Support and movement (1)

Support and Movement System

Objectives

• Types of movement.
• Importance of movement:
  • External body parts.
  • Internal body parts.
  • Movement within the cell.
• Types of cartilage, their structure, function of each part and cells.
• Why injured cartilage takes longer time to heal in compare to injured bones?
• Role of cartilage in movement of body parts.
• Role of ligament and tendon in movement.
• Features of bone.
• Types of bone
• Composition and structure of bone.
• Structure of long bone.
• Difference between long bones and spongy bones.
• Types of bone marrow and difference between them.
• Why long bones grow bi-directionally?
• Role of bone in movement.
• Why bone is called homeostatic tissue?
• Why Plaster of Paris is used for healing of fractured bones?
• Types of muscles and their structure.
• Structure and ultra structure of skeletal muscle.
• Sliding filament theory of muscle contraction.
• Role of calcium and neurotransmitters in muscle contraction.
• Physical and chemical changes during muscle contraction.
• Diagram and labelling.

Movement

• Definition: The act of changing of position or place by entire body of an organism or its one or more parts.
• Occurs at molecular level, cellular level, organ level and organism level.

Types of Movement

• Non-Muscular Movement
  • Cytoplasmic streaming movement (cyclosis)
  • Amoeboid
  • Ciliary movement
  • Flagellar movement
• Muscular Movement
• Movement within the cells

Advantages of Movement in Animals

1. Movement of external body parts.

• Movement of limbs, head, trunk change body posture which helps in maintaining equilibrium against gravity and for the rest.
• Movement of limbs helps in locomotion.
• Helps in capturing food and its ingestion.
• Movement of eyeball, external ear help in collection of information.
• Helps in mating and feeding young ones.

2. Movement of internal body parts.

• Heartbeats circulate blood in the body.
• Peristaltic movement of alimentary canal push food forward.
• Visceral movement helps in sound production, defaecation, urination.
• Movement of thoracic wall, ribs helps in ventilation/breathing.
• Peristaltic movement of ducts helps in secretion, movement of egg.

3. Movement within the cell.

• Streaming movement of cytoplasm helps in uniform distribution of materials within the cell.
• Movement of cytoplasm in amoeba helps in locomotion and capturing food.
• Phagocytosis in WBC helps in destroying germs enter the body.
• Pinocytosis helps in taking liquids in the cell whereas exocytosis helps in removal of substances from vacuole.

Special Connective Tissue

• Includes cartilage, bones, blood and lymph.
• This tissue have unique extra cellular matrix that helps to carryout special functions.
• It is of TWO types
  • Skeletal tissue
  • Fluid connective tissue

Skeletal tissue

• It is of TWO types

Cartilage

• Covering is called perichondrium, made of dense irregular connective tissue, have blood supply.
• Matrix is called chondrin, it is tough, transparent and homogenous, made of chondromucoid (proteoglycan = protein + carbohydrates). Chondromucoid is secreted by cartilage cells chondrocytes.
• Cartilage cells are called chondrocytes. Scattered in the matrix, enclosed in fluid filled space called lacunae. Cells are alive, cells receive nutrients and oxygen by diffusion through matrix from blood vessels present in perichondrium.
• Cartilage grows by adding new layer of matrix, by the division of chondrocytes and by the addition of chondroblast from fibroblast.
• Present at the auricular surfaces of bones, between vertebrae, tip of nose, pinna of ear, larynx.

Types of Cartilage

• Hyaline cartilage
  • Glassy, blueish white.
  • Matrix is homogeneous, translucent, fibreless and slightly elastic.
  • Form embryonic skeleton in vertebrates and skeleton of elasmobranch (cartilaginous) fishes.
  • In adults it is found in articular surface of bones and forms cushion at extremities of long bones.
  • Found between ribs and sternum, nasal septum, larynx, tracheal ring.
• Fibrous cartilage
  • Matrix contain fibres.
    • White fibrous cartilage: Contain bundle of collagen fibres. Found between vertebrae and pubic symphysis.
    • Yellow elastic cartilage: Contain yellow elastin fibres, provide elasticity. Found in external ears, eustachian tube.
• Calcified cartilage
  • There is deposition of salt of calcium in the matrix. Hard and inelastic.
  • Found between suprascapulla of pectoral gridle.

