Inhalt

Locomotion

Locomotion

Learning objectives

After studying this chapter you can understand about

Joints

Immovable or fixed or fibrous joint

Slightly movable or cartilagenous joint

Freely movable or synovial joint

Planar joint

Hinge joint

Pivot joint

Condyloid joint

Saddle joint

Ball and socket joint

Knee joint

Skeletal muscle

Anatomy and physiology

Structure of skeletal muscles

Process of muscle contraction

Sliding-filament theory of muscle contraction

Control of muscle contraction

Role of Ca++ in contraction + +

Classification of skeletal muscular system

Properties of muscles

Red and white muscle

Types of skeletal muscle contraction

Muscle fiber twitch

Summation

Treppe

Tetanus

Muscle fatigue

Rigor mortis

Isotonic and isometric contraction

Movement is a characteristic of all living things. There is movement within plant and animal cell. The movement of whole organisms from place to place is a somewhat different phenomenon, known as locomotion. The purpose of animal locomotion includes the search for food, avoidance of predators and other dangers, the search for a mate and in reproduction, migratory movements and the search for a more favorable environment. In many motile multicellular animals the support required is provided by the skeleton. The bones of the skeleton protect many internal organs, and the whole skeleton provides numerous points of attachment for the voluntary, skeletal muscles of the body. Locomotion is made possible by the contraction of these muscles, acting across joints. The movement is a complex series of coordinated functions of the skeletal, muscle and nervous system.

Joint

The skeletal movements of the body are produced by contraction and shortening of muscles. Skeletal muscles are generally attached by tendons to bones, so when the muscles shorten, the attached bones move. This movement of skeleton occurs at joints, or articulations, where one bone meets another. There are three main classes of joints.

1. Immovable or fixed or fibrous joints

These contain connective tissue with collagen fiber.
They contain no space between articulating joints and the synovial cavity.
They permit little or no movement.
Sutures uniting the bones of the skull (Fig. 14.1(a).

2. Slightly movable or cartilagenous joints

These joints are fixed or slightly movable.
There is no synovial cavity.
Bones are held together with cartilage.
This type of joint is found in vertebral bones at the spine which are separated by pads of cartilage called intervertebral disc. These types of joints allow some movement, primarily flexibility, while acting as efficient shock absorbers. (Fig. 14.1(b)).

3. Freely movable joints or synovial joints

The articulating ends of the bones are located within a synovial cavity or capsule filled with lubricating fluid.
The ends of the bones are capped with cartilage.
The synovial capsule is strengthened by ligaments that hold the articulating bones in place (Fig. 14.1(c)).
The articulate capsule has two layers :

Fibrous capsule : the outer layer
Synovial membrane: the inner layer that secretes synovial fluid which lubricates, reduces friction, supplies nutrients and move metabolic waste. It contains phagocytic cells that remove microbes and many debrises created from normal wear of the joint.

Fibrous capsule may contain bundles of fibers called ligaments, these are arranged in parallel bundles to help resist excess strain and prevent damages. Ligaments may lie inside or outside the articular capsule.

Ligaments are tough fibrous bands containing elastin fibers that allow the ligament to stretch. Ligaments are attached to both ends of the articulating bone to help keep the two articular cartilages together.

To reduce friction in joints that lie close to the skin, fluid-filled structures called bursae cushion. Bursae are filled with a fluid similar to synovial fluid and are present in the knee and shoulder joint.

Types of synovial joint

Synovial joints are classified into six sub-types, according to the range of movements they allow (Fig. 14.2).

a) Planar joints

This is also called gliding joint. The articulating surfaces of the bones are flat or slightly curved. These allow side to side and back and forth gliding movements.

b) Hinge joints

The articulating surfaces of the bones consist of one concave surface and one convex surface, where one bone fits into the other. A hint joint produces an open and close movement similar to the action of a hinge on a door.

c) Pivot joints

In this joint the end of one bone is rounded and the other has a ring or hole made of bone and ligament. A pivot joint allows rotational movement.

d) Condyloid joints

The articulating surface of one bone is an oval-shaped projection that fits into an oval-shaped depression of the other. This joint allows up and down and side to side movement.

e) Saddle joints

The articulating surface of one bone is saddle shaped with the articular surface of the other bone-shaped to fit into the saddle. This type of joint allows side to side and up and down movement.

f) Ball and socket joints

In this joint a rounded ball-shaped surface fits into a cup-shaped depression that allows movement in several directions.

