Muscles & Movement Skeletal Muscle neurons detect stimuli-produces response ... the ability to...
Transcript of Muscles & Movement Skeletal Muscle neurons detect stimuli-produces response ... the ability to...
11.2.1 State the roles of bones,
ligaments, muscles, tendons and
nerves in human movement.
1. Bones
2. Ligaments
3. Tendons
4. Muscles
5. Nerves
11.2.1 State the roles of bones,
ligaments, muscles, tendons and nerves
in human movement.
Bones
1) Provide a hard framework for
stability &
2) Provide attachment/anchoring
surfaces
3) Act as levers to facilitate
movement (usually 3rd class levers)
1st Class Lever
First-class levers
have the fulcrum
placed between
the load and the
effort, as in the
seesaw, crowbar,
and balance
scale.
2nd Class LeverSecond-class
levers have the
load between the
effort and the
fulcrum. A
wheelbarrow is a
second-class
lever.
3rd Class LeverThird-class levers
have the effort placed
between the load and
the fulcrum. In the
human forearm the
fulcrum is the elbow,
the effort is applied
by the biceps muscle,
and the load is in the
hand.
11.2.1 State the roles of bones,
ligaments, muscles, tendons and
nerves in human movement.
1. Bones
2. Ligaments
3. Tendons
4. Muscles
5. Nerves
11.2.1 State the roles of bones,
ligaments, muscles, tendons and nerves
in human movement.
Ligaments
1) Hold bones together (bone bone)
2) Stabilize joints (knee, shoulder, wrist,
hands, feet, etc.)
Ligaments: Bone Bone
Patellar ligament
(bone-bone (often
mislabeled patellar
tendon)
Lateral ligament
(bone-bone)
11.2.1 State the roles of bones,
ligaments, muscles, tendons and
nerves in human movement.
1. Bones
2. Ligaments
3. Tendons
4. Muscles
5. Nerves
11.2.1 State the roles of bones,
ligaments, muscles, tendons and nerves
in human movement.
Tendons
1) Attach muscle to bone
(muscle bone)
2) Stabilize joints (knee, shoulder, wrist,
hands, feet, etc.)
Tendons: Muscle Bone
Quadriceps Tendon
Muscle Bone
Quadriceps Patella
Action: Extends Knee
also stabilizes knee
11.2.1 State the roles of bones,
ligaments, muscles, tendons and
nerves in human movement.
1. Bones
2. Ligaments
3. Tendons
4. Muscles
5. Nerves
11.2.1 State the roles of bones, ligaments, muscles,
tendons and nerves in human movement.
Muscles
1) Provide the force required for movement
by moving one bone (point of insertion) in
relation to another (point of origin) (Attached to
tendon or bone)
2) Stabilize joints (knee, shoulder, wrist,
hands, feet, etc.)
11.2.1 State the roles of bones,
ligaments, muscles, tendons and
nerves in human movement.
1. Bones
2. Ligaments
3. Tendons
4. Muscles
5. Nerves
11.2.1 State the roles of bones, ligaments, muscles,
tendons and nerves in human movement.
Nerves (In this case, motor neurons)
1) Provide the stimulus for muscle movement
2) Co-ordinates sets of antagonistic muscles
(e.g., biceps/triceps; quads/hamstrings)
Sensory neurons detect stimuli-produces response
in motor neuron to send stimulus to motor end
plate for muscle to contract
11.2.2. Label a diagram of the human elbow joint,
including cartilage, synovial fluid, joint capsule, named
bones and antagonistic muscles (biceps and triceps).
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Olecranon
process
11.2.3. Outline the functions of the structures in the
human elbow joint named in 11.2.2
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Biceps: Bends-flexes the arm (flexor)
Triceps: Straightens the arm (extensor)
Scapula: Anchors muscle (Biceps & triceps muscle origins)
Humerus: Anchors muscle (triceps muscle origin)
Radius / Ulna: Acts as forearm levers (muscle insertion) -
radius acts as a lever for the biceps, ulna acts as a lever for
the triceps
Cartilage: Allows easy movement (smooth surface),
absorbs shock and distributes load
Synovial Fluid: Provides food, oxygen and lubrication to the
cartilage
Joint Capsule: Seals the joint space and provides passive
stability by limiting range of movement
11.2.4. Compare the movement of the hip joint and
the knee joint.
