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Unformatted text preview: pomyosin blocks the binding sites on
! The Release of Ca2+ from the Sarcoplasmic Reticulum Triggers Muscle Contraction 47.1 How Do Muscles Contract? When Ca2+ is released, it binds to troponin, which
changes conformation. If Ca2+ remains
conformation! Tropomyosin! ! myosin-movie.mov ! Troponin! Myosin
binding site! Ca2+! Myosin filament! Troponin is bound to tropomyosin—twisting of
tropomyosin exposes binding sites on actin. When Ca2+ pumps remove Ca2+ from sarcoplasm,
contraction stops. Ca2+ binds troponin
Ca2+ is released from
on actin! Power stroke:
ATP binds causing
actin! Myosin heads bind
actin; release of Pi
stroke! sliding-actin.mov ! Heart muscle cell ! Heart muscle cell: mitochondria ! Heart muscle cell: M-band Heart muscle cell: thin filaments (actin) ! ! Heart muscle cell: ribosomes ! Junction between two muscle cells ! Junction between two muscle cells: plasma membranes Junction between two muscle cells: desmosomes Junction between two muscle cells: Z-lines Junction between two muscle cells: T-tubules and SR ! ! ! ! Figure 47.7 There are Three Kinds of Muscle! Cardiac muscle
Cardiac muscle • Is also striated.
• Cells are smaller than skeletal muscle cells.
• Cells have one nucleus.
• Cardiac muscle cells also branch and
interdigitate: can withstand high pressures. ! Cardiac Muscle Pacemaker and conducting cells initiate and
coordinate heart contractions.
The heartbeat is myogenic—generated by the heart
The autonomic nervous system modifies the rate of
pacemaker cells, but is not necessary for their
! this makes heart transpla...
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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.
- Winter '08