Muscle Flashcards
3 types of contractile cells and what are their roles?
Myoepithelial cells- Surrounds glands and squeeze to help it release its contents.
Pericytes- Smooth muscle like cells that alter diameter of capillaries and venules . Used if needed to move blood to different places throughout body.
Myofibroblasts- Transformed fibroblasts that assist with wound healing. Capable of collagen synthesis.
Skeletal muscle layers
Myofilaments composed of actin and myosin
Myofibril- this is the muscle cell. Many nuclei that are displaced peripherally.
Muscle fiber
Fascicle
Muscle (largest)
Endomysium
Thin connective tissue that is vascularized and surrounds a muscle fiber.
Perimysium
Thin connective tissue that surrounds fascicle
Epimysium
Thin connective tissue that is vascularized and surrounds muscle
Sarcomere
Basic contractile unit of muscle. Z lines are the boundaries
Anchors for the actin myofilaments
Z lines
Z line is located in the middle of the ___ band
I band, which is strictly actin only
H band consists of which myofilaments
Myosin only
M line is in the middle of the ___ band
H band, which is myosin only
A band contains which myofilaments
overlapping actin and myosin filaments
During contraction, which two bands shrink?
HI:)
H (only myosin) and I bands (only actin) shrink.
causes overall sarcomere to shorten, and Z lines will come closer together
During contraction, what happens to the A band?
It stays constant, same size
T system
Facilitates synchronous contractions
T tubules
At the A band/ I band junction. Extension of plasma membrane.
Sarcoplasmic reticulum
Adjacent to t-tubules
Similar to smooth ER found in other types of cells
-Contains Ca2+, which is released during depolarization. Dispersed by T tubules and activates Actin and myosin sliding.
Where is cardiac muscle located
In the myocardium of the heart wall
Character of cardiac muscles
Has characteristics of both smooth muscle and skeletal muscle
Like smooth muscle, it has continuous contraction due to the autonomic nervous system
Like skeletal muscle in that the contractions are forceful and have multiple nuclei/mitochondria per cell. (Some cardiac cells have only 1 nuclei, but most have 2)
Involuntary (SM), forceful, continuous contraction, initiation of contraction modulated by autonomic nervous system
Contraction of cardiac muscles are coordinated by
Purkinje fibers, which are modified cardiac muscle cells
Cardiac muscle appearance
Woven appearance Striated structure Central nuclei- single of binucleate -Fiber ends branch longitudinally. -Contains intercalated discs. Contractile anchors between adjacent cells. Rapid conduction of depolarization.
How do cardiac muscles communicate
Gap junctions within intercalated discs. Intercalated discs anchor adjacent cells and allow rapid conduction of depolarization.
Intercalated discs
Site of gap junction. anchor adjacent cells and allow rapid conduction of depolarization.
Smooth muscle location
Typically lines walls of hollow viscera (gut, ureter, fallopian tubes)
Organization of smooth muscle
Circumferential, longitudinal,
innervation of smooth muscle
Involuntary, autonomic control in MOSTLY parasympathetic, but some sympathetic
__ fibers surround the outside of a smooth muscle cell
Elastic
Characteristics of smooth muscle
- Fusiform-shaped cell (spindle shape appearance)
- Single, central nuclei
- Contractions are sustained, forceful, require little ATP, contractions reduce lumen diameter
Also contains actin and myosin filaments and elastic fibers on the outside
How does smooth muscle appear when contracted
When contracted, it shrinks and twists (due to actin and myosin and elastic fibers) and appears like a cork screw
Two main types of smooth muscle activation
Electrical coupling
- Single unit smooth muscle
- Multi unit smooth muscle
Contractile responses
- Tonic (continuous)
- Phasic (rhythmic)
Are smooth muscles commonly single or multi unit?
Single unit is most common. This is when the cells contract as a single unit waves of slow, spontaneous contraction.
Found in gut, bladder
Characteristics of multi unit smooth muscle
Less common compared to single unit. Rapid, brief, and intermittent contraction.
Found in the iris, large arteries, and veins
Tonic vs phasic smooth muscle contractile responses
Tonic- Constant tone. BV walls airways and sphincters. Prevents muscle from being stretched out of shape.
Phasic- on/off/on/off. Typically not contracted, but has intermittent contractions.
GI, urinary, large arteries, reproductive tract
