Animal Muscles

This makes heart transplantations possible video 47

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Unformatted text preview: ntations possible ! Video-47-04.mpg! Gap Junctions •  Cardiac and smooth muscle cells are arranged in sheets. •  Cells in the sheet are in electrical contact via gap junctions. •  An action potential in one cell can spread to all others in the sheet. ! Figure 5.7 Junctions Link Animal Cells Together (C)! GAP GAP junctions: junctions •  Connect the cytoplasm of two neighboring cells. •  Allows direct electrical communication between cells. •  Allows direct chemical communication between cells (small second messengers, such as IP3 and Ca2+) •  Allows passage of molecules smaller than ~1,000 Daltons. •  Allow cardiac and smooth muscle cells to contract simultaneously. ! Gap junctions allow communication ! calcium-waves.mov Video-47-04.mpg! ! Tissue Layers of the Vertebrate Gut! Smooth Muscle Smooth muscle: •  Are the simplest muscle cells structurally. •  Single nucleus/cell. •  “Smooth” because actin/myosin are not as regularly arranged. •  Present in most internal organs (e.g. GI-tract, bladder, blood vessels) •  Under autonomic nervous system control. ! Smooth muscle cell and endothelial cell surrounding blood vessel and smooth muscle cell ! Jejunum ! 47.1 How Do Muscles Contract? What is a “twitch”? Skeletal muscle: minimum unit of contraction = a twitch. A twitch is measured in terms of tension, or force it generates. A single action potential generates a single twitch. ! 47.1 How Do Muscles Contract? Single twitch: if action potentials are close together in time, the twitches are summed, tension increases. Twitches sum because Ca2+ pumps can not clear Ca2+ from sarcoplasm before the next action potential arrives. Tetanus: when action potentials are so frequent there is always Ca2+ in the sarcoplasm. ! Twitches and Tetanus How Do Muscles Contract? How long muscle fiber can sustain tetanic co...
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This note was uploaded on 02/13/2014 for the course MCDB 1B taught by Professor Weimbs during the Winter '08 term at UCSB.

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