musculoskeletal lecture

Locomotion – Skeletal and Locomotion – Skeletal and Muscular SystemsMuscular Systems

Movement is Movement is based on based on Muscles acting Muscles acting on a rigid on a rigid skeletonskeleton

All animals All animals employ the use employ the use of musclesof muscles

Types of SkeletonsTypes of Skeletons HydrostaticHydrostatic

Fluid filled cavity encircled by Fluid filled cavity encircled by muscle fibers muscle fibers Soft-bodied invertebratesSoft-bodied invertebrates

ExoskeletonExoskeletonBody encased in hard shell Body encased in hard shell chitinchitinmost be shed for growthmost be shed for growthlimits body size as exoskeleton limits body size as exoskeleton has to grow increasingly has to grow increasingly thicker and heavierthicker and heavier

EndoskeletonEndoskeletonrigid internal skeleton of bonerigid internal skeleton of bone

Types of SkeletonsTypes of Skeletons Endoskeletons Endoskeletons - rigid internal skeleton - rigid internal skeleton

to which muscles are attachedto which muscles are attached composed of cartilage or bonecomposed of cartilage or bone vertebrate skeletonvertebrate skeleton

axial skeleton - forms axis of body and supports axial skeleton - forms axis of body and supports organs of the head, neck, and chestorgans of the head, neck, and chest

appendicular skeleton - includes bones of the appendicular skeleton - includes bones of the limbs, pectoral and pelvic girdleslimbs, pectoral and pelvic girdles

Exoskeleton and Exoskeleton and EndoskeletonEndoskeleton

SkeletonSkeleton

FunctionsFunctions HomeostaticHomeostatic

CaCa++ and P and P++ reservoirreservoir

BiomechanicalBiomechanical Attachment for Attachment for

musclesmuscles Protective covering Protective covering

brain and spinal brain and spinal cordcord

OverviewOverviewConnective TissueConnective Tissue

Extracellular matrix with Extracellular matrix with collagen fibers (flexible) collagen fibers (flexible) impregnated with impregnated with crystals of Calcium crystals of Calcium phosphate (rigidity)phosphate (rigidity)

Dynamic – Dynamic – reconstructionreconstruction

Bone TissueBone TissueStructureStructure

Consists of Haversian Consists of Haversian System System Run length of boneRun length of bone Nerves/bloodNerves/blood

Osteoblasts - matrixOsteoblasts - matrix Osteocytes – encasedOsteocytes – encased Osteoclast - breakdownOsteoclast - breakdown

Concentric lamellaeConcentric lamellae Around canalAround canal

Lacunae - Lacunae - CanaliculiCanaliculi

Classification of Joints Classification of Joints (articulations)(articulations)

Joints – places where 2 bones are attachedJoints – places where 2 bones are attached

TYPESTYPES Immovable joints – dense connective tissue - Immovable joints – dense connective tissue -

little little movement - suturesmovement - sutures Slightly movable joints – held together by Slightly movable joints – held together by

cartilagecartilage

Some flexibility not much (intervertebral Some flexibility not much (intervertebral and and symphyses)symphyses)

Freely movableFreely movable

Synovial JointsSynovial Joints

Capsule with Capsule with

fluidfluid

Cartilage end capsCartilage end caps

Types of JointsTypes of Joints

Types of JointsTypes of Joints

Types of JointsTypes of Joints

Levers for movementLevers for movement Muscles attach to bone to allow movement – Muscles attach to bone to allow movement –

contraction = movementcontraction = movement Origin – nonmovingOrigin – nonmoving Insertion – movingInsertion – moving Attach via tendonsAttach via tendons Muscles oppose each other – AntagonisticMuscles oppose each other – Antagonistic Muscles that cause the same action Muscles that cause the same action

synergistssynergists Isotonic contractionIsotonic contraction - muscle and all fibers - muscle and all fibers

shorten in length thus force of contraction shorten in length thus force of contraction remains relatively constantremains relatively constant

Isometric contractionIsometric contraction - tension is absorbed - tension is absorbed by tendons and other elastic tissue, and by tendons and other elastic tissue, and muscle does not change in lengthmuscle does not change in length

Flexor and Extensor Flexor and Extensor MusclesMuscles

Muscle Muscle StructureStructure MuscleMuscle Muscle fascicleMuscle fascicle Muscle fibers = cellMuscle fibers = cell MyofibrilsMyofibrils Thick and thin Thick and thin

myofilamentsmyofilaments

Myosin and ActinMyosin and Actin

Muscle Structure (Cont’d)Muscle Structure (Cont’d)

Striated due to dark Striated due to dark and light bandsand light bands Pattern = organization of Pattern = organization of

myofilamentsmyofilaments Repeating structureRepeating structure

““Sarcomere”Sarcomere”Dark bands = “A” myosinDark bands = “A” myosinLight bands = “I” actinLight bands = “I” actinZ line = actin attachmentZ line = actin attachmentH zone = myosin onlyH zone = myosin only

