold then there will be an Action Potential which spreads down the sarcolemma (muscle cell membrane)
What is the Sarcolemma?
the muscle cell membrane
What is an EMG?
electromyography: measures muscle electricity
what does an EMG measure?
it measures the frequency of action potentials (frequency) and the number of muscle cells that are stimulated (magnitude)
what is the magnitude of the EMG proportional to?
magnitude of EMG is proportional to the number of muscle cells that are excited
what is the number of muscle cells excited proportional to?
number of cells excited is proportional to force
what is the sarcoplasmic reticulum (S.R.) ?
a cistern for Ca2+; it stores Ca2+
what is the condition of the muscle cell at rest?
the intracellular concentration of Ca2+ is low because it is still being stored in the S.R
what happens when the muscle is excited?
the A.P stimulates the DHP receptor; DHP mechanically interacts with Ryanadine receptor which opens Ca2+ channels; Ca2+ flows out of S.R. into Intracellular fluid (ICF); intracellular concentration of Ca2+ increases
what is a t-tubule?
a deep invagination of the muscle cell membrane where the Action Potential travels to excited the muscle cell
what is the DHP receptor and where is it?
Dihydropyradine receptor attached to the muscle cell membrane
where is the ryanadine receptor?
attached to the sarcoplasmic reticulum
what are the 2 functional proteins in muscle?
G-actin (thin filament) and Myosin (thick filament)
at rest what is the conformation of the actin/myosin?
tropomyosin blocks binding site for myosin heads to bind to actin
what is a motor unit?
1 motor neuron and all of the muscle fibers that the neuron communicates with
what is the distribution of motor neurons like?
varies greatly throughout the body
ex: lots of motor neurons in finger tips
What is frequency of muscle stimulation proportional to?
force
what two things control muscle force?
- frequency of muscle stimulation
2. recruitment (the number of motor units activated; measured with EMG)
what is muscle recruitment?
the number of motor units activated and measured with EMG
what factors influence muscle force?
- size of muscle fibers (the number of sarcomeres (actin/myosin) packed in each muscle fiber)
what is a motor unit?
1 motor neuron and all of the muscle fibers that the neuron communicates with
what is the distribution of motor neurons like?
varies greatly throughout the body
ex: lots of motor neurons in finger tips
What is frequency of muscle stimulation proportional to?
force
what two things control muscle force?
- frequency of muscle stimulation
2. recruitment (the number of motor units activated; measured with EMG)
what is muscle recruitment?
the number of motor units activated and measured with EMG
what factors influence muscle force?
- size of muscle fibers (the number of sarcomeres (actin/myosin) packed in each muscle fiber)