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Similarities:
1) Both are synovial joints
2) Both are involved in movement
of the leg
11.2.4. Compare the movement of the hip joint and the
knee joint.
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Differences
11.2.4. Compare the movement of
the hip joint and the knee joint.
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11.2.5. Describe the structure of striated muscle fibres,
including the myofibrils with light and dark bands,
mitochondria, the sarcoplasmic reticulum, nuclei, and
sarcolemma.
First-Back up
• Lets learn basic functions & characteristics
of muscles
• Also the 3 types of muscle cells in human
body
Functions of the Muscular System
1. Body movement (Skeletal Muscle)
2. Maintenance of posture (Skeletal Muscle)
3. Respiration (Skeletal Muscle)
4. Production of body heat (Skeletal Muscle)
5. Communication (Skeletal Muscle)
6. Constriction of organs and vessels (Smooth Muscle)
7. Heartbeat (Cardiac Muscle)
Functional Characteristics of Muscle
1. Contractility: the ability to shorten
forcibly
2. Excitability: the ability to receive and
respond to stimuli
3. Extensibility: the ability to be stretched
or extended
4. Elasticity: the ability to recoil and
resume the original resting length
Types of Muscle Tissue
• The three types of muscle tissue are skeletal, smooth, and cardiac
• These types differ in
– Structure
– Location
– Function
– Means of activation
• Each muscle is a discrete organ composed of muscle tissue, blood vessels, nerve fibers, and connective tissue
Types of Muscle Tissue
• Skeletal muscles are responsible for most body
movements
– Maintain posture, stabilize joints, and generate heat
• Smooth muscle is found in the walls of hollow
organs and tubes, and moves substances through
them
– Helps maintain blood pressure
– Squeezes or propels substances (i.e., food, feces) through
organs
• Cardiac muscle is found in the heart and pumps
blood throughout the body
Skeletal Muscle Structure
• Skeletal muscle cells are elongated and are often called skeletal muscle fibers/fibres
• Each skeletal muscle cell contains several nucleilocated around the periphery of the fiber near the plasma membrane (=sarcolemma)
• Fibers appear striated due to the actin and myosin myofilaments
• Long - A single fiber can extend from one end of a muscle to the other
• Contracts rapidly but tires easily
• Is controlled voluntarily (i.e., by conscious control)
Skeletal Muscle Structure
• Fascia is a general term for connective tissue sheets
• The three muscular fascia, which separate and
compartmentalize individual muscles or groups of
muscles are:
– Epimysium: an overcoat of dense collagenous
connective tissue that surrounds the entire muscle
– Perimysium: fibrous connective tissue that surrounds
groups of muscle fibers called fascicles (bundles)
– Endomysium: fine sheath of connective tissue
composed of reticular fibers surrounding each muscle
fiber
Skeletal Muscle Structure
• The connective tissue
of muscle provides a
pathway for blood
vessels and nerves to
reach muscle fibers
Fig. 8.1
Skeletal Muscle Structure
• The connective
tissue of muscle
blends with other
connective tissue
based structures,
such as tendons,
which connect
muscle to bone
Fig. 8.2
Skeletal Muscle Structure
• Muscle Fibers
– Terminology
• Sarcolemma: muscle cell plasma membrane
• Sarcoplasm: cytoplasm of a muscle cell
• Myo, mys, and sarco: prefixes used to refer to
muscle
– Muscle contraction depends on two kinds of
myofilaments: actin and myosin
• Myofibrils are densely packed, rod-like contractile
elements
