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Joint`s structure relates to the movement of joint
Gliding Movement: Occurs in plane joints between two flat surfaces of bones which slide or glide over each other, eg. Between carpal bones
slight movement
Angular Movement:
When one part of the body bent relative to another part; thereby changing the angle between two parts
– Flexion and Extension
• Plantar and Dorsiflexion
– Abduction and Adduction
• Flexion: movement of a body part anterior to the
coronal plane
• Extension: movement of a body part posterior to
the coronal plane
– Plantar flexion:
standing on the toes
– Dorsiflexion: foot
lifted toward the shin,
such as walking on the
heels
• Abduction: movement
away from the median
plane
• Adduction: movement
toward the median plane
Abduction
Adduction
• Involves rotation of a structure around an axis or movement of the structure in an arc
• Rotation: turning of a structure on its long axis
– Examples: rotation of the head, humerus, entire body
– Medial rotation turns the bone inwards
– Lateral rotation turns the bone outwards
• Pronation/Supination:
• Unique rotation of the forearm
– Pronation: palm faces posteriorly
– Supination: palm faces anteriorly
• Circumduction
– The circular or conical
movement of a body part
– Consists of a combination of
flexion, extension, adduction,
and abduction
– Occurs at freely movable
joints
– Eg. Windmilling the arms or
rotating the hand from the
wrist
• Unique to only one or two joints
• Types
– Elevation and Depression
– Protraction and Retraction
– Excursion
– Opposition and Reposition
– Inversion and Eversion
• Elevation: moves a structure superior
• Depression: moves a structure inferior
• Examples: shrugging the shoulders, opening and closing the
mouth
• Protraction:
• Movement of a bone
anteriorly
• Eg. Thrusting the jaw
forward, shoulder forward
• Retraction:
• Moves structure back to
anatomic position or even
further posteriorly
• Lateral: moving mandible to the right or left of midline
• Such as in grinding the teeth or chewing the food
• Medial: return the mandible to the midline
• Opposition:
movement of thumb
and little finger toward
each other
• Reposition: return to
anatomical position
• Inversion:
• Inversion is a
movement in which
the soles are turned
medially
• Eversion:
• Eversion is a turning
of the soles to face
laterally
Muscle Function
Movement
Maintaining posture
Stabilizing joints
Heat generation
Muscle Histology
Muscle Cell = muscle fiber
Capable of : Contraction
Action potential
3 Types of Muscle Tissue:
Skeletal muscle (striated or voluntary)
Cardiac muscle
Smooth muscle (involuntary)
3 Types of Muscle
Tissue
Skeletal Muscle
Contractions for
body movement
Voluntary
Long, cylindrical, striated
cells
Multinucleated
Contracts rapidly, tires
easily
3 Types of muscle Tissue
Cardiac Muscle
In heart wall (Amitotic)
Involuntary
Striated, branching cell
Mono or binucleate
Intercalated discs
Self initiating contractions
3 Types of Muscle Tissue
Smooth (Visceral) Muscle
In walls of organs/ blood
vessels
Involuntary
Spindle-shaped, nonstriated
cells
Mononucleated
Slow, sustained contractions
MUSCLE FIBER
MYOFIBRIL
MYOFILAMENT
SARCOMERE
ACTIN AND MYOSIN
Skeletal Muscle Organization Tendon
Fascicle
Skeletal Muscle Structure
Tendon
Attaches muscle to bone
Nerve Ending
Found on each muscle fiber
Provide stimulation for contraction
Blood Vessels
Arteries throughout muscle
Veins carry away wastes
Connective Tissue Layers
endomysium
fascicle
muscle fiber fascicle
epimysium
Muscle tendon
perimysium
Skeletal Muscle Structure: Connective Tissue
Wrappings
Three layers of connective tissue surround skeletal
muscle:
Epimysium (fascia)
Wraps around entire muscle
Perimysium
Wraps around fascicles
Endomysium
Surrounds each muscle fiber
Skeletal Muscle Fiber Structure
Muscle Fiber
Composed of thousands of
myofibrils
muscle fiber
myofibril
sarcomere Myofibril Consists of smaller
contractile units called sarcomeres
Myofibril Structure
thin (actin) filament
muscle fiber
thick (myosin) filament
Muscle Fiber Structure
Sarcoplasm
Similar to cytoplasm
Contains myoglobin
Myoglobin
Red protein pigment
Stores oxygen
Sarcolemma
Plasma membrane of muscle fiber
Capable of carrying impulses initiated by nerves
Muscle Fiber Structure
Sarcolemma
T-tubules
Extensions of sarcolemma
Conduct impulses deep into muscle fiber
