A&P 1.13 Flashcards
Deltoids
general
3 branches - anterior, middle and posterior
Named for shape
anterior deltoid
A, O, I
O - lateral 1/3 of clavicle
A- all fibers: abduct the shoulder joint
Anterior: flex the humerus, medially rotate the shoulder joint, horizontally adduct the shoulder joint
I- deltoid tuberosity
middle deltoid
A, O, I
O - acromion
I- deltoid tuberosity
A- all fibers: abduct the shoulder joint
Posterior deltoid
A, O, I
O - spine of the scapula
I - deltoid tuberosity
A - all fibers: abduct the shoulder joint
Posterior: extend the humerus, laterally rotate the shoulder joint, horizontally abduct the shoulder joint
Deltoids
Summary
A, O, I
3 branches - anterior, middle and posterior
Named for shape
O- lateral 1/3 of clavicle (anterior), acromion (middle), and spine of the scapula (posterior)
I- deltoid tuberosity
A- all fibers: abduct the shoulder joint
Anterior: flex the shoulder joint, medially rotate the shoulder joint, horizontally adduct the shoulder joint
Posterior: extend the shoulder joint, laterally rotate the shoulder joint, horizontally abduct the shoulder joint
Antagonists
Defined
Perform opposite actions
Muscle belly contraction
2 types
Tetanus
muscle tone
tetanus
normal skeletal muscle contractions
smooth, sustained contractions resulting from coordinated contractions of different motor units within a muscle
muscle tone
a tonic contraction
it is continual, partial and low level
normally exhibited by individuals while awake in order to keep upright (posture)
Motor unit
Defined
A motor neuron and the fibers it innervates
It is the functional unit
Variable number of branches
Few fibers - more precise
More fibers - less precise
Neuromuscular junction
Defined
Synapse
end of axon near the surface of a muscle fiber at its motor end plate region
All or nothing principle
Defined
Action potentials
Similar to dominos, when a neuron reaches its threshold (enough excitation) the first domino is pushed and the entire row topples (as action potential occurs). There is no stopping once it starts
Pushing on the first domino produces an “all or nothing event”. All fall or none. Action potentials can travel long distances with out dying out thus can communicate over long or short distances.
Action potential
More info
Can travel long distances without dying out (neurons can be extremely long)
Different neurons have different thresholds for generation of an action potential but the threshold for each individual neuron remains constant
Types of contractions
Isotonic
Isometric
Isotonic Contraction
define & 2 types
MOVEMENT: a load is moved
Means the same as “dynamic tension”
Iso- equal Tonic - tension
The tone or tension within a muscle remains the same as the length of the muscle changes
concentric & eccentric