• They make up most of the muscle volume
Thick and Thin Myofilaments
• THIN FILAMENTS – form I bands• ACTIN (G-actin molecules joined together to form F
actin)
• Troponin –tropomyosin (regulatory protein complex)
• Nebulin—stabilizes actin in sarcomere
• THICK FILAMENTS – form A bands• MYOSIN – golf club shaped molecules bound
together
• Myosin occurs in center of sarcomere
• Titan - anchors myosin to Z discs, stabilizes
myosin
Actin- Thin myofiliaments
• Actin (thin) myofilaments consist of two helical
polymer strands of F actin (composed of G actin),
tropomyosin, and troponin
• The G actin contains the active sites to which
myosin heads attach during contraction
• Tropomyosin and troponin are regulatory subunits
bound to actin
Fig. 8.2
Myosin – Thick myofilaments
• Myosin (thick) myofilaments consist of myosin molecules
• Each myosin molecule has– A head with an ATPase, which breaks down ATP
– A hinge region, which enables the head to move
– A rod
• A cross-bridge is formed when a myosin head binds to the active site on G actin
Fig. 8.2
Sarcomere – Contractile Units
• Sarcomeres
– The smallest contractile unit of a muscle
– Sarcomeres are bound by Z disks that hold actin
myofilaments
– Six actin myofilaments surround a myosin myofilament
– Myofibrils appear striated because of A bands and I
bands
Fig. 8.2
Skeletal Muscle Structure
• Thick filaments: extend the entire length of an A band
• Thin filaments: extend across the I band and partway into the A band
• Z-disc: a coin-shaped sheet of proteins (connectins) that anchors the thin filaments and connects myofibrils to one another
• The arrangement of myofibrils within a fiber is so organized a perfectly aligned repeating series of dark A bands and light I bands is evident
• Thin filaments do not overlap thick filaments in the lighter H zone
• M lines appear darker due to the presence of the protein desmin
Sliding Filament Model
• Actin and myosin myofilaments do not change in length during contraction
• Thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater degree– Upon stimulation, myosin heads bind to actin and sliding begins
– Each myosin head binds and detaches several times during contraction (acting like a ratchet to generate tension and propel the thin filaments to the center of the sarcomere)
• In the relaxed state, thin and thick filaments overlap only slightly
• As this event occurs throughout the sarcomeres, the muscle shortens
• The I band and H zones become narrower during contraction, and the A band remains constant in length
Sliding Filament Model
• Actin and myosin myofilaments in a relaxed
muscle (below) and a contracted muscle are the
same length. Myofilaments do not change
length during muscle contraction
Fig. 8.4
Sliding Filament Model
• During contraction, actin myofilaments at each end of the sarcomere slide past the myosin myofilaments toward each other. As a result, the Z disks are brought closer together, and the sarcomere shortens
Fig. 8.4
Sliding Filament Model
• As the actin myofilaments slide over the myosin myofilaments, the H zones (yellow) and the I bands (blue) narrow. The A bands, which are equal to the length of the myosin myofilaments, do not narrow because the length of the myosin myofilaments does not change
Fig. 8.4
Sliding Filament Model
• In a fully contracted muscle, the ends of
the actin myofilaments overlap at the
center of the sarcomere and the H zone
disappears
Fig. 8.4
11.2.5. Describe the structure of striated muscle fibres,
including the myofibrils with light and dark bands,
mitochondria, the sarcoplasmic reticulum, nuclei, and
sarcolemma.
