Week 5 Flashcards
What is spatial summation?
occurs as stimuli are applied simultaneously but in different areas
What is temporal summation?
when a high frequency of action potentials in the presynaptic neuron elicits postsynaptic potentials that summate with each other.
What does a differential amplifier do?
Differential amplifiers are used mainly to suppress noise
At what hz range do most motor units fire at?
5-2000Hz
What does a high pass filter do?
attenuates low frequencies below a certain cutoff frequency and allows frequencies above to pass.
What does a low pass filter do?
Low pass filters are used to filter noise from a circuit (wires)
What is the frequency of firing?
the number of spikes over an interval of preselected length is counted and then divided by the length of the interval
What is integration in EMG?
the mathematical integral of the absolute value of the raw EMG signal.
What is rectification in EMG?
processing step to identify the overall strength of the neural drive to the muscle and is correlated with the strength of muscle contraction and its output
What is the difference between half and full-wave rectification?
- Full-wave rectification rectifies the negative component of the input voltage to a positive voltage, then converts it into DC (pulse current) utilizing a diode bridge configuration.
- Half-wave rectification removes just the negative voltage component using a single diode before converting to DC
What is passive insufficiency?
When a multi-joint muscle is lengthened to its fullest extent at both joints, but also preventing the full range of motion of each joint it crosses.
What is active insufficiency?
When a multi-joint muscle shortens over BOTH joints simultaneously, and hence, creates so much slack, that muscle tension is almost completely lost.
What factors influence a muscle’s ability to produce movement?
- Length of the muscle fibers
- Speed of contraction
- Muscle architecture
- Size of the muscle’s moment arm
- Number and type of motor units recruited
- Reflex drive
- Antagonist activity
- GTO inhibition
- Injury/immobilization
- Age
What is the resting length of a sarcomere?
The length at which actin and myosin are optimally overlapped for cross-bridge formation.
Within multiarticulate muscles which type of insufficiency can occur?
Active insufficiency
When a muscle can’t develop force due to the actin-myosin overlap reducing the number of available sites for cross-bridge formation, what is this an example of?
Active Insufficiency
As you stretch a muscle what happens to tension?
Tension progressively increases
Based on the passive length-tension curve, as you increase tension and increase muscle length exponentially what might occur?
If tension and length become too great the tissues will fail or rupture.
What is the utility of passive tension?
- Stores a fraction of energy when stretched
- Exhibits viscoelastic ← properties
- this means that it has both viscous and elastic properties to resist shear force. Think of asphalt
- Both are important for plyometrics
- Elasticity can serve to protect structural components of the muscle and tendons by absorbing forces.
Where does passive insufficiency occur?
Multiarticulate muscles
- Wrist flexors and extensors
- Hamstrings
- etc…
What is passive insufficiency?
In a lengthed muscle, the actin filaments are pulled away from the myosin heads so they cannot create as many crosses-bridges
A muscle that can’t stretch enough to achieve full range of motion at all joints it crosses is an example of what?
Passive insufficiency
What is the sensory receptor located within the muscle that is sensitive to stretch called?
Muscle spindle
The sensory receptor within the tendon that is sensitive to tension and forces the muscle to relax in order to prevent injury is called what?
Golgi Tendon Organ
A patient has had their elbow immobilized for an extended period of time in a fully flexed position, what are some of the effects on the muscle?
- Slow-twitch fibers are subjected to more disuse compared to fast-twitch
- Loss of strength is greatest in a shortened position
- Decrease in number of sarcomeres
- Increase in connective tissue
- Muscle atrophy
What are the phases for sit to stand?
- Flexion-momentum phase
- Momentum transfer phase
- Extension phase
- Stabilizaion phase
In sit to stand which phase has the largest ground reaction force?
The second phase, Momentum transfer phase
