the musculoskeletal system chapter 47. 2 types of skeletal systems changes in movement occur because...
TRANSCRIPT
The Musculoskeletal System
Chapter 47
2
Types of Skeletal Systems
Changes in movement occur because muscles pull against a support structure, called the skeletal system
-Zoologists recognize three types:
-Hydrostatic skeletons
-Exoskeletons
-Endoskeletons
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Chitinous outer covering
Exoskeleton
Sagittal section
Vertebral column
Pelvis
FemurTibiaFibula
UlnaRadius
Humerus
Skull
Scapula
Ribs
Exoskeleton
Endoskeleton
a.
b.
axial skeletonappendicularskeleton
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Changes in
movement
occur because
muscles pull
against a skeletal
system...
3 types
Hydrostatic skeletons
Found primarily in soft-bodied invertebrates
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Hydrostatic Skeletons
Chaetae get lifted in regions of circular muscle contraction.
During longitudinal muscles contraction, chaetae
anchor into the ground
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Hydrostatic SkeletonsLocomotion in aquatic
invertebrates occurs by
fluid ejections or jetting
-Jellyfish produce regular
pulsations in bell
-Squeezing some of water
contained beneath it
-Squids fill mantle cavity
with sea water
-Muscular contractions
expel water forcefully through
the siphon, and the animal
shoots backward
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-Unlike chitin, bone and cartilage are living tissues...they change and remodel in response to injury or physical stress
-Echinoderms have calcite skeletons, that have calcium carbonate
-Bone, on the other hand, has calcium phosphate. Vertebrate endoskeletons have bone and/or cartilage
Endoskeletons
Endoskeletons vs. Exoskeletons
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Undifferentiated Mesenchymal Cells
ChondroblastFibroblast Osteoblasts
ChondrocyteCollagen(fibrous tissue)
Osteocyte
Osteoclast
Secrete Alkaline phosphatasecauses Calcium Phosphate to formHydroxyapatiteIn the EXTRACELLULARMATRIX
Cells in Bone Tissue
Make cartilage = Chondroitin and collagen
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Endoskeleton Bone
Bone is unique to vertebrates
Bones can be classified by the two fundamental modes of development-Intramembranous development (simple)
-E.g.: External bones of skull-Endochondral development (complex)
-E.g.: Bones that are deep in the body
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Intramembranous Bone DevelopmentOsteoblasts from dermis in skin initiate bone development (onto collagen fiber scaffold).
Some cells become trapped in the bone matrix that they have produced... ...change into osteocytes, which reside in
tight spaces called lacunae The cells communicate through
little canals termed canaliculi.
Osteoclasts break down the bone matrix.
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*First there is cartilage in the general shape of the bone
*A fibrous sheath with osteoblasts surrounds cartilage
*Osteoblasts use cartilage to make Calcium Phosphate (Extracellular Matrix)
*Blood vessels from fibrous sheath (now periosteum) go deeper into the original cartilage
*Osteoblasts and Osteoclasts follow blood supply to further change cartilage into bone tissue
Endochondrial Bone Development
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Endochondral Development
Superficial cartilage that remains after the development of epiphyses serves as a pad between bone surfaces
Osteoclasts create medullary cavity
Growth plates made of cartilage grow towards distal ends until approaching bone coming from the shaft changes it all to bone
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Vascular Bone StructureMost mammals retain internal blood vessels and are called vascular bones
These typically have osteocytes and are also called cellular Bones & have a Haversian system
Not seen fish and birds
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Bone StructureBased on density and structure, bone falls into three categories
-Compact bone = Outer dense layer-Medullary bone = Lines the internal cavity...contains bone
marrow in some species (site of red blood cell production)
-Spongy bone = Honeycomb structure forms the epiphyses inside a thick shell of compact bone
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Joints are the locations where one bone meets another
3 general kinds
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Skeletal Muscle Structure
Each skeletal musclecontains numerous muscle fibers (CELLS)
Each muscle fiber encloses a bundle of structures called myofibrils
Each myofibril in turn is composed of thick and thin myofilaments
Bone periosteum& skeletal Muscle Are united by a tendon
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Thick filament is composed of myosin protein, two polypeptide chains w/ aglobular head wrapped around each other
Thin filament Is two chains of actin protein,twisted together in a helix
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Sarcomere
H band
A band I band
a.
b.
Z line
Thin filaments (actin) Thick filament (myosin)Cross-bridges
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Why do Myofibrils contract and shorten???Because thick and thin filaments slide over each other
Sarcomere = distance between 2 Zlines...Smallest subunit of muscle contraction
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Cross-bridge
cycle
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Relaxed Versus Contracted Muscle
Troponin + Tropomyosin = NO Muscle ContractionBecause Tropomyosin binds to Actin
Ca2+ + Troponin + Tropomyosin = Muscle Contraction Because Ca2+ + Troponin displace Tropomyosin...Actin-myosin cross-bridges form
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Myofibril
Na+
SarcolemmaNeuromuscularjunction
Motor neuron Nerveimpulse
Neurotransmitter
Sarcoplasmicreticulum
Transversetubule(T tubule)
Release of Ca2+Ca2+
Muscle depolarization
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Skeletal Muscle Contractionacetylcholine
-The membrane becomes depolarized-Depolarization is conducted down the transverse tubules (T tubules)
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A motor unit consists of a motor neuron and all of the muscle fibers it innervates
Recruitment is the cumulative increase in motor unit number and size leading to a stronger contraction
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Types of Muscle Fibers
A muscle stimulated with a single electric shock quickly contracts and relaxes in a response called a twitch
Summation is a cumulative response when a second twitch “piggy-backs” on the first
Tetanus occurs when there is no relaxation between twitches-A sustained contraction is produced
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Am
plit
ud
e o
f M
us
cle
Co
ntr
acti
on
s
Completetetanus
Twitches
Incompletetetanus
Time
Summation
Stimuli' ' ' ' ' '
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Types of Muscle FibersSkeletal muscle fibers can be divided based
on their contraction speed
-Slow-twitch, or Type I, fibers-Rich in capillaries, mitochondria and myoglobin pigment (red fibers)-Sustain action for long periods of time
-Fast-twitch, or Type II, fibers-Poor in capillaries, mitochondria and myoglobin (white fibers)-Adapted for rapid power generation
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Co
ntr
act
ion
Str
eng
th
Time (msec)
eye muscle (lateral rectus)
calf muscle (gastrocnemius)
deep muscle of leg (soleus)
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Types of Muscle Fibers
Skeletal muscles have different proportions of fast-twitch and slow-twitch fibers
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Types of Muscle Fibers
Skeletal muscles at rest get energy from aerobic respiration of fatty acids
During muscle use, energy comes from glycogen and glucose
Muscle fatigue is related with the production of lactic acid via anaerobic fermentation during glycolysis!!!