Chpt 39 - Part 1 - Muscle Contraction Flashcards
Action carried out by muscles or glands under control of the nervous system, in response to
environment stimuli
Multiple individual, simple behaviors collectively scale up to produce
complex behaviors such as limb movement or courtship behavior
Movement requires muscle activity in response to
the nervous system input
Skeletal muscle is under control of what motor?
Somatic division of the efferent peripheral nervous system
- only one!
What are fibers?
a whole muscle is comprised of numerous, elongated, parallel, and individual cells
Muscle fibers stimulated by ___ ___ at the ____ junction
motor neurons
neuromusclar
Neurotransmitter = ?
Acetylcholine or ACh effect is always stimulatory
which means the muscle fiber will always contract
What is a motor unit?
One motor neuron plus all of the individual muscle fibers it synapses with (stimulates to contract simultaneously)
What is recruitment?
the strength of a whole muscle contraction depends on the number of motor units recruited by the central nervous system (CNS).
Give an example of recruitment
lifting up something requires more muscle contraction then picking up a pencil
Why is recruitment important?
it always the muscles to contract in a graded fashion rather than an all or nothing
this allows for execution of fine motor behaviors
Each muscle fiber is made up of what?
repeating sections of sarcomeres
what are sarcomeres?
the contractile units of skeletal muscle
gray is what?
white is what?
gray is the soma
white is the axons
What are sarcomeres packed with ?
- actin (thin filament)
- myosin (thick filament)
What is the sliding filament mechanism?
At rest - contractile proteins overlap a little bit
When stimulated - each sarcomere shortens due to increased overlap between actin and myosin
List of the process of sliding filament mechanism
- myosin head is bound to ATP in a low energy configuration
- myosin head breaks down from ATP to ADP and is in a high energy configuration
- Myosin head binds to actin - grabs it, pulls, then repeats
- cross section releases ADP and returns myosin head to a low energy state
- binding of a new molecule of ATP releases the myosin head from actin and new cycle repeats
What is cross bridge cycling?
whole muscle contractions that require repeated cycling of binding and releasing of actin and myosin
What does the binding step require?
Calcium
What happens if there is no calcium (Ca^2+) in the binding step?
the actin’s binding heads are covered by a protein complex that prevents binding called troponin - tropomyosin
Stimulation from the motor neuron causes the release of Ca2+ from the muscle fiber cell’s
endoplasmic reticulum or sarcoplasmic reticulum
What does Ca2+ bind with?
Troponin
What does troponin do?
exposes actin’s binding sites which allows cross bridge cycling - shortening of muscles
As long as the motor neuron keeps firing..
the cycle of binding and releasing will repeat until the sarcomere fully shortens