Knee joint

The knee joint is the largest joint in the body

and it requires stabilizing by ligaments and

tendons. The knee joint is a hinge joint formed

by the condyles of the femur and tibia and the

posterior surface of the patella. The joint allows

flexion and extension and a small degree of side

to side movement when the knee is flexed. The

joint has a joint capsule and extra-capsular

and inter-capsular ligaments (cruciate ligaments )

to strengthen it by limiting movement. The joint

is further strengthened it by limiting movement.

The joint is further strengthened by two crescent

wedge-shaped pieces of fibrous tissue called the

menisci. The patella is a sesamoid bone that

lives within the joint capsule. If slides on the

patellar surface of the distal femur and its function

is to reduce friction during extension and protect

the knee joint (Fig. 14.3).

Capsular ligament helps to prevent dislocation, stabilizes joint.
Synovial membrane secretes synovial fluid to lubricate and supply nutrients. Phagocytic cells are present to keep fluid free debris.
Articular cartilage reduces friction and act as shock absorber.
Cruciate ligaments strengthen and limit movement.
Menisci – fibrous tissue to ensure tight fit between joint surfaces of different shapes.

Patella tendon helps prevent dislocation of patella, stabilizes joint.
Patella – sesamoid bone.
Prepatella bursa – sac of synovial fluid.
Bursa – sac of synovial fluid.

Skeletal muscle

Most skeletal muscle lies just below the skin and there are approximately 600 named muscles in the body. Skeletal muscle is the only muscle tissue that may be controlled voluntarily, although in many cases this control operates through reflexes.

Anatomy and physiology

A whole muscle is made up of numerous muscle fibers and enclosed in a layer of connective tissue. Skeletal muscles are well supplied with nerves and blood vessels. Skeletal muscle is stimulated by nerves of the peripheral nervous system and can produce rapid forceful contraction needed for movement. In most cases skeletal muscle has two ends that attach to other tissues and a wide middle section called the belly. Muscles connect to bone by tendons. Tendons are tough strands or cords of fibrous tissue.

Structure of skeletal muscle

Skeletal muscle or voluntary muscle mainly occurs attached to the skeleton in the trunk, limbs and head, either directly to the bone or indirectly via tendon. Skeletal muscle consists of thousands of elongated, cylindrical, multinucleated muscle fibers, lying parallel to one another. Skeletal muscle is also called striated muscle because the highly regular arrangement of its actin and myosin filaments gives it a striped appearance. This muscle is enclosed by a sheet of connective tissue – the deep fascia that separates and holds muscle together. The outer covers of the muscle fibers also extend and form tendons that are connective tissue that attaches the bone to the muscle. Under the deep fascia, there are bundles of muscle fiber which are called fascicles that are covered by perimysium. Each individual muscle fiber is covered with endomysium. The muscle fibers contain a series of transverse stripes of muscle protein., Each muscle fiber is covered with a plasma membrane called sarcolemma from which extend small vessels called transverse tubules. Sarcoplasm (the name of muscle cytoplasm ) in each muscle fiber stores glycogen and oxygen (myoglobin ) to provide energy during muscle contraction. Along the length of each muscle fiber are tube-like structure called myofibrils. The myofibrils consist of interlinking thick (myosin protein ) and thin (actin protein ) filaments. Thick and thin filaments overlap in pattern and form a functional unit of muscle. The units are called sarcomeres. Sarcomeres are separated from each other by a zigzag band of dense material that is called z band. One sarcomere is the region between two Z lines. Sarcomeres have bands of filaments. The A band extends along the length of the thick filament and its center is narrow band which is called the H zone. At each of the A band, thick and thin filaments overlap. Thin filaments create the I-band on either side of the A band. The I band is divided in half by a Z band.

