muscles l.
Skip this Video
Loading SlideShow in 5 Seconds..
MUSCLES PowerPoint Presentation
Download Presentation

Loading in 2 Seconds...

play fullscreen
1 / 159

MUSCLES - PowerPoint PPT Presentation

  • Uploaded on

MUSCLES. FUNCTIONS OF MUSCULAR SYSTEM. Body movement Maintain posture Respiration Produce body heat Communication Constriction of organs and blood vessels Heartbeat . Connective Tissue Sheaths in Skeletal Muscle. Figure 10.1a. Connective Tissue Sheaths.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'MUSCLES' - king

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
functions of muscular system

Body movement

Maintain posture


Produce body heat


Constriction of organs and blood vessels


connective tissue sheaths
Connective Tissue Sheaths
  • The MUSCLE FASCIA is loose connective tissue on the outside of the muscle. It creates a slippery surface for muscles to rub against each other. Superficial to the fascia is fat. Deep to the fascia is the EPIMYSIUM, (dense irregular fibrous connective tissue), and which eventually becomes the tendon (which is connected to bone). The epimycium extends into the muscle belly to form compartments called FASICLES. This tissue surrounding the fascicles is now called the PERIMYCIUM. Each fascicle contains MUSCLE FIBERS, which are individual muscle cells, each one surrounded by ENDOMYCIUM. When you eat steak and find it’s stringy, each string is a fascicle.
types of muscle patterns
parallel muscle

The fascicles are parallel. They are long fibers, which can contract to 75% of their length. They contract a long way, but they are relatively weak, because there are relatively few fascicles. E.g. Sternocleidomastoid.


PENNATE (means “feather shape”) MUSCLES: three types:

  • UNIPENNATE; looks like half a feather. The fascicles are short, but there are more of them. They are stronger, but do not have the same length contraction ability of the parallel muscles.
  • BIPENNATEare fascicles that insert into the tendon from both sides; they are stronger than unipennate (quadriceps).
  • MULTIPENNATE are the strongest (deltoid). The fascicles are in multiple bundles inserting on one tendon

CONVERGENT MUSCLE has more fibers than parallel, but contracts a greater distance than pinnate. E.g. Pectoralis major.

circular muscle

CIRCULAR MUSCLE (Sphincter) is arranged in a circle, with a small area of tendon on the sides. It allows closure of the eyes, mouth, etc. They are not very strong, but they don’t need to be.

  • ORIGIN = The region which usually doesn’t move when the muscle contracts. Look at the biceps brachii; does the shoulder move when I bend my arm? No; the shoulder = origin.
  • INSERTION= The point of attachment that moves; bend arm, radial tuberosity = attachment.
  • AGONIST = The main muscle for a particular action; bend arm, biceps = agonist.
  • ANTAGONIST = Does the opposite action; bend elbow, antagonist extends. Every muscle in the body has to have an antagonist.
  • SYNERGIST = The muscle that helps the agonist. There are several muscles that assist when the arm is bent.
muscle types
Muscle Types
  • Skeletal: elongated
    • Moves the skeleton
    • Voluntary
    • striated
  • Smooth: spindle shaped
    • Found in organs and lining of blood vessels
    • Involuntary
    • no striations
  • Cardiac: cylindrical shaped
    • involuntary (only responds to direct electrical stimulation)
    • striated
skeletal muscle characteristics
Skeletal Muscle Characteristics
  • Contractility
    • The ability to shorten with force
    • However, they lengthen passively, by gravity or by the contraction of an opposing muscle.
  • Excitability
    • Capacity to respond to a stimulus (nerves)
  • Extensibility
    • Can be stretched
    • After a contraction, they can be stretched to their normal resting length and beyond to a limited degree.
  • Elasticity
      • Can recoil to their original resting length after they have been stretched
  • Has thousands of nuclei per cell, unlike smooth and cardiac muscle
skeletal muscle
  • They have thousands of nuclei because they start from many stem cells that fuse together into one skeletal muscle fiber.
  • Theses are very long fibers (biceps muscle can be 8-10 cm).
skeletal muscle20
Skeletal Muscle
  • Myoblasts exist in adults, so muscle heals well.
  • A muscle cell torn in half can regenerate.
  • There are almost no muscle diseases for this reason (muscular dystrophy is the main muscle disease).
  • Muscles Overview Video
skeletal muscle longitudinal section
Skeletal Muscle: Longitudinal section

In skeletal muscle fibers, there are light and dark stripes called striations, which can be seen under a microscope.


A cross section of skeletal muscle looks like bundles of circles because you are looking at cut fascicles.

skeletal muscle24
Skeletal Muscle
  • The plasma membrane of muscles is called a SARCOLEMMA.
  • The cytoplasm of muscle cells is called SARCOPLASM.
  • Muscle cells contain many mitochondria and other organelles.
  • One type of unusual organelle found only in muscle cells is called a myofibril. They are packed in bundles and fill up most of the cell.


    • Cylindrical organelles found within muscle cells
    • Extend from one end of the muscle fiber (muscle cell) to the other
    • Contain sarcomeres joined end to end.
    • The sarcomeres are made of actin and myosin myofilaments
skeletal muscle longitudinal section26
Skeletal Muscle: Longitudinal section

These striations (stripes) are caused by dark and light bands.

The dark band is called an A band. (There is an “A” in dark)

The light band is called an I band. There is an “I” in light)



dark band + light band is one sarcomere

In the center of each light I band is a Z disc

One sarcomere is the area from one Z disc to the next Z disc.