T-Tubule s and Terminal Cisternae
T-tubules terminal cisternae
myofibril
sarcoplasmic reticulum
Muscle Fiber Structure
Sarcoplasmic Reticulum
System of ER surrounding each myofibril
Stores calcium ions
Calcium ions needed for muscle contraction
Terminal Cisternae
Widened regions of sarcoplasmic reticulum surrounding each T-
tubule
Sarcomere Structure
Sarcomere
The smallest contractile unit of a muscle fiber
Myofilaments (myosin and actin)
Each thick (myosin) filament is surrounded by 6 thin (actin)
filaments
Thick and thin myofilaments overlap in some areas
Arrangement of myofilaments = striated appearance
Myofibril Structure
Sarcomere
Each sarcomere contains stacked, rod-like proteins
called myofilaments
Thick myofilaments
Myosin protein
Thin myofilaments
Actin protein
Actin and myosin arrangement gives skeletal muscle its striated
appearance
Sarcomere Structure
Sarcomere
Extends from Z line to Z line
Z line A sheet of protein anchoring actin filaments Attaches one sarcomere to next
Z Z
Sarcomere Regions
Z Z
I band I band
M
A band
H zone
Muscle Action
Action = the joint movement caused by a muscle when it contracts
Origin
The nonmoving point of muscle attachment
Insertion
Point of muscle attachment where movement takes place
Synergists
Groups of muscles that work together to do the same action
The prime mover does most of the work
Antagonist
Muscles that work in opposition
The Neuromuscular Junction
Motor Neurons
Skeletal muscle: innervated
by motor neurons
Bundles of motor neuron axons
= nerves
Each muscle served by at
least one nerve
Neuron axons branch into
axon terminals
Motor Neuron
cell body
dendrites
axon terminal axon
Motor Unit
A motor neuron and all the
muscle fibers it supplies is called
a motor unit
One neuron may supply as few as 4
muscle fibers
A single neuron may supply several
hundred muscle fibers
motor unit 1
motor unit 2
The Neuromuscular Junction
Terminal does not touch
muscle fiber
Synaptic cleft
Neuromuscular Junction
Each axon terminal forms a neuromuscular junction with a single muscle fiber
axon terminal
synaptic cleft
The Axon Terminal and Synaptic Cleft
The Axon Terminal
Contains synaptic
vesicles
contain acetylcholine (ACh)
synaptic vesicles synaptic cleft
Acetylcholine Ach Neurotransmitter secreted
by the axon terminal Nerve impulse Calcium ions enter
terminal Synaptic vesicles migrate
towards neuron cell membrane Exocytosis of Ach into
synaptic cleft
Nerve Impulse
The Motor End Plate
Indented, trough area on muscle fiber
Ach released by the axon terminal into cleft
Numerous Ach receptors Ach binds to receptors on
motor end plate
Motor End Plate
Resting Membrane Potential
The inside of the sarcolemma is
more negative than the outside
More positive ions outside the cell
The difference between the charge
inside and outside the sarcolemma is
called the RESTING MEMBRANE
POTENTIAL (RMP)
+ + + + + + + + + + +
–– –– –– –– ––
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
k+
k+ k+
k+
Action Potential Generation at the Sarcolemma
ACh Released by the motor
neuron Binds to receptors on the
motor end plate Binding causes sodium
ion gates to open Sodium (Na+) is allowed
to enter sarcolemma
ACh
Ach receptor
K+
Na+ gates
Na+
Depolarization
Sodium gates open:
Influx of sodium
Inside of sarcolemma becomes less negative
Sudden positive change in membrane potential = DEPOLARIZATION
+ + + + + + + + + + +
–– –– –– –– –– –
Na+
Na+
Na+
Na+
Na+ Na+
Na+
Na+
k+
k+ k+
k+
Na+
Na+
Na+
++++ + + + + + + +
– – – – – – – – – –
Na+
Propagation
Depolarization spreads to adjacent areas
Continues down sarcolemma
Reaches T-tubules and terminal cisternae
Causes release of calcium into the sarcoplasm
Nerve Impulse
Ca2+ ions terminal cisternae
Repolarization
Occurs immediately following
depolarization
Sodium gates close (no longer
enters)
Potassium gates open (diffuse out
of fiber)
Sodium-potassium pumps moves
sodium out and potassium in to
restore RMP
RMP becomes negative once
again
+ + + + + + + + + + +
–– –– –– –– –– –
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
k+
k+
k+
k+
Na+
Na+
Na+
Na+
Na+
Absolute Refractory Period
Occurs during repolarization
Muscle fiber does not respond to a stimulus
The Action Potential
Consists of:
Depolarization
Membrane potential becomes more positive
Propagation
Depolarization travels down the sarcolemma and down the
T tubules, deep into the muscle fiber
Repolarization