Bones

• Hardest tissue of body.
• Protect and support soft part of body.
• Helps in locomotion.
• Give structure in vertebrates and form endoskeleton.
• It is a homeostatic organ because it maintains Ca^{2+} in blood.

Calcined and Decalcified Bone

• Bones without organic matter.
• Calcined bones are obtained by heating/exposing bones in high temperature.
• Bones with only organic matter/organic part called decalcified/demineralised bone.
• It is obtained by keeping bones in dilute HCl.
• Demineralised bones are used in reconstruction of new bone or bony parts when bone is damage.

Difference between Calcined/dried Bone and Decalcified/demineralized bone

Structure of Decalcified Mammalian Bone

• Covering is called periosteum.
• Periosteum is made of dense irregular fibrous tissue, fibres are called Sharphy – Schafer fibres.
• Periosteum contain blood and lymphatic vessels.
• Blood and lymphatic vessels are connected to Haversian canals.
• Bone forming cells are called osteoblast present below periosteum.
• Osteoblast cells divide to form osteocyte thus, bone grow in thickness.
• Periosteum is absent in articulating surface.
• Endosteum is innermost layer, it lines marrow cavity.
• Osteoblast present below periosteum and endosteum divide and add cells towards matrix, thus long/thick bones grow bidirectionally.
• Matrix is present between periosteum and endosteum.
• Matrix is dense, hard. It is formed of protein OSSEIN.
• Matrix contain interlacing collagen fibres. These fibres provide resilience.
• Matrix is highly deposited with salts of calcium and phosphorus. These salts provides hardness.
• There are 3 types of bone cells. That are Osteoblast, Osteocytes and Osteoclast.
• Osteoblast present inside periosteum and outside endosteum. They divide to form new lamellae. On deposition of mineral, they changed to OSTEOCYTES.
• Osteocytes are inactive bone cells enclosed in fluid filled LACUNA.
• Each lacuna connected to neighboring lacuna by canaliculi.
• Filopodia extended through canaliculi and connected to neighboring cells and lastly to Haversian canal to obtain food and O_2 from blood.
• Osteoclast(Bone phagocytes) are large multinucleate cells.
• Osteoclast are present on the surface of bony spicules of spongy bones.
• It digest small portion of spongy bones under influence of parathormone when calcium level is low in blood plasma.

Haversian System

• In mammalian bones calcified matrix is deposited in lamellae.
• Osteocytes and their canaliculi are arranged between lamellae.
• Lamellae are of 3 types
  • Haversian lamellae: Concentric cylindrical layer(s) around Haversian canal. This system is only found in mammalian compact bones not in spongy bones.
  • Interstitial lamellae: These are lamellae present between two Haversian system. Do not have concentric arrangement.
  • Circumferential lamellae: These are lamellae parallel to circumference of bone.

Bone Marrow

• Shaft of long bone is hollow, called marrow cavity filled with soft tissue called bone marrow.
• Bone marrow is of TWO types
  • Red bone marrow:
    • Present in epiphysis region of long bones.
    • Formed of loose reticular tissue.
    • Highly vascular.
    • It contains haemopoietic tissue that give rise to different types of blood cells.
  • Yellow bone marrow:
    • Present in the shaft region of long bones(Diaphysis region).
    • It is composed of adipose tissue thus store fat.
    • Produces blood cells at the time of excess blood loss.

Differences between Red Bone Marrow and Yellow Bone Marrow

Compact/Periosteal and Spongy Bones

• Compact bones:
  • It has two distinct regions namely DIAPHYSIS(central part) and EPIPHYSIS(end parts).
  • Diaphysis is formed of compact bones where lamellae are arranged regularly in Haversian system.
  • Have single marrow cavity filled with yellow bone marrow.
• Spongy bones/Cancellous bones:
  • Form epiphysis of long bones, vertebrae, ribs and sternum, cranial bones, gridles.
  • Formed of irregular network of calcified bony bars with spicules called TRABECULAE.
  • Lamellae and trabeculae are irregularly arranged.