Process of muscle contraction

The process of muscle contraction is stimulated by nerve impulses conducted via motor neurons. Neurons and muscles meet at the neuromuscular junction (NMJ). The NMJ provides a space/synapse across which message from the impulses will travel.
At the axon terminal there are vesicles containing neurotransmitter, i.e. Acetylcholine (Ach). When a nerve impulse is received the vesicle fuses with the cell membrane and released Ach.
The Ach is moved across the synapse due to active transport promoted by high concentration of sodium and potassium.
The Ach attached to Ach receptors on the muscle cell membrane (Sarcolemma) and this open up a channel to allow the high concentration levels of sodium to flood into the cell.
The change in sodium concentrations within the cell causes the shape of the troponin molecule and in turn the tropomyosin molecule, allowing the sliding filament mechanism of muscle contraction to take place.
To relax the muscle, Ach is removed from the synaptic cleft by the action of Acetylcholinesterase (AchE).

The sliding-filament theory of muscle contraction

Huge Huxley and Andrew Huxley proposed a molecular mechanism of muscle contraction. This theory is called the sliding-filament theory of muscle contraction. The repeating structure sarcomere is the smallest subunit of muscle contraction.

The thin filaments stick pathway into, and overlap with thick filaments on each side of an A band but in a resting muscle, do not project all the way to the center of the A band. As a result, the center of an A band (called an H band) is lighter than each side, which its interdigitating thick and thin filaments. These appearances of the sarcomeres change when the muscle contracts.

A muscle contracts and shortens because of myofibrils contract and shorten; instead, the thin filaments slide deeper into the A bands (Fig. 14.4). This makes the H band narrower until, at maximal shortening, they disappear entirely. It also makes I bands narrower, because the dark A bands are brought closer together. This is sliding filament mechanism of contraction.

Electron micrographs reveal cross-bridges that extend from the thick to the thin filaments, suggesting a mechanism that might cause the filaments to slide. Each thick filament is composed of many myosin proteins packed together, and every myosin molecule has a “head” region that protrudes from the thick filament (Fig. 14.5). These myosin heads form the cross bridges seen in electron micrographs.

Thin filaments are composed of globular actin protein. Two rows of actin proteins are twisted together in a helix to produce the thin filaments (Fig. 14.6). Other proteins tropomyosin and troponin, associate with the strands of actin and are involved in muscle contraction.

The interactions of thick and thin filaments in striated muscle sarcomere (molecular level) are depicted in figure (14.7(a)). The heads on the two ends of the thick filaments are oriented in opposite directions, so that the cross-bridges pull the thin filaments and the Z lines on each side of the sarcomere toward the center (Fig. 14.7(a)). The sliding of the filaments produces muscle contraction.

The heads on the two ends of the thick filaments are oriented in opposite directions, so that the cross-bridges pull the thin filaments and the Z lines on each side of the sarcomere toward the center (Fig. 14.7(a)). The sliding of the filaments produces muscle contraction.

Before the myosin heads bind to the actin of the thin filaments, they act as ATPase enzymes, splitting ATP into ADP and Pi. This activates the head so they can bind to actin and form a cross-bridge. Once a myosin head binds to actin, it undergoes a conformational (shape) change, pulling the thin filament toward the center of the sarcomeres (Fig. 14.5(b)) in a power stroke. At the end of the power stroke, the myosin head binds to a new molecule of ATP. This allows the cross-bridge cycle (Fig. 14.8), which repeats as long the muscle is stimulated to contract. The cross-bridge cycle in muscle contraction with ADP and Pi attached to the myosin head (Fig. 14.8(a)), the head is in a conformation that can bind to actin and form a cross-bridge (Fig. 14.8(b)). Binding causes the myosin head to assume a more bent conformation, moving the thin filament along with the thick filament and releasing ADP and Pi (Fig. 14.8(c)). Binding of ATP to the head detaches the cross-bridge; cleaved of ATP into ADP and Pi puts the head into its original conformation, allowing the cycle to begin again (Fig. 14.8(d)).

Control of muscle contraction

Role of Ca++ in contraction

When a muscle is relaxed, its myosin heads are “cocked” and ready, through the splitting of ATP, but are unable to bind to actin. This is because the attachment sites for the myosin heads on the actin are physically blocked by another protein, known as tropomyosin, in the thin filaments. Cross-bridges therefore cannot form in the relaxed muscle, and the filaments cannot slide.