RMP is restored back to its normal, negative state
Acetylcholinesterase
AChE
Enzyme that breaks down Ach
Assures muscle contraction is not continuous
Further nerve stimulation needed to continue a contraction
Destruction of ACh
AChE
Na+ gates
Na+
K+
ACh
Ach receptor
The Sliding Filament Mechanism for Muscle
Fiber Contraction
When a muscle fiber contracts:
Each sarcomere shortens
muscle cell length decreases
In a relaxed state:
Actin filaments overlap the myosin filaments but not one another
During a contraction:
Actin filaments are pulled inward so they overlap one another
distance between ‘Z lines’ is reduced
The overall length of the sarcomere is reduced
Myofilament Structure
Thick (Myosin) filament
Composed of myosin molecules
head of myosin molecule is on a flexible arm
Myosin heads are attracted to active sites on the actin filament
Myosin has ability to cleave ATP to form ADP and release energy (acts as an
ATPase enzyme)
head tail
ATP binding site
Myofilament Structure
Thin (Actin) Filament
2 actin strands coiled with a tropomyosin strand
Troponin (protein) molecules
Bound to both tropomyosin and actin
Binds readily to calcium ions
Relaxed state: tropomyosin covers the myosin binding sites on
the actin strands
actin troponin
tropomyosin
Steps of The Sliding Filament
When in a relaxed state:
ATP binds to the myosin head and is cleaved into ADP
The energy released is stored and the myosin head is moved to a ‘cocked’ position (perpendicular to the actin and myosin strands)
Steps of the Sliding Filament An action potential travels down the sarcolemma of the muscle cell T-tubules carry the impulse deep into the myofibrils
The impulse causes the release of calcium ions from the sarcoplasmic reticulum into the sarcoplasm
Nerve Impulse
Steps of the Sliding Filament Calcium ions bind to troponin Troponin and tropomyosin complex becomes buried deeper into the
actin filaments
The active sites for the binding of myosin become uncovered
Nerve Impulse
Steps of The Sliding Filament
Myosin heads bind to the uncovered sites on the actin strands
Once each myosin head binds to actin, the stored energy from the cleavage of ATP is used to tilt the head inward
Steps of The Sliding Filament As the myosin head tilts inward, the actin strand is pulled with it
This inward pulling of the actin by the myosin is called the power stroke
Steps of the Sliding Filament Once the power stroke has occurred, the myosin head releases the
ADP and a new ATP binds to the head
Binding of the ATP causes the detachment of the myosin head from the actin strand
Steps of the Sliding Filament
The newly attached ATP molecule is cleaved into ADP and the myosin head becomes cocked again ready to attach to a new active site
This process continues in a ratchet-like manner until the actin filaments are overlapping
Sliding Filament Mechanism of Contraction
Nerve Impulse
Sarcomere and Sliding Filaments
The All or None Response
When an action potential triggers a muscle fiber
contraction:
Fiber contracts completely or not at all
There are no partial contractions of a muscle fiber
Does not pertain to an entire muscle
Muscle Twitch
A quick contraction and following relaxation of a muscle caused by a single, brief stimulus
The strength of the twitch depends upon the
number of motor units involved
Three phases:
Latent period
Period of contraction
Period of relaxation
Three Phases of Muscle Twitch
Latent Period
1st few milliseconds following stimulation
No response yet
Period of Contraction
10-100ms long
From onset of shortening to peak contraction
Period of Relaxation
10-100 ms
Muscle tension decreases
Graded Muscle Responses
Variations in the degree of muscle contractions
Contractions do not normally occur as a single twitch
Two ways to grade muscle response: Change the speed of stimulation Wave summation
Tetanus
Change the number of motor units involved Multiple motor unit summation (recruitment)
Wave Summation
Two or more electrical stimuli are delivered in rapid succession
The muscle twitch from the second stimulus will be stronger than the first
Successive contractions are summed
Not true if the second stimulus occurs before the absolute refractory period is over
Tetanus
Smooth, sustained contraction
Caused by increasing the rate of stimulus
Relaxation time between contractions becomes shorter and shorter
Contractions fuse into one, sustained contraction