Sliding Filament Mechanism

Mechanism of muscle contractionNo shortening - sliding

The PlayersThe Players

muscle relaxed – myosin heads cocked – unable to Bind to actin due to sites blocked by protein - tropomyosin

In order to contract tropomyosin must be moved to expose binding sites on actin

Requires a regulatory protein troponin – troponin binds to tropomyosin changes the structure and exposes binding sites

Troponin regulated by Calcium stored in the muscle cells

If low calcium no binding sites exposed , if high calcium - exposed

Preparing for Sliding

ATP is requiredATP is required

Rigor mortis – body not make ATP Rigor mortis – body not make ATP (DEAD) cross-bridges cannot be broken(DEAD) cross-bridges cannot be broken

What causes sliding?What causes sliding?

Nervous system Nervous system involvementinvolvement

When stimulated, When stimulated, electrical impulse electrical impulse travels down travels down T-tubulesT-tubules

Causes sarcoplasmic Causes sarcoplasmic reticulum to releasereticulum to release Ca++Ca++

Control of Muscle Control of Muscle ContractionContraction

Nerves stimulate contractionNerves stimulate contraction Somatic motor neurons stimulate Somatic motor neurons stimulate

skeletal muscles.skeletal muscles. Axon extends from neuron cell body and Axon extends from neuron cell body and

branches to make synapses with a branches to make synapses with a number of muscle fibers.number of muscle fibers.

Control of Muscle Control of Muscle ContractionContraction

Somatic motor neuron stimulates Somatic motor neuron stimulates contraction:contraction: releasing acetylcholine neurotransmitter releasing acetylcholine neurotransmitter

(ACh).(ACh). impulses spread along membrane and impulses spread along membrane and

carried into the muscle fibers through the T carried into the muscle fibers through the T tubulestubules

T tubules conduct impulse toward the T tubules conduct impulse toward the sarcoplasmic reticulum, which releases Casarcoplasmic reticulum, which releases Ca++++

Excitation-contraction couplingExcitation-contraction coupling

Control of Muscle Control of Muscle ContractionContraction Motor units and recruitmentMotor units and recruitment

set of muscle fibers innervated by all axonal set of muscle fibers innervated by all axonal branches is defined as a motor unitbranches is defined as a motor unit

division of muscle into motor units allows division of muscle into motor units allows muscle’s strength of contraction to be finely muscle’s strength of contraction to be finely gradedgraded

– most muscles contain motor units in a variety of sizesmost muscles contain motor units in a variety of sizes recruitmentrecruitment - nervous system’s use of increased - nervous system’s use of increased

numbers and sizes of motor units to produce a numbers and sizes of motor units to produce a stronger contractionstronger contraction

Number and Size of Motor Number and Size of Motor UnitsUnits

Types of Muscle FibersTypes of Muscle Fibers

Muscle fiber twitchesMuscle fiber twitches muscle stimulated with a single electric muscle stimulated with a single electric

shockshock A second electrical shock delivered immediately A second electrical shock delivered immediately

after the first will produce a second twitch that after the first will produce a second twitch that may partially piggyback on the first may partially piggyback on the first ((summationsummation).).

– At a particular frequency of stimulation, there is no At a particular frequency of stimulation, there is no visible relaxation between successive twitches visible relaxation between successive twitches ((tetanustetanus).).

SummationSummation

Types of Muscle FibersTypes of Muscle Fibers

Skeletal muscle fibers can be divided on Skeletal muscle fibers can be divided on the basis of their contraction speed:the basis of their contraction speed: Type I – slow-twitch fibersType I – slow-twitch fibers

rich capillary supply, numerous mitochondria, rich capillary supply, numerous mitochondria, and high concentration of myoglobin pigment and high concentration of myoglobin pigment (red fibers)(red fibers)

Type II – fast-twitch fibersType II – fast-twitch fibers fewer capillaries and mitochondria and not as fewer capillaries and mitochondria and not as

much myoglobin (white fibers)much myoglobin (white fibers)

Types of Muscle FibersTypes of Muscle Fibers

Muscle metabolism during rest and Muscle metabolism during rest and exerciseexercise Skeletal muscles at rest obtain energy from Skeletal muscles at rest obtain energy from

aerobic respiration of fatty acids.aerobic respiration of fatty acids. Skeletal muscles respire anaerobically for the Skeletal muscles respire anaerobically for the

first 45-90 seconds of moderate to heavy first 45-90 seconds of moderate to heavy exercise.exercise.

Maximum rate of oxygen consumption in the Maximum rate of oxygen consumption in the body is called maximal uptake or aerobic body is called maximal uptake or aerobic capacity.capacity.