In order to contract a muscle, the tropomyosin

must be moved out of the way so that the

myosin heads can bind to the uncovered actin

attachment sites. This requires the action of

troponin, a regulatory protein complex that

holds tropomyosin and actin together. The

regulatory interactions between troponin and

tropomyosin are controlled by the calcium

ion (Ca++) concentration of the muscle cell

cytoplasm.

When the muscle is at rest, a long filament of

the protein tropomyosin blocks the myosin-binding

sites on the actin molecule. Because myosin is

unable to form cross-bridge with actin at those sites,

muscle contraction cannot occur and at this time

Ca++ concentration of muscle cell cytoplasm is

low (Fig. 14.9(a)). When the Ca++ concentration

is raised, Ca++ binds to troponin. This causes the

troponin-tropomyosin complex to be shifted away

from the attachment sites for the myosin heads on

the actin. Cross-bridges can thus form, undergo

power strokes and produce muscle contraction

(Fig. 14.9(b)).

Where does the Ca++ come from?

Muscle fibers store Ca++ in a modified endoplasmic reticulum called a sarcoplasmic reticulum or SR (Fig. 14.10). When a muscle fiber is stimulated to contract, an electrical impulse travels down into the muscle fiber through invaginations of the cell membrane called transverse tubule (T tubules). This triggers the release of Ca++ from the SR. Ca++ then diffuses into the myofibrils, where it binds to troponin and causes contraction. The contraction of muscle is regulated by nerve activity, and so nerves must influence the distribution of Ca++ in the muscle fiber.

Muscle contractions are initiated by action potentials from motor neurons arriving at the neuromuscular junctions. Motor neurons are generally highly branched and can synapse with up to a hundred muscle fibers each. All the fibers activated by a single motor neuron constitute a motor unit and contract simultaneously in response to the action potentials fired by the motor neurons. The particular motor neurons that stimulate skeletal muscles are called somatic motor neuron (Fig. 14.10). In human, each muscle fiber only has a single synapse with a branch of one axon.

Contraction of muscle by nervous stimulation has following events:

1. Motor neuron secretes acetylcholine (Ach) neurotransmitter which acts on muscle fiber membrane to stimulate muscle fiber to produce its own electrochemical impulses.

2. Impulses spread along membrane of muscle fiber and are carried into muscle fibers through T tubules.

3. T tubules conduct impulses toward SR, which then releases Ca++.

When impulses from the nerve ceases, the nerve stops releasing Ach. This stops the production of impulses in the muscle fiber. When the T tubules no longer produce impulses, Ca++ is pumped back into SR by active transport. Troponin is no longer bound to Ca++, so tropomyosin returns to its inhibitory position, allowing muscle to relax.

The involvement of Ca++ in muscle contraction is called excitation – contraction coupling because it is the release of Ca++ that links the excitation of muscle fiber by the motor neuron to the contraction of the muscle.

Classification of skeletal muscular system

Skeletal muscular system may be classified on the basis of function (Fig. 14.11). Muscle may work independently or in coordination to allow smooth and precise movement. Muscles attached to a joint often work in pairs so that if one muscle contracts the other muscle will relax.

Prime movers: Muscles that have the main responsibility for an action because they move and contract are called prime movers.
Antagonists muscle: Muscles that limit and counteract the movements are called antagonists. In a pair of working muscles the roles may be reversed.
Synergists: Groups of muscles that work together to produce a movement are called synergists. Synergists work to assist the prime mover and stabilize joints. Synergists may also prevent a movement at a joint, and the group of muscles is then called fixator.

The biceps are the prime movers to the flex the elbow, and they are the antagonist when the elbow is lowered.

Information on the tension and state of the muscles is transmitted to the brain via receptors in the muscle called muscle spindles. The muscle spindle is a collection of modified muscle fibers that are enclosed in connective tissue. The connective tissue connects the receptors to surrounding muscle fibers. As the muscle fibers move, the spindle becomes elongated and information about muscle activity is transmitted to the brain. Similar receptors are also present in the tendons.

