chapter 6: muscular system
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Chapter 6: Muscular System
Anatomy & PhysiologyKasprowicz
The essential function of muscle is contraction – making it responsible for
almost all body movement.
Types of Muscle
Types of Muscle1) Skeletal2) Cardiac3) Smooth
General Muscle Characteristics
• muscle cells are elongated = muscle fibers (smooth, skeletal)• contain myofilaments (ability to contract)• terminology: myo-, mys- = muscle sarco- = flesh
Skeletal Muscle
1) Very large, multinucleated cells2) Striated (visible stripes or banding
pattern)3) Voluntary (conscious) control; can
be reflexive too4) muscle fibers (cells) are bundled
together by strong connective tissues
exert great force, but tire easily
Connective Tissues in Skeletal Muscle
Deep fascia
Connective Tissues in Skeletal Muscles
· Endomysium – around single muscle fiber
· Perimysium – around a fascicle (bundle) of fibers
· Epimysium – covers the entire skeletal muscle
· Deep Fascia – on the outside of the epimysium
Connective Tissues in Skeletal Muscle
Connective Tissues in Skeletal Muscles
· tendon – dense connective tissue attaching muscle to bone (cord-like)
· aponeuroses – attach muscles indirectly to bone,cartilages or connective tissue coverings (sheet-like)
· Epimysium blends into a connective tissue attachment
Connective Tissues in Skeletal Muscles
Connective Tissues in Skeletal Muscles
Aponeurosis of the external oblique
Connective Tissues in Skeletal Muscles
Refer to pg. 272 in your textbook
Smooth Muscle
1) Spindle-shaped cells with one nucleus
2) no striations3) Involuntary (no conscious
control)4) Found in hollow visceral organs5) Have small amount of
endomysium
Smooth Muscle
6) slow, sustained, tireless movement
7) often layers in opposite directions
Smooth Muscle: Stomach Wall
Cardiac Muscle
1) Branching cells with one nucleus connected by intercalated discs2) Striated3) Involuntary (no conscious
control)4) small amounts of endomysium
Cardiac Muscle
5) Cardiac fibers are arranged in spiral or 8-
shaped bundles
Muscle Functions
1) Producing movement2) Maintaining posture3) Stabilizing joints4) Support soft tissues5) Generating heat6) Guard entrances and exits
Muscle Functions
Skeletal Muscle Fiber (Cell) Formation
Skeletal Muscle Fiber (Cell) Formation
Microscopic Anatomy of Muscle
· Cells are multinucleate· Nuclei are just beneath the sarcolemma
(1) sarcolemma - specialized plasma membrane of muscle cells
Microscopic Anatomy of Muscle
(2) Cytoplasm filled with myofibrils
myofibrils – perfectly aligned, ribbon- like organelles; give muscle fiber its striped appearance
Microscopic Anatomy of Muscle
(2) Cytoplasm filled with myofibrils
A closer look at the myofibrilLight (I) bands Dark (A) bands
Microscopic Anatomy of Muscle
(2) Cytoplasm filled with myofibrils
Banding Pattern: Light (I) bands contain the Z discDark (A) bands contain the H zoneM line - holds adjacent filaments together; center of H zone
Microscopic Anatomy of Muscle
An even closer look at the myofibril…(3) Sarcomere - contractile unit of the myofibril - Z disc to Z disc
Microscopic Anatomy of Muscle
An even closer look at the myofibril…(3) Sarcomere
Microscopic Anatomy of Muscle
Zooming in on the sarcomere…(4) Myofilaments - special proteins that cause muscle to contract
Two Types: a) myosin (thick filament) b) actin (thin filament)
Microscopic Anatomy of Muscle
Two Types: a) myosin (thick filament)
protein with heads that form cross bridges b/t thick & thin filaments during muscle contraction
Contain ATPase enzymes
Microscopic Anatomy of Muscle
Two Types: b) actin (thin filament)
Made of the contractile protein actin & some other regulatory proteins
Microscopic Anatomy of Muscle
Zooming in around the H zone….