So, each sarcomere extends from the middle of one light band to the middle of the next light band. In the center of the dark band is a lighter colored area called the H zone. It is the area of the myosin without heads.

  • The striations result from the internal structure of SARCOMERES within the sarcoplasm.
  • The sarcomere is the basic structural and functional unit of skeletal muscle. The sarcomere is what contracts.
  • Each sarcomere
    • Extends from one Z disc to the next Z disc
    • Has a light colored H zone in the center (found in the middle of the dark band, which is in the center of the sarcomere. It is the area of myosin in the center that does not have myosin heads).
    • Contains parts of two I (light) bands and all of one A (dark) band
    • Contains overlapping actin and myosin myofilaments.

Note: the I band consists only of actin myofilaments.

The A band consists of both actin and myosin.

actin and myosin
Actin and Myosin

Sarcomere model video 1

Sarcomere model video 2

  • Sarcomeres consist of two types of myofilaments made out of protein:
    • thin (ACTIN) myofilaments
      • Look like two strands of beads twisted together.
      • Actin myofilaments are attached to the Z disc at one end.
    • thick (MYOSIN) myofilaments.
      • Both ends of a thick filament are studded with knobs called myosin heads (look like little golf clubs).
      • Myosin is NOT attached to the Z disc.






Don’t confuse these terms!

MUSCLE FASCICLE: a group of muscle fibers, surrounded by perimysium.

MUSCLE FIBER: a single muscle cell

MYOFIBRIL: a long organelle inside a muscle fiber, contains actin and myosin myofilaments.

MYOFILAMENTS: these are proteins, and there are two types: actin (with troponin and tropomyosin) and myosin. The myofilament is the lowest level of organization that is composed of actin, myosin, troponin, and tropomyosin proteins.

Therefore, a myofilament is part of a myofibril, which is inside a muscle fiber, which is inside a muscle fascicle.

mechanism of contraction

The Sliding Filament Theory

  • Contraction results as the myosin heads of the thick filaments attach like hooks to the thin actin filaments at both ends of the sarcomere and pull the thin filaments toward the center of the sarcomere.
  • The myosin head is like a hook with a hinge. After a myosin head pivots at its hinge, it draws the actin closer, then lets go, springs up again to grab the actin filament again, pulls it closer, and it keeps repeating this until the entire actin filament has been drawn in as far as it can go.
  • The sites where the myosin heads hook onto the actin are called cross-bridges.
sarcomere contraction
Sarcomere Contraction
  • The complete process of contraction of the sarcomere takes only a fraction of a second.
  • The actin and myosin filaments do not shorten; they merely slide past each other.
  • The energy required is ATP.
  • The A band (dark stripe) in a sarcomere does not change length in a contraction.
  • This sliding filament mechanism begins whenever calcium ions bind to the thin filament.
  • Where does the calcium come from?
sarcoplasmic reticulum and t tubules
  • Within the cytoplasm of all body cells is an endoplasmic reticulum.
  • The endoplasmic reticulum in muscle cells is called the SACROPLASMIC RETICULUM.
  • It surrounds each sarcomere like the sleeve of a loosely crocheted sweater.

Sarcoplasmic reticulum is in blue

T tubules are in yellow

calcium is needed for muscle contraction
Calcium is needed for muscle contraction

The sarcoplasmic reticulum stores a lot of calcium ions, which are released when the muscle is stimulated to contract.

The calcium diffuses out of the sarcoplasmic reticulum and land on the actin filaments, where they trigger the sliding filament mechanism of contraction.

After the contraction, the calcium ions are pumped back into the sarcoplasmic reticulum for storage.

calcium is needed for muscle contraction42
Calcium is needed for muscle contraction
  • ACTIVE TRANSPORT is required to return the calcium ions to the sarcoplasmic reticulum.
  • It also requires energy to break the cross-bridge so the myosin head can cock back again, ready to spring onto the next binding site.
  • Therefore, ATP is used.
    • ATP is used to return calcium to the sarcoplasmic reticulum
    • ATP is used to cock back the myosin heads
atp is required for contraction
ATP is required for contraction
  • ATP attaches to the myosin myofilaments
    • Provides energy for the movement of the cross bridges
  • ATP is required for muscle relaxation
  • ATP releases part of its energy as heat.
    • That is why we get hot when we exercise
    • When we are cold, we shiver (muscle contraction) to warm up.
  • In order for the mitochondria to produce enough ATP, it needs oxygen and the sugars that are in storage.
for contraction to take place you need a nerve signal and calcium
For contraction to take place, you need a nerve signal and calcium
  • For skeletal muscle to contract, the synaptic knob of a neuron must first release a chemical called ACETYLCHOLINE onto the region where it sits on the muscle cell, known as the ENDPLATE.
  • Calcium is also needed for muscle contraction.
  • The nerve signal is called an ACTION POTENTIAL.
  • It causes a release of calcium from the sarcoplasmic reticulum, which causes contraction.
muscle contraction
Muscle Contraction

In a muscle fiber, an action potential results in muscle contraction. How does this happen?

The action potential continues to travel along the sarcolemma (cell membrane of the muscle).

Part of this electrical impulse breaks away from the sarcolemma and travels down the T-tubules, while the rest of the electrical impulse continues longitudinally down the muscle cell to the next sarcomere and T-tubule.

t tubules
  • T TUBULES (“T” stands for “transverse”) are continuations of the sarcolemma (cell membrane) which invaginate to the deepest regions of the muscle cell.
  • Since the T tubules conduct the nerve impulse throughout the muscle cell, all the sarcomeres of that cell contract at the same time.
muscle contraction48
Muscle Contraction
  • The action potential of the nerve goes down the T-tubules and causes calcium to leak out of the sarcoplasmic reticulum.
  • The calcium causes the muscle fibers to contract.
  • After a while, the calcium gets pumped back where it came from, the muscle fibers relax, although it requires gravity or another muscle to pull the sarcomere back to its original length.
  • How does the calcium cause the muscle fibers to contract?

