ch 11 muscular system
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What are lever systems?
What is a fulcrum?
a fixed point at which a lever moves (ex. joint)
What are rigid bars?
What do the joints and bones act as?
- joints - fulcrum
- bones - levers (rigid bars)
What is a mechanical advantage?
not much effort is needed
What is a mechanical disadvantage?
much effort is needed
What does the distance of the load and effort from the fulcrum determine?
if there is mechanical advantage or mechanical disadvantage
What is a first class lever?
- load-fulcrum-effort (ex. scissors)
- - raises your head off your chest
What is a second-class lever?
- fulcrum-load-effort (ex. wheelbarrow)
- - stand on tip toe's
What is third-class lever?
- load-effort-fulcrum (ex. tweezers or forceps)
- - flexing the forearm by the biceps rachii muscle
What influences the muscles function?
fascicles that are arranged in different patterns (can be seen with the naked eye)
What are the 4 arrangement of fascicles in muscles?
- 1. Parallel (ex. sartorius/biceps brachii/sternocleidomastoid)
- - fascicle axis is parallel to muscle with belly flanked by tendons
- - may be strap like or fusiform
- 2. Convergent (ex. pectoralis major)
- - converge at one tendon
- - resembles a triangle or fan-shaped
- - muscle fibers extend the length of the muscle from origin to insertion
- 3. Pennate-fasicles arranged along length of a tendon with the structure resembling a feather
- *multipennate (arranged side by side & end up connecting to 1 tendon, one of the strongest types of muscle)-deltoid
- *bipennate (fascicles are on both sides with tendon running down the middle)-rectus femoris/bicep femoris/
- *unipennate (fascicles on one side only)-excensor digitorum longus
- 4. Circular (orbicularis oris)
- - fascicles are arranged in concentric rings found at the opening of an organ, may be called sphincter or orbicularis
What may be called sphincter or orbicularis?
What is an agonist?
prime mover that produces the movement
What is antagonist?
- performs opposite action as agonist, but remains relaxed or stretched while agonist is contracting.
- bicep - agonist
- triceps -antagonist
What is a synergest?
muscle that works with an agonist to stabilize a joint or reduce unnecessary action at a particular joint.
What are fixators?
hold a bone in place to provide a stable base for an agonist
What do all muscles develop from?
mesoderm germ layer which folds into sections called myotomes and somitomeres.
What are the 4 major groups of the mesoderm germ layer?
1. visceral organ musculature- includes development of smooth and cardiac muscle
- 2. pharyngeal arch muscles
- include muscles of facial expression, chewing, swallowing, and some head neck muscles
3. axial muscles
4. limb muscles
What are the muscles that move mandible superiorly?
masseter and temporalis
What are the muscles that move the mandible laterally?
buccinator and pterygoid
What are the muscles that protract, retract, depress, elevate, and move the tongue laterally?
extrinsic tongue muscles
What happens as a person swallows?
muscles grouped as suprahyoid contract to prevent food from entering into respiratory tract
What happens when swallowing is complete?
infrahyoid muscles contract to return the hyoid bone to its original position
Why does other muscle contraction occur?
to prevent food from entering nasal cavity and to ensure that it enters the esophagus
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