24. Smooth muscle tissue. Structural, ultrastructural, chemical and functional characteristics.

Smooth muscle tissue is __________ and __________.

unstriated and involuntary.

The cells of smooth muscle tissue originate from __________.

mesenchyme.

Smooth muscle cells are __________ and __________ shaped.

elongated and spindle-like.

Smooth muscle tissue is found in __________, __________, and __________.

blood, lymph vessels, internal viscera.

The function of smooth muscle tissue is to generate force to __________ for vital activities.

contract muscle.

Smooth muscle consists of __________ cells that are arranged in __________ bundles.

mono-nucleated; parallel.

The cytoplasm of smooth muscle cells is called __________.

sarcoplasm.

The sarcoplasm contains __________, __________, and __________ filaments.

thick-myosin; thin-actin; intermediate.

The __________ binds to the myosin in smooth muscle contraction.

calmodulin.

Smooth muscle does not contain __________ but utilizes __________ for cross-bridge formation.

troponin; ATP.

The __________ of the muscle fibre is enveloped by the external lamina.

sarcolemma.

Caveolae provide a large surface area for the __________ of calcium ions.

release.

Smooth muscle contraction is __________ and can resist __________ for much longer.

slower; fatigue.

Smooth muscle contraction is regulated by the __________ nervous system.

autonomic.

Two types of intercellular junctions in smooth muscle are __________ and __________.

zonula adherens; gap junctions.

The presence of gap junctions allows the spread of __________ to adjacent smooth muscle cells.

excitation.

In smooth muscle, synaptic vesicles containing neurotransmitter come into contact with the __________.

sarcolemma.

what does it consists of?

mono-nucleated cells that are elongated and tapered. They are organised into sheets, arranged in parallel bundles, to achieve close packing the adjacent cells overlap and are bound by loose connective tissue

what in sarcoplasm?

the cytoplasm is sarcoplasm with the filaments thick-myosin, thin-actin, intermediate like desmin

have dense bodies scattered around the cell and link intermediate filaments (desmin) to the sarcolemma, allows the intermediate filaments to harness the force generated

caveolae

are small invaginations in the sarcolemma that play a role in signal transduction and calcium entry in smooth muscle cells, for contraction

how contraction is different in smooth muscles

when Ca2+ enter the muscles the Ca2+ bind to calmodium which enable myosin to interact with actin, the smooth muscle doesn’t have troponin so the cross-bridges form straight away with the help of ATP

what intercellular junctions do smooth muscles have?

• zonula adherens for adhesion and anchor cell during contraction

• gap junctions provide electrical coupling

how smooth muscles regulated

autonomic nervous system

axon have synaptic vesicles which come into contact with the sarcolemma and the presence of a gap junction allows the spread of excitation to adjacent cells therefore the contractions are synchronised