An example of stretch reflex triggered by passive muscle movement is the

• tendon reflex

• ipsilateral reflex

• flexor reflex

• patellar reflex

Achondroplasia is a disease related with the defect in the formation of

• membrane

• cartilage

• mucosa

• none of these

Assertion: On stimulation, a muscle cell releases calcium ions (Ca²⁺) from sarcoplasmic
reticulum.

Reason: By reacting with a protein complex, Ca uncover active sites on the actin filaments

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

184.

Which one of the following is not a mammalian character?

• Presence of milk producing glands

• Skin is unique in possessing hair

• Presence of external ears called pinnae

• Homodont type of dentition

The H-zone in the skeletal muscle fibre is due to

• the central gap between actin filaments extending through myosin filaments in the A-band

• extension of myosin filaments in the central portion ofthe A-band

• the absence of myofibrils in the central portion of A-band

• the central gap between myosin filaments in the A-band.

Select the correct option regarding A, B and C.

• A-Tropomyosin-runs close to F-actin throughout its length

• B-Troponin-complex protein distributed at regular interval of tropomyosin

• C-F actin-polymer of monomeric G-actin helically bound to each other

• None of these

Assertion: In a pivot joint, rounded or pointed bone fits into a shallow depression in another bone.

Reason: Pivot joints are present between the metacarpals and phalanges of the fingers.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

During muscular contraction, which of the following events occur

(i) H-zone disappears
(ii) A band widens
(iii) I band reduces in width
(iv) Width of A band is unaffected
(v) M line and Z line come closer

• (i), (iii), (iv) and (v)

• (i), (i) and (v)

• (ii), (iv) and (v)

• (i), (ii) and (iii)

Which of the following is true for the labelled parts in the figure below?

• A - Z- line - located at centre of I - band

• B - Thin filament - occurs in A- band only

• C - Thick filament - confined to I- band

• D - H- zone - located at centre of M - Line

Which of the following is correct about the given figure?

• The length ofthe thick and thin myofilaments has changed.

• Length of both anisotropic and isotropic band has changed.

• The myosin cross-bridges move on the surface of actin and the thin and thick myofilaments slide past each other.

• Length of the sarcomere remains same.