TROPOMYOSIN is a single long protein strand like a piece of yarn that winds around the actin filament.

  • Tropomyosin blocks actin’s attachment site for the myosin head, so the myosin “hook” has nothing to grab onto, thus preventing contraction.

TROPONIN is a globular complex of three proteins, and is found in clumps around the tropomyosin protein.

  • Troponin is the specific molecule that provides the calcium binding site on actin.
  • Calcium binds to troponin and causes troponin to move a little, taking the tropomyosin thread with it, so the attachment sites on the actin molecule are now exposed. The myosin heads can now hook into the exposed sites on the actin myofilament.

Both troponin and tropomyosin cover the actin filament when the muscle is relaxed.


This is an illustration of an actin molecule. You can see the thready tropomyosin and the globular troponin proteins wrapping around the double-stranded actin.


When calcium binds to the globular troponin, it moves, taking the tropomyosin thread with it. This exposes the myosin binding site on the actin.

calcium in muscle contraction
Calcium in muscle contraction
  • When the muscle cell is stimulated to contract by an action potential, calcium channels open in the sarcoplasmic reticulum and release calcium into the sarcoplasm.
  • Some of this calcium attaches to troponin, causing a conformational change that moves tropomyosin out of the way so that the myosin heads can attach to actin and produce muscle contraction.
  • When the calcium gets pumped back where it came from, the tropomyosin protein blocks the myosin head again so it can no longer get its hook into the actin filament, and the muscle will relax.
rigor mortis
Rigor Mortis

A new ATP molecule must bind to the myosin before the cross-bridge can be release. When ATP is not available after a person dies, the cross-bridges that have formed are not released, causing muscle to become rigid (rigor mortis)

NOTE: Sarcomeres lengthen during muscle relaxation only if gravity or an opposing muscle pulls the sarcomere back to its original length.

muscle contraction54
Muscle Contraction
  • Muscle Contraction
  • Sarcoplasmic Reticulum
sequence of events
Sequence of events

The action potential reaches the cell membrane

The action potential reaches the T-tubules

The ion channels in the sarcoplasmic reticulum open

Calcium ions move along their concentration gradient

Actin forms cross-bridges to myosin

The actin myofilaments move closer to each other, causing contraction of the sarcomere.

NOTE: A muscle fiber will not respond to a stimulus until that stimulus reaches the threshold level.

  • Troponin is found in both skeletal muscle and cardiac muscle, but not in smooth muscle.
  • Both cardiac and skeletal muscles are controlled by changes in the intracellular (“inside the cell”) calcium concentration (not blood calcium concentration).
  • When muscle calcium levels are normal, the muscles contract normally, and when muscle calcium levels fall, the muscles might not be able to contract.
muscle contraction57
Muscle Contraction

A muscle TWITCH is one single muscle fiber contraction.

  • It takes 1/20th of a second.
  • How is it that I can pick up and hold a chair if the fiber only contracts for 1/20th second?
  • There are ten thousand fibers per muscle; each one contracts at different intervals, so contraction is maintained, just like tug-of-war. One person in ten can drop the rope and get a better grip because the others are maintaining the tension.
motor units
Motor Units

A MOTOR UNIT is a single neuron and all of the muscle fibers on which it synapses.

If one neuron sends a signal, only its muscle fibers contract (the motor unit). This allows for strength variations in lifting a chair vs. an eraser. For full strength, all the motor units contract. For half strength, half of the motor units contract.

motor units59
Motor Units

There are 3 motor units in this diagram; that allows for 3 different levels of contraction. The more motor units there are, the more precisely the muscle can respond.

motor units60
Motor Units

The action potential continues from one motor neuron to the next motor neuron until the last neuron lands on its target cells; in this case, skeletal muscle fibers.

A single motor neuron and all the skeletal muscle fibers it innervates constitute a motor unit.

A muscle in your tongue may only have a few muscle fibers innervated by a neuron to allow for precise movement. However, large thigh muscles may have as many as 1000 muscle fibers per neuron, since precision is not necessary.

motor units61
Motor Units
  • The muscles of the back are larger motor units (many muscle fibers per neuron). Since there are fewer motor units present (one neuron for a thousand muscle cells, we get strength, but less precision.
  • The muscles that move the tongue have smaller motor units (one neuron for 10 muscle cells). Since there are many motor units present = less strength, more precision.
physiology of the neuromuscular junction
Physiology of the Neuromuscular Junction
muscle twitch phases
Muscle Twitch Phases


A muscle twitch has three phases

The lag phase is the time between the application of a stimulus and the beginning of contraction.

The contraction phase is the time of contraction.

The relaxation phase is the time during which the muscle relaxes.

The refractory period is the time between muscle twitches.



Refractory period

force of contraction
Force of Contraction


The strength of muscle contraction can vary from weak to strong. For example, the force generated by muscles to lift a feather is much less than the force required to lift a 25 pound weight.

The force of contraction produced by a muscle is increased in two ways:

Summation, which involves increasing the force of contraction of the muscle fibers within the muscle

Recruitment, which involves increasing the number of muscle fibers contracting



The force of contraction of individual muscle fibers is increased by rapidly stimulating them.