Microscopic Anatomy of Muscle
(5) Sarcoplasmic reticulum (SR) specialized smooth ER surrounding each myofibril stores calcium which is released when muscle is stimulated to contract
Microscopic Anatomy of Muscle
Sarcoplasmic reticulum (SR)
Microscopic Anatomy of Muscle
Sarcoplasmic reticulum (SR)
Let’s put this all together….
Microscopic Organization of Muscle: Level 1 (refer to Fig. 10-6, pg. 278)
Let’s put this all together….
Microscopic Organization of Muscle: Level 2
Let’s put this all together….
Microscopic Organization of Muscle: Level 3
Let’s put this all together….
Microscopic Organization of Muscle: Level 4
Let’s put this all together….
Microscopic Organization of Muscle: Level 5
Skeletal Muscle Activity: Initiating the Contraction
Special Functional Properties of Muscle
· Irritability – ability to receive and respond to a stimulus
(a property shared with neurons)
· Contractility – ability to shorten when an adequate stimulus is received
Skeletal muscles must bestimulated by a nerve to contract (motor neuron).
Quick Review of Neurons & Synapses
Quick Review of Neurons & Synapses
Quick Review of Neurons & Synapses
Nerve Stimulus to Muscle
Motor unit: One neuron & the muscle cells stimulatedby that neuron
Nerve Stimulus to Muscle
Neuromuscular junctions the neuron & muscle fibers do NOT touch
separated by a gap called the synaptic cleft which is filled w/ interstitial fluid
Nerve Stimulus to Muscle
Neuromuscular junctions
Transmission of Nerve Impulse to Muscle
Neurotransmitterschemical released by neurons used to “carry” the impulse across the synaptic cleft
Acetylcholine (ACh) is the neurotransmitter used at the neuromuscular junction of skeletal muscle
Transmission of Nerve Impulse to Muscle
Steps in Impulse Transmission· ACh is released by the pre-synaptic
axon terminal of the motor neuron · ACh crosses the synaptic cleft &
attaches to receptors on the sarcolemma
· Sarcolemma becomes permeable to sodium (Na+)
Transmission of Nerve Impulse to Muscle
Steps in Impulse TransmissionSodium floods into the cell generating an
action potential (electrical current)· Once started, muscle contraction cannot
be stopped !! · ACh is broken down by the enzyme
acetylcholinesterase This prevents continued contraction of the
muscle cell in the absence of additional nerve impulses.
Transmission of Nerve Impulse to Muscle
Steps in Impulse Transmission When an action potential sweeps along the sarcolemma and a muscle cell is excited, calcium ions are released from the sarcoplasmic reticulum
Transmission of Nerve Impulse to Muscle
Steps in Impulse Transmission
The flood of Ca+ ions is the final trigger for the contraction of the muscle
Skeletal Muscle Activity: Sliding Filament Theory of
Muscle Contraction
Mechanism of Muscle Contraction
Sliding Filament Theory: Overview · Myosin heads form cross bridges with binding sites on actin
· Myosin heads detach & then bind to the next site on actin
Resting Sarcomere
Sarcomere Contracts
Mechanism of Muscle Contraction
Sliding Filament Theory: Overview · This action continues, causing the myosin & actin to slide past each other
Sarcomere Contracts
Resting Sarcomere
Mechanism of Muscle Contraction
Sliding Filament Theory: Overview
Collective shortening of
the muscle cell
sarcomeres =
muscle contraction
Sarcomere Contracts
Resting Sarcomere
The Contraction Cycle : The Nitty Gritty
Step 1: Ca+ ions released from the SR attach to the troponin- tropomyosin complex
Binding sites on the actin filament are exposed
The Contraction Cycle : The Nitty Gritty
Step 1:
The Contraction Cycle : The Nitty Gritty
Step 2: myosin heads attach to actin binding sites, forming cross bridges
ATP was required to prep the myosin head (ATP ADP + P)
The Contraction Cycle : The Nitty Gritty
Step 2:
The Contraction Cycle : The Nitty Gritty
Step 3: ADP + P released from myosin head
myosin head flexes/pivots = “power stroke”
The Contraction Cycle : The Nitty Gritty
Step 3:
The Contraction Cycle : The Nitty Gritty
Step 4: ATP binds to myosin head, causing it to detach from the actin filament
The Contraction Cycle : The Nitty Gritty
Step 5: myosin head re-energized (ATP ADP + P)
Step 6: Ca+ ions pumped back into the SR troponin-tropomyosin complex moves back to its original position