Properties of muscles

There are seven properties that are required for muscle tissue functions:

Excitability: it reacts to electrical signals from the nervous system.
Contractibility: muscle tissue is able to become shorter and thicker (to contract).
Extensibility: muscle tissue is able to stretch(extend) without causing damage.
Elasticity: muscle tissue is able to go back to its original shape when relaxed.
Conductibility: once a part of the muscle fiber is stimulated by a stimulus of adequate strength, it is conducted within no time to all its other parts.
Threshold or liminal: All the muscles contract only when they receive the stimulation of certain strength. The lowest limit of stimulus capable to bring contraction in muscles is called threshold or liminal stimulus.
Refractory period: After stimulation, there is a brief period during which the muscle does not remain in a excitable state, this period is refractory period or the period of relaxation of muscle.

Red and white muscle

On the basis of concentration of hemoglobin present in skeletal muscle, it may be divided into red and white muscle.

Red muscle: This muscle contains very high concentration hemoglobin (which is called myoglobin).

White muscle: This muscle contains very low amount of myoglobin. Myoglobin can store oxygen which is utilized by the mitochondria for the synthesis of ATP as when required.

Types of skeletal muscle contraction

Muscles contract to produce tension that will maintain the bone of the muscle or move the skeleton. The tension of the muscle must be able to produce a force that will be sufficient to produce the movement required. Picking up a pencil or a bag full of books will demand different tensions to overcome the weight of the two objects.

Muscle fiber twitches

An isolated skeletal muscle can be studied by stimulating it artificially with electric shocks. If a muscle is stimulated with a single electric shock, it will quickly contract and relax in a response called a twitch.

Summation

Increasing the stimulus voltage increases the strength of the twitch up to maximum. If a second electric shock is delivered immediately after the first, it will produce a second twitch that may partially “ride piggy back” on the first. This cumulative response is called summation.

Treppe or staircase phenomenon

If the stimulus is repeated, the muscle continues spasmodic contractions that increase in intensity called treppe or staircase phenomenon. Warm-up exercises before physical activity are aimed at producing treppe to prepare the muscle to produce maximum effort.

Tetanus

If the muscle is not allowed to relax due to repeated stimulation, the twitch contraction will produce a powerful continuous contraction called tetanus. The powerful contraction reduces the oxygen supply to the muscle fibers and this causes pain.

Tetanus may occur following physical activity and it is called cramp. Cramp may also occur with lower-level muscle activity after sitting awkwardly and this is then called a spasm. If tetanus occurs there will be a period of intense pain until the muscle receives oxygen. Massage will help to speed up the return of the oxygen supply and relieves the pain.

Muscle fatigue

Muscle fatigue refers to the use-dependent decrease in the ability of a muscle to generate force. The reasons for fatigue are not entirely understood. In most cases, however muscle fatigue is correlated with the production of lactic acid by the exercising muscles. Lactic acid is produced by the anaerobic respiration of glucose, and glucose is obtained from muscle glycogen and from the blood. Lactate production and muscle fatigue are therefore also related to the depletion of muscle glycogen.

Fatigue muscle needs extra oxygen to dispose of excess lactic acid. After a strenuous exercise, faster breathing should be continued for some time to supply extra oxygen for oxidizing excess lactic acid. This results in the disappearance of fatigue.

Rigor mortis

In death, the cell can no longer produce ATP, and therefore the cross-bridges cannot be broken – this causes the muscle stiffness of death called rigor mortis. The cross-bridge is formed by binding myosin head with actin head after splitting ATP into ADP and Pi. A living cell, however, always has enough ATP to allow the myosin heads to detach from actin. How, then, is the cross-bridge cycle arrested so that muscle can relax? The regulation of muscle contraction and relaxation requires addition factors also. The muscle goes into a state of “death rigor”, and becomes stiff. Rigor mortis disappears some fifteen to twenty-five hours after death as proteins are degraded.

Isotonic and isometric contraction

Tension of the muscle is required to move an object, when the object is moving the muscle shortens as the skeletal joints moves. No further tension is required and this contraction is called isotonic.

When lifting a heavy object the tension of the muscle must be increased before the object can be moved. The muscle length stays the same although contraction is occurring. This contraction is called isometric. When lifting objects, isotonic and isometric contractions are needed for movements.