Stimulus frequency is the number of times a motor neuron is stimulated per second.

When the stimulus frequency is low, there is time for complete relaxation of muscle fibers between twitches.

As stimulation frequency increases, there is not enough time between contractions for muscles to completely relax.

Thus, one contraction summates, or is added onto, a previous contraction. As a result, the overall force of contraction increases.

Tetanus is the condition in which a muscle remains contracted between stimuli without relaxing.

tetanus toxin

The bacteria that make this toxin live deep in the soil and cannot survive in air.

If you step on something that imbeds soil deeply into your tissues (like a rusty nail), you might contract the bacteria.

You will need a tetanus shot before the toxins accumulate.

A toxin caused by a certain bacteria can cause muscle to remain contracted (in tetanus).

It quickly results in death because the diaphragm and other respiratory muscles cannot function properly, and the person suffocates.



In recruitment, the strength of contraction of the muscle is increased by increasing the number of motor units stimulated.

When only a few motor units are stimulated, a small force of contraction is produced, because only a small number of muscle fibers are contracting.

As the number of motor units stimulated increases, more muscle fibers are stimulated to contract, and the force of contraction increases.

Maximum force of contraction is produced in a given muscle when all the motor units of that muscle are stimulated, or recruited.



Motor unit recruitment allows muscles to have slow, smooth sustained contractions so our movements are not jerky.

If all the motor units in a muscle could be stimulated simultaneously, a quick, jerky motion would occur.

Because the motor units are recruited gradually so that some are stimulated and held in tetanus while additional motor units are recruited, slow, smooth, sustained contractions occur.

types of muscle contractions
Types of Muscle Contractions


Muscle contractions are classified as either isometric or isotonic. Most muscle contractions are a combination.

  • Isometric (equal distance)
      • tension increases during contraction
      • length of the muscle does not change
      • Example is when you push against a wall or try to pick up an object that is too heavy to lift
  • Isotonic (equal tension)
      • tension is generally constant during contraction
        • Although in one type of isotonic contraction, the tension increases
      • Length of the muscle changes (either increases or decreases).
      • Example is when you lift a weight.
concentric and eccentric contractions
Concentric and Eccentric Contractions


Two types of isotonic contractions:

CONCENTRIC CONTRACTIONS are isotonic contractions in which the muscle tension increases as the muscle shortens. Most movements performed by muscle contractions are of this type.

ECCENTRIC CONTRACTIONS are isotonic contractions in which tension is maintained as the muscle lengthens. An example is when a person lets down a heavy weight slowly. Substantial force is produced in the muscles and injuries can occur from repetitive eccentric contractions, such as in the hamstring muscles when a person runs downhill.

muscle tone
Muscle Tone

Even when muscles are relaxed, some of their fibers are still contracting, giving the muscle some tone.

Therefore, the normal state of a muscle, with some contraction, is called muscle tone. This is important in posture so you can stand upright but mostly relaxed.

Muscle tone refers to the constant tension produced by muscles of the body over long periods of time. It is responsible for keeping the back and legs straight, the head held in an upright position, and the abdomen from bulging. it declines during REM sleep.

motor neurons
Motor Neurons
  • A neuron (nerve cell) that innervates (supplies) skeletal muscle is called a motor neuron (causes the body to move). There are 2 motor neurons involved in this task.
  • The Upper Motor Neuron has its cell body in the brain, and its axon (like a stem) lands on the cell body of the Lower Motor Neuron, which is in the spinal cord.
  • The axon of the Lower Motor Neuron leaves the spinal cord and innervates the muscle.
upper and lower motor neurons in red
Upper and Lower Motor Neurons (in red)