The Contraction Cycle : The Nitty Gritty
The Contraction Cycle : The Nitty Gritty
Muscle Contraction Animations
http://www.mhhe.com/biosci/bio_animations/09_MH_MuscleContraction_Web/index.htmlMuscle Contraction 3-D Animation
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__action_potentials_and_muscle_contraction.html
Action Potentials & Muscle Contraction
https://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__breakdown_of_atp_and_crossbridge_movement_during_muscle_contraction.html
Break Down of ATP & Cross Bridge Attachmenthttps://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__sarcomere_contraction.html
Sarcomere Contraction
Contraction of the Whole Muscle
The “all-or-none” response of muscle contraction refers to the muscle cell, NOT the whole muscle
Whole muscle reacts with a graded response (different degrees of shortening)
Contraction of the Whole Muscle
Graded responses are produced in 2 ways:
1)Change the frequency of stimulation
2)Change the # of muscle cells stimulated/time - more activated muscle cells stronger FORCE of contraction
Contraction of the Whole Muscle
Muscle Twitch – 1 stimulus; single, brief, jerky contraction1
Changing Stimulation Frequency
Contraction of the Whole Muscle
Wave Summation– frequency of stimulus increases; less time to relax; contraction strength “summed”
2
Changing Stimulation Frequency
Contraction of the Whole Muscle
Incomplete Tetanus – frequency of stimulation increases even more
3
Changing Stimulation Frequency
Contraction of the Whole Muscle
Tetanus – frequency of stimulation very rapid; no evidence of relaxation; smooth, sustained contraction
4
Changing Stimulation Frequency
Energy for Muscle Contraction
· Initially, muscles used stored ATP for energy· ATP is hydrolyzed into ADP + P· Only 4-6 seconds worth of ATP is stored
by muscles· After this, other metabolic pathways
must be used to produce ATP
Energy for Muscle Contraction
Pathway 1: Direct Phosphorylation· Muscle cells contain creatine phosphate (CP)
·CP is a high-energy molecule that transfers energy to ADP, regenerating ATP
· CP supplies are exhausted in about 20 seconds
Energy for Muscle Contraction
Pathway 1: Direct
Phosphorylation
Energy for Muscle Contraction
Pathway 2: Anaerobic Respiration (a.k.a. lactic acid fermentation)
· breaks down glucose without oxygen· Glucose is broken down to pyruvic acid; 2 ATP are produced
· Pyruvic acid lactic acid
Energy for Muscle Contraction
Pathway 2: Anaerobic Respiration
(lactic acid fermentation)
Energy for Muscle Contraction
Pathway 2: Anaerobic Respiration · This reaction is not as efficient,
but it is fast· Huge amounts of glucose are needed· Lactic acid produces muscle fatigue
· Duration: 30-60 seconds
Energy for Muscle Contraction
Pathway 3: Aerobic Respiration · Series of metabolic pathways that occur in the mitochondria & require oxygen
· Glucose is broken down to carbon dioxide and water releasing energy
· This is a slower reaction that requires continuous oxygen
· High energy pay-off: 36 ATP
Energy for Muscle Contraction
Pathway 3: Aerobic Respiration
Muscle Fatigue & Oxygen Debt
· When a muscle is fatigued, it is unable to contract
· The common reason for muscle fatigue is oxygen debt· Oxygen must be “repaid” to tissue to remove
oxygen debt· Oxygen is required to get rid of accumulated
lactic acid· Increasing acidity (from lactic acid) and lack
of ATP causes the muscle to contract less
Types of Muscle Contraction
Isotonic Muscle Contraction· The myofilaments slide past each other muscle shortens movement occurs
Examples: bending knee, rotating the arms, smiling
Types of Muscle Contraction
Isometric Muscle Contraction muscle is not able to shorten muscle tension keeps increasingExamples:lifting a 1000 lb. object alone; pushing against an object thatdoesn‘t move
Muscle Tone
state of continuous partial contractions
Different fibers contract at different times to provide muscle tone
muscle remains firm, healthy & ready for action
Increasing muscle tone increases metabolic energy used, even at rest
Muscle Tone
Muscle Tone
If the nerve supply to a muscle isdestroyed, the muscle is nolonger stimulated in this manner,and it loses tone and becomesparalyzed. Soon after, it becomesflaccid (soft and flabby) andbegins to atrophy (waste away).
