Chapter 1 Flashcards
The Sliding Filament Theory of Muscle Contraction
actin that is present at the end of sarcomeres moves inward toward myosin, and this pulls the Z-lines in to the center of the sarcomere. Shortening the muscle fibre.
The Resting Phase: There is not a lot of calcium in the myofibril, so we don’t see many myosin cross bridges bound to actin.
The Excitation Contraction Coupling Phase: The sarcoplasmic reticulum releases calcium when it is stimulated. Calcium ions bond with troponin. All of this causes a shift in tropomyosin. Myosin cross bridges attach quicker to actin.
The Contraction Phase: Hydrolysis of ATP occurs and causes contractions of the fibers.
The Recharge Phase: This happens when calcium is available.
The Relaxation Phase: The stimulation stops. Calcium is pumped into the Sarcoplasmic reticulum for use later, thus actin and myosin cannot link.
Muscle Connective Tissues
Epimysium, Perimysium, Endomysium
Muscle Contraction Signal
Action potential discharging from a motor nerve releases calcium from sarcoplasmic reticulum. Enters the myofibril and develops tension.
Contraction of Myofibril
When stretched, H-zone and I-bands are longer, low potential for force due to reduced cross bridge to actin alignment. They shorten in a contraction.
Steps of Muscle Contraction
ATP splitting begins and myosin heads become “energized”. This allows movement into position for bonding with actin to the myosin heads.
Phosphate is released from ATP ad the myosin head changes shape and shifts.
The power stroke occurs as the actin filament is pulled toward the center of the sarcomere.
After the power stroke, myosin heads detach from actin as another ATP binds.
Muscle Spindles vs GTO
Proprioceptors
Spindles are in muscle sheath and activate to cause a contraction when muscle is stretched.
GTOs are in tendons and activate to inhibit action and reduce tension to protect tissue
Ventricle Functions
Right: lungs, Left: body
Heart Conduction System Series
SA Node, AV Node, AV Bundle, Bundle Branches, Purkinje Fibres
