Muscular Tissue (Smooth Muscle) Flashcards
regulatory protein that facilitates contraction in smooth muscles
calmodulin
sarcoplasmic structure that attaches to the sarcolemma and shortens the muscle as thin filaments slide past thick filaments
dense body
process in which one cell splits to produce new cells
hyperplasia
subset of a cross-bridge in which actin and myosin remain locked together
latch-bridges
cell that triggers action potentials in smooth muscle
pacesetter cell
relaxation of smooth muscle tissue after being stretched
stress-relaxation response
enlargement of neurons that release neurotransmitters into synaptic clefts
varicosity
Smooth muscle found in the walls of visceral organs
visceral muscle
named as such because the cells do not have striations
Smooth muscle
It is present in the walls of organs that contain a lumen like the urinary bladder, uterus, stomach, and intestines, and in the walls of large vascular tubes, such as the arteries and veins of the circulatory system.
Smooth muscle
(6) Smooth muscles are present in these organ walls that contain a lumen.
urinary bladder
uterus
stomach
intestines
in the walls of large vascular tubes, such as the arteries and veins of the circulatory system
These tracts contain smooth muscle.
The tracts of the respiratory, urinary, and reproductive systems
Smooth muscle is also present in this organ, where it functions to change the size of the pupil
Eye
Smooth muscle is also present here, where it causes hair to stand erect in response to low temperatures or fear. ).
skin
Smooth muscle is also present here, where it causes hair to stand erect in response to low temperatures or fear.
skin
It is referred to as an involuntary muscle since it is not under voluntary control. In certain locations, such as the walls of visceral organs, stretching the muscle can trigger its contraction (the stretch-relaxation response)
Smooth muscle
Smooth muscle contraction relies on the presence of ___________ similar to skeletal and cardiac muscle.
Ca++ ions
The influx of extracellular Ca++ ions, which diffuse into the sarcoplasm to reach a protein called __________.
calmodulin
A small amount of calcium remains in the ____________ to maintain muscle tone and keep the cells contracted to a small degree.
sarcoplasm
Functions of smooth muscle
Moves food, urine, and reproductive tract secretions
Controls diameter of respiratory passageways
Regulates diameter of blood vessels
Smooth muscle is not under voluntary control; thus, it is called ___________.
involuntary muscle
Enumerate the triggers for smooth muscle contraction
hormones;
neural stimulation by the ANS;
and local factors
Also, stretch-relaxation response
In certain locations, such as the walls of visceral organs, this one can also trigger the contraction.
stretching the muscle (stretch-relaxation response)
series of neurotransmitter-filled bulges
varicosities
It releases neurotransmitters into the synaptic cleft. Also, visceral muscle in the walls of the hollow organs (except the heart) contains pacesetter cells.
varicosity
It can spontaneously trigger action potentials and contractions in the muscle.
pacesetter cell
It is aseries of axon-like swelling, from autonomic neurons form motor units through the smooth muscle.
varicosities or “boutons,”
These are spindle-shaped (wide in the middle and tapered at both ends, somewhat like a football) and have a single nucleus; they range from about 30 to 200 μm (thousands of times shorter than skeletal muscle fibers), and they produce their own connective tissue, endomysium.
Smooth muscle fibers
Although they do not have striations and sarcomeres, they do have actin and myosin contractile proteins and thick and thin filaments. These thin filaments are anchored by dense bodies.
smooth muscle fibers
It is analogous to the Z-discs of skeletal and cardiac muscle fibers and is fastened to the sarcolemma. Calcium ions are supplied by the SR in the fibers and by sequestration from the extracellular fluid through membrane indentations called calveoli.
dense body
Smooth muscle is organized in two ways
a. as single-unit smooth muscle
b. as multiunit smooth muscle
It has its muscle fibers joined by gap junctions so that the muscle contracts as a single unit.
Single-unit muscle
This type of smooth muscle is found in the walls of all visceral organs except the heart (which has cardiac muscle in its walls), and so it is commonly called visceral muscle.
Single-unit muscle
It produces slow, steady contractions that allow substances, such as food in the digestive tract, to move through the body.
visceral smooth muscle
It is rarely possess gap junctions, and thus are not electrically coupled. As a result, contraction does not spread from one cell to the next, but is instead confined to the cell that was originally stimulated.
Multiunit smooth muscle cells
Stimuli for multiunit smooth muscles come from _____________ but not from stretching. This type of tissue is found around large blood vessels, in the respiratory airways, and in the eyes.
autonomic nerves or hormones
Unlike other muscle, smooth muscle can also divide to produce more cells, a process called ____________.
hyperplasia
This can most evidently be observed in the uterus at puberty, which responds to increased estrogen levels by producing more uterine smooth muscle fibers, and greatly increases the size of the myometrium.
Hyperplasia
These are nonstriated, but their sarcoplasm is filled with actin and myosin.
smooth cells
Single-unit smooth muscle in the walls of the viscera, which has a stress-relaxation response that permits muscle to stretch, contract, and relax as the organ expands.
visceral muscle
It do not possess gap junctions, and contraction does not spread from one cell to the next.
Multiunit smooth muscle cells
