Muscles 2 Flashcards
Steps that start a contraction
Step 1.
Ach is released at the neuromuscular junction and binds to ACh receptors on the sarcolemma
2.
An actuon potential is generated and spreads across the membrane surface of the muscle fibre and along the t tubules
3.
The sarcoplasmic reticulum releases stored Ca ions
4.
Ca ions bind troponin, exposing the active sites on the thin filaments. And cross bridges form when myosin heads bind to active sites
5
The contraction cured repeats itself
Steps that end a muscle contraction
- ACh is broken down by acetylcholinesterase ending the action potential generation
7.
Ca is pumped back into the the sarcoplasmic reticulum, decreasing its concentration
8.
Th tropomyosin returns back to its normal position and the active sites are covered up
9.
. Without have cross bridge formation, the co traction ends
10.
The muscles returns to resting
True or False
During muscle contraction, thin filaments become shorter while thick filaments stay the same length
False:
During contraction
- both thick and thin filaments don’t change in length, but they overlap more
An individual muscle twitch
A brief contraction of a muscle
- follows the all or non response(if stimuli is too low none of the muscles will contract)
Recorded by an electromyography(EMG)
Which period of a muscle twitch corresponds to excitation-contraction coupling?
The latent period
- stimulus is spread across the sarcolemma and the triad
Which period of muscle twitch corresponds to the cross bridges cycle
The contraction period
- tension builds up to peak value
The amount of tension developed in a skeletal muscle fibre depends on
Frequency of stimulation
Sacromere length
Frequencies of stimulation
Temporal summation: no time to completely relax between receiving more stimuli(relaxes around halfway)
- tension in increased
Tetanus; no time to relax between contractions and receiving more stimuli
- all possible cross bridges are formed
Sarcomere: Skeltal muscle fibres
- are elastic( like an elastic band, more tension is created to snap back the further it’s stretched)
- have a Rangel of ideal lengths that allow them to create max tension
Muscle contraction
One motor unit has 1 motor neuron and multiple muscles fibres
How do the functions of small and large motor units differ?
Small motor units produce smaller increments of tension
• E.g. extraocular eye muscles: 1 motor neuron + 3-6 muscle fibres
Large motor units produce larger increments of tension.
E.g. gastrocnemius muscle (calf): 1 motor neuron + 1000s fibres
In 1 muscle what type of motor units will be recruited last?
Large motor units with larger, less excitable neurons
Motor unit recruitment
The number of motor units activated at any one time
Follow the size principle
- for weaker contractions- happens in smaller increments
- for stronger contractions- happens in bigger increments
Isotonic contraction
Muscles maintain a constant tension when contracting
Conventric: muscles shorten(lifting weights)
Eccentric: muscles lengthens(lowering weights)
Isometric contractions
Muscles don’t change in length but tension increases