Differences between Compact Bone and Spongy Bones

Types of Bones on the Basis of Origin and Development

• Cartilaginous, Dermal/Investing/Membrane, Sesamoid and Visceral.

Muscle Tissue

• This tissue is responsible for outward manifestation.
• Made of specialised cells which are highly contractile due to presence of contractile protein ACTIN and MYOSIN in their cytoplasm.
• Muscle cells can be excited electrically due to potential difference across the plasma membrane.

Basic Features

• Cells are called muscle fibres/myocytes/sarcocytes.
• Have covering outside the cell membrane called sarcolemma.
• Cytoplasm is called sarcoplasm.
• Sarcoplasm contain sarcoplasmic reticulum.
• Contain fibres myofibrils that are arranged along the long axis of muscle fibres.
• Between the myofibrils present number of mitochondria called sarcosomes and glycogen molecules that provide energy by oxidation for the contraction.

Types of Muscle Fibres

Skeletal/Striated/voluntary muscles

• Cells are long, straight, unbranched cylindrical fibres.
• Nucleus towards periphery.
• Called voluntary muscle because their contraction is under our will.
• Found in limbs, body walls, tongue, pharynx…
• Can contract rapidly but for short period of time, get tired easily, accumulate lactic acid.
• Arranged in bundles, bundles of muscles attached to the bones by tendon.

Smooth/Non - Striated/Involuntary/Visceral muscles

• Cells are elongated, spindle shaped, occasionally branched.
• Nucleus present at the widest part of cell.
• Myofibrils present in cytoplasm lie parallel to long axis of the cell.
• Myofibrils are highly contractile, made of actin and myosin filaments.
• Sarcolemma is absent.
• Called involuntary muscle as their functions are not under our will.

Types of Smooth Muscles

• Functionally smooth muscle is of TWO types
  • Single unit smooth muscle: All cells in a sheet contract simultaneously. E.g. Gastrovascular tract, urinary bladder, sphincter, Blood vessels.
  • Multi unit smooth muscle: Muscle fibres contract independently as separate unit. E.g. Wall of esophagus and intestine.

Functions of Smooth Muscle

• Opening and closing of aperture.
• Narrow down blood vessels and tubes.
• Peristaltic movement.
• Churn food.

Cardiac muscle

• Found only in the wall of heart.
• Contract rapidly, rhythmically, tirelessly from embryonic stage to till death.
• They are branched, form network in the wall of heart.
• Muscle fibres are short, cylindrical and branched.
• Sarcolemma is thin.
• Fibres are uninucleate and the nucleus is centrally located.
• Myofibrils resembles to skeletal muscle.
• Fibres are joined end to end and interconnected by oblique bridge.
• End of fibres form zig zag junctions called INTERCALATED DISCS.
• Intercalated discs acts as boosters for the waves of muscle contraction.

Structure of Muscle

• Structure of sarcomere, contractile proteins and regulatory proteins.
• Sarcolemmal.
• Mitochondrion Myofilaments.
• Muscle fiber.
• Sarcoplasmic reticulum.
• T tubules.
• Nuclei.
• Sarcoplasmic reticulum.
• Z disc.
• Myofibrils.
• A band.
• I band.
• I band.
• Myofibril.
• Thick filament.
• Thin filament.
• Sarcomere.
• Z disc.
• Troponin complex.
• Actin Tropomyosin.
• Myosin.
• Muscle fibre.
• Myosin.
• Z disc.
• A band.
• Actin.
• Sarcomere.
• Actin filament.
• Actin.
• Troponin.
• Tropomyosin molecule.
• To Z line-
• Microfilament Structure and Assembly.
• cargo binding domains.
• heavy chain.
• Motor domains.
• Light chains.
• Myosin.
• Actin filament.
• Polymerized Actin Microfilament.
• Myosin V.
• Monomer Subunits.
• Myosin molecule.
• Rod.
• Actin.

