Motor Unit Recruitment Flashcards
Features of muscle contraction can be demonstrated by eliciting single muscle __________
Twitches
What are some characteristics of muscle contractions
Involuntary
Visible under the skin
Arises from spontaneous discharge of a bundle of skeletal muscle fibers
In the latent period of a single fiber contraction, there is a delay of how much
1-2ms
What occurs in the latent period of a single fiber contraction
Impulse travels along sarcolemma and down the t-tubules to sarcoplasmic reticulum (traids) Ca is released and binds to troponin Actin active site is exposed Myosin binds to actin Tension is observed
How long is the contraction period of a single fiber contraction
10-100 ms
What occurs in the contraction period of a single fiber contraction
Tension rises as cross-bridges swivel and pull actin filaments towards the M line
Sarcomere length shorten
How long is the relaxation period of the single fiber contraction
10-100ms
What occurs in the relaxation period of a single fiber contraction
Muscle relaxes as tension decreases with unflexing of myosin heads and calcium sequestration
Sarcomere length returns to its original length
What are the two ways in which muscle can contract
Isometric contraction, Isotonic Contraction
What does isometric contraction involve
Maintenance of constant muscle length
True or false, isometric contraction involves a contracted muscle against a load as it is unable to shorten because load is great
True
In Isometric Contraction, Energy is released as _______ rather than through performance
Heat
Give examples of isometric contraction
Pushing against a wall
Holding a weight in fixed position
Holding a stack of books
Body building Pose
Isotonic contraction, involves maintenance of ________
Constant muscle tension
True or false, Isotonic Contractions involve contracted muscle against a load due to the muscles maximal force of contraction exceeding the total load on the muscle
True
True or false, in isotonic contraction, muscle shortens in length (concentric), or lengthens (eccentric)
True
Give examples of isotonic contraction
Bicep curls, swimming, cycling, running
What is the term given to the adding of individual twitch contractions to increase the intensity of overall muscle contract
Summation
What are the two ways in which summation occurs
Multiple fibers (motor unit) summation Frequency (wave) summation
What type of summation occurs when there is an increasing number of motor units contracting simultaneously
Multiple fiber (motor unit) summation
What type of summation occurs when there is an increase in the frequency of contraction
Frequency wave summation
True or false, frequency summation occurs when there is a series of twitch contractions occurring one after the other at low frequency of stimulation
True
Frequency summation leads to
Treppe (the staircase effect)
Tetany/tetanization/tetanus
How does tetany arise
When enough calcium ions are maintained in the muscle sarcoplasm, even between APs, so that full contractile state is sustained without allowing any relaxation between the APs
What is treppe
Gradual increase in the strength of a muscle contraction to a plateau following rapidly repeated stimulation after a quiescent period
True or false, When a muscle begins to contract after a long period of rest, it’s initial strength of contraction may be as little as one half of its strength to 10 to 50 muscle twitches later
True
What is the primary cause of treppe ie the staircase effect
Increasing Ca2+ in the cystol because of the release of more and more ions from the SR with each successive muscle AP
Failure of SR to recapture the ions immediately
True or false, fatigue increases almost directly proportional to the rate of deletion of glycogen in the muscle
True
What causes muscle fatigue
Prolonged and strong contraction of muscles
According to Columbia university, what is the cause of fatigue
Calcium leaking into the muscle cells
True or false, treppe can lead to fatigue
True
If blood flow is interrupted while a muscle is contracting, almost complete muscle fatigue occurs within _________ minutes, due to a low supply of ________
1 or 2 minutes, oxygen
What can muscles provide alterations in, in order to better suit the function that is required
Diameter Length Strength Vascular supply Type of muscle fibers
What is muscle hypertrophy
When the total muscle mass increases due to an increase in size of fibers
I’m fiber Hyperplasia, though rare may arise in _____
Increase in fiber number
In Denervation sensitivity, there is promoted expression of _________ receptors on the sarcolemma
Nicotiinc acetylcholine receptors
True or false, rigor Mortis occurs when muscle fibers are completely depleted of ATP
True
True or false, in rigor mortis, nearly all the myosin heads are attached to actin but in a fixed abnormal and resistant manner
True
Muscles remain in rigor until the muscle proteins deteriorate in _________, this is as a result from ________
15-25 hours later, Enzymic autolysis
True or false, temperature increases the speed of the effects of rigor mortis
True
