Fundamental Human Mascular System

​1.Binding of ATP ->myosin heads in resting stage

2.Myosin heads split ATP and become reoriented and energized

3.Myosin heads bind to actin ( Calcium ion binds to troponin-> tropomyosin moves away from myosin-binding site )

4.Myosin filament moves toward center of sarcomere

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​- Striation from myofibril

- ​Location: attached to bone/skin

- Many nuclei per cell

- Cell: very long, cylindrical​

- No gap junction

- ​Voluntary system

- Speed of contraction: Slow to fast​

​Skeletal Muscle

Skeletal Muscle | 1

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​​Structure

​Sliding filament model

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​- No striation (No myofibrils /sarcomere pattern)

- ​Location: walls of visceral organ

- 1 nucleus per cell (central)

- Cell: spindle-shaped​

- Gap junction in single-unit muscle​

Structure

- Rhythmic contraction​/very slow

- Varicosities: autonomic nerve

- Calmoduin : calcium-binding protein​

Cell

- Dense body

- Thick myosin filament (longer than skeletal)​

- Thin actin filament (have tropomyosin/lack troponin)​

Contraction

​Smooth Muscle

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​Smooth Muscle | 2

• Location: walls of the heart

• 1-2 nuclei per muscle cell

• Branching chains of cell

• Intercalated discs between cell

• Gap junction : communicating between cells -> cell contract at the same time

• Involuntary system

• Slow rhythmic contraction

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Cardiac Muscle | 3

Cardiac Muscle

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Multiple Choice

Which is not correct about the muscle in picture?

• Related to involuntary system

• Cell has 1 nucleus

• No presence of gap junctions

• Has rhythmic contraction

Multiple Choice

Which of these graphs shows cardiac muscle's speed of contraction?

(Each graphs represents different muscle)

Multiple Choice

Which step (from 4 choices) happened first in sliding filament model?

• Calcium ion binds to troponin

• Actin filament moves toward center of sarcomere

• Myosin heads bind to actin

• Tropomyosin moves away from myosin-binding site