Download Muscle Notes - Cherokee County Schools

Muscular System
Types of Muscle
●Skeletal – striated & voluntary
●Smooth – involuntary
●Cardiac - heart
The word
“striated” means
striped. Skeletal
muscle appears
striped under a
microscope.
Muscles and Muscle Fiber Structure
Muscles are composed of many FIBERS that
are arranged in bundles
called FASCICLES
EPIMYSIUM = outermost layer, surrounds
entire muscle.
PERIMYSIUM = separates and surrounds
fascicles (bundles of muscle fibers)
ENDOMYSIUM
= surrounds
each individual
muscle fiber
This model of the muscles uses
straws to represent fibers.
Green = endomysium
Yellow = perimysium
Blue = epimysium
Muscle Layers
Muscle Fiber
Endomysium
Perimysium
Epimysium
Epimysium
Perimysium
Endomysium
Muscles / Cells
Sarcolemma = muscle fiber membrane
Sarcoplasm = inner material surrounding
fibers (like cytoplasm)
Sarcoplasmic Reticulum – Specialied ER
for transport of Calcium
Myofibrils = individual muscle fibers, made
of myofilaments
Nucleus
Sarcolemma
Mitochondrion
Sarcoplasm
Myofibril
Myofibrils are made of
ACTIN = thin filaments
MYOSIN = thick filaments
Myofilaments ACTIN (thin) and MYOSIN (thick)
-- form dark and light bands
 A band = dArk • thick (myosin)
 I band = lIght • thIn (actin)
 During contractions the 2 slide over
each other
It is important to remember the hierarchy
fasicles
myofibrils
myofilaments
actin
myosin
How Muscles Work with the Nervous System
Skeletal Muscle Activity
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Stimulation and Contraction of Single Skeletal
Muscle Cells
Skeletal muscles must be stimulated by nerve
impulses to contract.
One motor neuron may stimulate a few muscle
cells or hundreds of them.
One motor neuron and all the skeletal muscle
cells it stimulates are a MOTOR UNIT.
When the nerve impulse reaches the end of the
motor unit, a chemical referred to as a
NEUROTRANSMITTER is released. This
neurotransmitter is called ACETYLCHOLINE.
Motor Unit or Neuromuscular Junction
1. Neuron
3. Vesicle
2. Sarcolemma (or motor end plate)
4. Synapse
5. Mitochondria
The neurotransmitter that cross the gap is
ACETYLCHOLINE
The neurotransmitter that crosses the gap is ACETYLCHOLINE.
This is what activates the muscle.
Acetylcholine is
stored in vesicles
SLIDING FILAMENT THEORY (MODEL)
The theory of how muscle contracts is the sliding filament
theory. The contraction of a muscle occurs as the thin
filament slide past the thick filaments. This movement
requires ATP
 https://www.youtube.com/watch?v=pkGElMDd5jI
Other Terms
●1. Threshold Stimulus
●2. All-or-None Response
●3. Motor Unit
●5. Recruitment
●6. Muscle Tone
●7. Muscular Hypertrophy
●8. Muscular Atrophy
●9. Muscle Fatigue
●10. Muscle Cramp
●11. Oxygen Debt
1. Threshold Stimulus
Minimal strength required to cause a contraction
Motor neuron releases enough acetylcholine to
reach threshold
2. All-or-None Response
Fibers do not contract partially, they either do or
don't
3. Motor Unit
The muscle fiber + the motor
neuron
4. Recruitment
more and more fibers contract as
the intensity of the stimulus
increases
5. Muscle Tone
Sustained contraction of individual
fibers, even when muscle is at
rest
6. Hypertrophy
- muscles enlarge (working out or
certain disorders)
7. Atrophy - muscles become small and weak due to
disuse
8. Muscle Fatigue - muscle loses ability to
contract after prolonged exercise or strain
9. Muscle Cramp - a sustained involuntary
contraction
10. Oxygen Debt
oxygen is used to create
ATP, -- not have enough oxygen causes Lactic
Acid to accumulate in the muscles → Soreness
-
*See Magic School Bus
11. Origin and Insertion
Origin = the immovable
end of the muscle
Insertion = the movable
end of the muscle
The biceps brachii has two origins
(or two heads).
Muscle Movements, Types,
and Names

Types of Muscles – Muscle movement is the
result of the activity of two or more muscles
acting together or against each other.
–
Prime Mover - the muscle that has the major
responsibility for causing a particular movement
Muscle Movements, Types,
and Names

Types of Muscles Continued…
Antagonists – muscles that oppose or reverse a
movement
**When a prime mover is active, its antagonist is stretched
and relaxed**
– Synergists – help prime movers by producing the same
movement or by reducing undesirable movements
– Fixators – are specialized synergists that hold a bone still
so all the tension can be used to move another bone
–
Naming Skeletal Muscles

Use the following 7 criteria:
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Direction of the Muscle Fibers – Are the fibers parallel or
slanted?
Relative Size of the Muscle – Are the muscles large or
small?
Location of the Muscle
Number of Origins – 2 (bi-); 3 (tri-); 4 (quad)
Location of the Muscle’s Origin and Insertion
Shape of the Muscle
Action of the Muscle
Muscle Movements, Types,
and Names

Types of Body Movements (pages 199 – 202))
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Flexion
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Extension
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Brings 2 bones closer together
Example = Bending the knee and elbow
Increases the distance between 2 bones
Example = straightening the knee or elbow
Rotation
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Movement of a bone around an axis
Example = shaking your head “no”
Muscle Movements, Types,
and Names

Types of Body Movements (pages 199 – 202)
–
Abduction
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Adduction
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Moving the limb away from the midline of the body
Example = lifting arm or leg away from the body
Moving the limb toward the midline of the body
Example = bringing arm or leg in towards the body
Circumduction


A combination of flexion, extension, abduction, and
adduction (movement in a circle fashion)
Example = Movement of the shoulder
Muscle Movements, Types,
and Names

Special Movements – do not fit into the previous
categories
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Dorsiflexion – lifting foot towards the shin
Plantar Flexion- pointing the toes
Inversion – turning the sole of the foot medially
Eversion – turning the sole of the foot laterally
Supination – rotate the forearm so that the palm faces
anteriorly
Pronation – rotate the forearm so that the palm faces
posteriorly
Opposition – moving the thumb to touch the tips of the
other fingers