Summary

The movement is a complex series of coordinating functions of the skeletal, muscle and nervous system.
The movement of skeletal muscle occurs at joints or articulations, where one bone meets another.
Three main classes of joints are immovable, slightly movable and freely movable of synovial joints.
In immovable joints there is no space between articulating joints and the synovial cavity.
In slightly movable or cartilagenous joints, there is no synovial cavity and bones are held together with cartilage.
In synovial joint the articulating ends of the bones are located within a synovial cavity filled with lubricating fluid.
Synovial joints are classified into six subtypes according to the range of movements they allow. These are planner joints, hinge joints, pivot joints, condyloid joints, saddle joints, ball and socket joint.
Knee joint is the largest joint in the body and it requires stabilizing by ligaments and tendons.
Capsular ligament, synovial membrane, articular cartilage, cruciate ligament, menisci, patella tendon, patella, prepatella bursa and bursa reduce friction movement of knee joint.
Most skeletal muscle lies just below the skin and there are approximately 600 named muscles in the body. It is made up of numerous muscle fibers and enclosed in a layer of connective tissue.
Sarcolemma is the covering membrane of muscle fiber and sarcoplasm is the cytoplasm of muscle fiber.
Thick and thin filaments overlap in pattern and form, which is a functional unit of muscle. The units are called sarcomeres.
Sarcomeres are separated from each other by a zig zag band of dense material that is called Z lines. Sarcomeres have bands of filaments.
The process of muscle contraction is stimulated by nerve impulses conducted via motor neurons. At the axon terminal there are vesicles containing neurotransmitter, i.e. acetylcholine which move across the synapse due to active transport promoted by high concentration of sodium and potassium. Increases of sodium concentration allow the sliding filament mechanism of muscle contraction.
Huxley and Huxley proposed molecular mechanism of muscle contraction. This theory is called the sliding-filament theory of muscle contraction. Electron micrographs reveal cross-bridges that extend from the thick to the thin filaments, suggesting a mechanism that might cause the filaments to slide. Myosin heads of thick filament bind with actin of thin filament to form cross-bridge with the addition of ADP. ATP breaks to ADP and Pi and make the cross-bridge. This cross bridge pulls thin filaments. Therefore sliding of the filaments produce muscle contraction.
In order to contract muscle, the tropomyosin must be moved out of the way so that the myosin heads can bind to the uncovered actin attachment sites. The regulatory interactions between troponine and tropomyosin are controlled by the calcium ion (Ca++) concentration of the muscle cell cytoplasm. Muscle fibers store Ca++ in a modified endoplasmic reticulum called a sarcomere reticulum or SR. When a muscle fiber is stimulated to contract, an electrical impulse travels down into the muscle fiber through transverse tubule. Muscle contractions are initiated by action potentials from motor neurons arriving at the neuromuscular junction.
Skeletal muscular system may be classified on the basis of function. It consists of prime movers, antagonists muscle and synergists.
There are seven properties of muscles such as excitability, contractibility, extensibility, elasticity, conductibility, threshold and refractory period.
Red muscle contains very high concentration of hemoglobin while white muscle contains very low concentration of hemoglobin. Red muscles get energy by aerobic respiration but white muscles obtain energy by anaerobic respiration. Red muscle accumulates little lactic acid whereas white muscle accumulates high level of lactic acid.
Twitch is a response, which help to contract and relax the muscle, if a single electric shock is being given.
Increasing the stimulus voltage increases the strength of the twitch up to maximum. This cumulative response of twitch is called summation.
If the stimulus is repeated, the muscle continues spasmodic contractions that increase in intensity called treppe.
If the muscle is not allowed to relax due to repeated stimulation, the twitch contraction will produce a powerful continuous contraction called tetanus.
Muscle fatigue refers to the use-dependent decrease in the ability of a muscle to generate force. The reason for fatigue is not entirely understood.
In death, the cell can no longer produce ATP, and therefore the cross-bridge cannot be broken – this causes muscle stiffness of death called rigor mortis.
Tension of the muscle is required to move an object when the object is moving the muscle shortens as the skeletal joints moves. No further tension is required and this contraction is called isotonic.
When lifting a heavy object the tension of the muscle must be increased before the object can be moved. The muscle length stays the same although contraction is occurring. This contraction is called isometric.

