Zoology · Class 12 Science
Ch 11Musculo-Skeletal System — Class 12 Zoology, concept-first.
Movement in humans, as in other vertebrates, depends on two systems working together: the muscular system, which generates contractile force at the cellular level, and the skeletal system, which provides the rigid bones and the joints between them that this force is applied to as a set of levers.
Key concepts
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Motor Unit and the Triad System
A motor unit is the smallest functional unit through which the nervous system controls skeletal muscle: it consists of a single motor neuron together with every muscle fibre that neuron's axon branches out to supply.
Most relevant Q&A
Chapter contents
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Introduction to the Musculo-Skeletal System
Movement in humans, as in other vertebrates, depends on two systems working together: the muscular system, which generates contractile force at the cellular level, and the skeletal system, which provi…
The Motor Unit and the Triad System
A motor unit is the smallest functional unit through which the nervous system controls skeletal muscle: it consists of a single motor neuron together with every muscle fibre that neuron's axon branche…
Actin and Myosin — The Contractile Proteins
Skeletal muscle shortens because two kinds of protein filament interact: the thin filament, built mainly of actin, and the thick filament, built of myosin.
Red and White Muscle Fibres
Not every muscle fibre is built the same way metabolically.
Ultrastructure of the Skeletal Muscle Fibre
A whole skeletal muscle is a hierarchy of wrappings within wrappings. The entire muscle is enclosed by a connective-tissue sheath, the epimysium.
The Sarcomere
Each myofibril is not uniform along its length but is built of a repeating unit called the sarcomere, laid end to end — it is the sarcomere that gives skeletal muscle its striated (banded) appearance…
The Sliding Filament Theory of Muscle Contraction
The Sliding Filament Theory, put forward independently by Hugh Huxley and Jean Hanson (and by Andrew Huxley and colleagues) explains that a muscle shortens not because its individual filaments contrac…
The Cori Cycle
During brief, intense muscular activity, the demand for ATP can outstrip the rate at which oxygen can be delivered to the muscle.
The Human Skull
The human skeleton provides the framework and the joints that muscles pull against, and the skull is one of its most distinctive parts.
Joints of the Human Skeleton
Away from the skull, different joints of the body are shaped for the particular movement each location needs.
Bones of the Axial and Appendicular Skeleton
The rest of the skeleton follows a similar plan of an axial part (skull, vertebral column, ribs and sternum) and an appendicular part (limb bones and their girdles).
Disorders of Muscles and Joints — An Overview
27 QBeyond identifying names for common muscular and skeletal disorders, the source material available for this platform does not go into their detailed causes, symptoms or treatment — so what follows is…
+−Very Short Answer Questions17 questions
- Q1Define a motor unit.Free
- Q2What is the triad system in a skeletal muscle fibre?Free
- Q3Distinguish between actin and myosin.Free
- Q4Distinguish between red and white muscle fibres.Preview
- Q5Name the contractile proteins present in a myofilament.Preview
- Q6Name any two cranial sutures and mention where each is located.Preview
- Q7Which bone is called the “keystone bone” of the cranium, and why?Preview
- Q8Why is the human skull described as dicondylic?Preview
- Q9What are ear ossicles? What is their evolutionary origin?Preview
- Q10Name the type of joint found at the atlas-axis articulation and at the carpal-metacarpal joint of the thumb.Preview
- Q11Name the type of joint found at the atlanto-axial articulation and at the junction of the femur and the acetabulum.Preview
- Q12Name the type of joint found between the bones of the cranium and between the tarsal bones.Preview
- Q13Name the bones that make up the human cranium.Preview
- Q14How many pairs of ribs are present in man? Classify them.Preview
- Q15Name the bones of the human fore-limb.Preview
- Q16Name the bones of the human leg.Preview
- Q17Write short notes on any two disorders of the muscular or skeletal system.Preview
+−Short Answer Questions8 questions
- Q1Describe briefly the steps involved in the contraction of a skeletal muscle.Free
- Q2Describe the structure of a skeletal muscle, from the whole muscle down to the myofibril.Free
- Q3Draw and label the ultrastructure of a skeletal muscle fibre.Free
- Q4Draw and label the structure of a sarcomere.Preview
- Q5Explain Cori's cycle.Preview
- Q6Draw a labelled diagram of the skeleton of the human fore-limb.Preview
- Q7Draw a labelled diagram of the human pelvic girdle.Preview
- Q8Describe the structure of a synovial joint.Preview
Sample & Board Papers
Sample papers and previous-year board questions for this subject.
+−Show 12 questionsHide questions12 questions
- Q1Name the keystone bone of the cranium. Where is it located ?Preview
- Q2Draw a neat labelled diagram of pelvic girdle.Preview
- Q3What is triad system?Preview
- Q4Describe the important steps in muscle contraction.Preview
- Q5What is triad system?Preview
- Q6Human skull is described as dicondylic skull. Give reason.Preview
- Q7Write the difference between actin and myosin.Preview
- Q8Name the keystone bone of the cranium. Where is it located?Preview
- Q9Name the keystone bone of the cranium. Where is it located?Preview
- Q10What is Cori's cycle? Explain the process.Preview
- Q11Write any two differences between aerobic and anaerobic muscles.Preview
- Q12Name the keystone bone of the cranium. Where is it located ?Preview