Upper motor neuron

Lower motor neuron

muscle tone77
Muscle Tone
  • Hypertonia
    • Can present clinically as either spasticity or rigidity. Seen in upper motor neuron diseases, such as multiple sclerosis or cerebral palsy.
  • Hypotonia
    • Seen in lower motor neuron diseases (spinal cord damage and ALS/Lou Gehrig Disease)
    • Can present clinically as muscle flaccidity, where the limbs appear floppy, stretch reflex responses are decreased, and the limb’s resistance to passive movement is also decreased.
muscle tone78
Muscle Tone
  • Upper Extremity Tone, normal VIDEO
  • Upper Extremity Tone, abnormal VIDEO
  • Lower Extremity Tone, normal VIDEO
  • Lower Extremity Tone, abnormal VIDEO
muscle spasticity hypertonia
Muscle Spasticity: Hypertonia
  • Clinically spasticity is defined as velocity dependent resistance to stretch.
  • Passively moving (the doctor does the movement) the patient’s elbow or foot quickly will elicit spastic twitches, but passively moving elbow or foot slowly is normal.
  • It mostly occurs from upper motor neuron lesions (scar, tumor, or other damage), but it can also present in multiple sclerosis, which is an autoimmune condition. Can also be seen in cerebral palsy (lack of oxygen at birth).
muscle spasticity
Muscle Spasticity
  • There is a difference in cause of two of the most common spasticity conditions, spastic diplegia (cerebral palsy) and multiple sclerosis.
  • In spastic diplegia, the upper motor neuron lesion arises often as a result of neonatal asphyxia (lack of oxygen in a newborn), while in conditions like multiple sclerosis, spasticity is from multiple sclerosis, which is an autoimmune destruction of the myelin sheaths around nerve endings.
muscle spasticity81
Muscle Spasticity
  • Causes include
    • Spastic diplegia (Cerebral palsy)
    • Multiple sclerosis
    • Spinal cord injury
    • Stroke
  • Test for clonus to see if spasticity is present.
muscle clonus
Muscle Clonus
  • Clonus (from the Greek for "violent, confused motion") is a series of involuntary muscular contractions initiated by a reflex.
  • Clonus is a sign of certain neurological conditions, and is particularly associated with upper motor neuron lesions such as in spastic diplegia, stroke, multiple sclerosis, spinal cord damage.
  • Clonus is most common in the ankles, where it is tested by rapidly dorsiflexing the foot. If the foot then jerks 5 times or more, clonus is present. A positive clonus test means the patient has spasticity, usually due to an UMN disorder.
  • VIDEO: Ankle clonus
muscle rigidity
Muscle Rigidity
  • Unlike spasticity, rigidity is velocity-independent resistance to passive stretch.
  • There is uniform increased tone whether the elbow is passively moved quickly or slowly.
muscle fasciculations
Muscle Fasciculations
  • These are small, local, involuntary muscle contractions.
  • Fasciculations have a variety of causes, the majority of which are benign, but can also be due to disease of the lower motor neurons.
  • Fasciculations VIDEO
  • Tremor VIDEO
muscle fasciculations85
Muscle Fasciculations
  • Benign causes of fasciculations include:
    • Magnesium deficiency
      • Diarrhea
      • Overexertion
      • Inadequate intake from diet (almonds are a good source of magnesium)
    • Dehydration
    • Fatigue
    • A small neuron dying can also cause fasciculations.
muscle fasciculations86
Muscle Fasciculations
  • They can also be caused by long-term use of:
    • Benadryl (antihistamine)
    • Dramamine (for nausea and motion sickness).
    • Caffeine
    • Sudafed (for allergies)
    • Asthma medicines
    • ADD medicines
muscle fasciculations87
Muscle Fasciculations
  • More serious conditions causing fasciculations include
    • Fibromyalgia
    • Myasthenia Gravis
    • Lyme Disease
    • Rabies
  • We talked about hypertonia; some people have hyperreflexia.
  • The most common cause of exaggerated reflexes is spinal cord injuries (upper motor neuron diseases).
  • Other causes include
    • Medication
    • Stimulants
    • Hyperthyroidism
    • Electrolyte imbalance
    • Severe brain trauma.
  • This means diminished or absent reflexes.
  • The most common cause is lower motor neuron diseases.
muscle strength and coordination
Muscle Strength and Coordination
  • Upper Extremity Strength, normal VIDEO
  • Upper Extremity Strength, abnormal VIDEO
  • Lower Extremity Strength, normal VIDEO
  • Lower Extremity Strength, abnormal VIDEO
  • Strength Evaluation using squats VIDEO
  • Hand coordination using Rapid Alternating Movements (RAM) VIDEO
muscle contractures
Muscle Contractures
  • Muscle contractures can occur from paralysis, muscular atrophy (immobilization from a cast), muscular dystrophy, and chronic spastic conditions like cerebral palsy.
  • Fundamentally, the muscle and its tendons shorten, resulting in reduced flexibility.
  • Muscle contractures in tendons are caused from the fibrinogen leaking out of the fibroblasts, which turn the elastic fibers into inelastic fibers.
  • Most treatments involve surgery, so physical therapy efforts focus on prevention of contractures.
energy requirements of muscle
Energy Requirements of Muscle

What fuel does a car use?


What fuel does a candle use?


What fuel do humans use?








Where do we get ATP?

We can make a little ATP in the cytoplasm of our cells, but not enough to live on.

Most of our ATP is made by the mitochondria inside our cells.

Mitochondria are like little protozoa (animals) that live in our cells. Each cell has hundreds of them. Muscle cells have thousands of them.

What is their fuel?

Oxygen and glucose

THAT is why we need to inhale oxygen and consume sugars….to feed our mitochondria so they can make ATP for us!

energy requirements for muscle contraction
Energy Requirements For Muscle Contraction

In order for the muscle mitochondria to produce enough ATP, they need oxygen (for their own aerobic respiration) and sugars that are in storage.

Mitochondria can only perform aerobic respiration.

What can we do to make ATP if our muscle cells run out of oxygen?

Start performing anaerobic respiration.

We can do this ourselves in the cytoplasm of our cells.

making atp by aerobic respiration
Making ATP by Aerobic Respiration

Aerobic respiration

Takes place in the mitochondria

Requires oxygen

Breaks down glucose to produce ATP

Waste products are CO2 and H2O (we exhale them)

The good thing about making ATP from our mitochondria is that we can make a LOT of it.

The bad things are that it takes longer to make it, and it requires oxygen, and a muscle cell may have used up all the oxygen during a sprinting run.

making atp by anaerobic respiration
Making ATP by Anaerobic Respiration

Anaerobic respiration

Takes place in the cytoplasm

Does not require oxygen

Breaks down glucose to produce ATP

Waste product is lactic acid

The good thing about making ATP this way is that we can make it FAST.

The bad thing is that it does not make much ATP, and we deplete the reserves quickly.

lactic acid
Lactic Acid

The waste product of aerobic respiration is carbon dioxide and water. These are not a problem…we eliminate them by exhaling.

The waste product of anaerobic respiration is lactic acid, which can irritate muscle fibers, causing muscle pain (stitch in your side) and muscle cramps.

We deactivate lactic acid by adding oxygen to it. Therefore, breathing heavily adds the oxygen to our system to deactivate lactic acid, and the muscle pains go away.

atp and creatine phosphate
ATP and Creatine Phosphate

What do we do when we run out of ATP?

Muscle fibers cannot stockpile ATP in preparation for future periods of activity.