Terms to remember

Actin

One of the major proteins that makes up vertebrate muscle

Creatine phosphate

This high energy compound present in the muscle and it helps to convert ADP to ATP.

Ligament

Connective tissue of great tensile strength attaches bone to bone.

Myology

Study of muscles

Myosin

One protein component of microfilaments, a principal component of vertebrate muscles

Myosin ATPase

An enzyme that hydrolyzes ATP into ADP and Pi with the release of energy

Neuromuscular junction

The structure formed when the tips of axon contact (innervate) a muscle fiber.

Sarcolemma

The specialized cell membrane in a muscle cell

Sarcomere

Fundamental unit of contraction in skeletal muscle, repeating bands of actin and myosin that appear between two Z lines

Summation

Repetitive activation of the motor neuron resulting in maximum sustained contraction of muscle

Synovial fluid

Fluid present at the synovial joints in the synovial cavity such as elbow, shoulder etc.

Tendon

A collagen-containing band of tissue that connects a muscle with a bone

Questions for self- assessment

Very short answer questions 1 mark each

What is muscle twitch? (H.P.S.E.B. 2000)
Which myofilaments slide in a sarcomere during contraction?
What lubricates the freely movable joints at the shoulder? (C.B.S.E. 1994)
Name the chemical that causes fatigue in the muscle. (C.B.S.E. 1997)
Name the kind of skeleton joint which permits movements in a single plane only.(C.B.S.E. 1995)
Name the functional contractile unit of the muscle. (C.B.S.E. 1997)
Which type of movable joint is the shoulder joint? (C.B.S.E. 1996)
Which type of movable joint makes the hip joint? (C.B.S.E. 1996)
Mention one significant difference between muscle twitch and tetanus.(C.B.S.E. 1995)
What property of muscle fiber enables them to cause movement? (C.B.S.E. 1995)
Name the filaments that cause cross-bridges during muscle contraction. (C.B.S.E. 1995)
Name the tissue which connects muscle to a bone. (C.B.S.E. 1995)
Which term do you use for the muscles, which draw a bone away from the body midline? (C.B.S.E. 1994)
Name the thin and thick protein of muscle fibers. (C.B.S.E. 1993, 95)
Name two special proteins which constitute the contractile filaments of muscle fibers. (C.B.S.E. 1992)
Give the term for a continued state of contraction caused by many rapidly repeating stimuli in a muscle. (C.B.S.E. 1992)
What are two types of straited muscle filaments? (C.B.S.E. 1992)
Give one example each of fibrous joint and cartilagenous joints.(C.B.S.E. 1992)
Name the type of movable joint at the knee or at the elbow.(C.B.S.E. 1991, 93, 95)
What is synovial fluid? (C.B.S.E. 1987)
Name the two types of myofilaments in a sarcomere.
What is myoglobin?
Name the protein which constitutes I-band and A-band.
Name one set of muscles which work antagonistically.
Name the theory proposed by Huxley and others for the muscle contraction.

Answer

(1) See text. (2) Actin myofilaments. (3) Synovial fluid. (4) Lactic acid (5) Hinge joint. (6) Sarcomere. (7) Ball and socket type. (8) Ball and socket type. (9) See text. (10) Excitability and conductivity. (11) Actin and myosin filaments. (12) Tendon. (13) Abductors. (14) Myosin. (15) Actin and myosin. (16) Tetanus. (17) Actin and myosin. (18) Between bones of cranium, joints between the centra. (19) Hinge joint. (20) A lubricating fluid present in synovial cavity of movable joints. (21) Primary, thick or myosin, myofilaments and secondary, thin or actin myofilaments. (22) When red blood cell present in the muscle then it is called myoglobin. RBC of muscle combine with O2 to form oxy-myoglobin. This oxy-myoglobin release O2 during muscle contraction and become myoglobin. (23) Actin and myosin. (24) Biceps and triceps. (25) Sliding filament theory of muscle contraction.