Prolonged tetanus results in muscle fatigue
Multiple Motor Unit Summation
Called recruitment
Stimuli with increasing voltage
More muscle fibers respond to the stimulus as the voltage
increases
Threshold stimulus
Stimulus at which the first noticeable contraction occurs
Maximal stimulus
Point at which all motor units are responding
Increasing the intensity of the stimulus will no longer increase
the strength of contraction
Treppe
Staircase Effect
Stimulus of the same strength is repeated
Contractions become gradually stronger with each successive
stimulus
Increased calcium availability
Enzymes become more efficient due to increased heat from muscle
contraction
Muscle Tone
State of slight but constant contraction
Results in joint stability
Used for posture maintenance
Does not result in movement
Types of Contractions
Isotonic Contractions
Muscle contracts and shortens
Contraction causes movement of the load put upon it
Isometric Contractions Muscle contracts, tension
increases but the length of the muscle does not change No load movement
Energy for Contraction
Stored ATP
ATP the main source of energy for muscle fiber contraction
Needed for myosin head attachment and detachment
Muscles can only store enough ATP to last 4 to 6 seconds
ATP must be continually recycled to sustain a muscle contraction
ATP
Adenine Phosphates
Ribose
Three Pathways For Generating ATP in Muscle
Phosphorylation of ADP by creatine phosphate
Anaerobic glycolysis
Cellular respiration
ATP Sources in Muscle
Phosphorylation of ADP BY Creatine
Phosphate
Creatine phosphate= high energy molecule stored in
muscles
Contains a high energy phosphate bond
Energy stored in creatine phosphatetransferred to ADP
to re-form ATP
Transfer of a phosphate group + energy associated with it
= phosphorylation
Phosphorylation of ADP By Creatine
Phosphate
When ATP is depleted in a muscle cell:
Creatine phosphate couples with ADP
Phosphate and energy transferred to ADP
ADP ATP
Creatine phosphate reserves depleted in 15 to 20 seconds
During inactivity, creatine phosphate reserves replenished
Creatine P
ADP
Creatine
ATP
Aerobic Respiration
Glucose is broken down (with the use of oxygen) to release
energy
Energy is used to form ATP
Glucose broken down into carbon dioxide and water
Requires continuous oxygen and nutrients
Occurs mostly in the mitochondria
Fairly slow
Most of the energy during prolonged exercise must come from this
Enough energy to form 36 ATP
Glucose + Oxygen Carbon dioxide + H2O + ATP
AEROBIC RESPIRATION
Glucose
Pyruvic acid
In the Cytoplasm
Glycolysis
Aerobic Respiration
Oxygen
present
No Oxygen needed
2 ATP gain
H2O
34 ATP CO2
In the Mitochondria 34 ATP gain
Anaerobic Glycolysis and Lactic Acid
Formation
Glycolysis 1st step of both aerobic respiration and lactic acid formation Glucose is split into 2 pyruvic acid molecules 2 ATP are gained
If oxygen is available: The pyruvic acids continue to be broken down in the
mitochondria by aerobic respiration
If oxygen is not available: The pyruvic acids are converted into lactic acid in a
process called anaerobic glycolysis Provides energy for 30-60 seconds
LACTIC ACID FORMATION
Glucose
Pyruvic acid
In the Cytoplasm
Glycolysis
Aerobic Respiration
Oxygen
present
No Oxygen needed
2 ATP gain
H2O
34 ATP
In the Mitochondria 34 ATP gain
Lactic Acid No oxygen
present
CO2
Anaerobic Glycolysis and Lactic Acid
Formation
Inefficient energy source
Large amounts of glucose in/ small amounts of ATP out
Muscle fatigue and soreness may result
Use of Energy Systems
ATP & Creatine Phosphate Reserves
Stored ATP–4 to 6 seconds
Creatine phosphate–15 seconds
Used for a short, quick power surge (weight lifting, sprinting, diving)
Creatine Phosphate Reserves
1 ATP
Use of Energy Systems
Anaerobic Glycolysis
Used in activities with on-off bursts (tennis, soccer)
Kicks in early in exercise
Kicks in when muscle contraction is 70% of max or more
Muscles fatigue after 1 to 2 minutes
The point at which muscles convert over to anaerobic glycolysis is called anaerobic threshold
Glycolysis ATP Reserves
2 ATP
Use of Energy Systems
Aerobic Respiration
Used for prolonged activities (jogging, marathons, bicycling)
Can provide energy for hours
The length of time a muscle can contract using the aerobic pathway is called aerobic endurance
* The anaerobic mechanism will kick in any time the aerobic mechanism can’t keep up with ATP production
