Download Chapter 10 - Palm Beach State College

Chapter 10
Muscular Sytem
BSC 2085 A & P 1
Professor Tcherina Duncombe
PBSC
10-1
Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
The Functions of Muscles
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Movement of body parts and organ contents
Maintain posture and prevent movement
Communication - speech, expression and writing
Control of openings and passageways
Heat production
Glycemic control: absorbs/stores/use large amt glucose/stabilizes
bld glucose conc/Type 2 diabetes prevention
10-2
Location of Fascia
• Deep fascia
– found between adjacent muscles
• Superficial fascia (hypodermis)
– adipose between skin and muscles
Superficial Fascia
Deep Fascia
10-3
Muscle Attachments
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Direct (fleshy) attachment to bone
– epimysium is continuous with periosteum
– intercostal muscles
Indirect attachment to bone
– epimysium continues as tendon or
aponeurosis that merges into periosteum
as perforating fibers
– biceps brachii or abdominal muscle
Attachment to dermis
Stress will tear the tendon before pulling the
tendon loose from either muscle or bone
10-4
Skeletal Muscle Shapes 1
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Fusiform muscles
– thick in middle and tapered at ends
– biceps brachii m.
Parallel muscles have parallel fascicles
– rectus abdominis m.
Convergent muscle
– broad at origin and tapering to a narrower insertion
Pennate muscles
– fascicles insert obliquely on a tendon
– unipennate, bipennate or multipennate
– palmar interosseus, rectus femoris and deltoid
Circular muscles
– ring around body opening
– orbicularis oculi
10-5
Muscle Actions during Elbow Flexion
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Prime mover (agonist) = brachialis
Synergist = biceps brachii
Antagonist = triceps brachii
Fixator = muscle that holds scapula
firmly in place
– rhomboideus m.
10-6
Intrinsic and Extrinsic Muscles
• Intrinsic muscles are
contained within a
region such as the hand.
• Extrinsic muscles move
the fingers but are
found outside the
region.
10-7
Muscles of the Back
• Erector spinae group
– 3 columns muscle
– from sacrum to ribs
– extends vertebral
column
Semispinalis
• Semispinalis group
– vertebrae to vertebrae
– extends neck
Erector spinae
• Multifidis
– vertebrae to vertebrae
– rotates vertebral column
• Quadratus lumborum
– ilium to 12th rib
– lateral flexion
Multifidis
Quadratus
lumborum
10-8
Superficial Perineal Space
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3 Muscles found just deep to the skin
Ischiocavernosus = arises ischial and pubic ramus
Bulbospongiosus = covers bulb of penis or encloses vagina
Function during intercourse and voiding of urine
10-9
Muscles of UG diaphragm
• Middle layer of pelvic floor contains urogenital
diaphragm and external anal sphincter
• Urogenital diaphragm = 2 muscles
– deep transverse perineus m. supports pelvic viscera
– external urethral sphincter m. inhibits urination
10-10
Muscles of Pelvic Diaphragm
Levator ani
Coccygeus
• Deepest compartment of the perineum
• Pelvic diaphragm = 2 muscles
– levator ani m. supports viscera and defecation
– coccygeus m. supports and elevates pelvic floor
10-11
Hernias
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Protrusion of viscera through muscular wall of abdominopelvic cavity
Inguinal hernia
– most common type of hernia (rare in women)
– viscera enter inguinal canal or even the scrotum
Hiatal hernia
– stomach protrudes through diaphragm into thorax
– overweight people over 40
Umbilical hernia
– viscera protrude through the navel
10-12
Carpal Tunnel Syndrome
Repetitive motions cause
inflammation and
pressure on median nerve
10-13
Athletic Injuries
• Vulnerable to sudden and intense
stress
• Proper conditioning and warm-up
needed
• Common injuries
– shinsplints
– pulled hamstrings
– tennis elbow
• Treat with rest, ice, compression and
elevation
• “No pain, no gain” is a dangerous
misconception
10-14
Chapter 11
Muscular Tissue
BSC 2085 A & P 1
Professor Duncombe
PBCC
11-15
Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cell = fiber = myofiber
Introduction to Muscle
• Movement : fundamental
characteristic of all living things
• Cells capable of
shortening/converting chemical
energy of ATP into mechanical
energy
• Types of muscle
– skeletal, cardiac and smooth
• Physiology of skeletal muscle
– basis of warm-up, strength,
endurance and fatigue
Characteristics
 Responsiveness
 Conductivity
 Contractility
 Extensibility
 Elasticity
11-16
The Muscle Fiber: myoblasts (stem cells) fuse = many nuclei
Injury : satellite cells multiply = new fibers
fibroblast = fibrosis for most new fibers
Triads: contraction = activated by Ca2+
• glycogen: for energy
•Myoglobin: red pigment; stores O2
= SR=
Reservoir
of Ca2+
11-17
Overlap of Thick and Thin Filaments
11-18
Thick Filaments
• Made of 200 to 500 myosin molecules
– 2 entwined polypeptides (golf clubs)
• Arranged in a bundle with heads directed outward in a spiral array around the
bundled tails
– central area is a bare zone with no heads
11-19
Thin Filaments
• Two intertwined strands fibrous (F) actin
– globular (G) actin with an active site
• Groove holds tropomyosin molecules
– each blocking 6 or 7 active sites of G actins
• One small, calcium-binding troponin molecule on each
tropomyosin molecule
11-20
Regulatory and Contractile Proteins
• Myosin /actin = contractile proteins
• Tropomyosin /troponin = regulatory proteins
– Switch = starts/stops shortening of muscle cell
– contraction activated by release of calcium into sarcoplasm and its
binding to troponin,
– troponin moves tropomyosin off the actin active sites