11.2.5 -- Each muscle fibre has the following
specialised features designed to facilitate muscular
contraction:
•Many nuclei (fibres are long- formed from many
muscle cells fusing together, hence fibres are
multinucleated)
•Large number of mitochondria (muscle contraction
requires a lot of ATP)
11.2.5 (continued)
•Tubular myofibrils, divided into sections/sarcomeres,
made of two different myofilaments (proteins
responsible for contraction)
• Where thin (actin) and thick (myosin) filaments
overlap, a dark band occurs, and this is flanked by
light regions containing thin filament only
11.2.5 (continued)
• The membrane surrounding a muscle fibre is called
the sarcolemma
• The internal membranous network is called the
sacroplasmic reticulum, it is analogous to
endoplasmic reticulum but is specialised for muscle
contraction (it contains high levels of Ca2+ ions)
11.2.5 (continued)
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• Sarcoplasm—cytoplasm of skeletal muscle cell
• Sarcoplasmic reticulum—stores & pumps Ca+ ions
• T-tubules– tunnel like in-foldings of the sarcolemma;
in mammals 2 per sarcomere @ A-I band junction
• Myofibril- contractile elements-each muscle fiber contains may myofibrils
• Sarcomere—myofibrils arranged in compartments called sarcomeres
• Myofilaments-Protein filaments that make up myofibrils and form the structure of the sarcomere (Actin, Myosin, Titan)
IMPORTANT VOCABULARY TERMS
11.2.6 Draw and label a diagram to show the
structure of a sarcomere, including z-lines, actin
filaments, myosin filaments with heads, and the
resultant light and dark bands.
https://www.youtube.com/watch?v=xkbI1KX6D54
11.2.6 Draw and label a diagram to show the
structure of a sarcomere, including z-lines, actin
filaments, myosin filaments with heads, and the
resultant light and dark bands.
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11.2.6 Draw and label a diagram to show the
structure of a sarcomere, including z-lines, actin
filaments, myosin filaments with heads, and the
resultant light and dark bands.
http://www.ib.bioninja.com.au/higher-level/topic-11-human-health-and/112-muscles-and-movement.html
•The H zone is the area only occupied by the thick
filaments (myosin)
•The I bands (light) are the regions occupied by
only thin filaments (actin)
•The A bands (dark) are the regions occupied by
both filaments (overlap)
•The Z lines represent the extremities of a single
sarcomere
Physiology of Skeletal Muscle Fibers
• Membrane Potentials
– The nervous system stimulates muscles to contract
through electric signals called action potentials
– Plasma membranes are polarized, which means there
is a charge difference (resting membrane potential)
across the plasma membrane
– The inside of the plasma membrane is negative as
compared to the outside in a resting cell
– An action potential is a reversal of the resting
membrane potential so that the inside of the plasma
membrane becomes positive
Physiology of Skeletal Muscle Fibers
• Ion Channels
– Assist with the production of action potentials
• Ligand-gated channels
• Voltage-gated channels
Physiology of Skeletal Muscle Fibers
• Nerve Stimulus of Skeletal Muscle
– Skeletal muscles are stimulated by motor
neurons of the somatic nervous system
– Axons of these neurons travel in nerves to
muscle cells
– Axons of motor neurons branch profusely as
they enter muscles
– Each axonal branch forms a neuromuscular
junction with a single muscle fiber
Physiology of Skeletal Muscle Fibers
• The neuromuscular junction is formed from:
– Axonal endings
• Have small membranous sacs (synaptic vesicles)
• Contain the neurotransmitter acetylcholine (ACh)
– Motor end plate of a muscle
• Specific part of the sarcolemma
• Contains ACh receptors
• Though exceedingly close, axonal ends and
muscle fibers are always separated by a space
called the synaptic cleft
Motor neurons
stimulate
skeletal muscles
to contract by
releasing
acetylcholine (a
neurotransmitter)
at the
neuromuscular
junction
Excitation-Contraction Coupling
• In order to contract, a skeletal muscle
must:
– Be stimulated by a nerve ending
– Propagate an electrical current, or action
potential, along its sarcolemma (Na-K pump)
– Have a rise in intracellular Ca2+ levels, the
final trigger for contraction
• Linking the electrical signal to the
contraction is excitation-contraction
coupling
Excitation-Contraction Coupling
• Invaginations of the sarcolemma form T tubules, which
wrap around the sarcomeres and penetrate into the cell’s
interior at each A band –I band junction
• Sarcoplasmic reticulum (SR) is
an elaborate, smooth
endoplasmic reticulum that
mostly runs longitudinal and
surrounds each myofibril
– Paired terminal cisternae form
perpendicular cross channels
– Functions in the regulation of
intracellular calcium levels
• A triad is a T tubule and two
terminal cisternaeFig. 8.9
Excitation-Contraction Coupling
1. An action potential produced at the presynaptic terminal in the neuromuscular junction is propagated along the sarcolemma of the skeletal muscle. The depolarization also spreads along the membrane of the T tubules