Muscle Tone
Effects of Exercise
“use it or lose it” Aerobic (Endurance) Exercise Examples: jogging, biking, swimming stronger, more flexible muscles w/ greater resistance to fatigue
Effects of Exercise
Aerobic (Endurance) Exercise Physiological Effects 1) increased blood supply to muscles 2) more mitochondria 3) increased metabolism 4) keeps bones strong 5) improves neuromuscular coordination
Effects of Exercise
“use it or lose it” Resistance (Isometric) Exercise Examples: weight training increased muscle size and strength
Effects of Exercise
Aerobic (Endurance) Exercise Physiological Effects 1) increased # of myofilaments increased size of muscle fibers 2) more connective tissue 3) keeps bone strong
“Golden Rules” of Skeletal Muscle Activity
1) All (almost ) skeletal muscle cross a least one joint
2) Most of a skeletal muscle lies proximal to the joint crossed
3) All skeletal muscles have at least 2 attachments: the origin and the insertion
4) Skeletal muscles can only PULL (create tension)
5) When a muscle contracts, the insertion moves toward the origin
Types of Body Movements
· Movement occurs when a muscle contracts and moves an attached bone
· Muscles are attached to at least two points· Origin – attachment to a immoveable bone· Insertion – attachment to an movable bone
Types of Body Movements
When a skeletal musclecontracts, its insertionmoves toward its origin
Body Movements: Muscle Interactions
· prime mover – muscle primarily responsible for a certain movementExample: biceps, hamstrings(a.k.a. agonist)
· Antagonist – muscle that opposes or reverses a prime mover· Triceps when biceps flexes; quads
when hamstrings flex
Prime Mover – bicepsAntagonist – triceps
Prime Mover – triceps Antagonist – biceps
Body Movements: Muscle Interactions
· Synergist – muscle that aids a prime mover in a movement and helps prevent rotationExample: finger flexor muscles brachioradiulus & brachialis in
the forelimb
Types of Body Movements
1) Flexion decreases angle of joint, bringing
2 bones closer together common in hinge, ball & socket joints
2) Extension increases the angle of a joint,
moving the bones apart hyperextension >180° angle
Flexion & Extension
Hyperextension
Flexion & Extension
Types of Body Movements
3) Rotation movement of a bone around its
longitudinal axis common in ball & socket joints atlas (C1) around the axis (C2)
Rotation
Types of Body Movements
4) Abduction movement of a limb away from the
medial plane also used to refer to fanning of finger or toes
5) Adduction movement of a limb toward the
midline
Abduction & Adduction
Abduction & Adduction
Types of Body Movements
6) Circumduction proximal end is stationary; distal
end moves in a circle limb moves in a cone shape common in ball & socket joint combo of flexion, extension, abduction & adduction
Circumduction
Special Body Movements
1) Dorsiflexion (point toes up towards shin) & Plantar Flexion (pointing the toes)
Special Body Movements
2) Inversion (turn sole of foot medially) & Eversion (turn sole of foot laterally)
Special Body Movements
3) Supination & Pronation movements of the radius around
the ulna supination: palm forward; radius &
ulna are parallel (anatomical position); thumb lateral
pronation: palm facing back; radius crosses ulna; thumb medial
Special Body Movements
3) Supination & Pronation
Special Body Movements
4) Opposition movement of thumb across palm
to touch fingertips
Elevation & Depression
Protraction & Retraction
Naming Skeletal Muscles
1) Direction of muscle fibers in reference to an imaginary line
(midline of body, long axis of limb) ie. Rectus (fibers parallel to line)
Oblique (fibers at a slant to line)
Naming Skeletal Muscles
2) Relative Size
