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The Muscular System

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by

Cheryl Stover

on 22 October 2015

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Transcript of The Muscular System

Producing heat: involuntary contractions of skeletal muscle (shivering)
Functions of
Muscle Tissue

Producing body movements
Stabilizing body positions
Regulating organ volumes: bands of smooth muscle called sphincters
Movement of substances within the body: blood, lymph, urine, air, food and fluids, sperm
Types of
Muscle Tissue

Skeletal muscle
voluntary
non-branching
striated
multinucleated
attached to bone
Cardiac muscle
involuntary
branching
striated
single nucleus
heart muscle
Smooth muscle
involuntaryspindled
un-striated
single nucleus
walls of hollow organs
Skeletal
Cardiac
Smooth
Muscle Tissue
Microscopic Anatomy
of Skeletal Muscle

Skeletal Muscle Tissue Cell=Myofiber
Sarcolemma= plasma membrane
Nucleus
Nucleus
Myofibril
Myofibril
Myofibril
Myofibril
Myofibril
Sarcomere
Sarcomere
Sarcomere
Sarcomere
Sarcomere
Sarcomere
Sarcomere
Sarcomere
Sarcomere
:extensions of sarcolemma
:endoplasmic reticulum.
stores and releases Ca++
myofibril
myofibril
myofibril
myofibril
myofibril
myofibril
myofibril
sarcoplasmic reticulum
sarcoplasmic reticulum
sarcoplasmic reticulum
t-tubule
sarcoplasmic reticulum
t-tubule
t-tubule
t-tubule
sarcomere
sarcolemma
B
C
A
D
E
Sarcomere
Sarcomeres are made of myofilaments
actin: thin
mysin: thick
actin
actin
actin
actin
actin
actin
actin
actin
actin
actin
myosin
myosin
myosin
myosin
myosin
myosin
myosin
myosin
myosin
myosin
myosin
myosin
actin
endomysium
perimysium
epimysium
Skeletal Muscle
Activity

Motor Unit
motor neuron and all the myofibers it controls
Motor Neuron 1
Motor Neuron 2
neuromuscular junction (NMJ)
end of axon nears the surface of a muscle fiber
contract in an all or none fashion
size varies
NMJ
AXON
AP
A
B
C
Synaptic
Vesicle
Neurotransmitter
acetylcholine
AP
Receptor
sarcolemma
sarcolemma
Ach
Ach
Ach binds and opens Na+ Channel
Na+
This is _______________________
Enyme to break down Ach
acetylcholinesterase
Ach is removed and channel closes
Ach
AP moves down sarcolemma
AP moves down T-Tubles
Causes
to be released from SR
diffuses to sarcomere
UNCONTRACTED
CONTRACTED
Myosin
Actin
Actin
Actin
Actin
Actin
Actin
Actin
Actin
Myosin
Myosin
Head
Myosin binding site
Ca++
Ca++
Ca++
binds and lets myosin attach to binding sites
Cross-bridge
Mysosin changes orientation and pulls actin toward center of sarcomere
Filaments slide past each other
Sliding Filament Theory
Neuromuscular
Junction

Neuromuscular
Junction
Sliding Filament
Theory

Movements
Myofibrils & Myofilaments
• Muscle fibers are filled with threads called myofibrils separated by SR (sarcoplasmic reticulum)
• Myofilaments (thick & thin filaments) are the contractile proteins of muscle

Sarcoplasmic Reticulum (SR)
• System of tubular sacs like smooth ER in nonmuscle cells
• Stores Ca+2 in a relaxed muscle
• Release of Ca+2 triggers muscle contraction
Transverse Tubules
• T (transverse) tubules: elongated tube
– Found at the end of each A band-I band junction
– filled with extracellular fluid
– carry muscle action potentials down into cell
• Thick and thin filaments overlap each other in a pattern that creates striations
– light I bands and dark A bands
• The I band region contains only thin filaments.
• They are arranged in compartments called sarcomeres, separated by Z discs.
• In the overlap region, six thin filaments surround each thick filament
Filaments and the Sarcomere
Sliding Filament Mechanism Of Contraction
• Myosin cross bridgespull on thin filaments
• Thin filaments slide inward
• Z Discs come toward each other
• Sarcomeres shorten…The muscle fiber shortens…The muscle shortens
• Notice : Thick & thin filaments do not change in length

• Arrival of nerve impulse at nerve terminal causes release of ACh from synaptic vesicles
• ACh binds to receptors on muscle motor end plate opening the gated ion channels so that Na+ can rush into the muscle cell
• Inside of muscle cell becomes more positive, triggering a muscle action potential that travels over the cell and down the T tubules
• The release of Ca+2 from the SR is triggered and the muscle cell will shorten & generate force
• Acetylcholinesterase breaks down the ACh attached to the receptors on the motor end plate so the muscle action potential will cease and the muscle cell will relax.
– used to relax muscle during surgery
Events Occurring After a Nerve Signal
Muscle
ADDUCTOR MAGNUS
BICEPS BRACHII
BICEPS FEMORIS
BUCCINATOR
DELTOID
DIAPHRAGM
EXTERNAL OBLIQUE
FIBULARIS LONGUS
FRONTALIS
GASTROCNEMIUS
GLUTEUS MAXIMUM
GLUTEUS MEDIUS
GRACILIS
INTERNAL INTERCOSTALS
INTERNAL OBLIQUE
LATISSIMUS DORSI
MASSETER
OCCIPITALIS
ORBICULARIS OCULI
ORBICULARIS ORIS
PECTORALIS MAJOR
RECTUS ABDOMINUS
RECTUS FEMORIS
SARTORIUS
SEMIMEMBRANOUS
SEMITENDINOUS
SERRATUS ANTERIOR
STERNOCLEIDOMASTOID
TEMPORALIS
TIBIALIS ANTERIOR
TRANSVERSE ABDOMINUS
TRAPEZIUS
TRICEPS BRACHII
VASTUS LATERALUS
VASTUS MEDIALIS
ZYGOMATICUS
Videos
Skeletal Muscle Structure
Contraction Cycle
Skeletal Muscles, Tissues, Tendons, Muscular System
Effect of Calcium
myofiber
fasicle
perimysium
CT that surrounds fasicle
Endomysium
CT that surrounds myfiber
Epimysium
CT that surrounds muscle
endomysium
perimysium
epimysium
tendon
Connective tissue components of the muscle include
– Epimysium = surrounds the whole muscle
– Perimysium = surrounds bundles (fascicles) of 10-100 muscle cells
– Endomysium = separates individual muscle cells
All these connective tissue layers extend beyond the muscle belly to form the tendon
Skeletal Muscle -- Connective Tissue
Full transcript