Lecture 6: Introduction to the Muscular System Flashcards
What are the 3 types of Muscle?
- Skeletal
- Cardiac
- Smooth
What are the 4 Basic properties of muscles?
- Excitability
- Contractility
- Extensibility
- Elasticity
What is Excitability?
The ability to respond to stimuli
What is Contractibility?
Ability to shorten (pull/tension)
What is Extensibility?
Ability to contract over different lengths
What is Elasticity?
The ability to regain original length after contraction
What are the Major characteristics of Skeletal Muscle?
- Somatic structures
- Innervated by spinal nerves and cranial nerves
- Contractile organs that attach directly or indirectly to bones in the longitudal axis
- Their contractions produce motion of the body
What is meant by Skeletal muscles are somatic structures?
They are under voluntary control
Which nerves are Skeletal muscles innervated by?
Spinal nerves
Cranial nerves
Where do Cranial nerves originate from?
The brainstem
If a skeletal muscle attaches indirectly to bone what must it connect through?
A tendon
What kind of connective tissue are tendons?
Dense regular connective tissue
What are the major functions of Skeletal Muscle?
- Produce movement at various joints of the skeleton
- Maintain posture and body position
- Support soft tissues
- Regulate entering and exiting of material
- Maintain body temperature
How does the Skeletal muscle support soft tissues?
The Abdominal wall and pelvic floor support viscera
How does skeletal muscle regulate entering and exiting of material?
Sphincters in digestive and urinary systems
What does EVERY organ always have?
All 4 basic tissues
What is one muscle going to be wrapped in?
Connective tissue called Epimysium
What is Epimysium?
The connective tissue that wraps around one muscle
What separates the different compartments?
Fascia
What is the Epimysium continuous with?
The Fascia
What are skeletal muscles divided into?
Muscle Fascicle
What is a Fascle?
A bundle of Muscle cells
What is a Muscle fibre?
One nerve cell
How many muscle fibres are in each fasicle?
Multiple
What are Fascicles wrapped in?
Perimysium
What is every muscle fibre wrapped in?
Endomysium
How do a Nerve, arteries and veins enter the muscle?
Via the Epimysium
What is 1 axon associated with?
1 muscle fibre
Why do each muscle fibres have a lot of capillaries?
Because muscles need a lot of oxygen
Where do Capillaries of Skeletal muscle fibres sit?
In the Endomysium
What do Skeletal muscles look like?
- They are very long
- Striated
- They have multiple nuclei that are never in the middle
Why do Skeletal muscles only have nuclei in the periphery?
Because they develop from many myoblasts that form one muscle fibre
What are Myosatellite cell?
Skeletal fibre stem cells that remain stem cells into adulthood to repair damaged tissue
Where are Myosatellite cells found?
In the Endomysium of muscle fibres
What is the length of muscle fibres?
They are the entire length of muscles themselves
Where do we have all the contrile elements?
In the myofibrils
What are myofibrils made of?
Proteins that are thick and thin
What are the length of Myofibrils?
Every myofibril is the length of the muscle fibre
What is the Plasma membrane of muscle fibres known as?
Sarcolemma
What is the Cytoplasm of the muscle fibres known as?
Sarcoplasm
What is found within each muscle fibre?
Myofibrils
What is each myofibril wrapped in?
Sarcoplasmic reticulum
What is stored in the Sarcoplasmic reticulum?
Calcium ions
What are Transverse tubules?
Wrapping of a myofibril that conducts electrical impulses for a muscle fibre contraction
Where are Mitochondria and Glycogen granules found around the skeletal muscles?
Around myofibrils
What are both needed for the energy of contraction of muscle fibres?
Mitochondria and glycogen granules
What is the only thing were going to have multiple of the length of the Myofibril?
Sarcomeres (10000 per myofibril)
What is the Basic contractile unit of Skeletal muscles?
Sarcomeres
What are the boundaries of the Sarcomere?
Z lines
What is in the Middle of the sarcomere?
The M line
What are on the M line?
Thick filaments of Myosin
What go from the Myosin to the Z line?
Titin
What does Titin do?
Connect myosin to the Z line
What are the Thin myofilaments around Myosin?
Actin
What does the H band contain?
Thick filaments only
What does the I band contain?
Thin filaments only of Actin and Titin
What doed I band look like in microscopy?
They are lighter
What does the A-band contain?
Both thick and thin filaments
What is in the Zone of overlap?
Both thin and Thick filaments
What occurs in the zone of overlap?
Calcium ions are released
How are the length of filaments changed?
They never change length they only overlap more or less
What is Cross-Bridging?
When Myosin heads bind to Actin
What is required for Cross bridging to occur?
- Calcium ions
* ATP
Where does the Myosin push the actin?