Skeletal /Striated/Voluntary muscles Muscle bundles/Fasicles

• Each muscle is enclosed in sheath of dense connective tissue called EPIMYSIUM/FASCIA.
• Fascia encloses number of small bundles of muscles called fasciculi/muscle fascicles, each fasciculi enclosed in connective tissue called PERIMYSUM.
• Each fasiculum formed of several muscle fibers, each muscle fibre is covered by ENDOMYSIUM.

Structure of a muscle fibre/Muscle Cell/Myocytes

• Muscle fibres are structural and functional unit of muscle.
• Cells are long, unbranched, cylindrical.
• Covering of muscle cell is called SARCOLEMMA.
• Cytoplasm is called SARCOPLASM.
• Cells are multinucleate. Cytoplasm is SYNCYTICAL CYTOPLASM.
• Endoplasmic reticulum is called SARCOPLASMIC RETICULUM.
• Cytoplasm contain glycogen, calcium ions, number of mitochondria.
• Numbers of myofibrils/myofilaments/sarcostyles present in sarcoplasm.
• Myofibrils are contractile apparatus of muscle fibers.
• Sarcolemma is invaginated to form T – tubules, it facilitates transportation of nutrients and conduct signal of contraction.

Structure of Myofibrils

• Myofibrils are contractile apparatus of muscle fibers.
• Each myofibril has transverse striations in the form of alternate dark and light bands.
• Due to presence of striation these muscles are called STRIATED/STRIPED MUSCLES.

Light bands/Isotropic bands/I – Bands

• Made of thin actin filaments.
• One end of actin filaments are attached to Z – Disc.
• Appear nonrefractive under polarised light.
• It is also called ISOTROPIC BANDS/I – Bands because they appear non refractive under polarized light/have same refractive index in all planes.
• Each I – Band is bisected at mid - point by a thin dark membrane called Z – Line/Z- Disc.
• The part myofibril between two adjacent Z – Disc called SARCOMERE, the contractile unit.

Dark bands/Anisotropic bands/A – Bands

• Formed of thick myosin filament.
• Both eds are free(Not attached to Z - Disc).
• Appear doubly refractive.
• Also called as ANISOTROPIC BANDA/A – Bands as they are doubly refractive.
• Each A – Band is bisected at mid point by a thin pale line called H – line/ Henesen’s line.
• A narrow dark line passes through H – band/H – line called M – line/M – band.

I – Band vs A – Band

Ultrastructure of Myofibril

• Each myofibril is composed of serially repeated SARCOMERES, sarcomeres are separated from each other by Z – disc.
• Each sarcomere is made of two types of myofilaments, they are:
  • Myosin myofilaments:
    • They are thicker and are primary myofilaments.
    • Formed of protein MYOSIN.
    • Extended all along the length of A – Band.
    • They are slightly thicker in the middle region called M – line.
  • Actin myofilaments:
    • They are thinner than myosin filament and are called secondary myofilament.
    • Formed of protein actin, tropomyosin and troponin.
    • An end of each actin filament is attached to Z – disc where as other end/free end is extended A – bands towards H – disc.
    • Due to overlapping of both actin and myosin filaments I – band region of myofibrils appear dark.
    • H – zone of A – bands is without actin filaments.

Structure of Contractile Muscle Proteins

• Thick and thin filaments of striated muscles form contractile apparatus.
• Contractile apparatus/thick and thin filaments are made of THREE types protein:

Contractile Proteins

• These are MYOSIN and ACTIN.
• These two proteins interact to generate contractile effect.

Regulatory Proteins

• These are TROPOMYOSIN and TROPONIN.
• They are also called as RELAXATION proteins.
• They regulate interaction between myosin and actin.

Anchoring Proteins

• Anchor different types of proteins with each other. e.g k- kinase, a-kinase.

