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MUSCULAR SYSTEM
INTRODUCTION


What are the three muscle
types?
• Skeletal Muscle
• Smooth Muscle
• Cardiac Muscle
Skeletal muscle is an ...
Structure of a Skeletal Muscle






Fascia - a connective tissue that separates adjacent
muscles and attaches the mu...
Skeletal Muscle Fibers


A skeletal muscle fiber is a
single cell that contracts
and relaxes

What causes the cell to
con...
Skeletal Muscle Fibers


Myofibrols
– Play a fundamental roll in

muscle contraction.
– They contain two kinds of
protein...
Skeletal Muscle Fibers
The Striation part of skeletal pattern consist of two main parts
1. I Bands ( light

bands ) are
co...
Skeletal Muscle Fibers
 Sarcomere – the
segment of a myofibril
that extends from one
“z” line to another.

sarcomere

Z L...
Skeletal Muscle Fibers
 Sarcoplasmic

reticulum– network of

membranous channels… similar to
endoplasmic reticulum of oth...
Skeletal Muscle Fibers
Skeletal Muscle Fibers






Describe how connective tissue is part of a
skeletal muscle.
Describe the general structu...
Neuromuscular Junction


What is the stimulant that moves
a muscle?




Nerve impulse

Motor neuron – A nerve fiber tha...
Neuromuscular Junction

A neuromuscular junction showing motor end plate.

A motor unit. A muscle fiber
usually has a sing...
Skeletal Muscle Contraction
The role of myosin and actin





Myosin – contain protein
strands that look like
“Golf Club...
Skeletal Muscle Contraction


Sliding Filament Theory


The head of the myosin crossbridge attaches to the actin
binding...
Skeletal Muscle Contraction
Skeletal Muscle Contraction






Describe a neuromuscular junction.
Define motor unit.
Explain how the filaments of a...
Support & Movement


Oxygen Dept




When muscles are used during exercise
oxygen is used up quickly. The body reverts
...
Support & Movement
 Muscle Fatigue
 Muscles lose the ability to contract.
– Lactic acid
– Lack of acetylcholine
– Interr...
Muscle Responses


Threshold Stimulus




The minimal strength required to cause a
contraction.

All-or-None Response
–...
Muscle Responses


Latent Period




The time the stimulus is applied and the contraction
occurs (0.01s)

Muscle Tone
...
Support and Movement
Questions (p189)


Define threshold stimulus.



What is a none-or-all response?



Distinguish be...
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Muscular system

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Transcript of "Muscular system"

  1. 1. MUSCULAR SYSTEM
  2. 2. INTRODUCTION  What are the three muscle types? • Skeletal Muscle • Smooth Muscle • Cardiac Muscle Skeletal muscle is an organ of the muscular system and consist of skeletal muscle tissue, nervous tissue, blood, and connective tissue.
  3. 3. Structure of a Skeletal Muscle      Fascia - a connective tissue that separates adjacent muscles and attaches the muscle to the bone. Epimysium – a layer of connective tissue that closely surrounds a skeletal muscle. Perimysium – separates muscle cells into fascicles. Fascicles – bundles of skeletal muscle fibers. Endomysium – separates each individual muscle fiber. What do all of these have in common?
  4. 4. Skeletal Muscle Fibers  A skeletal muscle fiber is a single cell that contracts and relaxes What causes the cell to contract and relax?   Nerve stimulation Sarcolemma- muscle cell membrane.  Sarcoplasm- cell’s cytoplasm
  5. 5. Skeletal Muscle Fibers  Myofibrols – Play a fundamental roll in muscle contraction. – They contain two kinds of proteins filaments MYOSIN & ACTIN  Myofibril Myosin & Actin are responsible for the light and dark STRIATIONS or bands of skeletal muscle. Filaments Muscle fiber
  6. 6. Skeletal Muscle Fibers The Striation part of skeletal pattern consist of two main parts 1. I Bands ( light bands ) are composed of thin ACTIN filaments attached to Z lines. 2. A Bands ( dark bands ) are composed of overlapping thick & thin bands.
  7. 7. Skeletal Muscle Fibers  Sarcomere – the segment of a myofibril that extends from one “z” line to another. sarcomere Z Lines
  8. 8. Skeletal Muscle Fibers  Sarcoplasmic reticulum– network of membranous channels… similar to endoplasmic reticulum of other cells. • Responsible for releasing calcium ions.  Transverse tubules ( T-tubules ) – extent inward and contain extracellular fluid.
  9. 9. Skeletal Muscle Fibers
  10. 10. Skeletal Muscle Fibers     Describe how connective tissue is part of a skeletal muscle. Describe the general structure of a skeletal muscle fiber. Explain why skeletal muscle fibers appear striated. Explain the relationship between the sarcoplasmic reticulum and the transverse tubules.
  11. 11. Neuromuscular Junction  What is the stimulant that moves a muscle?   Nerve impulse Motor neuron – A nerve fiber that extends outward from the brain or spinal cord and connected to a skeletal muscle fiber.   The connection between the two is called a neuromuscular junction and motor end plate. Neurotransmitters – chemicals that are stored in tiny vesicles (synaptic vesicles) that stimulates muscle fiber to contract.
  12. 12. Neuromuscular Junction A neuromuscular junction showing motor end plate. A motor unit. A muscle fiber usually has a single motor end plate. However a motor neuron may connect to several muscle fibers.
  13. 13. Skeletal Muscle Contraction The role of myosin and actin   Myosin – contain protein strands that look like “Golf Clubs” called Cross Bridges. Actin molecule contains protein binding sites. Tropomyosin Actin Thick Filament Myosin Crossbridge
  14. 14. Skeletal Muscle Contraction  Sliding Filament Theory  The head of the myosin crossbridge attaches to the actin binding site & pulls the actin filament along.  ATP is used to set the crossbridge. relaxed  Myosin Z line As the cross-bridges pull, the actin filament moves toward the center of the sarcomere and they shorten. contracted Actin
  15. 15. Skeletal Muscle Contraction
  16. 16. Skeletal Muscle Contraction     Describe a neuromuscular junction. Define motor unit. Explain how the filaments of a myofibril interact during muscle contraction. Explain how a motor nerve impulse can trigger a muscle contraction.
  17. 17. Support & Movement  Oxygen Dept   When muscles are used during exercise oxygen is used up quickly. The body reverts to anaerobic respiration to produce oxygen, with the help of pyruvic acid. In low oxygen levels pyruvic acid reacts to produce lactic acid which accumulate in the muscles. As lactic acid accumulate a person develops Oxygen Dept.
  18. 18. Support & Movement  Muscle Fatigue  Muscles lose the ability to contract. – Lactic acid – Lack of acetylcholine – Interruption of blood supply  Cramps  A sustained involuntary contraction  Rigor Mortis, myosin and actin filaments remained linked until muscles begin to decompose. ( 72 hrs )
  19. 19. Muscle Responses  Threshold Stimulus   The minimal strength required to cause a contraction. All-or-None Response – A muscle fiber when excited does not contract partially, if it contracts at all, it contracts completely  Twitch  A single contration that lasts only a fraction of a second
  20. 20. Muscle Responses  Latent Period   The time the stimulus is applied and the contraction occurs (0.01s) Muscle Tone    Even when a muscle appears to be at rest, a certain amount of sustained contraction occurs in its fibers. Muscle tone is a response to nerve impulses that originate repeatedly. Is particularly important in maintaining posture.
  21. 21. Support and Movement Questions (p189)  Define threshold stimulus.  What is a none-or-all response?  Distinguish between a twitch and a sustained contraction.  How is muscle tone maintained?
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