Longus = longLongissimus = longestTeres = long and roundBrevis = shortMagnus = largeMajor = largerMaximus = largestMinor = smallMinimus = smallest
Naming Skeletal Muscles
3) Location of the Muscle in reference to the associated bone ie. temporalis (temporal bone)
frontalis (frontal bone)
Naming Skeletal Muscles
4) Number of origins ie. biceps, triceps, quadriceps
5) Location of the muscle’s origin and insertion
ie. Sternocleidomastoid muscle
Naming Skeletal Muscles
6) Shape of the muscle ie. Deltoid (triangular)
7) Action of the muscle ie. adductor muscle, extensor muscle
Head & Neck Muscles
Head and Neck Muscles
Facial Muscles • Frontalis raises eyebrows and wrinkles the forehead
• Orbicularis Oculi close, squint, blink and wink the eyes
• Orbicularis Oris closes the mouth and protrudes the lips; the “kissing” muscle
Head and Neck Muscles
• Buccinator
flattens the cheek (whistling or playing a trumpet); also a chewing muscle
• Zygomaticus “smiling” muscle; raises the corners of the mouth upward
Head and Neck Muscles
Chewing Muscles
• Buccinator• Masseter closes the jaw by elevating the mandible (prime mover)
• Temporalis helps masseter close the jaw (synergist)
Frontalis
Orbicularis oculi
ZygomaticusOrbicularis
oris
Buccinator
Masseter
Temporalis
Frontalis
Orbicularis oculi
Orbicularis oris
Zygomaticus Buccinator
Temporalis
Masseter
Frontalis
Zygomaticus
Orbicularis oris
Orbicularisoculi
Buccinator
Temporalis
Masseter
Head and Neck Muscles
Neck Muscles • Platysma pulls down corners of the mouth, downward sag of the mouth
• Sternocleidomastoid two-headed muscle; flex your neck (bowing of head); tilt head to side
Frontalis
Orbicularis oculi
ZygomaticusOrbicularis
oris
Buccinator
Masseter
Temporalis
PlatysmaSternocleido-mastoid
Frontalis
Orbicularis oculi
Orbicularis oris
ZygomaticusBuccinator
Temporalis
Masseter
SternocleidomastoidPlastysma
Frontalis
Zygomaticus
Orbicularis oris
Orbicularisoculi
Buccinator
Temporalis
Masseter
Sternocleido-mastoid
platysma
Trunk Muscles
Trunk Muscles • move the vertebral column (mostly posterior, anti-gravity muscles)
• anterior thorax muscles (move ribs, head & arms)
• muscles of the abdominal wall (help move vertebral column & form the “girdle” holding internal organs in place)
Trunk Muscles
Anterior Muscles: Thorax • Pectoralis Major - fan-shaped muscle - origin: sternum, pectoral girdle, ribs - insertion: humerus - adduct & flex the arm
Pectoralis major
Pectoralis minor
Trunk Muscles
Anterior Muscles: Thorax • Intercostal Muscles - deep muscles between the ribs - aid in breathing (external – inhale, internal – forcible exhale)
External intercostals
Internalintercostals
Trunk Muscles
Anterior Muscles: Abdominal Girdle • Rectus abdominus - pubis to rib cage - flex the vertebral column - compression of abdominal contents
Trunk Muscles
Anterior Muscles: Abdominal Girdle • External Oblique - lateral walls of abdomen - origin: ribs insertion: illium - flex the vertebral column, rotate/bend trunk
Trunk Muscles
Anterior Muscles: Abdominal Girdle • Internal Oblique - origin: iliac crest insertion: ribs - function same as external oblique
• Transversus abdominis - deepest muscle in abdomen - fibers run horizontally - compresses the abdominal contents
Trunk Muscles
Posterior Muscles • Trapezius - kite-shaped muscle - origin: occipital bone to last thoracic vertebrae insertion: scapula & clavicle - head extension & movement of scapula
Trunk Muscles
Posterior Muscles • Latissimus Dorsi - 2 large, flat muscles in the lower back - origin: lower spine & ilium insertion: proximal end of humerus - arm extension & adduction (“power stroke”)
Trunk Muscles
Posterior Muscles • Erector Spinae - prime mover of back extension (keep your body “erect”); control bending at the waist - paired; deep in the back - span vertebral column
