Muscles & Movement Skeletal Muscle - Wikispacesholdenscienceeducation.wikispaces.com/file/view/11.2_Muscles... · Types of Muscle Tissue • Skeletal muscles are responsible for most

Topic 11.2Muscles & Movement

Skeletal

Muscle

Fibres

(Cells)

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


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.

1st Class Lever

2nd Class LeverSecond-class

levers have the

load between the

effort and the

fulcrum. A

wheelbarrow is a

second-class

lever.

2nd 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.




1. Bones

2. Ligaments

3. Tendons

4. Muscles

5. 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)




1. Bones

2. Ligaments

3. Tendons

4. Muscles

5. Nerves



in human movement.

Tendons

1) Attach muscle to bone

(muscle bone)


hands, feet, etc.)

Tendons: Muscle Bone

Quadriceps Tendon

Muscle Bone

Quadriceps Patella

Action: Extends Knee

also stabilizes knee




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)


hands, feet, etc.)




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

Motor end plate of motor neuron

stimulates muscle movement

Motor Unit

Fig. 8.13

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).

http://www.ib.bioninja.com.au/higher-level/topic-11-human-health-and/112-muscles-and-movement.html

Olecranon

process

http://www.youtube.com/watch?v=SOMFX_83sqk




http://sambal.co.uk/elbow.html

http://sambal.co.uk/elbow.html

11.2.3. Outline the functions of the structures in the

human elbow joint named in 11.2.2


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.


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.


Differences

http://en.wikipedia.org/wiki/File:Knie_ct.gif

http://en.wikipedia.org/wiki/File:Knie_ct.gif



11.2.4. Compare the movement of

the hip joint and the knee joint.


Muscular System

Microscopic Anatomy & Sliding Filament Theory

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

Tab. 8.1Skeletal muscle fibre/cell

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)


• 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


• The connective tissue

of muscle provides a

pathway for blood

vessels and nerves to

reach muscle fibers

Fig. 8.1


• The connective

tissue of muscle

blends with other

connective tissue

based structures,

such as tendons,

which connect

muscle to bone

Fig. 8.2


• 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

Fig. 8.2

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


• 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

Fig.

8.3bc

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


• 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


• 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


• 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


• 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

http://www.brookscole.com/chemistry_d/templates/

http://www.brookscole.com/chemistry_d/templates/

http://media.pearsoncmg.com/bc/bc_campbell_biology_6/cipl/ins

http://media.pearsoncmg.com/bc/bc_campbell_biology_6/cipl/ins

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)


• 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

Anatomy of a single muscle

fiber/cell

TRIADS-Terminal Cisterns + T

tubule

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

https://www.youtube.com/watch?v=xkbI1KX6D54











•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


• Ion Channels

– Assist with the production of action potentials

• Ligand-gated channels

• Voltage-gated channels


• 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


• 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

Fig. 8.7

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


• 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


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

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


11.2.7 This Video Sums it All

UP!! Test Yourself!

https://www.youtube.com/watch?v=JOac0YeaK7w&feature=related

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:


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

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

Tab. 8.3

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Muscles & Movement Skeletal Muscle - Wikispacesholdenscienceeducation.wikispaces.com/file/view/11.2_Muscles... · Types of Muscle Tissue • Skeletal muscles are responsible for most