Structure of Actin Protein

• It is globular protein.
• Its monomeric unit is G – actin.
• 300 to 400 G – actin molecules are present in each actin filament called F – actin.
• Each myofilament is formed of TWO strands of F – actin coiled spirally.
• G – actin molecules have sites for the attachment of myosin, troponin, ATP and different types of ions.

Structure of Myosin Protein

• Its monomeric unit is MEROMYOSIN.
• Each meromyosin molecule has a tadpole like structure with TWO identical HEAVY CHAINS and FOUR LIGHT CHAINS.
• Each heavy chain has a globular head and a rod like tail.

HEAD

• Head of meromyosin is called HEAVY MEROMYOSIN(HMM) or S1.
• It is club – shaped, formed of globular protein that projects out from surface of myosin.
• Projected head with short neck called cross arm.
• Globular head is the active site of myosin because it contains Ca^{2+} , activated ATPase and binding site for ATP.

TAIL

• This part of meromyosin is called LIGHT MEROMYOSIN(LMM) or S2.
• It is made of double stranded rod, two strands are coiled helically.
• There are four light chains per myosin molecules, two on either side of the head.

Structure of Tropomyosin

• These are long filaments.
• Lie in the groove between two chains of actin molecules.
• With troponin molecule it covers active site on actin(where myosin head join).

Structure of Troponin

• These are small globular protein units.
• They bind to actin molecules.
• Binding of troponin to tropomyosin prevents the myosin heads from contacting actin and prevent contraction.

Mechanism of Muscle Contraction

• Myofibrils are apparatus of muscle contraction where as Sarcomere is the unit of muscle contraction.
• Each sarcomere is made of ½ I – band, 1 A- band and ½ I- band.
• At the time of rest (when muscle is in relaxed state) actin and myosin filaments are parallel to each other. Actin filament partially overlapping at two ends of myosin filament. H- zone, I- band and sarcomere are wide.
• At time of muscle contraction myosin join with actin filament (myosin head join with active site of actin filament) to form cross-bridge.
• Actin filament from both ends of sarcomare slide deep in to A- band towards H- zone, H- zone obliterate (disappear), Z- band move towards each other, I- band shorten, sarcomere shorten, muscle contract.
• At the time of muscle relaxation cross-bridge break, Z disc move away from each other, sarcomere widen muscle relax.
• (At the time of muscle contraction length of I- band change but length of A- band remain unchanged)

Prerequisites of Muscle Contraction/Things Needed for Muscle Contraction

• Nervous stimulus(To stimulate muscle fibres).
• ATP as the source of energy.
• Ca^{2+} to expose active site of actin filament and to initiate ATPase activity on myosin head. Therefor calcium ions have following roles during muscle contraction:
  • Expose active site of actin filament.
  • initiate ATPase activity on myosin head.

Resting Potential and Action Potential Across Sarcolemma

Resting Potential

• At resting state the sarcolemma of muscle fibre is in polarised state (Outer surface of sarcolemma is more positively charged in respect of inner surface).
• This difference in potential is called resting membrane potential.

How Resting Membrane Potential is Maintained?

• Sarcolemma is more permeable to potassium ions than sodium ions.
• As sarcolemma is more permeable to potassium ions than sodium ions, more potassium ions move out side the membrane than sodium ions move inside the membrane. As more sodium and potassium ions accumulates outside the sarcolemma makes it positively charged.
• Accumulation of sodium ions in the sarcoplasm establish sodium- potassium pump, it transport sodium ions out and pumps in potassium ions against the concentration gradient actively.

Action Potential

• Due to stimulation of muscle fibres sodium ions move in to sarcoplasm, sarcoplasm become positively charged, sarcolemma get depolarised, potential difference change, this change in potential difference called action potential

