Muscle Structure and Function

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Muscle Structure and Function

• Biology 2121
• Chapters 9-10

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Introduction

• 1. Functions
• Movement, Posture Heat and Joints
• 2. Naming (321)
• Location Shape (temporalis deltoid)
• Size (gluteus maximus)
• Fiber Direction (abdominus rectus)
• Origins (bicep)
• Location of Attachment (sternocleidomastoid)

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Major Muscle Groups
Chest and Shoulder Group
Abdominals
Quadriceps and Hamstring Group
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Histology of Muscle Tissue- Skeletal Muscle

• Voluntary
• Found in major muscle groups
• Striated
• Multinucleated
• Peripheral

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Smooth Muscle

1. Involuntary
2. Found in digestive system organs, bladder, etc.
3. Non-Striated
4. Uninucleated
5. Spindle-Shaped nuclei

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Cardiac Muscle

• Involuntary
• Heart only
• Branching Fibers
• Uni-Nucleated

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Gross Anatomy

• 1. Whole muscle
• Epimysium
• 2. Fascicles
• Perimysium
• 3. Muscle Fiber Cells
• Long and multi-nucleated
• Sarcolemma and sarcoplasma
• Endomysium

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Attachments

• Tendons
• Aponeurosis
• Direct or Indirect Attachments

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Microscopic Anatomy Myofibrils

• 1. Contractile proteins
• 2. Sarcomeres
• Actin and myosin
• 3. Myofilaments
• Actin (thin)
• Myosin (thick)

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Sarcomere

• 1. A sarcomere
• Z to Z
• I-Band (light zone)
• A-Band (dark zone)
• 2. Structural Proteins
• Elastic filaments Titan
• 3. Sliding Filament Model of Contraction
• Link

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Sarcomere Contraction
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Chemical Stimulation and Muscle Contractions

• 1. Stimulation and Neurotransmitters
• Acetylcholine
• 2. Neuromuscular Junction
• Junction muscle/nerve interface
• Separation synapse

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Neuromuscular Junction
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Events at the Neuromuscular Junction

• 1. Nerve Impulse
• 2. Calcium ions Axon Terminal of Nerve
• 3. Vesicle and release of ACh
• 4. ACh receptors and Acetylcholinesterase
• 5. Sodium-Potassium exchange
• 6. Action Potential formed

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Neuromuscular Junction
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Action Potential

• 1. Resting Membrane
• -70 mV
• Na and K
• 2. Reversal of Charges
• Depolarization
• 3. Moves in one Direction

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What Happens after the Action Potential is Formed?
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Excitation and Contraction

• 1. Action Potential moves along the sarcolemma
• 2. Down the T-Tubule
• 3. Sarcoplasmic Reticulum and Release of Ca
• 4. Ca moves to the sarcomere

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Formation of a Cross-Bridge

• 1. Ca interacts with troponin
• 2. Removes tropomyosin
• 3. Allows for Myosin Head Attachment
• 4. Formation of a cross- bridge

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Cross-Bridge Cycling

• 1. Myosin heads attach forming cross- bridge
• 2. Working Stroke
• 3. ATP breaks cross- bridge
• 4. ATP hydrolysis
• 5. High-energy configuration New Cross-bridge
  

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ATP and Muscle Metabolism
ATP Functions Driving Cellular Work
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ATP Production

• 1. Creatine Phosphate Quick and Fast!!!
• 2. Anaerobic Respiration
• Lactic Acid Fermentation
• 1 glucose molecule 2 ATP Net
• 3. Aerobic Respiration
• 1 glucose molecule 36 ATP Net
• Mitochondria of the Cell

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Aerobic Respiration
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Fermentation

• Glycolysis
• (2) Pyruvic acid molecules (3-C)
• Blood flow restricted during vigorous exercise
  (low oxygen)
• Lactic acid formed
• Anaerobic glycolysis