LEC-4 Smooth Muscle Physiology Flashcards
Elevated blood pressure in the systemic circulation is referred to as _____________.
Hypertension
Chronic hypertension may lead to _______________.
Cardiovascular disease
In atherosclerotic vessels, smooth muscle surrounding the vessel is known to (regress/proliferate)
Proliferate
Vascular smooth muscle may grow by (hypertrophy/hyperplasia/both).
Both
Smooth muscle cells range anywhere from ___ - ___ μm in length and ___ - ___ μm in diameter.
20-500 μm in length 1-5 μm in diameter
(T/F) Smooth muscle utilizes the same proteins and complexes as skeletal muscle for muscle contraction.
False. Skeletal muscle uses an actin/tropomyosin/troponin complex to complete muscle contraction. Smooth muscle, on the other hand, utilizes the following:
- Actin/tropomyosin/calmodulin/caldesmon complex.
Adjacent smooth muscle cells make use of _____________, low-resistance electrical pathways between cells.
Gap junctions
______________ serve as attachment points for thin actin filaments in smooth muscle cells, making them akin to Z-bands.
Dense bodies
The sarcoplasmic reticulum in smooth muscle cells is (smaller/larger/the same size) in relation to the sarcoplasmic reticulum of skeletal muscle.
Smaller
Small invaginations of the smooth muscle cell membrane are referred to as __________.
Caveolae
The absence of structure regularity in smooth muscle cells is noted as the reason for the absence of __________.
Striations
Myosin filaments within smooth muscle often have side-polar crossbridges, allowing for contraction of up to ___% of the fiber length versus the 30% that is possible in skeletal muscle.
80%
Smooth muscle cells possess a (more/less) efficient ATPase than that of skeletal muscle. This results in (faster/slower) cycling of myosin cross-bridges.
- Less efficient
- Slower cycling
Smooth muscle requires markedly (more/less) energy to complete a contraction than skeletal muscle.
Less
- Requires 1/10 - 1/300th the amount of energy as skeletal muscle
Smooth muscle possesses a “latch mechanism” that facilitates (shortened/prolonged) contraction.
Prolonged
(T/F) Due to the latch mechanism, once full contraction is achieved in smooth muscle, the amount of excitation and energy consumed to maintain contraction is greatly reduced.
True.
The maximum force of smooth muscle contraction is (greater/less) than that of skeletal muscle.
Greater
(T/F) It takes smooth muscle a considerable amount of time to return to its original state after being contracted or lengthened.
False. One of smooth muscle’s key characteristics is its ability to quickly return to its original state after contraction or lengthening. This allows smooth muscle to maintain the same amount of force within hollow organs.
(T/F) Smooth muscle does not use sodium as its primary depolarizing agent. Instead, it uses calcium and calcium-activated proteins to conduct muscle contraction. Calcium also extracellularly enters the smooth muscle cell fairly often, instead of just from the sarcoplasmic reticulum during contraction.
True.
_________________ serves to dephosphorylate myosin chains in smooth muscle when relaxation is necessary.
Myosin light chain phosphatase
What would the action potential of visceral smooth muscle look like in a non-pregnant uterus?
Image
What would the action potential of visceral smooth muscle look like in a ureter?
Image
What would the action potential of visceral smooth muscle look like in longitudinal muscle of the intestine or myometrium during parturition?
Image
Smooth muscle has a markedly (longer/shorter) latent period than does skeletal muscle.
Longer
(Diffuse/Contact) junctions consist of vesicle-filled varicosities in the vicinity of smooth muscle cells. They possess a 1-5μm distance between cells along with a widely varying number of innervated cells.
Diffuse (Visceral smooth muscle)
(Diffuse/Contact) junctions are morphologically similar to the neuromuscular junction of a skeletal muscle. They possess a 20nm synaptic cleft along with innervation for every cell.
Contact (Multi-unit smooth muscle)
