Smooth Muscle Tissue
is found in the walls of? (4)
& muscles that attach/adjust? (3)
walls of arteries, veins, hollow organs, airways to lungs
muscles that attach to hair follicles, adjust pupil diameter & adjust focus on lens in eye
Smooth Muscle contains ...? arrangement?
both thick and thin filaments
not arranged in sarcomeres
no regular pattern of overlap (not striated)
contains only small amount of stored Ca2+
In Smooth muscle fibers, thin filaments attach to?
dense bodies & stretch from one dense body to another
Dense bodies of smooth muscle tissue
function in same way as Z discs
during contraction, filaments pull on dense bodies causing shorting of muscle fiber
Contraction of smooth muscle lasts ____________than skeletal muscle contraction
initiated by? from?
longer (starts more slowly)
initiated by Ca2+ flow primarily from interstitial fluid & SR
Ca2+ moves slowly out of muscle fiber delaying relaxation
Able to sustain long-term muscle tone because?
Prolonged presence of Ca++ in the cell provides for a state of continued partial contraction
Smooth Muscle is imporant in (2)?
Gastrointestinal tract where a steady pressure is maintained on contents of the tract
In walls of blood vessels which maintain a steady pressure on blood
Most smooth muscle fibers contract or relax in response to? (4)
1) action potentials from autonomic nervous sytem
2) in response to stretching
4) changes in pH, oxygen & CO2 levels
Muscles of the body are derived from ____________
mesoderm except muscles of iris & arrector pili
As the mesoderm develops it becomes arranged in dense columns on either side of the developing spinal cord
These columns undergo?
segmentation into a series of cube-shaped structures (somites)
The cells of a somite differentiate into (3) regions
1) Forms skeletal muscles of head, neck, and limbs
2) Forms the connective tissues, including dermis of skin
3) gives rise to the vertebrae
Cardiac muscle and smooth muscle develop from migrating mesoderm cells that migrate to & envelop developing ___
cardiac muscle- migrate to & envelop developing heart while it is still in the form of endocardial heart tubes
smooth muscle - migrate to & envelop developing gastrointestinal tract & viscera
the attachment of a tendon to the stationary bone
the attachment of the muscle’s other tendon to the movable bone
the main movements of a muscle that occur during contraction
rigid structure (1) that can move around a fixed point (2)
A lever is acted on at two different points by (2) different forces:
1) effort - causes movement
2) load or resistance - opposes movement
1) force due to muscular contraction
2) weight that is moved
1) effort (E)
2) load or resistance
Motion occurs when?
the effort applied to bone at insertion exceeds load.
(3) types of levers that differ on the positions of the fulcrum, effort, and load
first-class levers - fulcrum between effort & load
second-class levers - load between fulcrum & effort
third-class levers - effort between fulcrum & load
attachement to stationary end of muscle
thickerm middle region of muscle
attachement to mobile end of muscle
All muscle fibers are parallel to one another within a single fascicle.
However, fascicles form patterns with respect to tendons (5)
thick in middle and tapered at ends
broad at origin and tapering to a narrower insertion
fascicles insert obliquely on a tendon
1) only on 1 side of tendon
2) both sides of centrally positioned tendon