Groas Muscle Funtion Lecture 21 Flashcards
Maximum muscle strength
True or false
Overextended or contracted muscle can produce maximum strength
In an over extended muscle there is little overlap between thick and thin filaments, producing very few power strokes initially
In over contexts contracted there is too much overlap limiting how many more crossbridges can form between actin and myosin
The optimum state is partial contractor (roughly about 50% of full contracture(
For this reason healthy muscles are always maintain a state of partial contracture called Tonus
False - they cannot produce maximum strength
True
True
True
List the states for gross muscle twitch
Threshold - is the minimal amount of nerve stimulus to elicit a response from a muscle. It must be enough to release ACH for opening the ligand-gates channels.
Latent period- is 1-2 msec long and is the time required for the depolarization wave to move throughout the sarcolemma (remember that can be feet long)
Contraction -from a single stimulus is called a twitch. This is quite rapid and can happen in as little as 7msec (an eye blink) but is usually longer
Relaxation - behinds immediately after depolarization as Ca++ is actively removed from the sarcoplasm. This phase ends once again covers the acting active sites.
Stages of gross muscle twitch
What is the front contraction from a single stimulus called ?
A twitch
When does relaxation begin?
It brings after depolarization as Ca++ is removed by the sarcoplasm. It
How long is latent period? What does the threshold important?
1-2 msec long. The threshold is the minimal amount of nerve stimulus to elicit response
Twitch and Tetanus
____ stimulates muscle fibers at different rates, using discrete impulses
Nerves
What is the result of the stimulus impulses to become of wide apart?
Separate twitches, which look like a tremor
When does the muscle being to fully relax again?
It doesn’t not fully relax before it begins contracting again.
If the rate exceed ____ pulses per second. There is is no time for relaxation between contractions and the muscle fiber sustained it’s contraction
50 pulses per second
What is the normal state of muscle contraction
50pulses per second (pps)
Muscle fiber classes
Define and describe the muscle fiber classes
Type 1 (slow twitch, slow oxidative, SO) - these muscle fibers are small in diameter, rich in myoglobin and are designed to produce a long term, sustained, contraction, based on the oxidative gylcolytic pathway. Because if high myoglobin (white meat) they appear dead red ( dark red in chicken or turkeys.) they are found in abundance in the back, neck and legs
Type 2 - (fast twitch, fast oxidative, FO) these muscles fibers are largest in diameter , have more creative and less myoglobin (white meat.) they are designed for strong, more rapid contractions but they also fatigue more quickly.
Motor units
How many muscle fibers does a single neuron control? And through what they do control the muscles fibers?
Several muscle fibers. Through what are called collaterally axons. Each ending in neuromuscular junction
So a single neuronal stimulus will activate al these fibers at once
An average motor unit consists of ____ fibers, but can vary.
How many fibers are in the muscle and face? And legs
150 fibers
10 fibers
2,000 - 3,000 per unit
True or false
Motor units contain only class fiber, either type 1 or type 2.
True
Recruitment and control contraction
Unlike isolated muscle fibers, Gross muscle is capable of gradated responses. Describe the several way:
Recruitment - by selected his many motor units are stimulated, the strength of contraction can be varied
Antagonistic dynastic tension - using agonist/antagonist pairs, it is possible to hold a position or to control the rate of contraction
The rate of nerve impulses stimulus can produce a full or partial tetany - such as contracting and relaxing your fingers quickly when playing an instrument