However, they can store another high energy molecule called creatine phosphate, which is the storage form of ATP.

Creatine phosphate is made from the excess ATP that we accumulate when we are resting.

During short periods of intense exercise, the small reserves of ATP existing in a cell are used first.

Then creatine phosphate is broken down to produce ATP.

aerobic vs anaerobic respiration
Aerobic vs. Anaerobic Respiration

Why does sprinting require anaerobic respiration?

We use up all of the ATP faster than we can make it.

When we run out of ATP, we break down creatine phosphate to make more ATP.

When we run out of ATP and creatine phosphate, we start using anaerobic respiration to make more ATP.

When we run out of glucose, or too much lactic acid is built up, we have to stop and rest.

Anaerobic metabolism is ultimately limited by depletion of glucose and buildup of lactic acid within the muscle fiber.

sprint runners
Sprint Runners

Why do sprint runners tire out during the last part of a fast run?

Sprinting is an anaerobic activity…the oxygen requirement is quickly exceeded, so the muscle has to use anaerobic respiration to continue to contract. This requires a lot of glucose and also results in a buildup of lactic acid.

Once the sprint-runner has used up the available glucose, or has produced too much lactic acid, the muscles fatigue.

Sprint Runners

oxygen debt
Oxygen Debt

Anaerobic respiration produces lactic acid, which causes the painful cramps because it creates an oxygen debt.

The amount of oxygen needed to replenish the supply following aerobic demand is called the oxygen debt.

When you continue to breathe heavily after exercising, it means you have an oxygen debt.

Muscles can do without oxygen for a while pretty well, unlike the brain.

To pay back a minor oxygen debt, you just have to breathe heavily for a while.

oxygen debt102
Oxygen Debt

This heavy breathing brings in oxygen, which is used to convert lactic acid to glucose, replenish the depleted ATP and creatine phosphate stores in the muscle fibers, and to replenish oxygen stores in the lung, blood, and muscles.

After the oxygen debt has been paid back, breathing returns to normal.

People who are in good physical condition can carry out both aerobic and anaerobic activities efficiently, and do not suffer from an oxygen debt for very long.

  • Myoglobin is an iron- and oxygen-binding protein found in the muscle tissue of mammals.
  • It is related to hemoglobin, which is the iron- and oxygen-binding protein in blood, specifically in the red blood cells.
  • The only time myoglobin is found in the bloodstream is when it is released following muscle injury. It is an abnormal finding, and can be diagnostically relevant when found in blood.
  • Myoglobin binds to oxygen more strongly than hemoglobin.
  • It acts as an oxygen-storage molecule and delivers the oxygen to cells when needed.
  • High concentrations of myoglobin in muscle cells allow organisms to hold their breaths longer.
  • Diving mammals such as whales and seals have muscles with particularly high myoglobin levels.
  • Myoglobin forms pigments responsible for making meat red. The color that meat takes is partly determined by the oxidation states of the iron atom in myoglobin.
  • When meat is raw, the iron atom is in the +2 oxidation state (Fe+2).
  • Meat cooked well done is brown because the iron atom is now in the +3 oxidation state (Fe+3), having lost an electron.
  • Under some conditions, meat can also remain pink all through cooking, despite being heated to high temperatures. If meat has been exposed to nitrites, it will remain pink because the iron atom is bound to NO, nitric oxide (e.g., corned beef or cured hams). Grilled meats can also take on a pink "smoke ring" that comes from the iron binding to a molecule of carbon monoxide.
  • Rhabdomyolysis is the condition when myoglobin is released from damaged muscle tissue.
  • Released myoglobin is filtered by the kidneys, but it damages them, so it can lead to renal failure.
  • High blood levels may indicate the person is having a heart attack, or it could just be a muscle injury.
  • Therefore, CK, cTnT, ECG, and clinical signs should be taken into account to make the diagnosis of a heart attack.
creatine kinase ck
Creatine kinase (CK)
  • CK is the enzyme used to get ATP out of storage (ATP is stored as creatine).
  • High blood levels of CK may indicate myocardial infarction (heart attack), rhabdomyolysis (severe muscle breakdown), muscular dystrophy, the autoimmune myositides, or acute renal failure.
troponin ctnt
Troponin (cTnT)
  • Troponin levels in the blood can be used as a test of several different heart disorders, including myocardial infarction.
  • Troponin-I is highly specific for cardiac muscle necrosis. Serum levels rise 4-8 hrs after onset of chest pains, peak at 12-16 hrs and return to baseline within 5-9 days.
  • There are many physiological benefits of exercise:

1. Improved muscular strength, endurance, flexibility

2. Improved cardio-respiratory endurance

3. Increased bone density and strength

4. Relief from depression

5. Increased HDLs

  • Weight training and other exercises can cause muscles to hypertrophy (enlarge). This occurs as more myofilaments and myofibrils are produced inside a myofiber (muscle cell), causing the muscle cell to enlarge. The number of mitochondria also increases, causing additional enlargement.
  • However, you don’t grow new muscle cells. The number of cells in a skeletal muscle remains relatively constant following birth. Myoblast stem cells don’t grow into new muscle cells; they just patch up damaged cells.
  • Hypertrophy can happen in two ways:
    • Increase in number of myofibrils inside a muscle cell
    • Which causes the increase in size of individual muscle cells (myofibers)
  • Muscle hypertrophy is greater in males due to the hormone testosterone.
  • Eating protein does not automatically increase muscle. The average person only needs three ounces of protein per day, six ounces if you work out.
  • Two ounces is the size of a deck of playing cards.
  • Three ounces is like one mini hamburger.
  • Most people eat too much meat.

