Download Force of Contraction Number of fibers and stimuli Temporal

Force of Contraction
Number of fibers and stimuli
Temporal
summation and
recruitment of
fibers
Size of muscle--larger muscle, larger force
Elastic Elements
-Non-contractile elements of muscle cells
1) Connective tissue
2) Tendons
3) Organelles
4) Sarcolemma
Supporting proteins
1) Titin
2) Nebulin
Tension
Overcome elasticity
a. Internal tension—overcome
noncontractile elements
b. External tension--overcome actual load
Velocity and Duration of Contraction
-Size of load determines velocity of shortening
Energy for Muscle Contraction
A. Metabolism--all biochemical events
1. Anabolism--build up
2. Catabolism--break down
3. Cellular (internal) Respiration--generate ATP
4. Metabolic Flow--from beginning to end
Process of taking energy in ! utilizing it to build
structural and functional products and ATP !
removing waste
Substrate Phosphorylation
--Typically see with formation of ATP
(Direct phosphorylation)
X䍐P + ADP ! X + ATP
Cofactors:
NAD+
FAD+
Oxidative Phosphorylation
Mitochondrion--electron transport chain--multistep process; involves oxygen
(Indirect phosphorylation)
Mechanisms of ATP Synthesis
1. Anaerobic Sources of ATP
a. Stored ATP--myosin head (pre-synthesized)
ATP
b. Creatine kinase
Creatine䍐P + ADP ! ATP + Creatine
Quickest sources of energy
Glycolysis--glucose breakdown
Yields the following from 1 molecule of glucose:
1) 2 pyruvates (pyruvic acid)
2) a net of 2 ATP (immediate energy)**
3) 2 forms of NAD+!
Pathway of Glycolosis--enzymes in cytoplasm of cell
a) sugar activation--invest 2 ATP
convert glucose to fructose
F-1,6-P
This molecule is “energized”
b) Sugar cleavage
Break 6-carbon molecule into 2, 3-carbon
molecules, each carrying phosphate
DHAP
G-3-P
c) Oxidation and ATP formation
C molecule is
oxidized: H atoms
removed and
transferred to NAD
(NADH + H+)
4 ADP are
phosphorylated to ATP
(net +2 ATP)
Glycolysis
Continue
Later
Aerobic Respiration
Mitochondrial--3 processes:
1) Conversion of pyruvate to Acetyl CoA (2
molecules)
3C pyruvate ! 2C (acetyl CoA); Release CO2
generate NADH +H+
;
2) Krebs Cycle
Acetyl CoA (2C) broken down completely to yield:
3 NADH + H+ x 2
1 FADH2, x 2
1 ATP x 2
Glucose was split in half during glycolysis.
Two “turns” of the Krebs cycle per glucose molecule.
CO2 is waste
Mitochondrial matrix
Enzymes
at each
step
3)! Electron Transport Chain
--extracts energy from
reduced compounds and synthesizes ATP
Splits H atom into proton and e-
Uses O2!!!
Summary of Energy Produced
Muscle Work
1. Energy Production
a. Anaerobic--does not require O2
b. Aerobic--requires O2
Anaerobic Threshold--during
heavy exercise, an increase in
blood lactate is seen.
Interpreted to mean that body
was converting from aerobic
(Krebs, etc) to anaerobic
(glycolysis) mechanisms for
ATP synthesis due to lack of
oxygen in mitochondrion.
This definition is untrue.
Oxygen is present in the
mitochondrion.
Krebs and e.t.c enzymes
have collectively slower
velocity than the
glycolysis enzymes.
During exercise, lactate
builds up.
Lactate is not a waste
product, it is also a fuel.
wrong
Fatigue
a. Definition--ATP production fails to keep pace
with usage
psychological factors, pH, neurological
transmission of action potential, mitochondrial
function (chronic fatigue syndrome)