11-21
Striations and Sarcomeres
11-22
Striations = Organization of Filaments
• Dark A bands (regions) alternating with lighter I bands (regions)
– anisotrophic (A) and isotropic (I) stand for the way these regions affect polarized light
• A band is thick filament region
– lighter, central H band area
contains no thin filaments
• I band is thin filament region
– bisected by Z disc protein called
connectin, anchoring elastic and thin
filaments
– from one Z disc (Z line) to the next is a sarcomere
11-23
Elastic Filaments
• Springy proteins called titin
• Anchor each thick filament to Z disc
• Prevents overstretching of sarcomere
11-24
Motor Units
• A motor neuron and the muscle fibers it
innervates
– dispersed throughout the muscle
– when contract together causes weak
contraction over wide area
– provides ability to sustain long-term contraction
as motor units take turns resting (postural
control)
• Fine control
– small motor units contain as few as
20 muscle fibers per nerve fiber
– eye muscles
• Strength control
– gastrocnemius muscle has 1000
fibers per nerve fiber
11-25
The Neuromuscular Junction
11-26
Neuromuscular Toxins
• Pesticides (cholinesterase inhibitors)
– bind to acetylcholinesterase and prevent it from
degrading ACh
– spastic paralysis and possible suffocation
• Tetanus or lockjaw is spastic paralysis caused by
toxin of Clostridium bacteria
– blocks glycine release in the spinal cord and causes
overstimulation of the muscles
• Flaccid paralysis (limp muscles) due to curare
that competes with ACh
– respiratory arrest
11-28
Muscle Contraction and Relaxation
• Four actions involved in this process
– excitation = nerve action potentials lead to action
potentials in muscle fiber
– excitation-contraction coupling = action potentials
on the sarcolemma activate myofilaments
– contraction = shortening of muscle fiber
– relaxation = return to resting length
11-29
Rigor Mortis
• Stiffening of the body beginning 3 to 4 hours after death
• Deteriorating sarcoplasmic reticulum releases calcium
• Calcium activates myosin-actin cross-bridging and muscle
contracts, but can not relax.
• Muscle relaxation requires ATP and ATP production is no
longer produced after death
• Fibers remain contracted until myofilaments decay
11-30
Isometric and Isotonic Contractions
• Isometric muscle contraction
– develops tension without changing length
– important in postural muscle function and antagonistic muscle
joint stabilization
• Isotonic muscle contraction
– tension while shortening = concentric
– tension while lengthening11-31
= eccentric
ATP Sources
• All muscle contraction depends on ATP
• Pathways of ATP synthesis
– anaerobic fermentation (ATP production limited)
• without oxygen, produces toxic lactic acid
– aerobic respiration (more ATP produced)
• requires continuous oxygen supply, produces H2O and CO2
11-32
Endurance
• Ability to maintain high-intensity exercise for
>5 minutes
– determined by maximum oxygen uptake
• VO2 max is proportional to body size, peaks at age 20, is
larger in trained athlete and males
– nutrient availability
• carbohydrate loading used by some athletes
– packs glycogen into muscle cells
– adds water at same time (2.7 g water with each
gram/glycogen)
» side effects include “heaviness” feeling
11-34
Oxygen Debt
• Heavy breathing after strenuous exercise
– known as excess postexercise oxygen consumption (EPOC)
– typically about 11 liters extra is consumed
• Purposes for extra oxygen
– replace oxygen reserves (myoglobin, blood hemoglobin, in
air in the lungs and dissolved in plasma)
– replenishing the phosphagen system
– reconverting lactic acid to glucose in kidneys and liver
– serving the elevated metabolic rate that occurs as long as
the body temperature remains elevated by exercise
11-35
Slow- and Fast-Twitch Fibers
• Slow oxidative, slow-twitch fibers
– more mitochondria, myoglobin and
capillaries
– adapted for aerobic respiration and resistant
to fatigue
– soleus and postural muscles of the back
(100msec/twitch)
11-36
Slow and Fast-Twitch Fibers
• Fast glycolytic, fast-twitch fibers
– rich in enzymes for phosphagen and glycogenlactic acid systems
– sarcoplasmic reticulum releases calcium quickly so
contractions are quicker (7.5 msec/twitch)
– extraocular eye muscles, gastrocnemius and
biceps brachii
• Proportions genetically determined
11-37
Strength and Conditioning
• Strength of contraction
– muscle size and fascicle arrangement
• 3 or 4 kg / cm2 of cross-sectional area
– size of motor units and motor unit recruitment
– length of muscle at start of contraction
• Resistance training (weight lifting)
– stimulates cell enlargement due to synthesis of more
myofilaments
• Endurance training (aerobic exercise)
– produces an increase in mitochondria, glycogen and density
of capillaries
11-38
Fig. 11.4
Muscular Dystrophy
• Hereditary diseases - skeletal muscles
degenerate and are replaced with adipose
• Disease of males
– appears as child begins to walk
– rarely live past 20 years of age
• Dystrophin links actin filaments to cell
membrane
– leads to torn cell membranes and necrosis
• Fascioscapulohumeral MD -- facial and shoulder
muscle only
11-40
Myasthenia Gravis
• Autoimmune disease - antibodies attack NMJ
and bind ACh receptors in clusters
– receptors removed
– less and less sensitive to ACh
• drooping eyelids and double vision, difficulty swallowing,
weakness of the limbs, respiratory failure
• Disease of women between 20 and 40
• Treated with cholinesterase inhibitors, thymus
removal or immunosuppressive agents
11-41
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Myasthenia Gravis
Drooping eyelids and weakness of muscles of eye movement
11-43