Fun Fact: -You use 200 muscles to take one step.

how much meat per day
How much meat per day?
  • Most people need around 0.8 grams of protein per day per 2.2 pounds of body weight, according to registered dietitian Reed Mangels.
  • Consuming around 46 grams of protein per day if you're female and 56 grams per day if you're male will meet your protein needs, whether you get your protein from meat or from plant sources.
  • A 3-ounce portion of meat contains 21 to 24 grams of protein.
  • Two 3-ounce meat servings per day would supply all your protein needs, but this much meat could include a large amount of saturated fat, which could increase your risk of heart disease.
fun facts
Fun Facts
  • A muscle cell is about as thin as a hair.
  • Muscles make up 1/3 of your body weight.
  • There are 655 muscles in the body…that is three muscles per bone!
  • We all have the same number of muscle cells.
  • Muscles can generate 40 pounds per square inch.
  • If all the muscles in the body were able to contract at once, they could pull 25 tons!
fun facts115
Fun Facts
  • Myths About Women’s Body Building

Lack of use causes muscle ATROPHY. This happens quickly. Astronauts can lose 40% of their muscle in two weeks! It is regained quickly, too.

Atrophy is a decrease in muscle size because of the decrease in myofilaments within muscle fiber.

Casting a broken limb also leads to temporary atrophy.

Severe atrophy involves the permanent loss of skeletal muscle fiber and the replacement of those fibers by connective tissue.

Damage to the nervous system, or a severed motor nerve can cause atrophy. The muscle becomes flaccid (having no tone) .

More info on Muscle Atrophy

muscular dystrophy
Muscular Dystrophy

This refers to a group of inherited muscle disorders in which skeletal, cardiac, and smooth muscle tissue degenerates and the person experiences progressive weakness and other symptoms, including heart problems.

The muscle is replacement by fat and other connective tissue.

muscular dystrophy118
Muscular Dystrophy
  • Duchenne muscular dystrophy is more common in males.


This is a genetic lack of a protein called DISTROPHIN. It causes the muscle tissue to harden, inhibiting contraction, causing progressive paralysis.

research on muscular dystrophy
Research on Muscular Dystrophy
  • Two new types of stem cells have been found that can seek out injured muscle tissue and replace the damaged cells.
  • Researchers in Italy used stem cells from blood vessels to repair muscle in mice with muscular dystrophy.
  • Canadian scientists found that stem cells from damaged muscle give rise to new muscle fibers.
muscle problems
Muscle Problems

Tendonitis is an inflammation of the tendon or its attachment point. It usually occurs from overuse of the muscle to which the tendon is attached.

A strain is a tear in a muscle. Remember, a sprain is a tear in a ligament.

A muscle strain will heal faster than a torn ligament because muscles have good blood supply and ligaments do not.

treatment for injuries rice
Treatment for Injuries: RICE
  • Rest
  • Ice
    • 20 minutes on, 20 minutes off for 3 days
    • Ice pack or frozen bag of peas!
  • Compression
    • Ace wrap from distal to proximal
    • Don’t leave any openings while wrapping
  • Elevation
    • Above the heart
treatment for injuries
Treatment for Injuries
  • Ice for the first 72 hours (NO heat!)
  • Anti-inflammatory medicines
    • Ibuprofin, 600 mg TID (3x a day)
    • Over the counter (OTC) pills are 200 mg
  • Heat and massage as needed after third day.
  • Can try a muscle stimulator too…works pretty well!
muscle spasms
Muscle Spasms
  • Muscle spasms/cramps are sudden and involuntary muscle contractions. They are painful, spastic contractions that are usually caused from overexertion. Lactic acid builds up and irritates the overused muscles, causing inflammation. If the muscle remains in spasm for longer than a few minutes, might need heat and massage to increase circulation.
  • Avoid spasms by stretching before and after activities.
  • For people with frequent low back spasms throughout the day, a portable muscle stimulator that clips to the belt will help a great deal.

Muscle stimulator to relieve muscle spasms or to prevent muscle atrophy in casts




fibromyalgia muscle and tissue pain
Fibromyalgia (muscle and tissue pain)

Common disorder in adults, especially women

Painful muscles, debilitating fatigue, sleep disturbance, and joint stiffness

Many trigger points: painful lumps in muscles

Treatment includes anti-inflammatory medicines, physical therapy, acupuncture, and exercise.

Muscle stimulators help

  • The American College of Rheumatology guidelines that require a minimum of 11 out of 18 specific tender points for a fibromyalgia diagnosis.
  • Fewer than 11 tender points may also indicate fibromyalgia, particularly if you also have severe fatigue and widespread pain that has lasted more than three months.
  • There is a blood test to help diagnose the condition.
  • The FM/a test identifies markers produced by immune system blood cells in people with fibromyalgia.
fibromyalgia treatment
Fibromyalgia Treatment
  • There is no cure for fibromyalgia, and people with the condition usually have it for life.
  • However, it is not likely to get worse as you age and it does not damage muscles, tendons, or ligaments.
  • Many people are able to reduce their symptoms with a combination of exercise, medication, physical therapy, and relaxation.
fibromyalgia treatment134
Fibromyalgia Treatment
  • Exercise
    • Daily walking, biking, water aerobics, or swimming for 20-30 minutes
  • Medication
    • B12 to help repair nerves
    • D5 Ribose to help you stay asleep better
    • Magnesium supplements
  • Physical therapy
    • Muscle stimulators
  • Relaxation
ganglion cysts
Ganglion Cysts

Ganglion cysts arise as outpouchings from fluid filled areas such as the fluid around tendon sheaths.

