Energy for Muscle Contraction
Direct Phosphorylation
Aerobic Respiration
Anaerobic Glycolysis
Vocabulary
• Aponeurosis: A sheetlike fibrous membrane that binds muscles together or as a means of connecting muscle to bone.
• Motor Unit: A single motor neuron and all the muscle fibers it stimulates.
• Ligament: A sheet or band of tough, fibrous tissue connecting bones or cartilages at a joint
Vocabulary
• Epimyusium: The external sheath of connective tissue surrounding a muscle. (outermost)
• Perimysium: The fibrous sheath enveloping each of the primary bundles of skeletal muscle fibers. (Middle)
• Endomysium: The connective tissue layer surrounding an individual skeletal muscle fiber. (Innermost)
Direct Phosphorylation
• Uses Creatine Phosphate – Found only in muscle – Regenerates ATP
from ADP– CP exhausted in 20
seconds– No Oxygen Used
Aerobic Respiration
• Generates ATP in mitochondria
• Uses Oxygen• Oxidative
Phosphorylation• Glucose is broken
down to CO2 and H2O– 36 ATP per 1 glucose– Slow process– Lasts for hours
Anaerobic Respiration
• Glycolysis uses no oxygen
• Occurs in cytosol• Broken down to pyruvic
acid which is converted to lactic acid when oxygen cannot keep up to demand
• 2 ATP per glucose• 30-60 seconds
Energy Sources
• First: Glucose• Second: Pyruvic
Acid• Third: Fatty Acids
stored in adipose tissue
• Fourth: Amino Acids from protein catabolism
Muscle Fatigue
• Muscle cannot contract even when stimulated
• Weaker and weaker until it stops
• Results from Oxygen debt
• Build up of lactic acid and lack of creatine phosphate and ATP reserves
Oxygen Debt
• Prolonged workouts
• Oxygen uptake can no longer keep up
• Results in rapid or deep breathing
• Muscle may quit entirely
Hitting the Wall
• Bonk• Glycogen depletion• Extreme fatigue• Remedied by
carbohydrates
Movements
• Flexion• Extension• Hyperextension
Movements
• Abduction• Adduction• Circumduction
Movement
• Plantar Flexion• Dorsiflexion
Movement
• Rotation• Medial Rotation• Lateral Rotation
Movement
• Supination• Pronation
Movement
• Inversion • Eversion
Review Sarcomere
More Vocabulary:
• Sarcolemma: Plasma membrane of a muscle cell
• Myofibril: Long organelles that fill the cell and are composed of myofilaments
• Myofilaments: threadlike protein fibers– Thick filaments = Myosin– Thin Filaments = Actin
Muscle Characteristics
• Skeletal: Multinucleate, Striated, Long Thin Cells. Attached to bones. Voluntary
• Cardiac: Branched, Uninucleate, Striated, Intercalated discs. Walls of Heart. Involuntary
• Smooth: Fusiform (tapered), Uninucleate, No striations. Involuntary.
Vocabulary• A Bands = Dark bands of a myofibril• I Bands = Light bands of a myofibril• Z Disc or Z Band= Interruption in the
center of the I Band• M Line: Holds thick filaments together and
can be seen in the center of the H zone• H Zone: Light central area of sarcomere
that lacks actin (also bare zone) this disappears during contraction when fibers overlap
Muscle Contraction Review
1. Motor neuron is stimulated and the action potential travels along the neuron.
Muscle Contraction
2. Acetylcholine is released from the neuron end plate into the neuromuscular junction
Muscle Contraction
3.Acetylcholine diffuses across the neuromuscular junction gap
Muscle Contraction
4. The muscle fiber membrane is stimulated, impulse travels through transverse tubules to sarcoplasmic reticulum
Muscle Contraction
5. Sarcoplaspic reticulum releases Ca+2 into the sarcoplasma
Muscle Contraction
6. Calcium binds to troponin on the actin (thin) filaments allowing myosin (thick) filaments to form cross-bridges
Muscle Contraction
7&8 Power Stroke occurs and repeats as long as calcium is present and the muscle shortens
Muscle Contraction
9. Motor neuron stimulation stops. Cholinesterase causes the breakdown of acetylcholine
Muscle Contraction
10. Calcium ions are pumped out into the sarcoplasmic reticulum using active transport
Muscle Contraction
11& 12 Linkages between actin and myosin are released. The muscle relaxes to its pre-stimulated length
Quiz Tuesday – Muscle Physiology
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