2. The depolarization of the T tubule causes gated Ca2+ channels in the SR to open, resulting in an increase in the permeability of the SR to Ca2+, especially in the terminal cisternae. Calcium ions then diffuse from the SR into the sarcoplasm
3. Calcium ions released from the SR bind to troponin molecules. The troponin molecules bound to G actin molecules are released, causing tropomyosin to move, exposing the active sites on G actin
4. Once active sites on G actin molecules are exposed, the heads of the myosin myofilaments bind to them to form cross-bridges
Excitation-Contraction Coupling
1. An action potential produced at the presynaptic terminal in the neuromuscular junction is propagated along the sarcolemma of the skeletal muscle. The depolarization also spreads along the membrane of the T tubules
2. The depolarization of the T tubule causes gated Ca2+ channels in the SR to open, resulting in an increase in the permeability of the SR to Ca2+, especially in the terminal cisternae. Calcium ions then diffuse from the SR into the sarcoplasm
3. Calcium ions released from the SR bind to troponin molecules. The troponin molecules bound to G actin molecules are released, causing tropomyosin to move, exposing the active sites on G actin
4. Once active sites on G actin molecules are exposed, the heads of the myosin myofilaments bind to them to form cross-bridges
Excitation-Contraction Coupling
1. An action potential produced at the presynaptic terminal in the neuromuscular junction is propagated along the sarcolemma of the skeletal muscle. The depolarization also spreads along the membrane of the T tubules
2. The depolarization of the T tubule causes gated Ca2+ channels in the SR to open, resulting in an increase in the permeability of the SR to Ca2+, especially in the terminal cisternae. Calcium ions then diffuse from the SR into the sarcoplasm
3. Calcium ions released from the SR bind to troponin molecules. The troponin molecules bound to G actin molecules are released, causing tropomyosin to move, exposing the active sites on G actin
4. Once active sites on G actin molecules are exposed, the heads of the myosin myofilaments bind to them to form cross-bridges
Excitation-Contraction Coupling
1. An action potential produced at the presynaptic terminal in the neuromuscular junction is propagated along the sarcolemma of the skeletal muscle. The depolarization also spreads along the membrane of the T tubules
2. The depolarization of the T tubule causes gated Ca2+ channels in the SR to open, resulting in an increase in the permeability of the SR to Ca2+, especially in the terminal cisternae. Calcium ions then diffuse from the SR into the sarcoplasm
3. Calcium ions released from the SR bind to troponin molecules. The troponin molecules bound to G actin molecules are released, causing tropomyosin to move, exposing the active sites on G actin
4. Once active sites on G actin molecules are exposed, the heads of the myosin myofilaments bind to them to form cross-bridges
Excitation-Contraction Coupling
1. An action potential produced at the presynaptic terminal in the neuromuscular junction is propagated along the sarcolemma of the skeletal muscle. The depolarization also spreads along the membrane of the T tubules
2. The depolarization of the T tubule causes gated Ca2+ channels in the SR to open, resulting in an increase in the permeability of the SR to Ca2+, especially in the terminal cisternae. Calcium ions then diffuse from the SR into the sarcoplasm
3. Calcium ions released from the SR bind to troponin molecules. The troponin molecules bound to G actin molecules are released, causing tropomyosin to move, exposing the active sites on G actin
4. Once active sites on G actin molecules are exposed, the heads of the myosin myofilaments bind to them to form cross-bridges
Muscle Relaxation
• Calcium ions are transported back into the
sarcoplasmic reticulum
• Calcium ions diffuse away from troponin
and tropomyosin moves, preventing
further cross-bridge formation
Sarcomere Shortening Video
https://www.youtube.com/watch?v=0kFmbrRJq4w
11.2.7– Bioninja:
1) An action potential from a motor neuron triggers the release of
Ca2+ ions from the sarcoplasmic reticulum
2) Calcium ions expose the myosin heads by binding to a blocking
molecule (troponin complexed with tropomyosin) and causing it to move
3) The myosin heads form a cross-bridge with actin binding sites
4) ATP binds to the myosin heads and breaks the cross-bridge
5) The hydrolysis of ATP causes the myosin heads to change shape and
swivel - this moves them towards the next actin binding site
6) The movement of the myosin heads cause the actin filaments to slide
over the myosin filaments, shortening the length of the sarcomere
7) Via the repeated hydrolysis of ATP, the skeletal muscle will contract
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11.2.7 This Video Sums it All
UP!! Test Yourself!
