skeleton muscle lecture copy -...

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The Musculo-Skeletal System Animal Skeletons Functions: Support Protection Movement all movement results from: muscle working against a skeleton 3 Types of skeletons hydrostatic exoskeleton endoskeleton Hydrostatic Skeletons A hydrostatic skeleton fluid held under pressure in a closed body compartment typical of cnidarians flatworms nematodes annelids Earthworm peristaltic movement

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Page 1: Skeleton Muscle Lecture copy - blogs.4j.lane.edublogs.4j.lane.edu/sanderson/files/2014/04/Skeleton-Muscle-Lecture... · •The mammalian skeleton is built from more than 200 bones

The Musculo-Skeletal System

Animal SkeletonsFunctions: •Support •Protection •Movement

all movement results from: muscle working against a skeleton

3 Types of skeletons •hydrostatic •exoskeleton •endoskeleton

Hydrostatic Skeletons• A hydrostatic skeleton • fluid held under pressure in a closed body

compartment • typical of • cnidarians • flatworms • nematodes • annelids

Earthworm peristaltic movement

Page 2: Skeleton Muscle Lecture copy - blogs.4j.lane.edublogs.4j.lane.edu/sanderson/files/2014/04/Skeleton-Muscle-Lecture... · •The mammalian skeleton is built from more than 200 bones

ExoskeletonHard encasement deposited on outside of animal Typical of

mollusca arthropoda

EndoskeletonHard supporting elements deposited on inside of animal

Typical of sponges echinoderms chordates

Thigh bone connected to the...• The mammalian skeleton is built from more than 200 bones

• Some fused together and others connected at joints by ligaments that allow freedom of movement

• are bones alive?• osteoblasts, osteocytes

Do you know your bones?

Page 3: Skeleton Muscle Lecture copy - blogs.4j.lane.edublogs.4j.lane.edu/sanderson/files/2014/04/Skeleton-Muscle-Lecture... · •The mammalian skeleton is built from more than 200 bones

Types of joints in the appendicular skeleton

Page 4: Skeleton Muscle Lecture copy - blogs.4j.lane.edublogs.4j.lane.edu/sanderson/files/2014/04/Skeleton-Muscle-Lecture... · •The mammalian skeleton is built from more than 200 bones

Vertebrate Skeletal Muscle

Contraction

Muscles move the skeleton• What is always the action of muscle cells?

• Skeletal muscles are attached to the skeleton in antagonistic pairs

Vertebrate Skeletal Muscle

Vertebrate Skeletal Muscle

Page 5: Skeleton Muscle Lecture copy - blogs.4j.lane.edublogs.4j.lane.edu/sanderson/files/2014/04/Skeleton-Muscle-Lecture... · •The mammalian skeleton is built from more than 200 bones

Vertebrate Skeletal Muscle

Sliding filament theory

• Mechanism of contraction? • thick and thin filaments... • slide past one another.

• Mechanism of sliding filaments? • Interaction between...

• actin and myosin: • The “head” of a myosin molecule binds to an actin

filament • Forming a cross-bridge and pulling the thin filament

toward the center of the sarcomere

Sliding filament theory

•ATP binds to myosin head •Head releases from actin site

Sliding filament theory

•Energized by phosphoryllation of ATP, •Myosin head now able to bind to actin site

Page 6: Skeleton Muscle Lecture copy - blogs.4j.lane.edublogs.4j.lane.edu/sanderson/files/2014/04/Skeleton-Muscle-Lecture... · •The mammalian skeleton is built from more than 200 bones

Sliding filament theory Sliding filament theory

•Binding to actin site releases ADP + Phosphate •Myosin head bends into low E config

Sliding filament theory

ActinTropomyosin Ca2+-binding sites

Troponin complex

(a) Myosin-binding sites blocked

• If ATP available, why doesn’t muscle just keep contracting? • Regulation

• Contraction stimulated by: • a motor neuron

• At rest, myosin-binding sites blocked by: • tropomyosin (regulatory protein)

The Role of Calcium and Regulatory Proteins

Page 7: Skeleton Muscle Lecture copy - blogs.4j.lane.edublogs.4j.lane.edu/sanderson/files/2014/04/Skeleton-Muscle-Lecture... · •The mammalian skeleton is built from more than 200 bones

The Role of Calcium and Regulatory Proteins

Ca2+

Myosin-binding site

(b) Myosin-binding sites exposed

• What do calcium ions (Ca2+) do? • Bind to the troponin complex, • which uncovers myosin-binding sites

• Where does Ca2+ come from? How do Ca2+ ions get released? • Action potential (AP) in a motor neuron that synapses w/

the muscle fiber… • releases acetylcholine (n.t.)… • depolarizes the muscle and causing it to produce an AP • causes the sarcoplasmic reticulum (SR) to release Ca2+

• “SR?” • = modified ER

The Role of Calcium and Regulatory Proteins

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Neural Control of Muscle Tension• Contraction of a whole muscle is graded

– Which means that we can voluntarily alter the extent and strength of its contraction

Page 8: Skeleton Muscle Lecture copy - blogs.4j.lane.edublogs.4j.lane.edu/sanderson/files/2014/04/Skeleton-Muscle-Lecture... · •The mammalian skeleton is built from more than 200 bones

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• There are two basic mechanisms by which the nervous system produces graded contractions of whole muscles – the number of fibers that contract – the rate at which muscle fibers are stimulated

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• In a vertebrate skeletal muscle – Each branched muscle fiber is innervated by

only one motor neuron

• Each motor neuron – May synapse with multiple muscle fibers

Figure 49.34

Spinal cord

Nerve

Motor neuroncell body

Motorunit 1

Motorunit 2

Motor neuronaxon

Muscle

Tendon

Synaptic terminals

Muscle fibers

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• A motor unit – Consists of a single motor neuron and all the

muscle fibers it controls

• Recruitment of multiple motor neurons – Results in stronger contractions

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• A twitch – Results from a single action potential in a

motor neuron

• More rapidly delivered action potentials – Produce a graded contraction by summation

Figure 49.35

Action potential Pair of

action potentials

Series of action potentials at

high frequency

Time

Tens

ion

Singletwitch

Summation of two twitches

Tetanus

Page 9: Skeleton Muscle Lecture copy - blogs.4j.lane.edublogs.4j.lane.edu/sanderson/files/2014/04/Skeleton-Muscle-Lecture... · •The mammalian skeleton is built from more than 200 bones

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Tetanus is a state of smooth and sustained contraction – Produced when motor neurons deliver a volley

of action potentials

Types of Muscle Fibers“Slow-twitch” vs “Fast twitch?” white meat vs dark meat

muscle that needs energy for prolonged contraction/exercise needs more Oxygen = more myglobin, more pigment, darker

Skeletal muscle fibers are classified as slow oxidative, fast oxidative, and fast glycolytic

Based on their contraction speed and major pathway for producing ATP

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• Types of skeletal muscles

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Other Types of Muscle• Cardiac muscle, found only in the heart

– Consists of striated cells that are electrically connected by intercalated discs

– Can generate action potentials without neural input

Page 10: Skeleton Muscle Lecture copy - blogs.4j.lane.edublogs.4j.lane.edu/sanderson/files/2014/04/Skeleton-Muscle-Lecture... · •The mammalian skeleton is built from more than 200 bones

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• In smooth muscle, found mainly in the walls of hollow organs – The contractions are relatively slow and may

be initiated by the muscles themselves

• In addition, contractions may be caused by – Stimulation from neurons in the autonomic

nervous system