Electrical and Biological Events During Muscle Contraction

• Depolarisation of sarcolemma
  • When neural signals reaches to motor endplate neurotransmitter(acetylcholine) released, it depolarises sarcolemma and develops action potential.
• Release of calcium ions
  • Action potential of sarcolemma transmitted to T- tubules causing release of calcium ions from T- tubules.
• Conformational changes in actin filaments
  • Released calcium ions binds to regulatory proteins troponin and tropomyosin which are closely associated to actin filament. This change 3 dimensional shape of troponin- tropomyosin- actin complex, active site for actin filament exposed.
• Activation of myosin head
  • Ca^{2+} also act on myosin head to activate ATPase to release energy from ATP. Energy released is utilized to move myosin head towards actin filament.
• Formation of cross-bridge
  • Myosin heads bind to active site of actin filament to form cross- bridges.
• Sliding of actin filaments over myosin filaments
  • As the cross-bridge form, myosin head rotates pulling actin filament towards H-zone of A- band.
• Contraction of muscle
  • Two Z- band of actin filaments move towards each other, sarcomere shorten, I -band shorten, H- zone disappear, muscle contract.
• Repolarisation of sarcolemma and relaxation of muscle
  • When stimulation of muscle stops, sodium ions move out of sarcoplasm, calcium ions returns to sarcoplasmic reticulum, troponin tropomyosin return to their original position blocking active site of actin filament, cross-bridge break, I-band returns to their original position, sarcomere return to original length, muscle relax.

Energy for Muscle Contraction

• Energy for the muscle contraction provided by hydrolysis of ATP by the enzyme ATPase.
• ATP is generated by aerobic respiration.
• When ATP consumption is more, muscle fibres produce ATP anaerobically (glycolysis). As a result of anaerobic respiration accumulation of lactic acid occur. Little amount of lactic acid enter relaxing muscle and converted into glycogen. Major amount of lactic acid is transported to the liver.
• 1/5 of lactic acid oxidised to carbon dioxide and water.
• Energy released by the above reaction is used to convert remaining 4/5 lactic acid in to glycogen.

Isotonic vs Isometric Contraction & Cori Cycle

• Isotonic contraction
  • Muscle shorten, does mechanical work but change in tone does not occur. Resistance offered less than tension developed. e.g. Contraction of leg muscles while walking.
• Isometric contraction
  • Length of muscle does not change, no movement of joints, tone increases. e.g. Rock climbing, gymnastic.

Outline of Cori Cycle

• Lactic acid in muscle -> Muscle glycogen -> Blood glucose
• Lactic acid in blood -> Lactic acid in liver -> 4/5 lactic acid converted in to glycogen in liver.
• 1/5 lactic acid oxidised to form carbon dioxide and water.

Some Important Terms

Oxygen Debt

• The extra oxygen required by the body over normal requirement of oxygen to oxidise accumulated lactic acid formed during anaerobic respiration.

Motor Unit

• The set of muscle fibres innervated by all the axon branches of a motor unit.

Neuromuscular Junction

• The site at which the terminal end of a motor neuron meet the skeletal muscle fibre.

Summation

• Muscle can not contract when stimulated by a single inadequate stimulus. When two or more inadequate stimuli below threshold intensity given in rapid succession contraction occur.

Threshold Stimulus/Liminal Stimulus

• Specific minimum intensity of nerve impulse needed to stimulate muscle fibres called threshold stimulus or liminal stimulus

Muscle Twitch

• It is single contraction of a muscle fibre in response to a single stimulus with appropriate intensity.
• Muscle twitch has THREE phases:
  • Latent Phase:
    • It is the interval period/time gap between application of stimulus and beginning of muscle contraction.
    • Its duration is 0.1s in skeletal muscle and it is nearly up to 3.0s in visceral muscle.
  • Contraction Phase:
    • During this phase muscle remain contracted.
    • Its duration is 0.04s in skeletal muscles and 20s in visceral muscles.
  • Relaxation Phase:
    • During this phase contacted muscle returns to its original relaxed/resting stage.
    • Its duration is 0.5s to 2 – 3s.

Muscle Fatigue

• Reduction in the force of contraction of muscle fibres due to prolonged contraction. It develops due to accumulation of lactic acid, fall of pH, exhaustion of glycogen or exhaustion of ATP.
• The graph that shows longer latent phase/period, it shows muscle fatigue.

All or None Law

• Muscle fails to contract if strength of stimulus is less than threshold. If the strength of stimulus equal to or higher than threshold stimulus, muscle contract with maximum force irrespective of strength of stimulus.