Types of Muscle FibersTypes of Muscle Fibers

Muscle fatigue and physical trainingMuscle fatigue and physical training Muscle fatigue refers to the use-dependent Muscle fatigue refers to the use-dependent

decrease in the ability of a muscle to decrease in the ability of a muscle to generate force.generate force.

usually correlated with the production of lactic usually correlated with the production of lactic acid by the exercising musclesacid by the exercising muscles

– also related to depletion of muscle glycogenalso related to depletion of muscle glycogen

Types of Muscle FibersTypes of Muscle Fibers

Endurance-trained athletes have a high Endurance-trained athletes have a high aerobic capacity, and thus can perform aerobic capacity, and thus can perform more exercise before lactic acid more exercise before lactic acid production and glycogen depletion production and glycogen depletion cause muscle fatigue.cause muscle fatigue. Weight training (resistance training) Weight training (resistance training)

causes muscle fibers to become thicker as causes muscle fibers to become thicker as a result of increased size and number of a result of increased size and number of myofibrils.myofibrils.

cause skeletal muscles to grow by cause skeletal muscles to grow by hypertrophyhypertrophy

Modes of Animal Modes of Animal LocomotionLocomotion

In large animals, active locomotion In large animals, active locomotion is almost always produced by is almost always produced by appendages that oscillate appendages that oscillate (appendicular locomotion) or by (appendicular locomotion) or by bodies that undulate, pulse, or bodies that undulate, pulse, or undergo peristaltic waves (axial undergo peristaltic waves (axial locomotion).locomotion).

Modes of Animal Modes of Animal LocomotionLocomotion

Locomotion in waterLocomotion in water Buoyancy reduces the influence of gravity.Buoyancy reduces the influence of gravity.

The primary force retarding forward movement The primary force retarding forward movement is frictional drag.is frictional drag.

– Swimming uses the body or its appendages to push Swimming uses the body or its appendages to push against the water.against the water.

Locomotion in WaterLocomotion in Water

Modes of Animal Modes of Animal LocomotionLocomotion

Locomotion on landLocomotion on land Mollusks slide along a path of mucus.Mollusks slide along a path of mucus. Vertebrates and arthropods have a raised Vertebrates and arthropods have a raised

body and move forward by pushing the body and move forward by pushing the ground with a series of jointed appendages.ground with a series of jointed appendages.

Vertebrates have four limbs, while arthropods Vertebrates have four limbs, while arthropods have six or more.have six or more.

– basic walking pattern of all tetrapod vertebrates LH – basic walking pattern of all tetrapod vertebrates LH – LF – RH – RFLF – RH – RF

Locomotion on LandLocomotion on Land Both arthropods and vertebrates achieve Both arthropods and vertebrates achieve

faster gaits by overlapping leg movements.faster gaits by overlapping leg movements. The highest running speeds of tetrapod The highest running speeds of tetrapod

vertebrates are obtained with asymmetrical vertebrates are obtained with asymmetrical gaits.gaits. galloping horse never supported by more than galloping horse never supported by more than

two legs, occasionally by nonetwo legs, occasionally by none reduces friction against groundreduces friction against ground

Many vertebrates use peristaltic Many vertebrates use peristaltic locomotion.locomotion.

Most snakes employ serpentine locomotion.Most snakes employ serpentine locomotion.

Modes of Animal Modes of Animal LocomotionLocomotion

Locomotion in airLocomotion in air Flight has evolved four times:Flight has evolved four times:

insects, pterosaurs, birds,and batsinsects, pterosaurs, birds,and bats propulsion achieved by pushing down against propulsion achieved by pushing down against

the air with wingsthe air with wings Raising and lowering wings is achieved by Raising and lowering wings is achieved by

alternate contraction of extensor muscles alternate contraction of extensor muscles and flexor muscles.and flexor muscles.

Modes of Animal Modes of Animal LocomotionLocomotion In some insect orders, flight In some insect orders, flight

muscles are not attached to the muscles are not attached to the wings, but rather to the stiff wall of wings, but rather to the stiff wall of the thorax.the thorax.

SummarySummary Characteristics of Epithelial TissueCharacteristics of Epithelial Tissue Tissue TypesTissue Types Types of SkeletonsTypes of Skeletons The Structure of BoneThe Structure of Bone Types of JointsTypes of Joints Actions of Skeletal MusclesActions of Skeletal Muscles Sliding Filament Mechanism of Sliding Filament Mechanism of

ContractionContraction Control of Muscle ContractionControl of Muscle Contraction Types of Muscle FibersTypes of Muscle Fibers Modes of Animal LocomotionModes of Animal Locomotion

Muscle Tissue TypesMuscle Tissue Types

Smooth MuscleSmooth Muscle

Striated MuscleStriated Muscle

SkeletalSkeletal

CardiacCardiac

Striated MuscleStriated Muscle

SkeletalSkeletal

CardiacCardiac

Skeletal MuscleSkeletal Muscle