Towards to the M line
Which band is constant?
The A band - the band of thick filaments only
How are the I band and H band affected by muscle contraction?
They reduce in size
When does the actin stop moving towards the M line?
When the myosin touches the Z line
What are muscle cells innervated by?
Motor Neurons and Sensory neurons
What does the one neuron Skeletal muscle penetrate?
The epimysium, then the perimysium and the one axon will end at the endomysium
What is the Neuromuscular Junction?
Where the axon of the neuron meets the muscle fibre where it releases ACh
How does a neuron stimulate a muscle to contract?
Contact with the sarcoplasmic reticulum changes the membrane potential signaling the sarcoplasmic reticulum to release calcium ions
How is a Muscle Contraction Ended?
- ACh is removes
- Sarcoplasmic reticulum recaptures Calcium
- Active sites covered, no cross bridge interactions
How many axons per each muscle fibre?
One axon per one muscle fibre
How many muscle fibres can a single motor neuron stimulates?
Multiple muscle fibres
What is a Motor unit?
All the muscle fibres controlled by a single motor neuron
What does the amount of Contraction depend on?
The number of motor units that are stimulated and the frequency that they are stimulated
What are small motor units needed for?
Very precise movement like eye muscle
What are large motor units required for?
More Power
What is a twitch?
When one quick motor unit is stimulated
How do muscles avoid Fatigue?
They activate the motor units on a rotating basis to avoid fatigue
What is Muscle tone?
Resting Tension in muscles
What is Isotonic contraction?
When tension produced is equal or greater than the resistance/load
What are the two main types of contraction?
Isotonic contraction
Isometric contraction
What are the two types of Isotonic Contraction?
Concentric and Eccentric
What is Concentric contraction?
Shortening of an active muscle
What is Eccentric contraction?
Lengthening of an active muscle
What is Isometric contraction?
When tension never exceeds the resistance/load and the active muscle does not change length in contraction
What are the two types of Skeletal muscles fibres?
Type I (Slow) and Type II (Fast)
What are the Characteristics of Slow fibers?
- Red due to numerous mitochondria and myoglobin
- Narrow diameter
- Takes a long time to contract
- Less myofibrils
- Resistant to fatigue but less powerful
- ATP produced by mitochondria through aerobic metabolism
- More extensive network of capillaries
- Associated with leg muscles and posture
What are the characteristics of Fast Fibres?
- White because less myoglobin and mitochondria
- Larger diameter, densely packed myofibrils, large glycogen reserve
- Few mitochondria
- Rapid contraction
- ATP generated by anaerobic glycolysis
- Associated with eye and hand muscles
What are the 4 types of Muscle Organization?
- Parallel muscles
- Convergent muscles
- Pennate muscles
- Circular muscles
What is the most common organization of Muscles?
Parallel muscles
What is the shape of Parallel muscles?
Flat or spindle shaped
What is the central portion of spindle shaped muscles?
The belly
What happens during contraction of Parallel muscles?
The muscle gets shorter and the belly gets wider
How do Parallel muscles exert force?
All fascicles pull in the same direction
What is the shape of Convergent muscles?
Fan shaped
Where do convergent muscle originate and converge?
The originate over a wide are but converge at a common attachment site
How can the direction of the pull change in Convergent muscles?
Depending on which fascicles contract
Why do Convergent muscles not exert the same amount of force as Parallel muscles?
Because not all the muscles pull in the same direction
What is the Shape of Pennate muscles?
Fan shaped
What is the benefit of the feather shaped fibers?
The fibers are able to stack more for a more forceful contraction
What are the 3 types of Pennate muscles?
- Unipennate
- Bipennate
- Multipennate
What is unipennate?
When muscle fibres are on one side of the tendon
What is Bipennate?
When muscle fibres are on both sides of the tendon
What is Multipennate?
When the tendon branches within the muscle
What does contraction of circular muscles allow?
The diameter of the opening to be reduced
What are Skeletal muscle named according to?
Structure or shape of the muscle, specific region of the body, attachment sites, relationship to other muscles, action of the muscle
Deltoideus
Triangulat
Maximus
Large
Brevis
Short
What is Action?
The type of movement (function of muscle)
What is Insertion?
Muscle attachment to moveable bone
What is Origin?
Muscle attachment to stationary bone
What are the 4 types of primary muscle actions?
- Agonist (Prime mover)
- Synergist
- Antagonist
- Fixators
What is Agonist mucle action?
Contraction produces a particular movement
What is Synergist muscle action?
Assists prime mover in performing anaction
What is Antagonist muscle action?
Opposes the movement
What is Fixator muscle action?
Agonist and antagonist muscle contracting at the same time to stabilize a joint