Refractory Period/Resting Period

• It is the time between two successive stimuli during which a muscle fail to respond to the second stimulus after the first excitation.

Single Muscle Twitch

• Single isolated contraction of muscle fibre.

Tetanus

• It is a condition in which muscle remain in contracted phase for longer time. It occurs when a muscle fibre is stimulated by a rapid succession due to repeated brief stimuli.

Death Rigor/Rigor Mortis

• The irreversible state of contraction of muscle. ATP is essential during muscle contraction for the breaking of cross bridge/actin myosin association and producing relaxation. After death, cells cannot synthesise ATP. Due to fall in ATP concentration, actomyosin – ADP bond formed during muscle contraction fail to break and muscle remain in contracted phase.

Types of Muscles on the Basis of Their Functions(Movement)

Abductors and Adductors

• Abductors: Contraction of this muscle move the bone or two parts away from middle line.
• Adductors: Contraction of this muscle move the bone or two parts towards middle line.

Rotators

• Rotator: Contraction of this muscle causes a part to rotate or pivot on its axis.

Pronator and Supinator

• Supinator: Contractor of this muscle rotates the forearm and turns head or palm upward.
• Pronator: Contraction of this muscle turn the hand or palm downward.

Flexors and Extensors

• Flexors: Contraction of these muscles the angle of a joint between anterior surface of bones/contraction of these muscle bring two bones closer.
• Extensors: Contraction of these muscles returns the parts to normal position/ contraction of these bones increase the angle of a joint.

Levators and Depressors

• Levators: Contraction of these muscles raises a part.
• Depressors: Contraction of these muscles lower a part.

Investors and Evertors

• Investors: Contraction of these muscles turn the sole inwards.
• Evertors: Contraction of these muscles turn sole outwards.

Tensors

• Contraction of these muscles make a part tense or more rigid.

Sphincters or Constrictors

• These muscles are arranged in a fashion of ring around an aperture. These muscle are responsible for the opening and closure of an aperture.

Insertion of Muscles to Bones

• Muscles are attached to the bones by TENDONS.
• Tendons are formed of white fibrous connective tissue made of collagen fibres.
• Tendons are tough and non elastic, capable of bearing sudden stress.
• Skeletal muscles have their origin in one bone and insertion in another bone.
• The broad end of muscle attached to relatively fixed bone called origin. It is mostly without tendon.
• The other end of muscle attached to relatively movable bone in the form of tendon called insertion.
• The thick part of muscle between two ends called belly.
• LIGAMENTS join two bones.

Principle of Antagonastic Muscles

• The set of muscles which contract to produce opposite movement at the same joint. e.g. biceps and triceps.

Red and White Muscle Fibers

Red Muscle Fibers

• Thinnker and darker in colour.
• Slow contraction rate.
• Contain red haem – protein MYOGLOBIN.
• Myoglobin has higher oxygen affinity than haemoglobin.
• Myoglobin can extract oxygen from blood.
• Oxyhaemoglobin can be stored in muscle fibres.
• Red muscle fires have large number of mitochondria.
• Undergo aerobic respiration.
• Do not accumulate lactic acid.
• Contract for longer duration without fatigue.

White Muscle Fibers

• Thicker and lighter in colour.
• Poor in myoglobin.
• Do not store oxygen.
• Have less number of mitochondria.
• Contraction rate is fast and more powerful.
• Undergo anaerobic respiration to supply energy.
• Accumulate lactic acid and get fatigued.

Red Muscle Fiber vs White Muscle Fiber

Prosthesis & Prosthetics

Prosthesis

• Definition: A prosthesis is a device designed to replace a missing part of the body or to make a part of the body work better.
• Examples of prosthesis:
  • Hand, foot, finger and toe prostheses.
  • Hearing aids.
  • Artificial eyeballs.
  • Ear, nose or eye socket replacements.
  • An artificial soft or hard palate (worn like a dental plate).
  • Artificial heart valves.
  • Different types of cr