Short answer questions 2 marks each

Which causes muscle fatigue? How is it removed? (H.P. 2002)
Why are movement and locomotion necessary among animal?
Differentiate between tendon and ligament.
What actually leads to shortening of a sarcomere?
What is summation?
Explain important features of synovial joints.
What is joint? Give examples of ball and socket and hinge joint.
Explain and differentiate the terms movement and locomotion.
Where from muscle gets energy for contraction?
Differentiate between sarcoplasm and sarcolemma.
What are isotonic and isometric contractions?
Why are muscles rich in the compound creatin phosphate?
Differentiate between fibrous joints and cartilagenous joints.
What cause muscle fatigue? How it is removed?
Differentiate between actin and myosin.
What is summation?
What is myosin ATPase?
Differentiate between H-band and M-band.
What is knee joint?
What is sarcomere?

Short answer questions 3 marks each

Explain the sliding filament theory of muscle contraction. (C.B.S.E. 2001)
What make the synovial joint freely movable? List the various types of synovial joints. (C.B.S.E. 1999)
Explain the principle of antagonistic muscles. Give one example of such muscles.(C.B.S.E. 1999)
Write short note on muscle fatigue.
What is the biological significance of (a) myoglobin (b) phospho creatinine (c) red bone marrow.
How does the body muscle act?
What is the significance of locomotion? Write three points about it.
Differentiate between red and white muscle.
Distinguish between (a) Fibrous joints and cartilagenous joints. (b) Active and myosin. (c) Isotonic and isometric contraction of muscle.
What is antagonistic muscle? Explain with example.
How are red muscle fibers specialized for sustained work over a prolonged period?
How does calcium affect the process of muscle contraction?
How does skeletal muscle contract?
How are thick and thin filaments arranged in a muscle fiber?
What are biceps and triceps?

Long answer questions 5 marks each

1. Write briefly the biological importance of the following :

(a) Myoglobin

(b) Active and myosin filament

(d) Fibrous joints

(e) Lactic acid (C.B.S.E. 1999)

2. What chemical changes occur during contraction of a skeletal muscle? (C.B.S.E. 1995)

3. Describe the various kinds of skeletal joints in human body according to their mobility, giving one example each. (C.B.S.E. 1994)

4. How does the muscle shorten during its contraction and lengthen during its relaxation? Explain with diagram. (C.B.S.E. 1991)

5. How is the structure a sarcomere suitable for the contractility of the muscle? Explain its function according to sliding filament theory. (C.B.S.E. 1990)

6. Differentiate between

(a) Tendon and ligament.

(b) White and red muscle fibers.

(d) Actin and myosin.

7. Enumerate the events of muscle contraction.

8. How is energy supplied for muscle contraction.

9. Describe the structure of striated muscle.

10. Name only different types of joints.

11. Distinguish between

(a) Muscle twitch and tetanus

(b) Ball and socket-point and hinge joint. (H.B.S.E.B. 2001)

12. Answer the following briefly :

(a) How does the muscle shorten during its contraction and lengthen during its relaxation?

(b) How biological functions are served by the skeletal system?

(c) Why a red muscles fiber can work a prolonged period while a white muscle fiber suffers from fatigue after a shorter work?

(d) Where from the muscle gets energy for its contraction. (N.C.E.R.T.)

13. Match the items of Column A with B.

	Column A	Column B
1.	Myoglobin	Skeletal muscle
2.	Actin	Muscle fiber filament
3.	Planar	Neurotransmitter
4.	Acetylcholine	Red muscle fiber
5.	Prime movers	Synovial joint

14. Differentiate between red and white muscle fibers with their examples.

15. Enumerate the events of muscle contraction.

16. Write briefly the biological importance of the following :

(a) Fibrous joints;

(b) Synovial joints;

(d) Lactic acid;

(e) Myoglobin;

17. What is a joint? Write its type with examples.

18. Describe in brief sliding-filament theory of muscle contraction.

19. Write the differences between :

(a) Actin and myosin;

(b) Red and white muscle;

20. Match the items of Column A with B.

	Column A	Column B
1.	Myoglobin	Smooth muscle
2.	Involuntary	Tropomyosin
3.	Third class lover	Red muscle
4.	Thin filament

Impressum

Tag der Veröffentlichung: 07.03.2016

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