Membrane potential in cardiac muscle Resting membrane potential in cardiac muscle The resting membrane potential in cardiac muscle is – 90 mV, but has long action potential (250msec). Cardiac muscle = – 85 to – 95 mV Conduction system = – 90 to -100 mV Ventricle muscle = -100 to -105 mV S.A. node = […]
Physiology of Cardiac muscle Involuntary, single centrally located nucleus, numerous mitochondria. The T-tubular of mammalian cardiac muscles are larger (esp. in Ventricles) than those of skeletal muscles and are located at the Z lines rather than at the A – I band junction as in skeletal muscles fibers. While the groups of skeletal muscle fibers
Action potential in smooth muscle Slow wave rhythm Some smooth muscles are self excitatory i.e. elicite AP with out an extrinsic stimuli; due to waxing and waning of pumping of Na+ outward – if rapid sudden decrease in electronegativity, if slow gradual decrease in electronegativity and once reaches – 35 mv causing action potential. ie., most of
Smooth muscle tissue Contains action and myosin filaments with are not orderly arranged. So there no striations present in smooth muscle tissue. Two types of smooth muscles- 1. Visceral smooth muscles About 99% of the smooth muscles are of the unitary type. The fibers are tightly bound together top form continuous network called ‘syncytium’ and wrap
Work done by the muscle Work done (W) = (Hxl)/L here- L – Length bet fulcrum and the tip of the lever L – Length bet fulcrum and the weight load H – Observed HT on contraction The chemical energy liberated during contraction is party converted into mechanical energy with fibers indicated fraction of total
Muscle metabolism Sarcoplasm contains creatine kinase and also myosin kinase. ADP degraded to AMP and ATP. AMP produced is degraded to IMP – inositol monophosphate by adenylic deaminase, which again converted to uric acid and excreted. Hydrolysis of ATP produces 7.3 kcal/mol. ATP + H2O → ADP + H3PO4 + 7.3 Kcal Metabolism of glucose
Thermal changes during muscle contraction Out of total energy liberated by the hydrolysis of ATP in a contracting muscle, only 40-45% can be converted into work energy and the rest is evolved as heat; i.e. the efficiency of muscle contraction is about 45%. It is recorded by using thermopile. Thermopile has plates of antimony and bismuth
Rigor mortis in muscles Process that causes the muscles in the body to stiffen resulting in rigidity due to a range of chemical changes in the muscle structure. Rigor mortis starts in the 2nd hour and is completed in 3 hrs after death. Rigor mortis disappears 24 – 36 hrs after death due to autolysis. Deficiency
Muscle fatigue Muscle Fatigue is the decrease in the working capacity of a muscle or tiredness of the muscle when it is continuously stimulated. It is characterized by diminished force of contraction, increased latent period and contraction period and prolonged relaxation period. The relaxation is incomplete i.e., the muscle is in a state of contracture‚
Factors influencing the strength of contraction in muscles Starling’s law The first factor is governed by the strength of stimulus. The second is mostly by the rate of effective stimuli. The last is by the initial length of the muscle fiber. In cardiac muscle, mechanical summation is impossible because of prolonged action potential (250msec.) almost completely overlaps
Factors influencing the strength of contraction in muscles Read More »