https://www.youtube.com/watch?v=JOac0YeaK7w&feature=related
Fatigue
• The decreased ability to do work
• Can be caused by
– The central nervous system (psychologic fatigue)
– Depletion of ATP in muscles (muscular fatigue)
• Physiologic contracture (the inability of muscles to contract or relax) and rigor mortis (stiff muscles after death) result from inadequate amounts of ATP
11.2.8 Analyze electron micrographs to find the state of
contraction of muscle fibres (Bioninja.com).
• Muscle fibres can be fully relaxed, slightly
contracted, moderately contracted and
fully contracted
• The sarcomere gets shorter when the
muscle contracts, however the A band
does not, showing that the filaments are
not themselves contracting
• Instead, the filaments are sliding over
each other and increasing their overlap,
which can be seen as the gradual
reduction in the H zone
11.2.8– Bioninja:
http://www.ib.bioninja.com.au/higher-level/topic-11-human-health-and/112-muscles-and-movement.html
11.2.8 Analyze electron micrographs to find the
state of contraction of muscle fibres.
Shorter I band – A band remains same
Energy Sources
• Creatine phosphate
– ATP is synthesized
when ADP reacts
with creatine
phosphate to form
creatine and ATP
– ATP from this
source provides
energy for a short
time
Fig. 8.18
Energy Sources
• Anaerobic respiration
– ATP synthesized provides
energy for a short time at
the beginning of exercise
and during intense
exercise
– Produces ATP less
efficiently but more rapidly
than aerobic respiration
– Lactic acid levels increase
because of anaerobic
respiration
Fig. 8.18
Energy Sources
• Aerobic respiration
– Requires oxygen
– Produces energy
for muscle
contractions under
resting conditions
or during
endurance exercise
Fig. 8.18
Speed of Contraction
• The three main types of skeletal muscle
fibers are
– Slow-twitch oxidative (SO) fibers
– Fast-twitch glycolytic (FG) fibers
– Fast-twitch oxidative glycolytic (FOG) fibers
• SO fibers contract more slowly than FG
and FOG fibers because they have slower
myosin ATPases than FG and FOG fibers
Fatigue Resistance
• SO fibers are fatigue-resistant and rely on aerobic respiration
– Many mitochondria, a rich blood supply, and myoglobin
• FG fibers are fatigable
– Rely on anaerobic respiration and have a high concentration of glycogen
• FOG fibers have fatigue resistance intermediate between SO and FG fibers
– Rely on aerobic and anaerobic respiration
Functions
• SO fibers maintain posture and are involved with prolonged exercise– Long-distance runners have a higher percentage of
SO fibers
• FG fibers produce powerful contractions of short duration– Sprinters have a higher percentage of FG fibers
• FOG fibers support moderate-intensity endurance exercises– Aerobic exercise can result in the conversion of FG
fibers to FOG fibers