The Muscular System

Chapter 6

Muscle Functions Producing movement – complex movement

such as walking, or simple facial movement Maintain Posture – tiny adjustments

happen constantly to keep balance Stabilizing Joints – muscles and tendons

keep bones of various joints together. Generating Heat – Muscle activity produces

heat

Smooth Muscle No Striation Involuntary. Walls of hollow organs Uninucleated Slow moving but

tireless

Cardiac Muscle Only in Heart Striated Involuntary Branching cells

Skeletal Muscle Aka striated muscle Multinucleated cells Voluntary Soft and fragile, but

can exert tremendous power.

Skeletal Muscle Muscle cells need to be wrapped and

supported by connective tissue to make sure they do not rip apart.

A pulled muscle can sometimes be a breaking of this connective tissue sheet.

Muscles are bundled multiple times for added strength.

Tendons The connective tissue that surround muscle cells

will gather at the ends of muscles to form tendons.

Tendons are slender and strong, attaching the muscle to bones and other muscles.

They are more durable then muscle cells and can wrap over bone without breaking, they are also thinner allowing for more to cross over joints.

Micro Lab

Skeletal Muscle Anatomy

Muscle Cell Anatomy The muscle cell is full

of myofibrils. The striation or stripes

of a skeletal muscle cell come from Sarcomeres – active section of the myofibrils that line up end to end like cars in a train.

Sarcomere Anatomy The sarcomere is

made up of two main parts. Actin and Myosin.

Myosin (red) Actin (blue) Notice the space

between the actin – important for contractions

Mechanism of Muscle Contractionsliding filament

Sarcomere Anatomy When each individual

sarcomere shortens the entire muscle shortens. This is a contraction.

Contractions are started by nerve impulses, more on that next chapter.

Exercise Aerobic/Endurance – Increases blood flow

to muscles, more mitochondria in cells. Muscle cells do not increase in size. Helps in digestion, strengthens skeleton, heart

Resistance/Isometric – muscles are pitted against immovable objects. Actin and myosin filaments get thicker to be able to hold better. Makes the cells thicker. No new cells for the most part.

Isometric Contractions Muscles do not always contract when

nerves signal them too. When pushing against an immovable

object, myosin tries to grab and pull actin, however, their grip slips and actin doesn’t move. Think about a car spinning its wheels, gas is being used, but the car isn’t moving.

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Muscle Energy Millions of molecules or ATP are used just to

contract one muscle once. Where does it come from?

Aerobic Respiration – making ATP from breaking down food. 36 ATP : 1 Glucose

Anerobic Respiration – lactic acid fermentation. Without oxygen, the muscle will make ATP and lactic acid through a type of fermentation. 2 ATP : 1 Glucose

Muscle Energy Direct phosphorylation by Creatine

phosphate – Creatine phosphate found in the muscles can artificially add a phosphate to ADP to make ATP, giving it more energy again. Can only occur for about 20 seconds before the creatine is depleted.

Muscle Fatigue Usually due to oxygen debt. Muscles with good blood supply will fatigue

less. Oxygen debt must be paid back, even after

activity stops. We will breathe heavily and deeply after a run until our muscles receive the oxygen they lack.

Hand Dynamometer Activity

Muscle Attachment Origin – attachment to

the immovable bone. Insertion – attachment

to the movable bone

Five Golden Rules of Muscles Most muscles cross at least one joint Most of the muscle lies proximal to the joint

crossed All muscles have at least two attachments. Muscles can only pull, never push During contraction, the insertion always

moves toward the origin.

Finish Lab

Types of body movements Flexion – generally

makes decreases the angle of the joint. Hinge joints

Extension – opposite of flexion, increases the angle of the joint.

Hyperextension – when the joint bends in a way that it normally wouldn’t

Types of body movements Rotation – movement

of bones back and forth around an axis. Shaking your head no is a rotation.

Types of boy movements Abduction – moving a

limb away from the midline of the body

Adduction – moving a limb toward the midline of the body.

Types of body movements Circumduction –

Combination of flexion, extension, abduction, and adduction. Seen in ball and socket joints.

Muscle interactions Muscles can only pull, never push. Because of this, muscles usually work in

pairs, when one contracts, the other relaxes.

Prime Mover vs. Antogonist. Synergists – muscles that help prime

movers.

Face and Neck

Shoulder and Chest

Abdominal Muscles

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