University:
Glendale Community College
Course:
BIO160 | Introduction to Human Anatomy and Physiology
Academic year:

2019
Views:

467

Pages:

4
Author:

Davon Fischer

Smooth Muscle • Fusiform cells with one nucleus – no visible striations or sarcomeres – thin filaments attach to dense bodies scattered throughout sarcoplasm and attached to the sarcolemma – thick filaments are suspended between the thin filaments – gap junctions spread depolarization from cell to cell – calcium for contractions comes from poorly developed SR and from extracellular fluid • If present, nerve supply is autonomic – Neurotransmitter can be either ACh or norepinephrine – Neurotransmitters have different effects in different locations • Contraction and relaxation is very slow in comparison to striated muscle. • Smooth Muscle is very efficient and uses 300 times less ATP to maintain a given tension than skeletal muscle • Smooth muscle can be stimulated by neurotransmitters, hormones, high CO2, low O2, low pH, stretch. Responses of Smooth Muscle to Stretch • Stretch opens mechanically-gated calcium channels causing muscle contraction. – example: food in the intestines brings on peristalsis • Stress-relaxation response necessary for hollow organs that gradually fill (urinary bladder). – when stretched gently, tissue briefly contracts then relaxes • Contracts forcefully when greatly stretched. • Contraction force matches degree of stretch. Contraction of Smooth Muscle Cells These cultured rat aorta smooth muscle cell were immunofluorescently labeled with primary anti-vinculin mouse monoclonal antibodies followed by goat anti-mouse Fab fragments conjugated to Cy3 (red fluorescence emission). Note the prominent staining of the cellular attachment network in the central portion and periphery of these cells. In addition, the specimen was simultaneously stained for DNA with the ultravioletabsorbing probe DAPI, and for the cytoskeletal filamentous actin network with Alexa Fluor 488 conjugated to phalloidin. Images were recorded in grayscale with a QImaging Retiga Fast-EXi camera system coupled to an Olympus BX-51 microscope equipped with bandpass emission fluorescence filter optical blocks provided by Omega Optical. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.