Aerobic Respiration ATP Reserves
36 ATP
Muscle Fatigue
Muscle loses its ability to contract
Usually a result of strenuous exercise
ATP production is less than ATP usage
May be from inadequate blood supply
May be from lactic acid accumulation (low pH prevents muscle fibers from
contracting)
If no ATP available, contractures occur
Oxygen Debt
= the amount of extra oxygen that must be taken in
following exercise in order to restore all oxygen-
requiring activities that were put on hold during
exercise
ATP reserves must be replenished
Creatine phosphate reserves must be restored
Muscle oxygen reserves must be replaced
Oxygen Debt
Heat Production 20 to 25% of the energy produced during muscle contraction is used for
work
Most of the energy is given off as heat
Body responds by dilating blood vessels in the skin and sweating
Rapid muscle contractions will produce heat when the body is too cold (shivering)
Force, Velocity and Duration of Muscle
Contraction
The strength or force of
muscle contraction is
affected by:
1) The number of fibers
contracting
The more motor units recruited, the
stronger the contraction
Large number of muscle fibers
Large muscle fibers
2) The relative size of the muscle The greater the muscle bulk, the greater
its strength Strength increases with regular use of
the muscle (causes hypertrophy)
Force, Velocity and Duration of Muscle
Contraction
The strength or force of muscle contraction is affected by:
3) Series-elastic elements
Noncontracting components (series elastic elements) are stretched by the force of the contractile elements (myofibrils)
Once stretched, the elastic elements will transfer the tension to the load
The more rapidly a muscle is stimulated, the more force it exerts
Single twitches exert less force Tetanic contraction adequately stretches the series-elastic elements
Force, Velocity and Duration of Muscle
Contraction
The strength or force of muscle
contraction is affected by: 4) The degree of muscle stretch
Optimal length of a skeletal muscle =
80 to 100% of resting length
Most maintain length by the way they
are attached to bone
Muscle and sarcomere length slightly over
100% of resting length
Load Movement
Load
Resistance to a contracting
muscle
If force of contraction > than the
load:
Movement occurs (isotonic
contraction)
If load > force of contraction:
Muscle length does not change and
load does not move (isometric
contraction)
Muscle Fiber Types Three Types of Muscle Fibers
Red Fibers (slow twitch)
White Fibers (fast twitch)
Intermediate Fibers
Muscle Fiber Types
Red Muscle Fibers
Thin cells
Rich in myoglobin
Contract slowly
Abundant oxygen for aerobic
pathway
Contract for long periods of time
Fatigue resistant
Not powerful
Used for endurance events
Muscle Fiber Types
White Muscle Fibers
Large cells
Light colored fibers with little
myoglobin
Contract rapidly
Depend upon the anaerobic
pathway for ATP
Fatigue easily
Powerful
Used for sprint type events
Muscle Fiber Types
Intermediate Muscle Fibers
Reddish or pink color
Intermediate size
Quick contractions
Depend upon the aerobic pathway
Fatigue resistant but less than
slow twitch fibers
Muscle Fiber Types Most muscles contain a mixture of all 3 muscle fiber types
The percentage of each fiber type is genetically predetermined
Effect of Exercise on Muscle
Aerobic exercise results in:
Increased capillaries to skeletal muscle
Increase in number of mitochondria in each muscle fiber
More myoglobin production by muscle fibers
Improved delivery of nutrients and oxygen to body tissues by cardiovascular and respiratory systems
Development of an increased heart stroke volume
capillaries
Disuse Atrophy
Disuse of muscle results in:
Degeneration of muscle
Loss of muscle mass (atrophy)
Caused by:
Lack of neural stimulation
Bed rest
Immobilization
Neuromuscular Junction
synaptic cleft
The Motor End Plate
Binding of ACH
ACh
Ach receptor
K+
Na+ gates
Na+
Depolarization + + + + + + + + + + +
–– –– –– –– –– –
Na+
Na+
Na+
Na+
Na+ Na+
Na+
Na+
k+
k+ k+
k+
Na+
Na+
Na+
++++ + + + + + + +
– – – – – – – – – –
Na+
The Sliding Filament Mechanism
Nerve Impulse
Steps of the Sliding Filament
Nerve Impulse
Steps of the Sliding Filament
Head and Neck Muscles
Posterior Shoulder Muscles
Anterior Shoulder Muscles
Abdominal Muscles
Arm Muscles
Anterior Posterior
Forearm Muscles
Anterior Posterior
Respiration Muscles
Inferior
Thigh Muscles
Leg Muscles