When the fluid, called synovial fluid, leaks out from these spaces, it can become a cystic structure.

Treatment is to drain the fluid with a needle, but the fluid can be jelly-like and difficult to remove, and they frequently grow back.

If conservative treatments fail to correct the cyst, an operation can be done to excise the cyst.

Then you do a surgery to scoop out the whole cyst, find the stalk and tie it off.

baker s cyst
Baker’s Cyst

A Baker's Cyst, or popliteal cyst, is a collection of fluid in the back of the knee joint.

A Baker's cyst is usually a symptom of another problem, or it may be an incidental finding with no significant meaning.

Most often in adults the Baker's cyst is found in conditions where there is chronic swelling or fluid accumulation in the knee joint.

These conditions include knee arthritis, meniscus injuries, and ligamentous injuries.

baker s cyst138
Baker’s Cyst

Treatment of a Baker's cyst that is the result of a problem within the knee consists of treating the underlying problem. These treatments may include anti-inflammatory medications and cortisone injections.


What is the Rotator Cuff?

  • Rotator Cuff Injury
  • How do rotator cuff injuries occur?
  • What is an MRI?
  • How does a CT scan work?

With aging, fibrous connective tissue replaces some muscle fibers, causing decreased strength.

As people age, the number of muscle fibers decreases, and new ones cannot be added.

fun facts about strength

The strongest humans can lift about 3 times their own body weight, but the average gorilla can lift 10 times its own body weight! Gorillas can lift 4,600 pounds. By the way, they don’t drink water. They get it by eating 50 pounds of plants a day.

The rhino beetle can carry 800 times its own weight.

And, pound for pound, the African Crowned Eagle can carry more than a cargo plane, because it can fly carrying up to 4 times it's own weight. Something that would keep a cargo plane grounded.

But the strongest creature is the ant. If you had the strength of an ant, you could lift over your head and carry 6,600 pounds.

fun facts143
  • If we could jump like a locust, we could jump 300 feet. Locusts have massive muscles in their thighs and it has elastic bands in its knees that are like stretchy springs that store energy. The tendons in our fingers store enough energy for us to snap our fingers.
  • At 60 mph, the cheetah is fast, but the basilisk lizard runs so fast that it can walk on water and the ostrich is just about the fastest animal on two legs.
  • What’s the fastest animal on Earth? The tiger beetle, which can run up to 171 times its size in one second. Despite its famous reputation, the cheetah would have to run 770 kilometres per hour just to catch up with it.
  • What’s the slowest animal in the world? The sloth. It is a species that moves just five times faster than a snail! 
  • The penguin burns twice as much energy as any other animal when walking. This is due to the fact that its legs are very short, and so it must expend a lot of effort in order to get moving.
  • Elephants can't jump, not even with the help of hurricane-force winds. It is too heavy to lift all four legs at the same time.
  • The flea, however, can jump up to 200 times its own height. This is equivalent to a man jumping the Empire State Building in New York.
smooth muscle cells
  • These are found around internal organs (intestines, uterus, blood vessels).
  • They are involuntary and not striated.
  • When smooth muscle contracts around the intestines, the movement is called PERISTALSIS.
smooth muscle cells147
  • Smooth muscle cells are small and spindle shaped, usually with one nucleus per cell.
  • They contain less actin and myosin, and the microfilaments are not organized into sarcomeres.
  • As a result, smooth muscle cells are not striated.
  • They contract more slowly and do not develop an oxygen debt.
  • Smooth muscle cells can spontaneously generate action potentials that cause the cell to contract.
smooth muscle cells148
  • Smooth muscle is not under voluntary control, whereas skeletal muscle is voluntary.
  • Some hormones in the digestive system can stimulate smooth muscles to contract.
  • They have specialized cell to cell contacts that allow the action potential to spread to all of the smooth muscle cells in a given tissue.
  • This allows them to function as a unit and contract at the same time.
characteristics of smooth muscle
Characteristics of smooth muscle

There are no distinct sarcomeres

They contract more slowly than skeletal muscle…their twitch time is very long = several seconds

It doesn’t get tired (“I’m too tired to urinate!”)

They contract in response to neurons as well as hormones and changes in local environment (amount of oxygen, lactic acid, etc).

They may be autorhythmic (self-exciting); they can contract spontaneously without being stimulated (like cardiac muscle).

They do not develop oxygen debt.

cardiac muscle cells

Only found in the heart.

The cells are involuntary (like smooth muscle) and striated (like skeletal muscle).

They have intercalated discs which join each cell.

cardiac muscle154
Cardiac Muscle

Cardiac cells are long, striated, and branching, with one nucleus per cell.

The actin and myosin myofilaments are organized into sarcomeres, but not as uniformly as in skeletal muscle.

As a result, cardiac muscle cells are striated, but not as distinctly as skeletal muscle.

Cardiac muscle is involuntary and does not fatigue.

cardiac muscle155
Cardiac Muscle

Cardiac muscle cells are connected to one another by intercalated discs which facilitate action potential conduction between themselves.

This allows them to function as a unit and they all contract together.

Contraction of cardiac cells is influenced by hormones, such as epinephrine.

cardiac muscle156
Cardiac Muscle

As one cell contracts, the action potential goes through all the cells, and they all contract as a unit. That’s why the heart contracts all at once.

It has an intrinsic beat. The cells contract on their own, without a signal.

Even if you chop a heart up, each piece will beat by itself!

muscle musician
Muscle Musician