Trunk Muscles
Posterior Muscles • Qudratus lumborum - posterior abdominal wall - flex spine laterally, extend vertebral column - origin: iliac crest insertion: upper lumbar vertebrae
Trunk Muscles
Posterior Muscles • Deltoids - triangular muscle forming shoulder - origin: spine of scapula to clavicle insertion: proximal humerus - prime mover of arm abduction
Muscles of the Upper Limb
• The anterior arm muscles cause elbow
flexion strongest: brachialis biceps brachii “weakest”: brachioradialis
• posterior arm: triceps brachii
Muscles of the Upper Limb
Anterior Arm Muscles • Biceps brachii - origin: 2 heads in pectoral girdle insertion: radius - prime mover of forearm flexion & supination
Muscles of the Upper Limb
Anterior Arm Muscles • Brachialis - origin: humerus insertion: ulna - forearm flexion
• Brachioradialis - origin: humerus insertion: distal forearm
Muscles of the Upper Limb
Posterior Arm Muscles • Triceps brachii - origin: 3 heads in pectoral girdle insertion: olecranon process of ulna - prime mover of elbow extension - biceps brachii antagonist
Muscles of the Lower Limb
• cause movement of hip, knee &
foot joints• some of the largest, strongest muscles in the body• specialized for walking & balance• many of the muscles cross 2 joints and can cause movement at both
Muscles of the Lower Limb
Muscles that Move the Hip Joint • Gluteus Maximus - forms most of the flesh of the buttock - origin: sacrum & illiac insertion: femur & iliotibial tract - hip extensor (important when climbing and jumping)
Muscles of the Lower Limb
Muscles that Move the Hip Joint • Gluteus Medius - beneath gluteus maximus - hip abductor; steadies pelvis when walking
• Iliopsoas (two, fused muscles) - prime mover of hip flexion; keeps upper body from falling backward when standing
Muscles of the Lower Limb
Muscles that Move the Hip Joint • Adductor Muscles - group of muscles; medial thigh - adduct, or press, thighs together - origin: pelvis insertion: femur - tend to get flabby
Iliopsoas
Adductor muscles
AnteriorView
Posterior View
Gluteus medius
Gluteus maximus
Adductor magnusIliotibial tract
Muscles of the Lower Limb
Muscles that Move the Knee Joint • Hamstring Group - group of muscles; posterior thigh - biceps femoris, semimembranosus, semitendinosus - origin: ischium insertion: tibia - prime movers of thigh extension & knee flexion
Muscles of the Lower Limb
Muscles that Move the Knee Joint • Sartorius - thin, strap-like, relatively weak flexor - most superficial thigh muscle - synergist in sitting “criss cross applesauce”
Muscles of the Lower Limb
Muscles that Move the Knee Joint • Quadriceps Group - group of muscles; anterior thigh - rectus femoris & 3 vastus muscles - origin: pelvis & thigh insertion: tibia via patellar ligament - prime movers of knee extension; hip flexion
Iliopsoas
Iliopsoas
Adductor muscles
AnteriorView
SartoriusRectus femorisVastus lateralis
Vastus medialis
QUADS
Posterior View
Muscles of the Lower Limb
Muscles that Move the Ankle & Foot • Tibialis Anterior - superficial muscle of anterior leg (shin) - origin: tibia insertion: tarsals - dorsiflex & invert the foot
• Fibularis Muscles - plantar flexion and eversion - origin: fibula insertion: metatarsals
Muscles of the Lower Limb
Muscles that Move the Ankle & Foot • Gastrocnemius - forms curved calf; 2 parts - origin: femur insertion: heel using Achille’s tendon - prime mover of plantar flexion
Muscles of the Lower Limb
Muscles that Move the Ankle & Foot • Soleus - deep to gastrocnemius - origin: tibia & fibula (no effect on knee) insertion: heel using Achille’s tendon - plantar flexion
AnteriorView
PosteriorView
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